Food Chemistry 168 (2015) 417–422
Contents lists available at ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Characterisation of spray dried soy sauce powders made by adding crystalline carbohydrates to drying carrier Wei Wang a, Weibiao Zhou a,b,⇑ a b
Food Science & Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore National University of Singapore (Suzhou) Research Institute, 377 Linquan Street, Suzhou Industrial Park, Jiangsu, 215123, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 11 February 2014 Received in revised form 31 May 2014 Accepted 10 July 2014 Available online 18 July 2014 Keywords: Drying carrier Soy sauce powder Spray drying Caking Stickiness
a b s t r a c t This study aimed to reduce stickiness and caking of spray dried soy sauce powders by introducing a new crystalline structure into powder particles. To perform this task, soy sauce powders were formulated by using mixtures of cellulose and maltodextrin or mixtures of waxy starch and maltodextrin as drying carriers, with a fixed carrier addition rate of 30% (w/v) in the feed solution. The microstructure, crystallinity, solubility as well as stickiness and caking strength of all the different powders were analysed and compared. Incorporating crystalline carbohydrates in the drying carrier could significantly reduce the stickiness and caking strength of the powders when the ratio of crystalline carbohydrates to maltodextrin was above 1:5 and 1:2, respectively. X-ray Diffraction (XRD) results showed that adding cellulose or waxy starch could induce the crystallinity of powders. Differential Scanning Calorimetry (DSC) results demonstrated that the native starch added to the soy sauce powders did not fully gelatinize during spray drying. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Soy sauce is a traditional condiment popularly produced and consumed in East Asian countries, such as Japan, Korea and China. Soy sauce has mainly been used in liquid form in the past, but recently, different types of soy sauce powders have been developed and marketed. Commercially available soy sauce powders are mainly manufactured by spray drying, although other dehydration methods, such as freeze drying and drum drying, can also be used. Powdered soy sauce was firstly used in the soup base of instant noodles. Now the application has expanded to powdered seasoning, frozen food and processed meat (Okayasu & Hamano, 2003). For spray dried amorphous food powders, including soy sauce powders, stickiness or caking under relatively high humidity or over a long storage period is always an issue. This is because spray drying usually generates powders in amorphous states due to its short drying time. The amorphous glass will start to flow and become sticky when environmental temperature exceeds its glass transition temperature (Tg) at which glass-rubbery transition happens. The most widely used method for solving stickiness problems is to add large molecular weight carbohydrates, like maltodextrin, to increase powder Tg and reduce hygroscopicity. ⇑ Corresponding author at: Food Science & Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore. Tel.: +65 6516 3501; fax: +65 6775 7895. E-mail address: [email protected] (W. Zhou). http://dx.doi.org/10.1016/j.foodchem.2014.07.065 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved.
Maltodextrin has a good solubility and a high Tg. Therefore, it has been widely used as the drying carrier for making instant food powders (Cai & Corke, 2000; Ersus & Yurdagel, 2007; Goula & Adamopoulos, 2008, 2010; Sablani, Shrestha, & Bhandari, 2008; Tonon, Brabet, & Hubinger, 2008). However, due to its amorphous nature, maltodextrin will also become hygroscopic and sticky when exposed to a high relative humidity environment. Identifying alternative dying carriers to address stickiness or caking issues of amorphous food powders is of both academic and industrial interest. According to Cano-Chauca, Stringheta, Ramos, and Cal-Vidal (2005), adding waxy starch or microcrystalline cellulose as a drying aid was able to produce a partial crystalline surface in spray dried mango juice powder. The semi-crystalline powders had reduced stickiness compared to the ones made using only maltodextrin. Spray dried soy sauce powders containing maltodextrin as the drying carrier are mixtures of NaCl crystals and amorphous carbohydrates, amino acids and proteins (Wang & Zhou, 2012). The salt crystals adsorb moisture only when equilibrium water activity reaches 0.753 (Hartmann & Palzer, 2010). So salt is not likely to cause moisture adsorption and sintering of particles when exposed to low or medium relative humidity. However, the amorphous phase is metastable and liable for moisture adsorption and sintering of particles under low relative humidity. Therefore, to incorporate crystalline or semi-crystalline carbohydrates instead of maltodextrin in order to increase the crystallinity of soy sauce powder has great potential to improve stability. The crystalline carrier may produce a semi-crystalline powder and reduce
418
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
inter-particle powder adhesions. However, due to the insoluble nature of large molecular carbohydrates (i.e. starch and cellulose), preparing feed solutions containing them, as well as reconstitution of the powders, needs to be understood and optimised. The objective of the study was to explore the addition of waxy starch or microcrystalline cellulose together with maltodextrin as drying carriers to produce soy sauce powders. The crystallinity of soy sauce powders was studied and related to the stickiness and caking behaviour of the powders under testing conditions. The study aimed to improve the stability of spray dried soy sauce powders by providing an alternative approach to the current practice, and lay a foundation for industrial production and application of soy sauce powders.
System, UK) was used in this study to provide a constant compression force and to measure the tension force. The TA.XT plus library program of dough stickiness was used. The compression force selected was at 40 g. The diameter of the plexiglass probe was 25 mm. The trigger force was set at 5 g. The compression travel speed for the probe was 2 mm/s. The probe reversing speed was 10 mm/s, which was the maximum reversing speed of the texture analyzer. The holding time was 0.1 s. The probe distance was selected as 4 mm. For stickiness measurements, the samples were mixed with glycerol in a proportion of 2 g powder to 5 ml glycerol, forming a homogeneous dough. The dough was placed in the instrument and the test was performed in triplicate. 2.6. Caking test
2. Materials and methods 2.1. Raw materials Naturally brewed soy sauce was obtained from Kikkoman Pte. Ltd. (Singapore) with a protein content of 10.3% (w/w), carbohydrates of 8.1% (w/w) and NaCl of 16.5% (w/w) and the rest being water. Maltodextrin 10 DE was purchased from Suntop Enterprise (Singapore). Microcrystalline cellulose was purchased from Sigma–Aldrich (Singapore). Corn waxy starch was obtained from National Starch Co. (Singapore). 2.2. Spray drying A pilot-scale spray dryer (Mobile MinorTM, GEA, China) was used in the study. Co-current flow regime and a two-fluid nozzle atomizer were used for the spray drying process. The inlet air temperature was set to 160 °C and outlet temperature was maintained at 75 °C, by adjusting the feed flow rate via a peristaltic pump. The compression air pressure for atomisation was controlled at 2 bars, with an air flow rate of 4 m3/h. Dried powders were collected from the base of a cyclone separator of the drier. Drying carriers with maltodextrin DE 10 only, mixtures of maltodextrin and waxy starch and mixtures of maltodextrin and cellulose were added into liquid soy sauce respectively with an uniform carrier concentration of 30% (w/v). For the combination of maltodextrin and cellulose/starch, specifically, ratios of cellulose/starch to maltodextrin at (1:5), (2:4) and (3:3) were applied, respectively. All the samples were spray dried into powders and stored in desiccators containing silica gel until being analysed.
Caking tests were performed based on the method described previously in Wang and Zhou (2012). Briefly, 4 g of soy sauce powder was placed in a cylindrical plastic bottle, tapped gently to make a flat layer, and then compacted under a Texture Analyzer-XT2i (Stable Micro System, UK) with a load force of 1 kg for 1 min. After that, the compacted powder sample together with the plastic bottle was stored in a desiccator with relative humidity (RH) of 43.2%, at 25 °C for ten days. At the end of the storage period, the powder cake plug was gently taken out of the bottle. A compression test for analysing hardness of the powder cake plug was carried out by using the TA-XTplus Texture Analyzer. The test protocol included trigger force: 0.005 kg, test speed: 1 mm/s, distance: 4 mm, and cylinder probe diameter: 6 mm. The peak force prior to breaking the powder cake plug was used to compare the caking strength of the different powders. 2.7. Solubility analysis Solubility of all powder samples was determined according to the method of Cano-Chauca et al. (2005) with modifications. Specifically, 50 ml of deionized water was transferred into a 200 ml beaker. Five grams of soy sauce powder was added into the beaker and then the beaker was put onto a magnetic stirrer at 800 rpm, for 5 min at room temperature. The mixture was centrifuged at 3000g for 5 min to separate the insoluble substances. Then 25 ml of supernatant was transferred into a metal plate and oven dried at 100 °C for 5 h. The solubility (%) was calculated as the weight of dry matters in the supernatants versus the weight of dry matters in the powders. 2.8. Starch gelatinization
2.3. Scanning electronic microscopy (SEM) Powder samples were mounted on aluminum stubs using doublesided adhesive tape. The sample was then coated with platinum in a sputter coater. SEM was performed using a JSM-5200 SEM system (JEOL, Tokyo, Japan), which was operated at an accelerating voltage of 15 kV. The samples were observed with a magnification of 1000.
Starch gelatinization analysis was performed by using the method described by White, Abbas, Pollak, and Johnson (1990). Using a differential scanning calorimeter (Mettler-Toledo DSC822e, Switzerland), a starch suspension (10% w/w) in cold water was analysed in the temperature range of 25–90 °C with a scanning rate of 5 °C/min. In particular, the presence of a gelatinization endothermic peak was investigated.
2.4. X-ray powder diffraction 2.9. Statistical analysis The crystallinity of the powders was identified by using the powder X-ray diffraction (XRD) method. X-ray powder diffraction (XRD, Bruker AXS D8 Advance, Germany) for phase analysis was carried out for identification of crystalline phases, by using CuKa radiation (k = 1.5406 Å), at 40 kV and 40 mA with a step size of 0.02°. The diffraction followed ah/2h Bragg–Brentano geometry and the 2h range was varied from 5° to 50°.
One-way ANOVA was conducted for determination of differences between samples using the SPSS 17.0 software. Duncan’s test was also employed. A probability level of p 6 0.05 was considered to be significant for all statistical procedures. 3. Results and discussion
2.5. Stickiness test
3.1. SEM analysis
Stickiness was determined according to the Chen and Hoseney method (1995). A Texture analyzer (TA.XT plus, Stable Micro
Fig. 1 shows the SEM micrographs of soy sauce powders produced by adding microcrystalline cellulose and maltodextrin
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
a
c
419
b
d
Fig. 1. Scanning electron micrographs of soy sauce powders by adding cellulose and maltodextrin as carriers (a) cellulose to maltodextrin ratio of 0:6 (b) cellulose to maltodextrin ratio of 1:5 (c) cellulose to maltodextrin ratio of 2:4 (d) cellulose to maltodextrin ratio of 3:3.
a
b
c
d
Fig. 2. Scanning electron micrographs of soy sauce powders by adding waxy starch and maltodextrin as carriers (a) waxy starch to maltodextrin ratio of 0:6 (b) waxy starch to maltodextrin ratio of 1:5 (c) waxy starch to maltodextrin ratio of 2:4 (d) waxy starch to maltodextrin ratio of 3:3.
together as the carrier. When only maltodextrin was added, the powder particles were fairly spherical and had smooth surfaces. However, with an increased ratio of cellulose to maltodextrin, powder particles with irregular shapes and holes on the surface were observed. This was probably caused by the insoluble nature
of the cellulose. During spray drying, the feed solution was atomised into tiny droplets by compressing air. Since maltodextrin dissolves well into liquid feed, fairly homogenous and uniform droplets can be sprayed out and consequently dried. However, with the presence of an insoluble bulking agent (i.e. cellulose),
420
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
the homogeneity of the droplets would be changed and it would no longer be isotropic, so the spray dried powder particles would display irregular shapes. Fig. 2 shows the SEM micrographs of soy sauce powders produced by adding a mixture of waxy starch and maltodextrin as carriers. The powder particles with waxy starch showed no apparent morphological difference from the one using only maltodextrin. It is interesting to observe that with higher ratios of starch to maltodextrin (Fig. 2c and d), some particles with tiny pore or small hole on the surface showed up. This was probably due to the existence of insoluble starch particles which hindered film formation for atomised droplets during spray drying. During spray drying, a skin developed first on the droplet surface, followed by a deflation of the powder particles (Nijdam & Langrish, 2006). Starch is insoluble and might damage the elasticity of the drying films and therefore results in the formation of pores on the particle surfaces. Although soy sauce liquid has a high salt concentration of 16.5%, NaCl crystals were not easily identified from all the SEM micrographs of the spray dried soy sauce powders. According to Walton and Mumford (1999), the skin-forming material rather than the crystalline material dominated particle morphology in drying semi-instant skimmed milk. Therefore, the sodium chloride crystals were most likely located on the inside of the particle structure and could not be found on the surface. Similar results were shown in spray dried fish sauce powders with high NaCl concentrations (Chindapan, Devahastin, & Chiewchan, 2010). 3.2. XRD analysis The presence of diffuse and large peaks in a X-ray diffraction profile indicates amorphous materials, however crystalline materials yield sharp and defined peaks since they are presented in a largely ordered state. For the soy sauce powders, three crystalline peaks with strong intensity at about 27° (2h), 31° (2h), and 45° (2h) were categorised as NaCl crystals by Chindapan et al. (2010) in the XRD patterns of spray dried fish sauce powders. Fig. 3 shows the XRD profiles of microcrystalline cellulose alone as well as the soy sauce powders produced by adding cellulose and maltodextrin. The XRD profile of cellulose was similar to the results reported by Cano-Chauca et al. (2005), although the major crystalline peaks showed some small differences in the 2-theta angle values. For the soy sauce powders with cellulose, a new crystalline peak around the diffraction angle of 22° was observed, with an increased cellulose concentration resulting in a stronger peak intensity. This result indicates that the addition of cellulose could induce the formation of partial crystalline structures in the soy sauce powders. The powdered soy sauce produced by using maltodextrin and waxy starch as the carriers were also analysed by XRD (results not shown). Compared with the control samples with only maltodextrin added, the powders with waxy starch added produced new crystalline peaks with a very small intensity. A crystalline peak at about 23° can be observed for the powders with a starch to maltodextrin ratio of 3:3. However, a similar peak was hardly identifiable from the samples with lower starch concentrations. This is most likely because the small crystalline peaks were masked by the baseline noise. The waxy starch was composed mainly of amylopectin, which is a semi-crystalline material. Adding waxy starch possibly produced semi-crystalline powders if the starch did not fully gelatinize during the spray drying.
Fig. 3. X-ray diffraction profile of (a) microcrystalline cellulose (b) soy sauce powder with cellulose to maltodextrin ratio of 1:5 (c) soy sauce powder with cellulose to maltodextrin ratio of 2:4 (d) soy sauce powder with cellulose to maltodextrin ratio of 3:3.
Table 1 Caking and stickiness of soy sauce powders produced by using different drying aids.
a–d
Formulation of drying aids
Stickiness (g)
Caking strength (kg)
Maltodextrin only Waxy starch to maltodextrin ratio (1:5) Waxy starch to maltodextrin ratio (2:4) Waxy starch to maltodextrin ratio (3:3) Cellulose to maltodextrin ratio (1:5) Cellulose to maltodextrin ratio (2:4) Cellulose to maltodextrin ratio (3:3)
196.6 ± 23.1a 152.2 ± 11.5b
7.5 ± 1.4a 6.0 ± 0.8bc
144.3 ± 3.9b
6.6 ± 1.3ab
119.5 ± 1.5c
5.3 ± 1.0bc
153.1 ± 5.8b 119.5 ± 1.9c 110.4 ± 3.3c
6.7 ± 1.4ab 4.5 ± 1.0cd 2.9 ± 1.0d
Different letters in each column indicate significant difference at p 6 0.05.
3.3. Analysis of stickiness and caking Table 1 shows the stickiness and caking strength of the soy sauce powders produced with mixtures of cellulose and maltodextrin or mixtures of waxy starch and maltodextrin. The results showed that the stickiness and caking of the soy sauce powders
decreased significantly by introducing cellulose or waxy starch as the drying carriers. The decreased cohesive force in the stickiness test can be correlated to the increased crystallinity of the powders shown in the XRD profiles (Fig. 3). The sticky problem of
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
421
for powders when a maltodextrin to starch ratio of 1:5, as well as a maltodextrin to cellulose ratio of 2:4 were used. A lower caking strength was found in powders with higher concentrations of cellulose or waxy starch. The reduced caking strength by adding cellulose or waxy starch could be correlated with the decreased stickiness of the soy sauce powders as mentioned above. In addition, the powder particles with cellulose displayed irregular shapes and wrinkled surfaces, in contrast to the relatively spherical and smooth surface of the powders with waxy starch. It is possible that the morphological differences had affected caking behaviour of the soy sauce powders with the two different drying carriers. 3.4. Test of solubility Fig. 4. Solubility of powdered soy sauce with different carrier formulations (A) maltodextrin only (B) waxy starch to maltodextrin ratio of 1:5 (C) waxy starch to maltodextrin ratio of 2:4 (D) waxy starch to maltodextrin ratio of 3:3 (E) cellulose to maltodextrin ratio of 1:5 (F) cellulose to maltodextrin ratio of 2:4 (G) cellulose to maltodextrin ratio of 3:3. (a–d Different letters indicate significant difference at p 6 0.05.).
3.5. Starch gelatinization analysis Fig. 5 shows the thermograms of the water insoluble sediments separated from the soy sauce powders produced by adding waxy starch. Native starch without spray drying was analysed using the same thermal program for determining its gelatinization temperature. The results showed that the sediments presented a clear endothermic peak at about 71 °C, which agreed to the native
Heat
Flow
Endothermal
(w/g)
amorphous powders is generally recognised as a result of glass transition. The stickiness point is about 10–20 °C above the glass transition temperature, and various techniques and instruments have been developed for characterising the stickiness behaviour of powder particles (Adhikari, Howes, Lecomte, & Bhandari, 2005; Boonyai, Bhandari, & Howes, 2004). However, recently the surface composition of powder particles has been found to significantly affect the stickiness of spray dried food powders (Adhikari, Howes, Wood, & Bhandari, 2009; Cano-chauca et al., 2005). According to Cano-chauca et al. (2005), a decrease in the stickiness of mango juice powder was caused by the formation of crystalline surfaces after adding microcrystalline cellulose. In our research, as the XRD results only indicated crystallinity of an entire powder particle, its surface characteristic is not conclusive and requires further investigations. Caking is a serious quality issue for powdered food. During caking, free flowing powders are transformed into lumps and agglomerates with growing inter-particle bridge formation. The caking severity of hygroscopic food powders are affected mainly by factors like Tg, powder morphology and particle size (Aguilera, del Valle, & Karel, 1995; Fitzpatrick et al., 2007). As shown in Table 1, a significant reduction in the caking strength was found
Fig. 4 shows the solubility of the soy sauce powders with different cellulose or starch concentrations. The results indicated that the soy sauce powders with only maltodextrin as the carrier had a high degree of solubility, reaching a value of 97.9%. However, after adding starch or microcrystalline cellulose, the powder solubility decreased. For the powders with a waxy starch or cellulose to maltodextrin ratio of 3:3, their solubility was reduced to 80.2% and 80.8%, respectively. Cano-Chauca et al. (2005) reported similar effects of microcrystalline cellulose or waxy starch on the solubility of spray dried mango juice powders. Native starch is completely water insoluble without gelatinization. Ferrari et al. (1997) reported that spray drying itself was not capable of inducing waxy starch gelatinization. In our research, it was quite possible that the waxy starch still existed in its native state after spray drying. Therefore, it was reasonable to find a decreased solubility with an increased waxy starch concentration. A similar effect on the solubility was exhibited by adding microcrystalline cellulose, which is also water insoluble and has a very high degradation temperature (El-Sakhawy & Hassan, 2007).
Temperature (ഒ) Fig. 5. DSC thermograms of a 10% (w/w) water suspension of (A) native waxy starch (B) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 1:5 (C) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 2:4 (D) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 3:3.
422
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
starch reference. It verified that spray drying with a very short heating time could not induce a full gelatinization of waxy starch, as reported by Ferrari et al. (1997). The starch without gelatinization could still preserve its semi-crystalline structure, which was also confirmed by the XRD analysis of powder crystallinity. 4. Conclusion Cellulose or waxy starch used as a drying carrier together with maltodextrin could induce partial crystallinity of the soy sauce powders made by spray drying liquid soy sauce. The resultant soy sauce powders were significantly less sticky and less liable to caking when certain concentrations of starch or cellulose were adopted. This was probably resulted from the increased crystallinity of the powders as shown by the XRD analysis. However, the solubility of the powders was reduced by adding the insoluble carriers. Acknowledgement The authors are grateful to the National University of Singapore (Suzhou) Research Institute under the Grant number NUSRI2011007. References Adhikari, B., Howes, T., Lecomte, D., & Bhandari, B. R. (2005). A glass transition temperature approach for the prediction of the surface stickiness of a drying droplet during spray drying. Powder Technology, 149, 168–179. Adhikari, B., Howes, T., Wood, B. J., & Bhandari, B. R. (2009). The effect of low molecular weight surfactants and proteins on surface stickiness of sucrose during powder formation through spray drying. Journal of Food Engineering, 94, 135–143. Aguilera, J. M., del Valle, J. M., & Karel, M. (1995). Caking phenomena in amorphous food powders. Trends Food Science Technology, 6, 149–155. Boonyai, P., Bhandari, B., & Howes, T. (2004). Stickiness measurement techniques for food powders: a review. Powder Technology, 145, 34–46. Cai, Y. Z., & Corke, H. (2000). Production and properties of spray-dried amaranthus betacyanin pigments. Journal of Food Science, 65, 1249–1252.
Cano-Chauca, M., Stringheta, P. C., Ramos, A. M., & Cal-Vidal, J. (2005). Effect of the carriers on the microstructure of mango powder obtained by spray drying and its functional characterization. Innovative Food Science and Emerging Technologies, 6, 420–428. Chen, W. Z., & Hoseney, R. N. (1995). Development of an objective method for dough stickiness. Lebensmittel-Wissenschaft und Technologie, 28, 467–473. Chindapan, N., Devahastin, S., & Chiewchan, N. (2010). Effect of electrodialysis pretreatment on physicochemical properties and morphology of spray-driedfish sauce powder. Journal of Food Engineering, 99, 31–39. El-Sakhawy, M., & Hassan, M. L. (2007). Physical and mechanical properties of microcrystalline cellulose prepared from agricultural residues. Carbohydrate Polymers, 67, 1–10. Ersus, S., & Yurdagel, U. (2007). Microencapsulation of anthocyanin pigments of black carrot (Daucus carota L.) by spray drier. Journal of Food Engineering, 80, 805–812. Ferrari, F., Rossi, S., Martini, A., Muggetti, L., De Ponti, R., & Caramella, C. (1997). Technological induction of mucoadhesive properties on waxy starches by grinding. European Journal of Pharmaceutical Sciences, 5, 277–285. Fitzpatrick, J. J., Hodnett, M., Twomey, M., Cerqueira, P. S. M., O’Flynn, J., & Roos, Y. H. (2007). Glass transition and the flowability and caking of powders containing amorphous lactose. Powder Technology, 178, 119–128. Goula, A. M., & Adamopoulos, K. G. (2008). Effect of maltodextrin addition during spray drying of tomato pulp in dehumidified air: I. Drying kinetics and product recovery. Drying Technology, 26, 714–725. Goula, A. M., & Adamopoulos, K. G. (2010). A new technique for spray drying orange juice concentrate. Innovative Food science and Emerging Technology, 11, 342–351. Hartmann, M., & Palzer, S. (2010). Caking of amorphous powders-material aspects, modeling and applications. Powder Technology, 206, 112–121. Nijdam, J. J., & Langrish, T. A. G. (2006). The effect of surface composition on the functional properties of milk powders. Journal of Food Engineering, 77, 919–925. Okayasu, M., & Hamano, K. (2003). Powdered soy sauce. In T. Furuta, A. S. Murase, S. Tsujimoto, & T. Nakamura (Eds.), High Performance Powder of Food. Encapsulation Technique (pp. 311–315). Japan: Science Forum. Sablani, S. S., Shrestha, A. K., & Bhandari, B. R. (2008). A new method of producing date powder granules: physicochemcal characteristics of powder. Journal of Food Engineering, 87, 417–421. Tonon, R. V., Brabet, C., & Hubinger, M. D. (2008). Influence of process conditions on the physicochemical properties of açai (Euterpe oleraceae Mart) powder produced by spray drying. Journal of Food Engineering, 88, 411–418. Walton, D. E., & Mumford, C. J. (1999). The morphology of spray-dried particles: the effect of process variables upon the morphology of spray-dried particles. Chemical Engineering Research and Design, 77, 442–460. Wang, W., & Zhou, W. (2012). Characterization of spray-dried soy sauce powders using maltodextrins as carrier. Journal of Food Engineering, 109, 399–405. White, P., Abbas, I., Pollak, L., & Johnson, L. (1990). Intra-and interpopulation variability of thermal properties of maize starch. Cereal Chemistry, 67, 70–73.
Contents lists available at ScienceDirect
Food Chemistry journal homepage: www.elsevier.com/locate/foodchem
Characterisation of spray dried soy sauce powders made by adding crystalline carbohydrates to drying carrier Wei Wang a, Weibiao Zhou a,b,⇑ a b
Food Science & Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore National University of Singapore (Suzhou) Research Institute, 377 Linquan Street, Suzhou Industrial Park, Jiangsu, 215123, People’s Republic of China
a r t i c l e
i n f o
Article history: Received 11 February 2014 Received in revised form 31 May 2014 Accepted 10 July 2014 Available online 18 July 2014 Keywords: Drying carrier Soy sauce powder Spray drying Caking Stickiness
a b s t r a c t This study aimed to reduce stickiness and caking of spray dried soy sauce powders by introducing a new crystalline structure into powder particles. To perform this task, soy sauce powders were formulated by using mixtures of cellulose and maltodextrin or mixtures of waxy starch and maltodextrin as drying carriers, with a fixed carrier addition rate of 30% (w/v) in the feed solution. The microstructure, crystallinity, solubility as well as stickiness and caking strength of all the different powders were analysed and compared. Incorporating crystalline carbohydrates in the drying carrier could significantly reduce the stickiness and caking strength of the powders when the ratio of crystalline carbohydrates to maltodextrin was above 1:5 and 1:2, respectively. X-ray Diffraction (XRD) results showed that adding cellulose or waxy starch could induce the crystallinity of powders. Differential Scanning Calorimetry (DSC) results demonstrated that the native starch added to the soy sauce powders did not fully gelatinize during spray drying. Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction Soy sauce is a traditional condiment popularly produced and consumed in East Asian countries, such as Japan, Korea and China. Soy sauce has mainly been used in liquid form in the past, but recently, different types of soy sauce powders have been developed and marketed. Commercially available soy sauce powders are mainly manufactured by spray drying, although other dehydration methods, such as freeze drying and drum drying, can also be used. Powdered soy sauce was firstly used in the soup base of instant noodles. Now the application has expanded to powdered seasoning, frozen food and processed meat (Okayasu & Hamano, 2003). For spray dried amorphous food powders, including soy sauce powders, stickiness or caking under relatively high humidity or over a long storage period is always an issue. This is because spray drying usually generates powders in amorphous states due to its short drying time. The amorphous glass will start to flow and become sticky when environmental temperature exceeds its glass transition temperature (Tg) at which glass-rubbery transition happens. The most widely used method for solving stickiness problems is to add large molecular weight carbohydrates, like maltodextrin, to increase powder Tg and reduce hygroscopicity. ⇑ Corresponding author at: Food Science & Technology Programme, c/o Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore. Tel.: +65 6516 3501; fax: +65 6775 7895. E-mail address: [email protected] (W. Zhou). http://dx.doi.org/10.1016/j.foodchem.2014.07.065 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved.
Maltodextrin has a good solubility and a high Tg. Therefore, it has been widely used as the drying carrier for making instant food powders (Cai & Corke, 2000; Ersus & Yurdagel, 2007; Goula & Adamopoulos, 2008, 2010; Sablani, Shrestha, & Bhandari, 2008; Tonon, Brabet, & Hubinger, 2008). However, due to its amorphous nature, maltodextrin will also become hygroscopic and sticky when exposed to a high relative humidity environment. Identifying alternative dying carriers to address stickiness or caking issues of amorphous food powders is of both academic and industrial interest. According to Cano-Chauca, Stringheta, Ramos, and Cal-Vidal (2005), adding waxy starch or microcrystalline cellulose as a drying aid was able to produce a partial crystalline surface in spray dried mango juice powder. The semi-crystalline powders had reduced stickiness compared to the ones made using only maltodextrin. Spray dried soy sauce powders containing maltodextrin as the drying carrier are mixtures of NaCl crystals and amorphous carbohydrates, amino acids and proteins (Wang & Zhou, 2012). The salt crystals adsorb moisture only when equilibrium water activity reaches 0.753 (Hartmann & Palzer, 2010). So salt is not likely to cause moisture adsorption and sintering of particles when exposed to low or medium relative humidity. However, the amorphous phase is metastable and liable for moisture adsorption and sintering of particles under low relative humidity. Therefore, to incorporate crystalline or semi-crystalline carbohydrates instead of maltodextrin in order to increase the crystallinity of soy sauce powder has great potential to improve stability. The crystalline carrier may produce a semi-crystalline powder and reduce
418
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
inter-particle powder adhesions. However, due to the insoluble nature of large molecular carbohydrates (i.e. starch and cellulose), preparing feed solutions containing them, as well as reconstitution of the powders, needs to be understood and optimised. The objective of the study was to explore the addition of waxy starch or microcrystalline cellulose together with maltodextrin as drying carriers to produce soy sauce powders. The crystallinity of soy sauce powders was studied and related to the stickiness and caking behaviour of the powders under testing conditions. The study aimed to improve the stability of spray dried soy sauce powders by providing an alternative approach to the current practice, and lay a foundation for industrial production and application of soy sauce powders.
System, UK) was used in this study to provide a constant compression force and to measure the tension force. The TA.XT plus library program of dough stickiness was used. The compression force selected was at 40 g. The diameter of the plexiglass probe was 25 mm. The trigger force was set at 5 g. The compression travel speed for the probe was 2 mm/s. The probe reversing speed was 10 mm/s, which was the maximum reversing speed of the texture analyzer. The holding time was 0.1 s. The probe distance was selected as 4 mm. For stickiness measurements, the samples were mixed with glycerol in a proportion of 2 g powder to 5 ml glycerol, forming a homogeneous dough. The dough was placed in the instrument and the test was performed in triplicate. 2.6. Caking test
2. Materials and methods 2.1. Raw materials Naturally brewed soy sauce was obtained from Kikkoman Pte. Ltd. (Singapore) with a protein content of 10.3% (w/w), carbohydrates of 8.1% (w/w) and NaCl of 16.5% (w/w) and the rest being water. Maltodextrin 10 DE was purchased from Suntop Enterprise (Singapore). Microcrystalline cellulose was purchased from Sigma–Aldrich (Singapore). Corn waxy starch was obtained from National Starch Co. (Singapore). 2.2. Spray drying A pilot-scale spray dryer (Mobile MinorTM, GEA, China) was used in the study. Co-current flow regime and a two-fluid nozzle atomizer were used for the spray drying process. The inlet air temperature was set to 160 °C and outlet temperature was maintained at 75 °C, by adjusting the feed flow rate via a peristaltic pump. The compression air pressure for atomisation was controlled at 2 bars, with an air flow rate of 4 m3/h. Dried powders were collected from the base of a cyclone separator of the drier. Drying carriers with maltodextrin DE 10 only, mixtures of maltodextrin and waxy starch and mixtures of maltodextrin and cellulose were added into liquid soy sauce respectively with an uniform carrier concentration of 30% (w/v). For the combination of maltodextrin and cellulose/starch, specifically, ratios of cellulose/starch to maltodextrin at (1:5), (2:4) and (3:3) were applied, respectively. All the samples were spray dried into powders and stored in desiccators containing silica gel until being analysed.
Caking tests were performed based on the method described previously in Wang and Zhou (2012). Briefly, 4 g of soy sauce powder was placed in a cylindrical plastic bottle, tapped gently to make a flat layer, and then compacted under a Texture Analyzer-XT2i (Stable Micro System, UK) with a load force of 1 kg for 1 min. After that, the compacted powder sample together with the plastic bottle was stored in a desiccator with relative humidity (RH) of 43.2%, at 25 °C for ten days. At the end of the storage period, the powder cake plug was gently taken out of the bottle. A compression test for analysing hardness of the powder cake plug was carried out by using the TA-XTplus Texture Analyzer. The test protocol included trigger force: 0.005 kg, test speed: 1 mm/s, distance: 4 mm, and cylinder probe diameter: 6 mm. The peak force prior to breaking the powder cake plug was used to compare the caking strength of the different powders. 2.7. Solubility analysis Solubility of all powder samples was determined according to the method of Cano-Chauca et al. (2005) with modifications. Specifically, 50 ml of deionized water was transferred into a 200 ml beaker. Five grams of soy sauce powder was added into the beaker and then the beaker was put onto a magnetic stirrer at 800 rpm, for 5 min at room temperature. The mixture was centrifuged at 3000g for 5 min to separate the insoluble substances. Then 25 ml of supernatant was transferred into a metal plate and oven dried at 100 °C for 5 h. The solubility (%) was calculated as the weight of dry matters in the supernatants versus the weight of dry matters in the powders. 2.8. Starch gelatinization
2.3. Scanning electronic microscopy (SEM) Powder samples were mounted on aluminum stubs using doublesided adhesive tape. The sample was then coated with platinum in a sputter coater. SEM was performed using a JSM-5200 SEM system (JEOL, Tokyo, Japan), which was operated at an accelerating voltage of 15 kV. The samples were observed with a magnification of 1000.
Starch gelatinization analysis was performed by using the method described by White, Abbas, Pollak, and Johnson (1990). Using a differential scanning calorimeter (Mettler-Toledo DSC822e, Switzerland), a starch suspension (10% w/w) in cold water was analysed in the temperature range of 25–90 °C with a scanning rate of 5 °C/min. In particular, the presence of a gelatinization endothermic peak was investigated.
2.4. X-ray powder diffraction 2.9. Statistical analysis The crystallinity of the powders was identified by using the powder X-ray diffraction (XRD) method. X-ray powder diffraction (XRD, Bruker AXS D8 Advance, Germany) for phase analysis was carried out for identification of crystalline phases, by using CuKa radiation (k = 1.5406 Å), at 40 kV and 40 mA with a step size of 0.02°. The diffraction followed ah/2h Bragg–Brentano geometry and the 2h range was varied from 5° to 50°.
One-way ANOVA was conducted for determination of differences between samples using the SPSS 17.0 software. Duncan’s test was also employed. A probability level of p 6 0.05 was considered to be significant for all statistical procedures. 3. Results and discussion
2.5. Stickiness test
3.1. SEM analysis
Stickiness was determined according to the Chen and Hoseney method (1995). A Texture analyzer (TA.XT plus, Stable Micro
Fig. 1 shows the SEM micrographs of soy sauce powders produced by adding microcrystalline cellulose and maltodextrin
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
a
c
419
b
d
Fig. 1. Scanning electron micrographs of soy sauce powders by adding cellulose and maltodextrin as carriers (a) cellulose to maltodextrin ratio of 0:6 (b) cellulose to maltodextrin ratio of 1:5 (c) cellulose to maltodextrin ratio of 2:4 (d) cellulose to maltodextrin ratio of 3:3.
a
b
c
d
Fig. 2. Scanning electron micrographs of soy sauce powders by adding waxy starch and maltodextrin as carriers (a) waxy starch to maltodextrin ratio of 0:6 (b) waxy starch to maltodextrin ratio of 1:5 (c) waxy starch to maltodextrin ratio of 2:4 (d) waxy starch to maltodextrin ratio of 3:3.
together as the carrier. When only maltodextrin was added, the powder particles were fairly spherical and had smooth surfaces. However, with an increased ratio of cellulose to maltodextrin, powder particles with irregular shapes and holes on the surface were observed. This was probably caused by the insoluble nature
of the cellulose. During spray drying, the feed solution was atomised into tiny droplets by compressing air. Since maltodextrin dissolves well into liquid feed, fairly homogenous and uniform droplets can be sprayed out and consequently dried. However, with the presence of an insoluble bulking agent (i.e. cellulose),
420
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
the homogeneity of the droplets would be changed and it would no longer be isotropic, so the spray dried powder particles would display irregular shapes. Fig. 2 shows the SEM micrographs of soy sauce powders produced by adding a mixture of waxy starch and maltodextrin as carriers. The powder particles with waxy starch showed no apparent morphological difference from the one using only maltodextrin. It is interesting to observe that with higher ratios of starch to maltodextrin (Fig. 2c and d), some particles with tiny pore or small hole on the surface showed up. This was probably due to the existence of insoluble starch particles which hindered film formation for atomised droplets during spray drying. During spray drying, a skin developed first on the droplet surface, followed by a deflation of the powder particles (Nijdam & Langrish, 2006). Starch is insoluble and might damage the elasticity of the drying films and therefore results in the formation of pores on the particle surfaces. Although soy sauce liquid has a high salt concentration of 16.5%, NaCl crystals were not easily identified from all the SEM micrographs of the spray dried soy sauce powders. According to Walton and Mumford (1999), the skin-forming material rather than the crystalline material dominated particle morphology in drying semi-instant skimmed milk. Therefore, the sodium chloride crystals were most likely located on the inside of the particle structure and could not be found on the surface. Similar results were shown in spray dried fish sauce powders with high NaCl concentrations (Chindapan, Devahastin, & Chiewchan, 2010). 3.2. XRD analysis The presence of diffuse and large peaks in a X-ray diffraction profile indicates amorphous materials, however crystalline materials yield sharp and defined peaks since they are presented in a largely ordered state. For the soy sauce powders, three crystalline peaks with strong intensity at about 27° (2h), 31° (2h), and 45° (2h) were categorised as NaCl crystals by Chindapan et al. (2010) in the XRD patterns of spray dried fish sauce powders. Fig. 3 shows the XRD profiles of microcrystalline cellulose alone as well as the soy sauce powders produced by adding cellulose and maltodextrin. The XRD profile of cellulose was similar to the results reported by Cano-Chauca et al. (2005), although the major crystalline peaks showed some small differences in the 2-theta angle values. For the soy sauce powders with cellulose, a new crystalline peak around the diffraction angle of 22° was observed, with an increased cellulose concentration resulting in a stronger peak intensity. This result indicates that the addition of cellulose could induce the formation of partial crystalline structures in the soy sauce powders. The powdered soy sauce produced by using maltodextrin and waxy starch as the carriers were also analysed by XRD (results not shown). Compared with the control samples with only maltodextrin added, the powders with waxy starch added produced new crystalline peaks with a very small intensity. A crystalline peak at about 23° can be observed for the powders with a starch to maltodextrin ratio of 3:3. However, a similar peak was hardly identifiable from the samples with lower starch concentrations. This is most likely because the small crystalline peaks were masked by the baseline noise. The waxy starch was composed mainly of amylopectin, which is a semi-crystalline material. Adding waxy starch possibly produced semi-crystalline powders if the starch did not fully gelatinize during the spray drying.
Fig. 3. X-ray diffraction profile of (a) microcrystalline cellulose (b) soy sauce powder with cellulose to maltodextrin ratio of 1:5 (c) soy sauce powder with cellulose to maltodextrin ratio of 2:4 (d) soy sauce powder with cellulose to maltodextrin ratio of 3:3.
Table 1 Caking and stickiness of soy sauce powders produced by using different drying aids.
a–d
Formulation of drying aids
Stickiness (g)
Caking strength (kg)
Maltodextrin only Waxy starch to maltodextrin ratio (1:5) Waxy starch to maltodextrin ratio (2:4) Waxy starch to maltodextrin ratio (3:3) Cellulose to maltodextrin ratio (1:5) Cellulose to maltodextrin ratio (2:4) Cellulose to maltodextrin ratio (3:3)
196.6 ± 23.1a 152.2 ± 11.5b
7.5 ± 1.4a 6.0 ± 0.8bc
144.3 ± 3.9b
6.6 ± 1.3ab
119.5 ± 1.5c
5.3 ± 1.0bc
153.1 ± 5.8b 119.5 ± 1.9c 110.4 ± 3.3c
6.7 ± 1.4ab 4.5 ± 1.0cd 2.9 ± 1.0d
Different letters in each column indicate significant difference at p 6 0.05.
3.3. Analysis of stickiness and caking Table 1 shows the stickiness and caking strength of the soy sauce powders produced with mixtures of cellulose and maltodextrin or mixtures of waxy starch and maltodextrin. The results showed that the stickiness and caking of the soy sauce powders
decreased significantly by introducing cellulose or waxy starch as the drying carriers. The decreased cohesive force in the stickiness test can be correlated to the increased crystallinity of the powders shown in the XRD profiles (Fig. 3). The sticky problem of
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
421
for powders when a maltodextrin to starch ratio of 1:5, as well as a maltodextrin to cellulose ratio of 2:4 were used. A lower caking strength was found in powders with higher concentrations of cellulose or waxy starch. The reduced caking strength by adding cellulose or waxy starch could be correlated with the decreased stickiness of the soy sauce powders as mentioned above. In addition, the powder particles with cellulose displayed irregular shapes and wrinkled surfaces, in contrast to the relatively spherical and smooth surface of the powders with waxy starch. It is possible that the morphological differences had affected caking behaviour of the soy sauce powders with the two different drying carriers. 3.4. Test of solubility Fig. 4. Solubility of powdered soy sauce with different carrier formulations (A) maltodextrin only (B) waxy starch to maltodextrin ratio of 1:5 (C) waxy starch to maltodextrin ratio of 2:4 (D) waxy starch to maltodextrin ratio of 3:3 (E) cellulose to maltodextrin ratio of 1:5 (F) cellulose to maltodextrin ratio of 2:4 (G) cellulose to maltodextrin ratio of 3:3. (a–d Different letters indicate significant difference at p 6 0.05.).
3.5. Starch gelatinization analysis Fig. 5 shows the thermograms of the water insoluble sediments separated from the soy sauce powders produced by adding waxy starch. Native starch without spray drying was analysed using the same thermal program for determining its gelatinization temperature. The results showed that the sediments presented a clear endothermic peak at about 71 °C, which agreed to the native
Heat
Flow
Endothermal
(w/g)
amorphous powders is generally recognised as a result of glass transition. The stickiness point is about 10–20 °C above the glass transition temperature, and various techniques and instruments have been developed for characterising the stickiness behaviour of powder particles (Adhikari, Howes, Lecomte, & Bhandari, 2005; Boonyai, Bhandari, & Howes, 2004). However, recently the surface composition of powder particles has been found to significantly affect the stickiness of spray dried food powders (Adhikari, Howes, Wood, & Bhandari, 2009; Cano-chauca et al., 2005). According to Cano-chauca et al. (2005), a decrease in the stickiness of mango juice powder was caused by the formation of crystalline surfaces after adding microcrystalline cellulose. In our research, as the XRD results only indicated crystallinity of an entire powder particle, its surface characteristic is not conclusive and requires further investigations. Caking is a serious quality issue for powdered food. During caking, free flowing powders are transformed into lumps and agglomerates with growing inter-particle bridge formation. The caking severity of hygroscopic food powders are affected mainly by factors like Tg, powder morphology and particle size (Aguilera, del Valle, & Karel, 1995; Fitzpatrick et al., 2007). As shown in Table 1, a significant reduction in the caking strength was found
Fig. 4 shows the solubility of the soy sauce powders with different cellulose or starch concentrations. The results indicated that the soy sauce powders with only maltodextrin as the carrier had a high degree of solubility, reaching a value of 97.9%. However, after adding starch or microcrystalline cellulose, the powder solubility decreased. For the powders with a waxy starch or cellulose to maltodextrin ratio of 3:3, their solubility was reduced to 80.2% and 80.8%, respectively. Cano-Chauca et al. (2005) reported similar effects of microcrystalline cellulose or waxy starch on the solubility of spray dried mango juice powders. Native starch is completely water insoluble without gelatinization. Ferrari et al. (1997) reported that spray drying itself was not capable of inducing waxy starch gelatinization. In our research, it was quite possible that the waxy starch still existed in its native state after spray drying. Therefore, it was reasonable to find a decreased solubility with an increased waxy starch concentration. A similar effect on the solubility was exhibited by adding microcrystalline cellulose, which is also water insoluble and has a very high degradation temperature (El-Sakhawy & Hassan, 2007).
Temperature (ഒ) Fig. 5. DSC thermograms of a 10% (w/w) water suspension of (A) native waxy starch (B) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 1:5 (C) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 2:4 (D) insoluble fraction of soy sauce powders with starch to maltodextrin ratio of 3:3.
422
W. Wang, W. Zhou / Food Chemistry 168 (2015) 417–422
starch reference. It verified that spray drying with a very short heating time could not induce a full gelatinization of waxy starch, as reported by Ferrari et al. (1997). The starch without gelatinization could still preserve its semi-crystalline structure, which was also confirmed by the XRD analysis of powder crystallinity. 4. Conclusion Cellulose or waxy starch used as a drying carrier together with maltodextrin could induce partial crystallinity of the soy sauce powders made by spray drying liquid soy sauce. The resultant soy sauce powders were significantly less sticky and less liable to caking when certain concentrations of starch or cellulose were adopted. This was probably resulted from the increased crystallinity of the powders as shown by the XRD analysis. However, the solubility of the powders was reduced by adding the insoluble carriers. Acknowledgement The authors are grateful to the National University of Singapore (Suzhou) Research Institute under the Grant number NUSRI2011007. References Adhikari, B., Howes, T., Lecomte, D., & Bhandari, B. R. (2005). A glass transition temperature approach for the prediction of the surface stickiness of a drying droplet during spray drying. Powder Technology, 149, 168–179. Adhikari, B., Howes, T., Wood, B. J., & Bhandari, B. R. (2009). The effect of low molecular weight surfactants and proteins on surface stickiness of sucrose during powder formation through spray drying. Journal of Food Engineering, 94, 135–143. Aguilera, J. M., del Valle, J. M., & Karel, M. (1995). Caking phenomena in amorphous food powders. Trends Food Science Technology, 6, 149–155. Boonyai, P., Bhandari, B., & Howes, T. (2004). Stickiness measurement techniques for food powders: a review. Powder Technology, 145, 34–46. Cai, Y. Z., & Corke, H. (2000). Production and properties of spray-dried amaranthus betacyanin pigments. Journal of Food Science, 65, 1249–1252.
Cano-Chauca, M., Stringheta, P. C., Ramos, A. M., & Cal-Vidal, J. (2005). Effect of the carriers on the microstructure of mango powder obtained by spray drying and its functional characterization. Innovative Food Science and Emerging Technologies, 6, 420–428. Chen, W. Z., & Hoseney, R. N. (1995). Development of an objective method for dough stickiness. Lebensmittel-Wissenschaft und Technologie, 28, 467–473. Chindapan, N., Devahastin, S., & Chiewchan, N. (2010). Effect of electrodialysis pretreatment on physicochemical properties and morphology of spray-driedfish sauce powder. Journal of Food Engineering, 99, 31–39. El-Sakhawy, M., & Hassan, M. L. (2007). Physical and mechanical properties of microcrystalline cellulose prepared from agricultural residues. Carbohydrate Polymers, 67, 1–10. Ersus, S., & Yurdagel, U. (2007). Microencapsulation of anthocyanin pigments of black carrot (Daucus carota L.) by spray drier. Journal of Food Engineering, 80, 805–812. Ferrari, F., Rossi, S., Martini, A., Muggetti, L., De Ponti, R., & Caramella, C. (1997). Technological induction of mucoadhesive properties on waxy starches by grinding. European Journal of Pharmaceutical Sciences, 5, 277–285. Fitzpatrick, J. J., Hodnett, M., Twomey, M., Cerqueira, P. S. M., O’Flynn, J., & Roos, Y. H. (2007). Glass transition and the flowability and caking of powders containing amorphous lactose. Powder Technology, 178, 119–128. Goula, A. M., & Adamopoulos, K. G. (2008). Effect of maltodextrin addition during spray drying of tomato pulp in dehumidified air: I. Drying kinetics and product recovery. Drying Technology, 26, 714–725. Goula, A. M., & Adamopoulos, K. G. (2010). A new technique for spray drying orange juice concentrate. Innovative Food science and Emerging Technology, 11, 342–351. Hartmann, M., & Palzer, S. (2010). Caking of amorphous powders-material aspects, modeling and applications. Powder Technology, 206, 112–121. Nijdam, J. J., & Langrish, T. A. G. (2006). The effect of surface composition on the functional properties of milk powders. Journal of Food Engineering, 77, 919–925. Okayasu, M., & Hamano, K. (2003). Powdered soy sauce. In T. Furuta, A. S. Murase, S. Tsujimoto, & T. Nakamura (Eds.), High Performance Powder of Food. Encapsulation Technique (pp. 311–315). Japan: Science Forum. Sablani, S. S., Shrestha, A. K., & Bhandari, B. R. (2008). A new method of producing date powder granules: physicochemcal characteristics of powder. Journal of Food Engineering, 87, 417–421. Tonon, R. V., Brabet, C., & Hubinger, M. D. (2008). Influence of process conditions on the physicochemical properties of açai (Euterpe oleraceae Mart) powder produced by spray drying. Journal of Food Engineering, 88, 411–418. Walton, D. E., & Mumford, C. J. (1999). The morphology of spray-dried particles: the effect of process variables upon the morphology of spray-dried particles. Chemical Engineering Research and Design, 77, 442–460. Wang, W., & Zhou, W. (2012). Characterization of spray-dried soy sauce powders using maltodextrins as carrier. Journal of Food Engineering, 109, 399–405. White, P., Abbas, I., Pollak, L., & Johnson, L. (1990). Intra-and interpopulation variability of thermal properties of maize starch. Cereal Chemistry, 67, 70–73.
