Dysphagia DOI 10.1007/s00455-014-9581-2
ORIGINAL ARTICLE
Physical Properties of Root Crops Treated with Novel Softening Technology Capable of Retaining the Shape, Color, and Nutritional Value of Foods Shingo Umene • Masahiro Hayashi Kumiko Kato • Hiroaki Masunaga
•
Received: 28 May 2014 / Accepted: 15 October 2014 Ó Springer Science+Business Media New York 2014
Abstract Hard, difficult-to-eat root crops (carrots and burdock roots) were homogeneously softened by an enzyme permeation method so that they could be mashed easily by the tongue while retaining appearance, flavor, and nutrients. The appearance, color, and nutritional value of these foods were equivalent to those of normally cooked root crops of the same type. The firmness of the softened root crops was at least 100 times as low as normally cooked root crops and lower than some care food products for patients with swallowing disorders. Compared with control root crops, which were treated with a freeze–thaw infusion method, the treated foods were 10 to 25 times as soft, with significantly lower rates of foodstuff syneresis and better preservation of color and nutritional value. Furthermore, the cell walls of the treated burdock roots resembled those of normally cooked ones, while the cells of freeze–thaw infusion burdock roots were destroyed and few cell walls remained. It was expected that these root crops softened by the enzymatic processing could be one of the best model foods for patients with masticatory disturbance or swallowing disorders or both. Keywords Softened root crops Homogeneous enzyme permeation method (HEPM) Appearance Physical properties Care food product Deglutition
S. Umene (&) M. Hayashi K. Kato H. Masunaga Tokyo Laboratory, EN Otsuka Pharmaceutical Co., Ltd., 1-11-10 Kinshi, Sumida-ku, Tokyo 130-0013, Japan e-mail: [email protected]
Introduction The elderly population (65 years or older) in Japan accounted for 23 % of the total population in 2010 and will continue to grow [1]. Age-related deterioration of the masticatory or swallowing function makes oral intake difficult and increases the need for soft foods such as care food. At hospitals and nursing homes, chopped foods and paste foods, which are less palatable in appearance and flavor than normally cooked foods, are served [2]. Under the circumstances, foods processed in a blender and reshaped into something similar to the original, and foods softened by retort cooking have been developed. In these days, merkmals to categorize these foods, such as Food for Special Dietary Uses (FOSDU) approval [3], Universal Design Food (UDF) [4], and Dysphagia diets pyramid [5], also have been established in Japan. Conventional techniques to soften foods, while maintaining shapes, for example, using pineapple in sweet-and-sour pork, a Chinese dish, to tenderize pork with its enzyme, have also been well known. Recently, a method to soften foods by combining freezing tissue cells and thawing [6–8] based on a technique of infiltrating foods with colors and flavors under reduced pressure [9] has been used. Even with these techniques, however, it is difficult to provide patients with foods that meet their needs in terms of appearance, physical properties, and nutritional value. We investigated material processing techniques with degradative enzymes in the development of preparations for enteral and oral feeding [10–15]. In the continuing study, we reported a novel softened rice [16, 17], meats [18, 19], and vegetables [20, 21], which were treated by homogenous enzyme permeation method (HEPM). HEPM is a food softening technique that can make foodstuffs, such as potato, lotus root, bamboo shoot, beans, and
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maroon, soft enough to be mashed by the tongue, while retaining appearance, flavor, and nutritional value equivalent to those of normally cooked foods. Actually, ‘‘iEatÒ’’, the products manufactured by combination of HEPM, are sold in Japan for around JPY500 [22–24]. In this report, we compared the appearance, physical properties, and nutritional value of the root crops treated by HEPM with those of normally cooked ones, the ones treated by freeze–thaw infusion and some care food products to assess its suitability for elderly people and patients with swallowing disorders.
Materials and Methods Samples Carrots Before experiments, carrots were prepared as follows: Carrots were peeled and both ends were cut off. The carrots were then cut into rounds about 10 mm thick and soaked in plain water at room temperature for 30 min to remove harsh taste. The softened carrots (SC) were prepared by HEPM as follows: Carrot materials were heated at 0.20 MPa and 120 °C for 10 min, and an enzyme solution containing hemicellulase and trehalose in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0) was added in an amount of 20 wt% of the carrot weight with a sprayer. After 4 cycles of 1-minute treatment under reduced pressure (-0.095 MPa), the enzyme solution was removed. The carrots were replaced in plates before sealing. The following operations proceeded in the plate. After the carrots were allowed to stand at 4 °C for 16 h, they were heated at 50 °C for 40 min for enzyme reaction followed by 85 °C for 5 min to terminate the reaction, and quickly frozen. The obtained SC were thawed and used as samples. Also, a whole carrot was softened in the same way without cutting off. In addition, carrots replaced in plates after heated at 98 °C for 5 min under atmospheric pressure were used as normally cooked carrots (NCC), and carrots softened by freeze–thaw infusion (FIC) were prepared in accordance with a freeze–thaw infusion method described by Nakatsu and others [7]. That is, carrots blanched at 98 °C were frozen at -30 °C and thawed in an enzyme solution containing hemicellulase in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0). The enzyme solution for thawing was added in an amount of at least 250 wt% of the carrot weight. After the reduced pressure (-0.095 MPa) was maintained for 5 min using a vacuum pump with the carrots placed in the enzyme solution, the pressure was returned to normal.
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After the freeze–thaw infusion treatment, the carrots were removed from the enzyme solution, replaced in plates before sealing, heated at 50 °C for 1 h followed by 85 °C for 5 min, and quickly frozen. The obtained FIC were thawed and used as samples. Burdock Root Burdock roots were peeled and cut diagonally into 10-mm pieces. The slices were soaked in plain water at room temperature for 30 min to remove harsh taste, and used as materials. The burdock roots used for light microscopy were cut into rounds about 1 mm thick. The softened burdock roots (SB) were prepared by HEPM as follows: Burdock roots were heated at 0.20 MPa and 120 °C for 20 min, and an enzyme solution containing hemicellulase and trehalose in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0) was added in an amount of 20 wt% of the burdock root weight with a sprayer. After 4 cycles of 1-minute treatment under reduced pressure (-0.095 MPa), the enzyme solution was removed. The burdock roots were replaced in plates before sealing. The following operations proceeded in the plate. After the burdock roots were allowed to stand at 4 °C for 16 h, they were heated at 50 °C for 40 min for enzyme reaction followed by 85 °C for 5 min to terminate the reaction, and quickly frozen. The obtained SB were thawed and used as samples. For microscopy, burdock roots that had been allowed to stand at 4 °C for 16 h and had not yet been heated at 50 °C for 40 min were used as samples. In addition, burdock roots replaced in plates after heated at 98 °C for 5 min under atmospheric pressure were used as normally cooked burdock roots (NCB), and burdock roots softened by freeze–thaw infusion (FIB) were prepared in accordance with the freeze–thaw infusion method described by Nakatsu and others [7]. That is, burdock roots blanched at 98 °C were frozen at -30 °C and thawed in an enzyme solution containing hemicellulase in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0). The enzyme solution for thawing was added in an amount of at least 250 wt% of the burdock root weight. After the reduced pressure (-0.095 MPa) was maintained for 5 min using a vacuum pump with the burdock roots placed in the enzyme solution, the pressure was returned to normal. After the freeze–thaw infusion treatment, the burdock roots were taken out of the enzyme solution, replaced in plates before sealing, heated at 50 °C for 1 h followed by 85 °C for 5 min, and quickly frozen. The obtained FIB were thawed and used as samples. For microscopy, burdock roots that had been treated by the freeze–thaw infusion treatment and not yet been heated at 50 °C for 1 h were used as samples.
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Care Food Product Care food products were used for comparison as follows: ‘‘V CRESS jelly cup type carrot (VC) (NUTRI Co., Ltd),’’ ‘‘AI ALL soft (AI) (NUTRI Co., Ltd)’’ which is soymilkbased concentrated solid food, and ‘‘Isocal jelly KURIN plum flavor (IJ) (Nestle Health Science S.A.).’’ These products are manufactured as a shelf stable food and sold for patients with masticatory disturbance or swallowing disorders or both. Texture Measurement The texture of each sample was measured using a creep meter (RE2-33005B, Yamaden), in accordance with the testing method provided in the ‘‘Testing Method for Foods for People with Difficulty in Swallowing’’ [3]. That is, samples were placed on 40-mm plates and compressed twice with a 20-mm plastic plunger at a rate of 10 mm/s and measurement distortion rate of 66.7 %. The firmness, adhesiveness, cohesiveness, and gumminess of the samples were measured five times at 20 ± 2 °C. Typical stress-time curves are shown in Fig. 1, and firmness, adhesiveness, cohesiveness, and gumminess were calculated by data on stress (S) and areas under curve (A) of the stress-time curves. The firmness is maximum stress of first compression cycle (=S1), and shows the force required to bite some foods. The adhesiveness is negative stress area required to pull the plunger away from the sample (=A3) and thus, parameter correlated with removing a sample from the mouth during eating that adheres to tongue and mucosal tissues. The cohesiveness is a ratio of the positive stress area under first and second compression cycle (A2/A1) and thus, parameter representing the difficulty in breaking down foods. The gumminess is product of firmness and cohesiveness, and thus, the energy required to treat the food for being ready to be swallowed [25, 26].
calculated using the following formula: Syneresis rate = (weight before thawing - weight after thawing and removing the liquid)/weight before thawing 9 100. The liquids of the care food products were collected without thawing. The measurement was performed three times. Nutritional Analysis The content of water, protein, fat, ash, and potassium in each sample was measured. In addition, beta-carotene content in each carrot was measured. Water content was measured by the air-oven method [27], protein content was measured by the Kjeldahl method [28], fat content was measured by acid hydrolysis method [29], and ash content was measured by direct ashing method [27]. Carbohydrate content was calculated using the following formula: 100 - (water ? protein ? fat ? ash). Energy content was calculated based on the following conversion factors: protein = 4, fat = 9, and carbohydrate = 4. Potassium was measured by atomic absorption spectrophotometry, and beta-carotene was measured by high-performance liquid chromatography [30]. Light Microscopy Light microscopy was performed using a digital microscope (VHX-1000, Keyence Corporation) at a magnification of 200X. Samples were stained with a few drops of 0.2 % safranine solution. Statistical Analyses Welch’s t test was used to compare the root crops treated by HEPM with the normally cooked ones, the ones treated by freeze–thaw infusion, and the care food products, on the assumption that the populations of all groups were normal. The level of significance was set at p \ 0.05.
Syneresis Measurement The weight of liquid separated from each sample after thawing was determined, and the rate of syneresis (%) was
Results and Discussion Appearance: Fig. 2a, b
Fig. 1 Typical stress-time curve with S stress, A area under curve
Figure 2a shows the appearance of whole carrot softened by HEPM. The carrot was easily mashed by spoon with good appearance. Figure 2b shows the appearance of carrot samples, burdock root samples, and care food products. The appearance of SC was similar to that of NCC. FIC had round edges and were slightly spongy overall. Syneresis was rarely seen in SC and NCC, while it was prominent in FIC. A loss of color was also observed in FIC. As SC was, the appearance of SB was similar to that of NCB. FIB also
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S. Umene et al.: Physical Properties of Root Crops Fig. 2 a Appearance of whole carrot softened by Homogenous Enzyme Permeation Method (HEPM). b Appearance of carrot samples, burdock root samples, and care food products. NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
had round edges and looked blackish and turbid. Syneresis was rarely seen in SB and NCB, while it was prominent in FIB. These results suggested that the excessive destruction did not occur in SC and SB treated by HEPM because enzyme could spread through foodstuff and decompose it appropriately. On the other hand, it was assumed that the
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cells of FIC and FIB were damaged by freezing and thawing [31, 32]. The appearances of care food products were far from normally cooked meals. The appearances of foods are recognized as an important attribute [33–35]. Thus, the root crops treated by freeze–thaw infusion and the care food products are not sufficient for patients to be
S. Umene et al.: Physical Properties of Root Crops
satisfied with, and the root crops softened by HEPM may be one of the best model foods for good appearance. It also has been reported that ‘‘iEatÒ’’, the food product manufactured by HEPM, satisfies patients with mastication difficulty due to its appearance [22]. Eating is important for the elderly in terms of joy and purpose, and mealtimes were reported to be the number one joy for elderly people admitted to nursing care facilities [36, 37]. It is expected for these reports that HEPM and ‘‘iEatÒ’’ will improve ‘‘quality of life’’ of elderly people and patients with mastication. Texture: Fig. 3 Figure 3 shows firmness, adhesiveness, cohesiveness, and gumminess of carrot samples, burdock root samples, and care food products. The firmness of SC was B1/100 that of NCC, B1/25 that of FIC, lower than those of VC and AI, and not significantly different from that of IJ. Similarly, the firmness of SB was B1/90 that of NCB, B1/10 that of FIB, lower than those of VC and AI, and not significantly different from that of IJ. Thus, it was showed that SC and SB **
1,000
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10 3 N/m 2 )
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Firmness (
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10 3 N/m 2 )
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were not only softer than softened foods treated by conventional techniques but also as soft as care food products for patients with swallowing disorders. As McCullough proposed, it was very important factor that foods for patients with dysphagia were soft [38]. The root crops treated with HEPM might be possible to provide for people with swallowing problems. In 2013 Cichero and others who are leading dysphagic research have reported international definitions for texture-modified foods used in dysphagia management [39]. In this report, they mentioned that Japanese system of identifying texture-modified foods is very advanced, thus we have reflected these values in FOSDU approval [3]. The firmness of SC and SB was in the most appropriate range of approval standard 1 (2,500–10,000 N/m2). The adhesiveness of SC was higher than those of IJ and VC, and not significantly different from those of NCC, FIC, and AI. The adhesiveness of SB was higher than those of NCB, IJ, and VC, lower than those of AI, and not significantly different from that of FIB. The cohesiveness of SC was higher than those of NCC and VC, and not significantly different from those of FIC, IJ, and AI. The cohesiveness of SB was lower than those of NCB,
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Fig. 3 Firmness, adhesiveness, and cohesiveness of carrot samples, burdock root samples, and care food products. n = 5, mean ± standard deviation. All differences between SC and NCC, FIC, IJ, VC, and AI were significant (*p \ 0.05, **p \ 0.01,). All differences between SB and NCB, FIB, IJ, VC, and AI were significant
0.0 NCC NCB
FIC
FIB
IJ
VC
AI
( p \ 0.05, p \ 0.01,). NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
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Syneresis rate
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Fig. 4 Syneresis rate of carrot samples, burdock root samples, and care food products. n = 3, mean ± standard deviation. All differences between SC and NCC, FIC, IJ, VC, and AI were significant (*p \ 0.05, **p \ 0.01). All differences between SB and NCB, FIB, IJ, VC, and AI were significant ( p \ 0.05, p \ 0.01). NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
FIB, IJ, and AI, and not significantly different from that of VC. These results indicated that the adhesiveness and cohesiveness of SC and SB were in the same range as those of the care food products [39]. As the firmness of SC and SB was, the adhesiveness and the cohesiveness of them were in approval standard range [3] (adhesiveness: less than 1,500 J/m3, cohesiveness: 0.2–0.9). Momosaki and others concluded that semisolid food possessing high adhesiveness is related with the appearance of pharyngeal residue and should be avoided for dysphagic patients with weak pharyngeal contraction [40]. Thus even though SC and SB were in the appropriate range, they could have pharyngeal residue, because their texture profiles were almost corresponding those of residue (?) samples which were tested by Momosaki and others (Firmness: 9,885 N/m2, Cohesiveness: 0.33, Adhesiveness: 320 J/m3, Gumminess: 3,117 N/m2). With respect to adhesiveness, it was reported that high-adhesiveness foods were easy to adhere the oral surfaces and the pharynx [40–42], therefore, SC and SB might have to become less adhesive to reduce risk of residue or avoid aspiration. In any case, it would be necessary to test SC and SB in a clinical trial. The gumminess of SC was lower than that of NCC, FIC and AI, and not significantly different from that of IJ and VC. The gumminess of SB was lower than that of NCB, FIB, VC, and AI, and not significantly different from that of IJ. As gumminess represents the energy required to treat the food for being ready to be swallowed and it was reported that foods of high gumminess may put patients at risk of suffocation [25, 40], the gumminess of SC and SB was also lower than the semisolid foods judged as aspiration (-). Therefore, it is
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confirmed that aspiration risk of SC and SB is very low for patients with masticatory disturbance or swallowing disorders or both. For the reasons above, it was considered that the physical properties of root crops treated with HEPM were appropriate for elderly people and patients with swallowing disease to eat them. Fujishima and others examined the possibility of using ‘’iEatÒ’’ as a texturemodified food for use in swallowing modified diet 2-2 (categorized as a puree food by the Japanese Society of Dysphagia Rehabilitation in 2013), and at least more than 60 % of dysphagia professionals evaluated their efficacy for the swallowing modified diet 2-2 [24]. Syneresis: Fig. 4 Figure 4 shows syneresis rate of carrot samples, burdock root samples, and care food products. The syneresis rate of SC was higher than those of NCC, IJ and AI, but lower than that of FIC. There was no significant difference between SC and VC. The syneresis rate of SB was also higher than that of NCB, IJ, and AI, but lower than those of FIB and VC. Thence, the syneresis rate of SC and SB were approximately equivalent to those of the care food. Liquid separation from foods can create a risk of aspiration [43, 44]. Also, Nayebzadeh and others reported that a little liquid of food could reduce the friction between bolus and throat, and make bolus easy to swallow [45]. For these reasons, a little syneresis from the root crops treated with HEPM might be moderate for people with dysphagia to swallow them. Nutritional Analysis of Carrots and Burdock Roots: Table 1 Table 1 shows the nutritional components of the carrot and burdock root samples. The water content per 100 g edible portion was lower in SC than in NCC and FIC, and energy, potassium, and beta-carotene contents retained in SC were Table 1 Nutritional components of carrots and burdock roots (per 100 g edible portion) Water (g) Energy (kcal) Potassium (mg) b-carotene (lg) NCC 89.2
39
220
FIC
93.7
25
155
7,870 7,960
SC
87.7
48
322
11,700
NCB 81.8
58
247
–
FIB
93.7
24
94
–
SB
80.4
77
218
–
NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots
S. Umene et al.: Physical Properties of Root Crops Fig. 5 Light microscopy images of burdock roots arrows indicate blank space. NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots
500μm
NCB
500μm
500μm
FIB
SB
higher than those in NCC and FIC. The water content per 100 g edible portion in SB was equivalent to those in NCB and lower than in FIB. The energy content retained in SB was at higher than in NCB and FIB. The potassium content retained in SB was lower than in NCB but higher than in FIB. The nutrients of the root crops treated by HEPM were maintained during the process of HEPM. On the other hands, the cells of root crops treated by freeze–thaw infusion were damaged by freezing and particularly thawing and lost water-soluble potassium [46]. From the reasons, it was anticipated that HEPM could keep nutrients of foods as much as normally cooking [47, 48]. Therefore, the root crops treated by HEPM would be helpful to control nutrition for elderly people and patients who have difficulty with mastication or swallowing or both.
retained because of preventing excessive cell destruction. And water-soluble flavor of SB may be also retained.
Light Microscopy of Burdock Roots: Fig. 5
Conflict of interest
Figure 5 shows light microscopy images of burdock roots. Burdock roots were stained with a 0.2 % safranine solution for light microscopy. NCB were shown to have regular cell shapes and regularly lined cell walls. In FIB, most cell walls were destroyed and cells did not retain their shapes. Many blank spaces, which might be the cavity made by thawing frozen water of cells, were also observed in FIB [31, 32]. Although cells of SB were partially decomposed, their shapes were well maintained, compared to the cells of FIB. Thus, it has become clear that the potassium of SB was
Conclusions The HEPM is considered to be a novel technique that can appropriately control appearance, physical properties, and nutritional value of foods by inhibiting excessive cell destruction and adjusting the reaction of enzymes. The physical properties of the root crops softened by the HEPM are similar to those of care food products. From these results, it is expected that the root crops softened by the HEPM will be one of the best model food for patients with masticatory disturbance or swallowing disorders or both. We have no conflict of interest.
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22. Higashiguchi T. Novel diet for patients with impaired mastication evaluated by consumption rate, nutrition intake, and questionnaire. Nutrition. 2013;29:858–64. 23. Gonzalez-Fernandez M, Huckabee ML, Doeltgen SH, Inamoto Y, Kagaya H, Saitoh E. Dysphagia rehabilitation: similarities and differences in three areas of the world. Curr Phys Med Rehabil Rep. 2013;1:296–306. 24. Fujishima I, Nagao N, Otsuka J, Shigematsu T, Hojyo K, Kanazawa H. Study of the possibility of using ‘iEatÒ’ produced according to the enzyme homogeneous permeation method for sensory evaluation. Deglutition. 2014;3:110–7 (in Japanese). 25. AI-Muhtaseb AH, McMinn W, Megahey E, Neill G, Magee R, Rashid U. Textural characteristics of microwave-baked and convective-baked Madeira cake. J Food Process Technol. 2013;4:209. doi:10.4172/2157-7110.1000209. 26. Siefarth C, Tran TBT, Mittermaier P, Pfeiffer T, Buettner A. Effect of radio frequency heating on yoghurt, II: microstructure and texture. Foods. 2014;3:369–93. doi:10.3390/foods3020369. 27. A. O. A. C. Official methods of analysis of AOAC. 17th ed. Washington, D. C: Association of Official Analytical Chemists; 2002. 28. Kjeldahl J. A new method for the estimation of nitrogen in organic compounds. Z fuer Anal Chem. 1883;33:366. 29. A. O. A. C. Official methods of analysis of AOAC. 13th ed. Washington, D. C: Association of Official Analytical Chemists; 1980. 30. Britton G, Liaaen-Jensen S, Pfander H, (Ed). Carotenoids, vol. 1A. (1995) Isolation and Analysis. Birkuhauser. Basel. 31. Takagi S. Behaviors of tissues and pectic substances of foods of plant origins at heating and freezing states. J Cook Sci Jpn. 1991;24(2):150–6 (in Japanese). 32. Phothiset S, Charoenrein S. Effects of freezing and thawing on texture, microstructure and cell wall composition changes in papaya tissues. J Sci Food Agric. 2013;. doi:10.1002/jsfa.6226 [Equb ahead of print]. 33. Stanga Z, Zurfluh Y, Roselli M, Sterchi AB, Tanner B, Knecht G. Hospital food: a survey of patients’ perceptions. Clin Nutr. 2003;23(3):241–6. 34. Nishinari K. Rheology, food texture and mastication. J Texture Stud. 2004;35:113–24. 35. Nieuwenhuizen WF, Weenen H, Rigby P, Hetherington MM. Older adults and patients in need of nutritional support: review of current treatment options and factors influencing nutritional intake. Clin Nutr. 2010;29:160–9. 36. Shibata S, Saitoh E. Dysphagia. Med Pract. 2010;27(10):1683–7 (in Japanese). 37. Kaneko N, Nohara K, Asano M, Sakai T, Mitsuyama M. Risk criteria tag of help with eating for elderly residents in nursing home. Jpn J Gerodontol. 2012;27(1):18–24 (in Japanese). 38. McCullough G, Pelletier C, Steele C. National Dysphagia Diet: What to swallow? ASHA Lead. 2003. 39. Cichero JAY, Steele C, Duivestein J, Clave P, Chen J, Kayashita J, Dantas R, Lecko C, Speyer R, Lam P, Murray J. The need for international terminology and definitions for texture-modified foods and thickened liquids used in dysphagia management: foundations of a global initiative. Curr Phys Med Rehabil Rep. 2013;1:280–91. 40. Momosaki R, Abo M, Kobayashi K. Swallowing analysis for semisolid food texture in poststroke dyphagic patients. J Stroke Cerebrovasc Dis. 2013;22(3):267–70. 41. Koc H, Vinyard CJ, Essick GK, Foegeding EA. Food Oral Processing: conversion of food structure to textural perception. Annu Rev Food Sci Technol. 2013;4:237–66. 42. Tokifuji A, Matsushima Y, Hachisuka K, Yoshioka K. Texture, sensory and swallowing characteristics of high-pressure-heat-
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treated pork meat gel as a dysphagia diet. Meat Sci. 2013;93: 843–8. Clave P, de Kraa M, Arreola V, Girvent M, Farre R, Palomera E, Serra-Prat M. The effect of bolus viscosity on swallowing function in neurogenic dysphagia. Aliment Pharmacol Ther. 2006;24: 1385–94. Ozaki K, Kagaya H, Yokoyama M, Saitoh E, Okada S, Gonza´lezFerna´ndez M, Palmer JB, Uematsu H. The risk of penetration or aspiration during videofluoroscopic examination of swallowing varies depending on food types. Tohoku J Exp Med. 2010;220(1): 41–6. Nayebzadeh K, Chen J, Dickinson E, Moschakis T. Surface structure smoothing effect of polysaccharide on a heat-set protein particle gel. Langmuir. 2006;22(21):8873–80. Naito H. Estimation of soaking conditions for edible burdock in preparing low potassium diets. Jpn J Nutr. 1991;49(5):273–9 (in Japanese).
47. Shabala S, Pottosin I. Regulation of potassium transport in plants under hostile conditions: implications for abiotic and biotic stress tolerance. Physiol Plant. 2014;. doi:10.1111/ppl.12165. 48. Cherel I, Lefoulon C, Boeglin M, Sentenac H. Molecular mechanisms involved in plant adaptation to low K? availability. J Exp Bot. 2014;65(3):833–48.
Shingo Umene Msc Masahiro Hayashi
Msc
Kumiko Kato Msc Hiroaki Masunaga
PhD
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ORIGINAL ARTICLE
Physical Properties of Root Crops Treated with Novel Softening Technology Capable of Retaining the Shape, Color, and Nutritional Value of Foods Shingo Umene • Masahiro Hayashi Kumiko Kato • Hiroaki Masunaga
•
Received: 28 May 2014 / Accepted: 15 October 2014 Ó Springer Science+Business Media New York 2014
Abstract Hard, difficult-to-eat root crops (carrots and burdock roots) were homogeneously softened by an enzyme permeation method so that they could be mashed easily by the tongue while retaining appearance, flavor, and nutrients. The appearance, color, and nutritional value of these foods were equivalent to those of normally cooked root crops of the same type. The firmness of the softened root crops was at least 100 times as low as normally cooked root crops and lower than some care food products for patients with swallowing disorders. Compared with control root crops, which were treated with a freeze–thaw infusion method, the treated foods were 10 to 25 times as soft, with significantly lower rates of foodstuff syneresis and better preservation of color and nutritional value. Furthermore, the cell walls of the treated burdock roots resembled those of normally cooked ones, while the cells of freeze–thaw infusion burdock roots were destroyed and few cell walls remained. It was expected that these root crops softened by the enzymatic processing could be one of the best model foods for patients with masticatory disturbance or swallowing disorders or both. Keywords Softened root crops Homogeneous enzyme permeation method (HEPM) Appearance Physical properties Care food product Deglutition
S. Umene (&) M. Hayashi K. Kato H. Masunaga Tokyo Laboratory, EN Otsuka Pharmaceutical Co., Ltd., 1-11-10 Kinshi, Sumida-ku, Tokyo 130-0013, Japan e-mail: [email protected]
Introduction The elderly population (65 years or older) in Japan accounted for 23 % of the total population in 2010 and will continue to grow [1]. Age-related deterioration of the masticatory or swallowing function makes oral intake difficult and increases the need for soft foods such as care food. At hospitals and nursing homes, chopped foods and paste foods, which are less palatable in appearance and flavor than normally cooked foods, are served [2]. Under the circumstances, foods processed in a blender and reshaped into something similar to the original, and foods softened by retort cooking have been developed. In these days, merkmals to categorize these foods, such as Food for Special Dietary Uses (FOSDU) approval [3], Universal Design Food (UDF) [4], and Dysphagia diets pyramid [5], also have been established in Japan. Conventional techniques to soften foods, while maintaining shapes, for example, using pineapple in sweet-and-sour pork, a Chinese dish, to tenderize pork with its enzyme, have also been well known. Recently, a method to soften foods by combining freezing tissue cells and thawing [6–8] based on a technique of infiltrating foods with colors and flavors under reduced pressure [9] has been used. Even with these techniques, however, it is difficult to provide patients with foods that meet their needs in terms of appearance, physical properties, and nutritional value. We investigated material processing techniques with degradative enzymes in the development of preparations for enteral and oral feeding [10–15]. In the continuing study, we reported a novel softened rice [16, 17], meats [18, 19], and vegetables [20, 21], which were treated by homogenous enzyme permeation method (HEPM). HEPM is a food softening technique that can make foodstuffs, such as potato, lotus root, bamboo shoot, beans, and
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maroon, soft enough to be mashed by the tongue, while retaining appearance, flavor, and nutritional value equivalent to those of normally cooked foods. Actually, ‘‘iEatÒ’’, the products manufactured by combination of HEPM, are sold in Japan for around JPY500 [22–24]. In this report, we compared the appearance, physical properties, and nutritional value of the root crops treated by HEPM with those of normally cooked ones, the ones treated by freeze–thaw infusion and some care food products to assess its suitability for elderly people and patients with swallowing disorders.
Materials and Methods Samples Carrots Before experiments, carrots were prepared as follows: Carrots were peeled and both ends were cut off. The carrots were then cut into rounds about 10 mm thick and soaked in plain water at room temperature for 30 min to remove harsh taste. The softened carrots (SC) were prepared by HEPM as follows: Carrot materials were heated at 0.20 MPa and 120 °C for 10 min, and an enzyme solution containing hemicellulase and trehalose in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0) was added in an amount of 20 wt% of the carrot weight with a sprayer. After 4 cycles of 1-minute treatment under reduced pressure (-0.095 MPa), the enzyme solution was removed. The carrots were replaced in plates before sealing. The following operations proceeded in the plate. After the carrots were allowed to stand at 4 °C for 16 h, they were heated at 50 °C for 40 min for enzyme reaction followed by 85 °C for 5 min to terminate the reaction, and quickly frozen. The obtained SC were thawed and used as samples. Also, a whole carrot was softened in the same way without cutting off. In addition, carrots replaced in plates after heated at 98 °C for 5 min under atmospheric pressure were used as normally cooked carrots (NCC), and carrots softened by freeze–thaw infusion (FIC) were prepared in accordance with a freeze–thaw infusion method described by Nakatsu and others [7]. That is, carrots blanched at 98 °C were frozen at -30 °C and thawed in an enzyme solution containing hemicellulase in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0). The enzyme solution for thawing was added in an amount of at least 250 wt% of the carrot weight. After the reduced pressure (-0.095 MPa) was maintained for 5 min using a vacuum pump with the carrots placed in the enzyme solution, the pressure was returned to normal.
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After the freeze–thaw infusion treatment, the carrots were removed from the enzyme solution, replaced in plates before sealing, heated at 50 °C for 1 h followed by 85 °C for 5 min, and quickly frozen. The obtained FIC were thawed and used as samples. Burdock Root Burdock roots were peeled and cut diagonally into 10-mm pieces. The slices were soaked in plain water at room temperature for 30 min to remove harsh taste, and used as materials. The burdock roots used for light microscopy were cut into rounds about 1 mm thick. The softened burdock roots (SB) were prepared by HEPM as follows: Burdock roots were heated at 0.20 MPa and 120 °C for 20 min, and an enzyme solution containing hemicellulase and trehalose in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0) was added in an amount of 20 wt% of the burdock root weight with a sprayer. After 4 cycles of 1-minute treatment under reduced pressure (-0.095 MPa), the enzyme solution was removed. The burdock roots were replaced in plates before sealing. The following operations proceeded in the plate. After the burdock roots were allowed to stand at 4 °C for 16 h, they were heated at 50 °C for 40 min for enzyme reaction followed by 85 °C for 5 min to terminate the reaction, and quickly frozen. The obtained SB were thawed and used as samples. For microscopy, burdock roots that had been allowed to stand at 4 °C for 16 h and had not yet been heated at 50 °C for 40 min were used as samples. In addition, burdock roots replaced in plates after heated at 98 °C for 5 min under atmospheric pressure were used as normally cooked burdock roots (NCB), and burdock roots softened by freeze–thaw infusion (FIB) were prepared in accordance with the freeze–thaw infusion method described by Nakatsu and others [7]. That is, burdock roots blanched at 98 °C were frozen at -30 °C and thawed in an enzyme solution containing hemicellulase in 2.0 9 10-2 mol/l citrate buffer (pH: 5.0). The enzyme solution for thawing was added in an amount of at least 250 wt% of the burdock root weight. After the reduced pressure (-0.095 MPa) was maintained for 5 min using a vacuum pump with the burdock roots placed in the enzyme solution, the pressure was returned to normal. After the freeze–thaw infusion treatment, the burdock roots were taken out of the enzyme solution, replaced in plates before sealing, heated at 50 °C for 1 h followed by 85 °C for 5 min, and quickly frozen. The obtained FIB were thawed and used as samples. For microscopy, burdock roots that had been treated by the freeze–thaw infusion treatment and not yet been heated at 50 °C for 1 h were used as samples.
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Care Food Product Care food products were used for comparison as follows: ‘‘V CRESS jelly cup type carrot (VC) (NUTRI Co., Ltd),’’ ‘‘AI ALL soft (AI) (NUTRI Co., Ltd)’’ which is soymilkbased concentrated solid food, and ‘‘Isocal jelly KURIN plum flavor (IJ) (Nestle Health Science S.A.).’’ These products are manufactured as a shelf stable food and sold for patients with masticatory disturbance or swallowing disorders or both. Texture Measurement The texture of each sample was measured using a creep meter (RE2-33005B, Yamaden), in accordance with the testing method provided in the ‘‘Testing Method for Foods for People with Difficulty in Swallowing’’ [3]. That is, samples were placed on 40-mm plates and compressed twice with a 20-mm plastic plunger at a rate of 10 mm/s and measurement distortion rate of 66.7 %. The firmness, adhesiveness, cohesiveness, and gumminess of the samples were measured five times at 20 ± 2 °C. Typical stress-time curves are shown in Fig. 1, and firmness, adhesiveness, cohesiveness, and gumminess were calculated by data on stress (S) and areas under curve (A) of the stress-time curves. The firmness is maximum stress of first compression cycle (=S1), and shows the force required to bite some foods. The adhesiveness is negative stress area required to pull the plunger away from the sample (=A3) and thus, parameter correlated with removing a sample from the mouth during eating that adheres to tongue and mucosal tissues. The cohesiveness is a ratio of the positive stress area under first and second compression cycle (A2/A1) and thus, parameter representing the difficulty in breaking down foods. The gumminess is product of firmness and cohesiveness, and thus, the energy required to treat the food for being ready to be swallowed [25, 26].
calculated using the following formula: Syneresis rate = (weight before thawing - weight after thawing and removing the liquid)/weight before thawing 9 100. The liquids of the care food products were collected without thawing. The measurement was performed three times. Nutritional Analysis The content of water, protein, fat, ash, and potassium in each sample was measured. In addition, beta-carotene content in each carrot was measured. Water content was measured by the air-oven method [27], protein content was measured by the Kjeldahl method [28], fat content was measured by acid hydrolysis method [29], and ash content was measured by direct ashing method [27]. Carbohydrate content was calculated using the following formula: 100 - (water ? protein ? fat ? ash). Energy content was calculated based on the following conversion factors: protein = 4, fat = 9, and carbohydrate = 4. Potassium was measured by atomic absorption spectrophotometry, and beta-carotene was measured by high-performance liquid chromatography [30]. Light Microscopy Light microscopy was performed using a digital microscope (VHX-1000, Keyence Corporation) at a magnification of 200X. Samples were stained with a few drops of 0.2 % safranine solution. Statistical Analyses Welch’s t test was used to compare the root crops treated by HEPM with the normally cooked ones, the ones treated by freeze–thaw infusion, and the care food products, on the assumption that the populations of all groups were normal. The level of significance was set at p \ 0.05.
Syneresis Measurement The weight of liquid separated from each sample after thawing was determined, and the rate of syneresis (%) was
Results and Discussion Appearance: Fig. 2a, b
Fig. 1 Typical stress-time curve with S stress, A area under curve
Figure 2a shows the appearance of whole carrot softened by HEPM. The carrot was easily mashed by spoon with good appearance. Figure 2b shows the appearance of carrot samples, burdock root samples, and care food products. The appearance of SC was similar to that of NCC. FIC had round edges and were slightly spongy overall. Syneresis was rarely seen in SC and NCC, while it was prominent in FIC. A loss of color was also observed in FIC. As SC was, the appearance of SB was similar to that of NCB. FIB also
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S. Umene et al.: Physical Properties of Root Crops Fig. 2 a Appearance of whole carrot softened by Homogenous Enzyme Permeation Method (HEPM). b Appearance of carrot samples, burdock root samples, and care food products. NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
had round edges and looked blackish and turbid. Syneresis was rarely seen in SB and NCB, while it was prominent in FIB. These results suggested that the excessive destruction did not occur in SC and SB treated by HEPM because enzyme could spread through foodstuff and decompose it appropriately. On the other hand, it was assumed that the
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cells of FIC and FIB were damaged by freezing and thawing [31, 32]. The appearances of care food products were far from normally cooked meals. The appearances of foods are recognized as an important attribute [33–35]. Thus, the root crops treated by freeze–thaw infusion and the care food products are not sufficient for patients to be
S. Umene et al.: Physical Properties of Root Crops
satisfied with, and the root crops softened by HEPM may be one of the best model foods for good appearance. It also has been reported that ‘‘iEatÒ’’, the food product manufactured by HEPM, satisfies patients with mastication difficulty due to its appearance [22]. Eating is important for the elderly in terms of joy and purpose, and mealtimes were reported to be the number one joy for elderly people admitted to nursing care facilities [36, 37]. It is expected for these reports that HEPM and ‘‘iEatÒ’’ will improve ‘‘quality of life’’ of elderly people and patients with mastication. Texture: Fig. 3 Figure 3 shows firmness, adhesiveness, cohesiveness, and gumminess of carrot samples, burdock root samples, and care food products. The firmness of SC was B1/100 that of NCC, B1/25 that of FIC, lower than those of VC and AI, and not significantly different from that of IJ. Similarly, the firmness of SB was B1/90 that of NCB, B1/10 that of FIB, lower than those of VC and AI, and not significantly different from that of IJ. Thus, it was showed that SC and SB **
1,000
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were not only softer than softened foods treated by conventional techniques but also as soft as care food products for patients with swallowing disorders. As McCullough proposed, it was very important factor that foods for patients with dysphagia were soft [38]. The root crops treated with HEPM might be possible to provide for people with swallowing problems. In 2013 Cichero and others who are leading dysphagic research have reported international definitions for texture-modified foods used in dysphagia management [39]. In this report, they mentioned that Japanese system of identifying texture-modified foods is very advanced, thus we have reflected these values in FOSDU approval [3]. The firmness of SC and SB was in the most appropriate range of approval standard 1 (2,500–10,000 N/m2). The adhesiveness of SC was higher than those of IJ and VC, and not significantly different from those of NCC, FIC, and AI. The adhesiveness of SB was higher than those of NCB, IJ, and VC, lower than those of AI, and not significantly different from that of FIB. The cohesiveness of SC was higher than those of NCC and VC, and not significantly different from those of FIC, IJ, and AI. The cohesiveness of SB was lower than those of NCB,
†
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Gumminess (
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AI
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SB
Fig. 3 Firmness, adhesiveness, and cohesiveness of carrot samples, burdock root samples, and care food products. n = 5, mean ± standard deviation. All differences between SC and NCC, FIC, IJ, VC, and AI were significant (*p \ 0.05, **p \ 0.01,). All differences between SB and NCB, FIB, IJ, VC, and AI were significant
0.0 NCC NCB
FIC
FIB
IJ
VC
AI
( p \ 0.05, p \ 0.01,). NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
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S. Umene et al.: Physical Properties of Root Crops 25%
**
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Syneresis rate
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5%
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*
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0% NCC NCB
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Fig. 4 Syneresis rate of carrot samples, burdock root samples, and care food products. n = 3, mean ± standard deviation. All differences between SC and NCC, FIC, IJ, VC, and AI were significant (*p \ 0.05, **p \ 0.01). All differences between SB and NCB, FIB, IJ, VC, and AI were significant ( p \ 0.05, p \ 0.01). NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots, IJ Isocal jelly KURIN, VC V CRESS jelly, AI AI ALL soft
FIB, IJ, and AI, and not significantly different from that of VC. These results indicated that the adhesiveness and cohesiveness of SC and SB were in the same range as those of the care food products [39]. As the firmness of SC and SB was, the adhesiveness and the cohesiveness of them were in approval standard range [3] (adhesiveness: less than 1,500 J/m3, cohesiveness: 0.2–0.9). Momosaki and others concluded that semisolid food possessing high adhesiveness is related with the appearance of pharyngeal residue and should be avoided for dysphagic patients with weak pharyngeal contraction [40]. Thus even though SC and SB were in the appropriate range, they could have pharyngeal residue, because their texture profiles were almost corresponding those of residue (?) samples which were tested by Momosaki and others (Firmness: 9,885 N/m2, Cohesiveness: 0.33, Adhesiveness: 320 J/m3, Gumminess: 3,117 N/m2). With respect to adhesiveness, it was reported that high-adhesiveness foods were easy to adhere the oral surfaces and the pharynx [40–42], therefore, SC and SB might have to become less adhesive to reduce risk of residue or avoid aspiration. In any case, it would be necessary to test SC and SB in a clinical trial. The gumminess of SC was lower than that of NCC, FIC and AI, and not significantly different from that of IJ and VC. The gumminess of SB was lower than that of NCB, FIB, VC, and AI, and not significantly different from that of IJ. As gumminess represents the energy required to treat the food for being ready to be swallowed and it was reported that foods of high gumminess may put patients at risk of suffocation [25, 40], the gumminess of SC and SB was also lower than the semisolid foods judged as aspiration (-). Therefore, it is
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confirmed that aspiration risk of SC and SB is very low for patients with masticatory disturbance or swallowing disorders or both. For the reasons above, it was considered that the physical properties of root crops treated with HEPM were appropriate for elderly people and patients with swallowing disease to eat them. Fujishima and others examined the possibility of using ‘’iEatÒ’’ as a texturemodified food for use in swallowing modified diet 2-2 (categorized as a puree food by the Japanese Society of Dysphagia Rehabilitation in 2013), and at least more than 60 % of dysphagia professionals evaluated their efficacy for the swallowing modified diet 2-2 [24]. Syneresis: Fig. 4 Figure 4 shows syneresis rate of carrot samples, burdock root samples, and care food products. The syneresis rate of SC was higher than those of NCC, IJ and AI, but lower than that of FIC. There was no significant difference between SC and VC. The syneresis rate of SB was also higher than that of NCB, IJ, and AI, but lower than those of FIB and VC. Thence, the syneresis rate of SC and SB were approximately equivalent to those of the care food. Liquid separation from foods can create a risk of aspiration [43, 44]. Also, Nayebzadeh and others reported that a little liquid of food could reduce the friction between bolus and throat, and make bolus easy to swallow [45]. For these reasons, a little syneresis from the root crops treated with HEPM might be moderate for people with dysphagia to swallow them. Nutritional Analysis of Carrots and Burdock Roots: Table 1 Table 1 shows the nutritional components of the carrot and burdock root samples. The water content per 100 g edible portion was lower in SC than in NCC and FIC, and energy, potassium, and beta-carotene contents retained in SC were Table 1 Nutritional components of carrots and burdock roots (per 100 g edible portion) Water (g) Energy (kcal) Potassium (mg) b-carotene (lg) NCC 89.2
39
220
FIC
93.7
25
155
7,870 7,960
SC
87.7
48
322
11,700
NCB 81.8
58
247
–
FIB
93.7
24
94
–
SB
80.4
77
218
–
NCC normally cooked carrots, FIC carrots softened by freeze–thaw infusion, SC softened carrots, NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots
S. Umene et al.: Physical Properties of Root Crops Fig. 5 Light microscopy images of burdock roots arrows indicate blank space. NCB normally cooked burdock roots, FIB burdock roots softened by freeze–thaw infusion, SB softened burdock roots
500μm
NCB
500μm
500μm
FIB
SB
higher than those in NCC and FIC. The water content per 100 g edible portion in SB was equivalent to those in NCB and lower than in FIB. The energy content retained in SB was at higher than in NCB and FIB. The potassium content retained in SB was lower than in NCB but higher than in FIB. The nutrients of the root crops treated by HEPM were maintained during the process of HEPM. On the other hands, the cells of root crops treated by freeze–thaw infusion were damaged by freezing and particularly thawing and lost water-soluble potassium [46]. From the reasons, it was anticipated that HEPM could keep nutrients of foods as much as normally cooking [47, 48]. Therefore, the root crops treated by HEPM would be helpful to control nutrition for elderly people and patients who have difficulty with mastication or swallowing or both.
retained because of preventing excessive cell destruction. And water-soluble flavor of SB may be also retained.
Light Microscopy of Burdock Roots: Fig. 5
Conflict of interest
Figure 5 shows light microscopy images of burdock roots. Burdock roots were stained with a 0.2 % safranine solution for light microscopy. NCB were shown to have regular cell shapes and regularly lined cell walls. In FIB, most cell walls were destroyed and cells did not retain their shapes. Many blank spaces, which might be the cavity made by thawing frozen water of cells, were also observed in FIB [31, 32]. Although cells of SB were partially decomposed, their shapes were well maintained, compared to the cells of FIB. Thus, it has become clear that the potassium of SB was
Conclusions The HEPM is considered to be a novel technique that can appropriately control appearance, physical properties, and nutritional value of foods by inhibiting excessive cell destruction and adjusting the reaction of enzymes. The physical properties of the root crops softened by the HEPM are similar to those of care food products. From these results, it is expected that the root crops softened by the HEPM will be one of the best model food for patients with masticatory disturbance or swallowing disorders or both. We have no conflict of interest.
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Shingo Umene Msc Masahiro Hayashi
Msc
Kumiko Kato Msc Hiroaki Masunaga
PhD
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