Food Chemistry 146 (2014) 412–422

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Effects of ripeness and cultivar on chemical composition of strawberry (Fragaria  ananassa Duch.) fruits and their suitability for jam production as a stable product at different storage temperatures Sebastian Piotr Mazur a,b,⇑, Arnfinn Nes a, Anne-Berit Wold b, Siv Fagertun Remberg b, Berit Karoline Martinsen c, Kjersti Aaby c a

Norwegian Institute for Agricultural and Environmental Research, Arable Crops Division, N-2849 Kapp, Norway Department of Plant and Environmental Sciences, Norwegian University of Life Sciences, P.O. Box 5003, N-1432 Aas, Norway c Nofima, Norwegian Institute of Food, Fisheries and Aquaculture Research, Osloveien 1, N-1430 Aas, Norway b

a r t i c l e

i n f o

Article history: Received 29 January 2013 Received in revised form 13 September 2013 Accepted 16 September 2013 Available online 25 September 2013 Keywords: Strawberry Fragaria  ananassa ‘Blink’ ‘Polka’ ‘Senga Sengana’ Ripeness Polyphenols Anthocyanins Ascorbic acid Jam Storage

a b s t r a c t Effects of ripeness (nearly ripe, ripe, fully ripe) and cultivar (‘Blink’, ‘Polka’ and ‘Senga Sengana’) on colour and chemical composition of strawberry fruits and their suitability for jam production, evaluated as stability during storage at 4 and 20 °C for 3 and 6 months, were investigated. Quality traits of fruits and jams were significantly affected by both ripeness stage and cultivar. However, after 6 months of storage, particularly at 20 °C, the effects of fruit ripeness and cultivar were considerably reduced. During jam storage, anthocyanins, ascorbic acid, chroma and hue were least stable in jams made from the least ripe fruits. Quality traits in jams made from ‘Senga Sengana’ were best preserved during storage, while quality and chemical composition in jams made from ‘Blink’ changed the most. In conclusion, fully ripe fruits were best suited for jam processing. Storage at low temperature was preferable and ‘Senga Sengana’ was the most and ‘Blink’ the least suitable cultivar for processing. Ó 2013 Elsevier Ltd. All rights reserved.

1. Introduction Strawberry fruits with great flavour and highly desirable taste are common and widely consumed both fresh and processed. Due to the economic importance of the species, many studies have been carried out to evaluate effect of different factors on sensorial and nutritional traits of the fruits and their products. Physical and sensory quality of strawberry fruits are associated with traits like size, firmness, colour, pH, sugar/acid ratio, taste and aroma (Kafkas, Kosar, Paydas, Kafkas, & Baser, 2007; Montero, Mollá, Esteban, & López-Andréu, 1996; Nunes, Brecht, Morais, & Sargent, 2006; Shin,

⇑ Corresponding author at: Bioforsk – Norwegian Institute for Agricultural and Environmental Research, N-2849 Kapp, Norway. Tel.: +47 90083750; fax: +47 61160313. E-mail addresses: [email protected] (S.P. Mazur), arfinn.nes@ bioforsk.no (A. Nes), [email protected] (A.-B. Wold), [email protected] (S.F. Remberg), berit.karoline.martinsen@nofima.no (B.K. Martinsen), kjersti.aaby@ nofima.no (K. Aaby). 0308-8146/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodchem.2013.09.086

Ryu, Liu, Nock, & Watkins, 2008). Nutritional properties are related to the content of ascorbic acid and secondary plant metabolites, such as phenolic compounds, which have been reported to have potential beneficial health properties (Kafkas et al., 2007; Kosar, Kafkas, Paydas, & Baser, 2004; Pineli et al., 2011; Tulipani et al., 2008). Significant differences in phenolic profile have been observed in strawberry cultivars (Aaby, Mazur, Nes, & Skrede, 2012; Kosar et al., 2004). Besides genetic and environmental factors, ripeness (Tulipani et al., 2011) and storage conditions (Shin et al., 2008) affect overall fruit quality. Harvesting at the right maturity stage is crucial for keeping optimal quality during storage and handling (Sturm, Koron, & Stampar, 2003). The colour expression of strawberry fruits is associated with concentration and composition of anthocyanins. The major anthocyanins are pelargonidin-3-glucoside, pelargonidin-3-malonylglucoside, pelargonidin-3-rutinoside and cyanidin-3-glucoside, but the composition varies with genotype (Aaby et al., 2012; Tulipani et al., 2008). While total concentration of anthocyanins increases significantly during ripening, the anthocyanin composition,

S.P. Mazur et al. / Food Chemistry 146 (2014) 412–422

however, is hardly changed in the fruits in the late ripening stages (Aaby et al., 2012). Since strawberry fruits are a good source of ascorbic acid, which is one of the most important antioxidants in plants, the changes of this compound during fruits ripening was examined. Some studies have reported an increase in vitamin C content with increasing ripeness of strawberry fruits (Kafkas et al., 2007; Nunes et al., 2006; Tulipani et al., 2011), whereas Pineli et al. (2011) observed the highest concentrations of ascorbic acid in half ripe fruits. The influence of different processing methods on preservation of bioactive compounds in different products have been studied (Hartmann, Patz, Andlauer, Dietrich, & Ludwig, 2008), and differences between cultivars and species after processing fruits into jams have been reported (Kim & Padilla-Zakour, 2004). Considerable losses were detected in the content of anthocyanins, ascorbic acid and total phenolics after processing. Quality of strawberry jam has been found to be significantly influenced by storage conditions (García-Viguera et al., 1999; Patras, Brunton, Tiwari, & Butler, 2009; Wicklund et al., 2005). In general, storage at higher temperatures for a longer period of time has negative influence on most of the quality parameters measured. The hypothesis of the present study was that jam quality and stability is influenced by ripeness and genotype of strawberry fruits. Except for an early American study where jams were prepared from a blend of ripe and immature strawberry fruits (Spayd & Morris, 1981), effect of fruit ripeness on quality and storage stability of strawberry jams has not been investigated. Different cultivars might also be differently influenced by ripening. The main aim of the present study was thus to determine the effects of ripeness, cultivar, storage time (0, 3 and 6 months) and storage temperature (4 and 20 °C) and their interactions on stability of colour and bioactive compounds (ascorbic acid and phenolic compounds) in jams. The ripeness of the fruits were within the normal range of strawberry when harvested (partly red, red and dark red) and the cultivars studied (‘Blink’, ‘Polka’ and ‘Senga Sengana’) are commonly grown in Norway. Further objective was to investigate relationships between the measured quality parameters in the jams. 2. Materials and methods 2.1. Chemicals Pelargonidin-3-glucoside was obtained from Polyphenols AS (Sandnes, Norway). Acetone, acetonitrile, L-(+)-ascorbic acid (AA), citric acid, sodium acetate, sodium carbonate, sodium dihydrogen phosphate dihydrate (NaH2PO42H2O), sodium hydroxide, disodium hydrogen phosphate dihydrate, disodium EDTA, n-dodecyltrimethylammonium chloride, methanol and potassium chloride were obtained from Merck KGAa (Darmstadt, Germany). Dehydro-L-(+)-ascorbic acid dimer (DHAA), tris[2-carboxyethyl]-phosphate, gallic acid, quercetin-3-rhamnosylglucoside (rutin), catechin, ellagic acid, Folin–Ciocalteu’s phenol reagent and DLmalic acid were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Metaphosphoric acid was purchased from Sigma– Aldrich Chemie GmbH (Steinheim, Germany). Chlorogenic acid and formic acid were obtained from Fluka (Buchs, Switzerland). Pectin LM-102 As was obtained from CP Kelco (Lile Skensved, Denmark). All solvents were of HPLC grade and water was of Milli-Q-quality (Millipore Corp., Bedford, MA, USA). 2.2. Plant material Fruits of strawberry (Fragaria  ananassa Duch.), cultivars ‘Blink’, ‘Polka’ and ‘Senga Sengana’, were harvested from a commercial field in the South – East of Norway (60°460 N, 10°480 E) in

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2010. The plants were grown in a two row planting system on low ridges. The middle of the ridges was 1.6 m apart, the distances between the double rows were 40 cm and the distances between plants were 30 cm giving about 42,000 plants/ha. The fields had a morainic loam soil with 6–8% humus and water pH was 5.5–5.7. Berries of the three cultivars were harvested at three times with 3–4 days intervals in the first part of July and graded in three ripening stages (nearly ripe = partly red, ripe = red and fully ripe = dark red) (Aaby et al., 2012). Samples were frozen at 20 °C within 3 h after harvest. Samples of the same ripening stage from the three harvests were mixed prior to analyses and processing. 2.3. Production of strawberry jam Samples of frozen strawberries (2.4 kg) were mixed with water (250 ml) and heated to 85 °C before sugar (1.2 kg) was added, and the temperature was kept at 85 °C for 5 min. Then potassium sorbate (4 g dissolved in a small amount of water) and a pectin solution (16 g pectin type LM-102 as dissolved in 250 ml water) were added. The temperature of the mixture was reduced to 70 °C, and 16 ml of a 50% solution of malic acid (w/v) was added followed by further cooling to 55 °C. The jam was then filled in 400 g glass jars and immediately sealed with metal lids. Some samples were directly frozen at 20 °C, and the other stored in darkness at 4 and 20 °C for 3 and 6 months. After the storage period all samples were frozen and kept at 20 °C until analysis. 2.4. Determination of dry matter (DM), soluble solids (SS), pH and titratable acids (TA) in the fruits Prior to analyses thawed fruits (150 g) were homogenised using a food processor (CombiMax 700, Braun GmbH, Kronberg, Germany). The content of DM was determined by the vacuum drying method (Bøgh-Sørensen, 2002). Homogenised fruits (10 g) were dried in a vacuum oven (type RVT 360, Heraeus GmbH, Hanau, Germany) for 24 h at 70 °C and DM expressed as % (g/100 g of fresh weight (FW)). SS content was determined using a digital refractometer (RE40, Mettler Toledo, Japan) and expressed as °Brix (%). The pH was determined at 20 °C with a pH meter (827 pHlab, Metrohm, Switzerland). For determination of TA, homogenised samples (30 g) were further homogenised for 45 s using a PolytronÒ homogenizer (PT-MR 3100, Kinematica AG, Switzerland), and centrifuged at 39191g for 10 min at 4 °C (Avanti J-26 XP. Beckman Coulter, USA). The supernatant (5 ml) was diluted 1:10 with distilled water followed by titration to pH 8.1 with 0.1 M NaOH using an automatic titrator (T50, Mettler Toledo, Switzerland). The content of TA was calculated as citric acid (mg/100 g FW). All berries were analysed in duplicates for DM and TA, and triplicates for SS and pH. 2.5. Colour measurements Fifteen randomly selected frozen fruits were thawed for 45 min at room temperature. Semi-thawed samples were homogenised using a food processor (CombiMax 700, Braun GmbH, Kronberg, Germany) and the colour of the puree was measured after 15 min, when the samples were completely thawed. The measurements were conducted with a Hunter Lab colour system (LabScan XE, Reston,Virginia, USA). The 1976 CIE L⁄, a⁄ and b⁄ system was used for evaluation of colour (illuminant D65, 10° observer, mode (geometry): 0°/45°, and area view 0.500 , port size 0.700 . L⁄ defines lightness where lower values indicate darker colour (0 = black) and higher values indicate lighter colour (100 = white). Negative a⁄ values indicate green and positive values red colour, while negative b⁄ values imply bluish and positive values yellow colour. Hue angle (colour shade) was computed as arctan (b⁄/a⁄) and chroma

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(colour saturation) as square root (a⁄2 + b⁄2). High values of hue angle indicate more red-orange and low values more red-bluish colour. Chroma shows transition from grey (low values) to pure colour (high values). The instrument was calibrated using a standard white (X = 80.86, Y = 85.69 and Z = 91.51) and a standard black reflective plate. 2.6. Total ascorbic acid Total ascorbic acid content was quantified in accordance with the method previously described by Karlsen, Blomhoff, and Gundersen (2005) and modified by Aaby, Wrolstad, Ekeberg, and Skrede (2007). Ascorbic acid in fruits and jams was extracted with 4.5% metaphosphoric acid before separation and detection on an Agilent 1000 series HPLC system (Agilent Technologies, Waldbronn Germany) with monolithic Chromolith Performance RP-18e column fitted with a Chromolith RP-18e guard cartridge, both from Merck KGaH (Darmstadt, Germany). L-ascorbic acid (AA) was detected at 264 nm and quantified by external standard. Total ascorbic is the sum of AA and dehydroascorbic acid (DHAA) in the samples and was determined after reduction of DHAA present. The content of total ascorbic acid was expressed as mg AA per 100 g FW. The samples were analysed in duplicates. 2.7. Extraction of phenolic compounds Phenolic compounds for analyses of total phenolics (TP), total monomeric anthocyanin (TMA) and individual phenolic compounds by HPLC were extracted by acetone as previously described (Aaby et al., 2012). The samples were extracted in duplicates and stored at 80 °C until analysis. 2.8. Analyses of total monomeric anthocyanins (TMA) and total phenolics (TP) TMA were determined by the pH-differential method (Giusti & Wrolstad, 2001). After 30 min incubation in room temperature of extracts diluted with buffers (pH 1 or 4.5), the absorbance was measured at 520 and 700 nm (Agilent 8453 spectrophotometer, Agilent Technologies). The anthocyanins were quantified as cyanidin-3-glucoside equivalents (mg/100 g FW). TP was determined by using the Folin–Ciocalteu colourimetric method as previously described (Aaby et al., 2007; Kähkönen et al., 1999). Suitable diluted extracts (0.2 ml) were mixed with Folin–Ciocalteu’s reagens (1.0 ml) and after further 3 min mixed with 7.5% sodium carbonate (0.8 ml) before incubation for 60 min at room temperature and measurement of absorbance at 765 nm (Agilent 8453 spectrophotometer, Agilent Technologies). TP content was expressed as mg gallic acid equivalents (GAE) per 100 g fresh weight (mg GAE/ 100 g FW). 2.9. Analysis of phenolic compounds by HPLC-DAD-MSn Extracts of phenolic compounds filtered through a Millex HA 0.45 lm filter (Millipore Corp., Billerica, MA, USA) were analysed on an Agilent 1100 series HPLC system (Agilent Technologies, Waldbronn, Germany) equipped with an autosampler cooled to 6 °C, a diode array detector, and a MSD XCT ion trap mass spectrometer fitted with an electrospray ionisation interface as previously described (Aaby et al., 2012). Chromatographic separation was performed on a Synergi 4 lm MAX RP C12 column (250 mm  2.0 mm i.d.) equipped with a C12 guard column (4.0 mm  2.0 mm i.d.), both from Phenomenex (Torrance, CA, USA), with mobile phases consisting of A; formic acid/water (2/98, v/v) and B; acetonitrile. The phenolic compounds were identified based on their UV–Vis spectra (220–600 nm), mass spectra

and comparison with previous characteristics (Aaby et al., 2012). The phenolic compounds were classified based on their characteristically UV–Vis spectra and quantified by external standards. Anthocyanins were quantified as pelargonidin-3-glucoside (at 520 nm), flavonols as rutin (at 360 nm), ellagic acid conjugates, i.e. ellagic acid glycosides and ellagic acid, as ellagic acid (at 360 nm), and the ellagitannin agrimoniin as gallic acid (at 260 nm). Coumaroyl hexose (at 320 nm) and cinnamoyl glucose (at 280 nm) were quantified as chlorogenic acid (at 320 nm). All results were expressed as mg per 100 g FW. 2.10. Statistical analysis Statistical analysis was performed using R statistical software (version 2.14.1, The R Foundation for Statistical Computing, Wirtschaftsuniversity at Wien, Austria). Significant (p < 0.05) differences between means were estimated by use of factorial analysis of variance (ANOVA) followed by Tukey’s multiple comparison test. The effects of fruit ripeness, cultivar, storage time and temperature, as well as significance of two and three factor interactions during jam storage were investigated. To examine significant relationships between measured parameters, Pearson correlation coefficients were calculated. 3. Results and discussion 3.1. Fresh strawberries; influence of ripeness and cultivar 3.1.1. Quality parameters DM content increased significantly during ripening from ripe to fully ripe fruits of all cultivars, most apparently in ‘Blink’ and ‘Senga Sengana’ (Table 1). The opposite tendency was noted by Tulipani et al. (2011), but the divergence between ripeness stages (green–red) was much higher in that work. The highest average DM content was found in ‘Polka’ (11.6 g/100 g FW), while ‘Blink’ and ‘Senga Sengana’ contained 9.6 and 10.3 g/100 g FW, respectively. The highest SS content was found in fully ripe fruits of ‘Polka’ and ‘Blink’. SS increased during ripening in ‘Polka’ and ‘Blink’, but decreased in ‘Senga Sengana’. The highest TA content was found in nearly ripe fruits of ‘Blink’. Otherwise the TA content was very similar in all fruits, independent on ripeness and cultivar. The SS/TA ratio have been reported to affect the overall flavour of strawberry fruits more than the content of sugars or acids alone (Perkins-Veazie, 1995). In the present study, the SS/TA ratio increased most considerably during ripening in Blink (1.7-fold), whereas the highest SS/TA ratio in average in fruits of all ripeness stages was found in ‘Polka’ (10.4). Large diversity in SS/TA ratio between both cultivars and ripeness stages was also observed formerly (Kafkas et al., 2007; Sturm et al., 2003). In the present study, the highest increase in pH was observed in ‘Blink’ and the lowest in ‘Senga Sengana’. The lowest pH values measured in nearly ripe fruits of ‘Blink’ were linked with the high concentrations of TA. Variation among the genotypes was insignificant. Montero et al. (1996) reported a decrease of pH in strawberry fruits during the early stages of fruit development followed by an increase during the latest stages. The values of DM, SS, TA and pH of the strawberry fruits in the present study were in the same range as previously reported for strawberries (Skrede, Martinsen, Wold, Birkeland, & Aaby, 2012), indicating that fruits from all three ripeness stages was within the commercial ripeness range for fruits when harvested. 3.1.2. Colour and content of total monomeric anthocyanins (TMA) Mean values of all colour parameters decreased during ripening (Table 1), indicating that more ripe berries were darker (lower L⁄)

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Table 1 Dry matter (DM), soluble solids (SS), titratable acids (TA), SS/TA ratio, pH, colour parameters (L⁄, chroma, hue), total monomeric anthocyanins (TMA), ascorbic acid and total phenolics (TP) in strawberry fruits of the cultivars ‘Blink’, ‘Polka’ and ‘Senga Sengana’ at three stages of ripeness (nearly ripe, ripe and fully ripe).

Nearly ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean Ripe ‘Blink’ ‘Polka’ ‘Senga ’ Mean

a b

DM (%)

SS (%)

TAa (mg/ 100 g FW)

SS/TA ratio

pH

L⁄

Chroma

Hue

TMA (mg/ 100 g FW)

Ascorbic acid (mg/ 100 g FW)

TP (mg GAE / 100 g FW)

9.2 ± 0.1 11.7 ± 0.1 9.9 ± 0.1 10.3a

8.0 ± 0.1 9.1 ± 0.1 9.0 ± 0.1 8.7a

1.4 ± 0.0 1.1 ± 0.0 1.1 ± 0.0 1.2a

5.6 ± 0.1 8.6 ± 0.0 8.0 ± 0.1 7.4b

3.3 ± 0.0 3.5 ± 0.0 3.5 ± 0.0 3.4a

29.0 ± 0.6 25.6 ± 1.5 27.7 ± 1.1 27.4a

29.2 ± 0.1 28.0 ± 0.4 31.1 ± 0.1 29.4a

29.9 ± 0.1 30.9 ± 0.1 29.6 ± 0.3 30.1a

12.6 ± 0.2 12.2 ± 1.7 14.1 ± 0.3 13.0c

49.4 ± 6 36.9 ± 2 46.4 ± 1 44a

195 ± 7 200 ± 1 185 ± 2 193a

9.3 ± 0.0 11.1 ± 0.0 10.0 ± 0.0

8.2 ± 0.1 9.5 ± 0.1 8.7 ± 0.0

1.1 ± 0.0 0.9 ± 0.0 0.9 ± 0.0

7.1 ± 0.1 10.4 ± 0.1 9.2 ± 0.1

3.5 ± 0.0 3.6 ± 0.0 3.6 ± 0.0

20.6 ± 0.3 26.5 ± 1.5 17.8 ± 0.1

23.0 ± 0.4 31.8 ± 0.3 27.9 ± 0.3

28.3 ± 0.5 30.3 ± 0.1 30.2 ± 0.2

33.6 ± 1.5 24.7 ± 1.2 17.4 ± 0.7

44.6 ± 8 45.2 ± 2 42.4 ± 2.0

203.7 ± 7 183.7 ± 5 163.6 ± 10

10.1a

8.8a

1.0a

8.9a

3.6a

21.6b

27.6b

29.6a

25.2b

44a

184a

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

10.1 ± 0.1 12.0 ± 0.1 11.0 ± 0.1 11.0b

8.7 ± 0.1 10.7 ± 0.0 8.3 ± 0.1 9.4a

0.9 ± 0.0 0.9 ± 0.0 1.1 ± 0.0 1.0a

9.4 ± 0.1 12.2 ± 0.3 8.3 ± 0.1 10.0a

3.7 ± 0.0 3.7 ± 0.0 3.6 ± 0.0 3.6a

18.4 ± 0.1 21.4 ± 0.4 16.2 ± 0.3 18.7c

22.0 ± 1.1 30.0 ± 1.2 28.7 ± 0.5 26.9b

26.4 ± 1.0 29.8 ± 1.1 31.9 ± 0.3 29.4a

42.1 ± 1.5 32.8 ± 0.2 24.5 ± 0.1 33.1a

53.9 ± 6 46.5 ± 6 41.9 ± 2 47a

202 ± 7 219 ± 2 169 ± 7 196a

Valuesb ‘Blink’ ‘Polka’ ‘Senga’

9.6a 11.6c 10.3b

8.3a 9.8b 8.7ab

1.2a 1.0a 1.0a

7.3b 10.4a 8.5b

3.5a 3.6a 3.5a

22.7b 24.5a 20.6c

24.8b 30.0a 29.2a

28.2b 30.3a 30.5a

29.4a 23.2b 18.7c

49a 43a 44a

200a 173a 201a

Titratable acidity is expressed as citric acid content. Average values. Values with different letters are significantly different (p 6 0.05) based on Tukey’s comparison test.

with more dull (lower chroma) and more red bluish colour (lower hue) than less ripe berries. The highest reduction during ripening was observed for L⁄ and chroma, while only small changes for hue values were observed. All colour parameters decreased during ripening in ‘Blink’. Insignificant increase of chroma was observed in ‘Polka’ and a generally small, although significant, for hue in ‘Senga Sengana’. The same changes in colour during ripening (three-quarters and full red stage) as well as significant differences between cultivars were previously observed by Nunes et al. (2006). The TMA content in nearly ripe fruits were similar in all cultivars (Table 1). TMA increased significantly from nearly ripe to fully ripe fruits in all cultivars, and most extensively in ‘Blink’ (3.3-fold) followed by ‘Polka’ (2.7-fold) and ‘Senga Sengana’ (1.7-fold). Large increase in anthocyanins during ripening fruit and significant divergences between cultivars have been reported formerly (Kosar et al., 2004; Montero et al., 1996). 3.1.3. Total ascorbic acid content The nutritional value of strawberry fruits has often been connected with a high content of ascorbic acid, which is the most important non-phenolic antioxidant in strawberries (Aaby et al., 2007). There were observed insignificant differences in ascorbic acid content both between ripeness stages and cultivars (Table 1). Diverging effects of ripening on vitamin C content was reported formerly. Kafkas et al. (2007) and Shin et al. (2008) observed an increase in ascorbic acid content during fruit ripening. Nunes et al. (2006) and Tulipani et al. (2011) noted the same trend, but with some variation between cultivars, whereas Pineli et al. (2011) found the highest ascorbic acid content in pink fruits of the cultivars ‘Osogrande’ and ‘Camino Real’. Olsson et al. (2004) did not observe any significant changes during berry ripening in ascorbic acid content in fruits of ‘Senga Sengana’. Interestingly, in the latest study, Pincemail, Kevers, Tabart, Defraigne, and Dommes (2012) reported significant changes in vitamin C content during the harvest period, independently of various cultivation conditions. 3.1.4. Total phenolic content (TP) TP content in fruits was not significantly affected either by ripeness or by cultivar (Table 1). Tulipani et al. (2011) and Shin et al.

(2008) reported a significant decrease in TP during fruit ripening of strawberry when the differences between the ripeness stages were much larger than in our study. Nunes et al. (2006) and Montero et al. (1996) registered a similar decrease during the early stages of fruit ripening followed by a later increase (colour break – fully red), while Pineli et al. (2011) observed the highest TP values in pink strawberries. 3.2. Strawberry jam; effect of fruit ripeness, cultivar, storage time and temperature During processing, cell structures are disrupted and constituents in the fruits become prone to enzymatic and non-enzymatic oxidation (Pourcel, Routaboul, Cheynier, Lepiniec, & Debeaujon, 2007). In addition, heating leads to further degradation of compounds present. The impact of processing was determined by comparing the concentrations of TMA, ascorbic acid and TP in berries (Table 1) with the content in freshly processed jam (Table 2). Since the jam consisted of 60% fruits, jam values are divided by 0.6 to obtain the concentrations on a fruit basis. The recovery of TMA, ascorbic acid and TP after jam processing varied substantially. In average, about 85% of TMA, ascorbic acid and TP in the fruits were recovered in the jam after processing, which is in the same range as previously reported (Aaby et al., 2007; Klopotek, Otto, & Böhm, 2005).The degradation of health related compounds, such as ascorbic acid and polyphenols, initiated during processing, will continue during storage and the losses observed in stored products can often be more severe than those observed during processing. The contents of quality and health related compounds varied in fruits of different cultivars and at different ripeness stages, which could influence the changes that occur during jam storage. Therefore, the effects of different factors, i.e. cultivar, fruit ripeness, storage time, storage temperature and their interactions on colour and health related compounds were investigated. 3.2.1. Colour and content of total monomeric anthocyanins As expected, fresh jams prepared from nearly ripe fruits of ‘Blink’ and ‘Polka’ were lighter (higher L⁄-values) than jams prepared from more ripe fruits (Table 2). More surprisingly, the

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Table 2 Colour parameters (L⁄, chroma, hue), total monomeric anthocyanins (TMA), ascorbic acid and total phenolics (TP) in strawberry jam of nearly ripe, ripe and fully ripe fruits of the cultivars ‘Blink’, ‘Polka’ and ‘Senga Sengana’ during 0, 3 and 6 months of storage at 4 and 20 °C. L⁄

Chroma

Hue

TMA (mg/100 g FW)

Ascorbic acid (mg/100 g FW)

TP (mg GAE/100 g FW)

14.1 ± 0.3 17.0 ± 0.0 8.8 ± 0.3 13.3

22.4 ± 0.1 21.4 ± 0.2 16.4 ± 0.2 20.1

28.7 ± 0.7 29.7 ± 0.4 27.0 ± 0.5 28.5

9.4 ± 0.0 7.7 ± 0.2 7.4 ± 0.2 8.2

19.6 ± 1.2 27.1 ± 1.5 22.2 ± 1.7 22.9

134 ± 2 93 ± 0 73 ± 5 100

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

10.7 ± 1.0 10.9 ± 0.4 11.1 ± 0.3 10.9

21.9 ± 1.2 19.9 ± 0.4 19.1 ± 0.0 20.3

28.4 ± 1.2 29.2 ± 0.1 27.1 ± 0.7 28.2

13.9 ± 0.0 9.3 ± 1.3 9.9 ± 0.4 11.0

15.2 ± 0.8 24.4 ± 0.0 26.4 ± 0.5 22.0

140 ± 1 73 ± 15 71 ± 5 95

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

7.4 ± 0.6 9.5 ± 0.7 12.2 ± 0.2 9.7

19.4 ± 0.6 21.3 ± 0.5 19.9 ± 0.3 20.2

23.2 ± 0.4 28.6 ± 1.0 28.8 ± 0.3 26.9

20.5 ± 0.3 15.6 ± 0.5 12.4 ± 1.2 16.1

16.9 ± 1.0 25.4 ± 0.4 25.9 ± 0.5 22.8

125 ± 2 80 ± 5 88 ± 0 98

Jam stored for 3 months at 4 °C Nearly ripe ‘Blink’ 18.7 ± 0.4 ‘Polka’ 14.6 ± 0.6 ‘Senga’ 4.6 ± 0.4 Mean 12.7

14.9 ± 0.0 17.1 ± 0.0 9.8 ± 0.6 13.9

29.9 ± 0.0 28.2 ± 0.1 21.0 ± 0.0 26.4

3.1 ± 0.0 4.8 ± 0.1 6.4 ± 0.2 4.8

2.4 ± 0.4 5.5 ± 0.2 11 ± 0.1 6.3

111 ± 1 99 ± 7 61 ± 4 90

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

8.9 ± 0.3 8.8 ± 0.2 11.4 ± 0.4 9.7

16.9 ± 0.1 16.6 ± 0.3 16.9 ± 0.0 16.8

26.5 ± 0.5 25.9 ± 0.4 27.7 ± 0.6 26.7

7.6 ± 0.1 7.3 ± 0.2 8.2 ± 0.2 7.7

1.9 ± 0.1 4.4 ± 0.0 8.3 ± 0.6 4.9

132 ± 1 85 ± 2 73 ± 5 97

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

12.1 ± 0.3 9.3 ± 0.6 10.6 ± 0.0 10.7

19.9 ± 0.2 20.0 ± 0.4 17.4 ± 0.1 19.1

26.9 ± 0.1 26.8 ± 1.3 27.4 ± 0.1 27.0

11.8 ± 0.1 11.9 ± 0.0 10.0 ± 0.7 11.2

1.2 ± 0.5 7.2 ± 0.5 11.4 ± 0.2 6.6

130 ± 2 87 ± 1 77 ± 7 98

Jam stored for 3 months at 20 °C Nearly ripe ‘Blink’ 12.6 ± 0.2 ‘Polka’ 10.6 ± 0.0 ‘Senga’ 7.6 ± 1.6 Mean 10.3

8.9 ± 0.0 10.3 ± 0.6 9.2 ± 0.7 9.5

49.8 ± 0.3 40.2 ± 0.9 31.8 ± 3.9 40.6

0.2 ± 0.1 1.6 ± 0.0 2.7 ± 0.2 1.5

0.6 ± 0.1 3.6 ± 0.1 6.7 ± 0.0 3.7

117 ± 2 65 ± 1 62 ± 5 81

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

15.2 ± 0.4 13.9 ± 0.2 10.5 ± 0.1 13.2

13.5 ± 0.8 14.5 ± 0.1 11.7 ± 0.2 13.3

46.7 ± 0.1 38.3 ± 0.6 35.0 ± 0.5 40.0

0.6 ± 0.1 2.7 ± 0.0 3.7 ± 0.3 2.3

0.0 ± 0.0 3.2 ± 0.1 5.1 ± 0.6 2.8

129 ± 5 73 ± 5 65 ± 4 89

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

10.7 ± 0.1 11.4 ± 0.1 8.3 ± 0.1 10.1

13.8 ± 0.3 15.8 ± 0.1 12.9 ± 0.4 14.2

36.7 ± 0.6 34.7 ± 0.1 31.4 ± 0.8 34.3

2.4 ± 0.1 4.8 ± 0.2 5.2 ± 0.0 4.1

0.0 ± 0.0 2.4 ± 0.3 8.7 ± 0.8 3.7

120 ± 1 88 ± 6 66 ± 0 91

Jam stored for 6 months at 4 °C Nearly ripe ‘Blink’ 14.2 ± 0.2 ‘Senga’ 10.2 ± 0.4 Mean 12.2

11.5 ± 0.2 13.3 ± 0.0 12.4

32.4 ± 0.5 35.1 ± 1.1 33.7

2.1 ± 0.1 3.1 ± 0.0 2.6

0.0 ± 0.0 2.1 ± 0.4 1.1

100 ± 0 100 ± 1 100

Ripe ‘Blink’ ‘Polka ‘Senga’ Mean

13.9 ± 0.4 15.2 ± 0.2 9.6 ± 4.1 12.9

15.2 ± 0.3 16.4 ± 0.1 12.0 ± 1.7 14.5

27.3 ± 0.8 34.2 ± 0.2 31.4 ± 5.6 31.0

4.9 ± 0.1 4.3 ± 0.1 5.0 ± 0.1 4.7

0.0 ± 0.0 0.9 ± 0.0 5.1 ± 0.0 2.0

101 ± 2 125 ± 3.3 93.4 ± 1 107

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

11.1 ± 0.1 11.7 ± 0.6 4.3 ± 0.0 9.0

17.7 ± 0.3 16.4 ± 0.7 8.1 ± 0.1 14.1

27.3 ± 0.6 31.0 ± 1.0 25.3 ± 0.5 27.9

9.9 ± 0.3 7.8 ± 0.1 6.7 ± 0.1 8.1

0.0 ± 0.0 1.1 ± 0.3 6.5 ± 0.1 2.5

107 ± 1 140 ± 5 100 ± 4 116

9.2 ± 0.2 10.5 ± 0.4 10.7 ± 1.2

53.4 ± 0.2 59.6 ± 0.4 57.2 ± 0.2

0.1 ± 0.1 0.3 ± 0.1 0.5 ± 0.1

0.0 ± 0.0 0.7 ± 0.3 2.2 ± 0.6

96 ± 2 131 ± 1 93 ± 0

Freshly processed Nearly ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

jam

Jam stored for 6 months at 20 °C Nearly ripe ‘Blink’ 12.2 ± 0.1 ‘Polka’ 16.7 ± 0.1 ‘Senga’ 12.7 ± 0.3

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S.P. Mazur et al. / Food Chemistry 146 (2014) 412–422 Table 2 (continued) L⁄

Chroma

Hue

TMA (mg/100 g FW)

Ascorbic acid (mg/100 g FW)

TP (mg GAE/100 g FW)

Mean

13.8

10.1

56.7

0.3

1.0

107

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

10.6 ± 0.2 10.5 ± 0.5 11.0 ± 0.1 10.7

10.7 ± 0.2 10.1 ± 0.5 11.6 ± 0.4 10.8

43.0 ± 0.2 47.9 ± 1.2 54.5 ± 0.6 48.5

0.3 ± 0.0 0.8 ± 0.0 0.9 ± 0.0 0.7

0.0 ± 0.0 0.6 ± 0.1 2.4 ± 0.4 1.0

102 ± 1 108 ± 4 91 ± 2 100

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

9.6 ± 0.2 11.2 ± 0.1 8.6 ± 0.3 9.8

11.4 ± 0.3 13.0 ± 0.3 10.3 ± 0.1 11.6

38.4 ± 0.2 44.4 ± 0.2 47.8 ± 0.1 43.5

1.7 ± 0.2 1.9 ± 0.1 1.1 ± 0.2 1.6

0.0 ± 0.0 0.7 ± 0.1 2.7 ± 0.6 1.1

103 ± 7 126 ± 0 102 ± 1 110

opposite trend was observed for ‘Senga Sengana’. The colour saturation (chroma) of freshly processed jam was not affected by ripeness. The colour attributes of strawberry jams were influenced in various ways by several factors during the storage period (Table 3). Jams prepared from ‘Senga Sengana’ were significantly darker than jams made from the other two cultivars. The jam lightness was not significantly affected by storage time or temperature. In accordance with these results, García-Viguera et al. (1999) did not detect any significant influence of temperature (20, 30 and 37 °C) on L⁄ values during 200 days of storage of strawberry jams. Wicklund et al. (2005) observed higher L⁄ values of jams stored for three months at 20 °C compared to 4 °C. In the present study, chroma decreased and hue values increased more significantly during storage at higher temperature (20 °C) and after prolonged storage time (Table 3), indicating that the jams turned more dull and orangered during storage at these conditions. There was significant interaction between ripeness and storage time (R  S) for hue, i.e. the

changes in hue during storage was more extensive in jams prepared from the least ripe fruits (Table 2). The average hue values did not differ significantly among cultivars (Table 3), however, significant interactions between cultivar and storage (C  S) was found. Jams made of the cultivar ‘Blink’ were more affected by storage, especially during the first three months of storage (Table 2). Those changes in colour may be connected with the formation of brown polymers made by TMA transformations and additionally reinforced by simultaneously vitamin C and sugar degradation (Krifi & Metche, 2000). After 3 months of storage, 60% degradation of TMA was observed in jams prepared from nearly ripe fruits, 52% in jams made from ripe fruits and 50% in jams from fully ripe fruits. After six months, a reduction of 85%, 75% and 70%, respectively, was observed. Freshly processed jams from ‘Blink’ contained higher TMA than jams from ‘Polka’ and ‘Senga Sengana’ (Table 2). However, the rapid pigment degradation observed during the first three months of storage was most extensive in jams made from ‘Blink’

Table 3 Influence of ripeness, cultivar, storage time and storage temperature on colour parameters (L⁄, chroma and hue) and concentrations (mg/100 g FW) of total monomeric anthocyanins (TMA), ascorbic acid and total phenolics (TP) in strawberry jam.

a b

L⁄

Chroma

⁄⁄

⁄⁄

⁄⁄⁄

⁄⁄

⁄⁄⁄

ns

ns ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄

Ascorbic acid

TP

⁄⁄⁄

⁄

ns

ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄

ns ns

ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄

⁄

⁄

⁄⁄⁄⁄

⁄⁄⁄

ns

ns

ns

ns

⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

ns

ns

ns

⁄⁄⁄

ns ns ns

12.6a 11.4ab 9.8b

14.5b 16.0a 16.6a

35.9a 33.8a 31.1b

5.9a 5.6a 8.7b

10.2a 9.1b 9.9a

96a 97a 102a

Cultivar ‘Blink’ ‘Polka’ ‘Senga Sengana’

11.9a 12.3a 9.7b

16.2a 16.8a 14.1b

33.3a 34.5a 32.9a

7.3a 6.7a 6.3a

6.1c 10.8b 12.3a

119a 95 b 80c

Storage Fresh processed 3 Months 6 Months

11.3a 11.1a 11.4a

20.2a 14.5b 12.2c

27.9c 32.5b 40.6a

11.8a 5.3b 3.0c

22.6a 4.7b 1.5c

97b 91c 107a

Temperature 4 °C 20 °C

11.2a 11.3a

17.0a 14.4b

28.3b 38.6a

8.5a 5.1b

10.5a 9.0b

100a 97b

Significancea Ripeness (R) Cultivar (C) Storage time (S) Storage temperature (T) CR CS RS RT ST CRT

ns ns ns ns ns

Valuesb Ripeness Nearly ripe Ripe Fully ripe

Hue

TMA

Level of significance: ⁄p 6 0.05; ⁄⁄p 6 0.01; ⁄⁄⁄p 6 0.001; ns – non significant. Average values. Values with different letters are significantly different (p 6 0.05) based on Tukey’s comparison test.

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S.P. Mazur et al. / Food Chemistry 146 (2014) 412–422

(C  S interaction), giving almost the same average TMA content for all cultivars (Table 3). The TMA degradation was highly affected both by length of storage and high temperature (Table 3). 4.2.2. Individual phenolic compounds The most abundant anthocyanins in fresh strawberry jams were pelargonidin-3-glucoside (Pg-3-glc) (74.3%) followed by pelargonidin-3-malonylglucoside (Pg-3-malglc) (16.9%), cyanidin-3-glucoside (Cyd-3-glc) (6.2%) and pelargonidin-3-rutinoside (Pg-3-rut) (2.7%) (Table 4). The concentrations of all individual anthocyanins were in average 2-fold higher in fresh jams prepared from fully ripe fruits compared with jams prepared from nearly ripe fruits. The anthocyanin composition differed between the three cultivars. Jams made from Blink had the highest content of Cyd-3-glc and Pg3-glc, but did not contain Pg-3-rut. The anthocyanin composition in jams was as reported for the berries (Aaby et al., 2012). The concentration of anthocyanins decreased more during the first three months of storage than during the next 3 months, and jams stored at 20 °C contained only half of the anthocyanin content as jams stored at 4 °C. All main factors and all two factor interactions, except for C  T for Pg-3-glc, affected significantly content of all individual anthocyanins (Table 5). These results are in fairly good agreement with the results based on colourimetric measurement of anthocyanins (TMA) (Section 3.2.1, Table 3). Agrimoniin, the major ellagitannin in strawberries (Aaby et al., 2012), and ellagic acid conjugates (EAC), comprising ellagic acid and two ellagic acid glycosides, were quantified (Table 4). The content of these compounds containing ellagic acid was highest in jams prepared from ‘Blink’, while there was no effect of ripeness of the fruits (Table 5). The findings in jams were not in accordance with the findings in berries, where no differences between cultivars were found and the least ripe berries contained the highest concentrations of agrimoniin and ellagic acid conjugates (Aaby et al., 2012). The concentrations of quantified EAC increased during storage. The achenes contain higher levels of EAC than the pulp (Aaby, Skrede, & Wrolstad, 2005; Williner, Pirovani, & Güemes, 2003), and release from the achenes to the pulp during storage may facilitate extraction of these compounds and thus an apparent increase in EAC. The increase observed may also be due to conversion to compounds quantified in the study, especially ellagic acid, which has been shown to increase during storage in berry products due to hydrolysis of ellagitannins present (Aaby et al., 2007; Zafrilla, Ferreres, & Tomás-Barberán, 2001). In the present study, higher EAC content was found in jams stored at low temperature (Table 5). The effect of temperature was dependent on cultivar. The contents of flavonols, cinnamoyl glucose and coumaroyl hexose increased with ripeness and were 1.3- to 2.4-fold higher in jams prepared from the most ripe fruits compared to the least ripe fruits (Table 5). The highest concentration of flavonols was found in jams prepared from Blink, which is in accordance with findings in the berries (Aaby et al., 2012). Stored jams had higher flavonol contents than freshly prepared jams, with no significant effect of storage temperature. The content of coumaroyl hexose was not affected by cultivar and there were observed only small changes during storage of the jams. Unlike the content of most other phenolic compounds, the cinnamoyl glucose content was lowest in jams made from ‘Blink’. The concentration of cinnamoyl glucose decreased during storage, but was not significantly affected by storage temperature. 3.2.2. Total ascorbic acid content In contrast to the highest ascorbic acid content observed in fruits of ‘Blink’ (Table 1), the jams made from ‘Blink’ contained lower concentrations of ascorbic acid than jams made from ‘Polka’ and ‘Sengana Sengana’ (Table 3). Thus, the highest percentage loss of vitamin C during processing was observed in ‘Blink’ (Tables 1 and 2). After six months of storage, in average for both storage

temperatures, the highest ascorbic acid preservation was found in jams made of ‘Senga Sengana’ (13.9%), lower in jams of ‘Polka’ (3.2%) and no in jams of ‘Blink’ (0%). At the same time, clear distinction in preservation of ascorbic acid was found in jams made from fruits at different ripeness stages from ‘Senga Sengana’ (nearly ripe 9.8%, ripe 14.3%, fully ripe 17.6%), with less obvious difference in jams made for Polka (2.7%, 3.1% and 3.6%, respectively). The rapid degradation of ascorbic acid during the first three months of storage was significantly higher when stored at 20 °C compared to 4 °C (Table 3). This is in agreement with previous studies (Aaby et al., 2007; Patras et al., 2009; Spayd & Morris, 1981). Ascorbic acid is found to have negative effects on colour stability in berry products, and the content of ascorbic acid have also been reported to have a negative correlation with taste (Skrede, 1982). 3.2.3. TP content The TP content in freshly processed jams made from fruits of different ripening stages were quite similar (Table 2). Regardless of ripeness, cultivar or storage temperature, the TP content in the jams decreased during the first three months of storage followed by a significant increase (Table 3). The highest average TP content was detected in jams prepared from fully ripe fruits and the lowest from nearly ripe fruits, but no significant differences were found. However, there were significant interactions between ripeness and storage time (R  S), ripeness and cultivar (C  R) and cultivar and storage time (C  S). The TP content in jams prepared from nearly ripe fruits decreased during the first 3 months of storage, while TP in jams prepared from more ripe fruits was almost unchanged regardless of storage temperature (Table 2). During the first 3 months of storage, the loss of TP was insignificant for all cultivars. During the last 3 months, TP increased in all jams prepared from ‘Polka’ and ‘Senga Sengana’, while in ‘Blink’ a further TP decrease was observed. The highest average TP content in jams, regardless of ripeness stage, was found in ‘Blink’. This may partly be due to high content of anthocyanins, agrimoniin, EAC and flavonols in this cultivar (Table 5). Significantly higher amounts of TP were detected in jams stored at 4 °C compared to jams stored at 20 °C. Spayd and Morris (1981) observed a small increase in TP content after 12 months of storage. This was most significant in jams stored at lower temperature and with a lower content of immature fruits, while Hartmann et al. (2008) reported a slow degradation of TP during storage of different strawberry products independently of choice of processing method. It is difficult to explain these contradictory observations of TP transformation, but Nicoli, Anese, Parpinel, Franceschi, and Lerici (1997) in addition to Nicoli, Anese, and Parpinel (1999) suggested that loss or formation of different bioactive compounds in foods may be influenced by both different processing methods as well as interactions between phytochemicals and different food components during storage. 3.2.4. Correlations As expected, a high positive correlation (R = 1.00, p < 0.001) was found between total monomeric anthocyanins measured colorimetrically (TMA) and total content of anthocyanins measured as the sum of individual anthocyanins after HPLC-analysis (results not shown). High correlations were also found between TMA and individual anthocyanins, except for Pg-3-rut (Table 6), probably because this anthocyanin was not present in jams of the cultivar ‘Blink’. There was no significant correlation between the content of individual anthocyanins and TMA and instrumentally measured lightness (L⁄). However, anthocyanins were highly positively correlated with chroma and negative correlated with hue values. That means that samples with low content of anthocyanins, i.e. stored strawberry jams, were associated with higher hue-values and more orange colour indicating that the colour parameters chroma and

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Table 4 Concentrations of selected phenolic compounds (mg/100 g FW) in strawberry jams of nearly ripe, ripe and fully ripe fruits of the cultivars ‘Blink’, ‘Polka’ and ‘Senga Sengana’ during 0, 3 and 6 months of storage at 4 and 20 °C.a Cyd-3-glc

Pg-3-glc

Pg-3-rut

Pg-3-malglc

EAC

Flavonols

Coum-hex

Cinn-Glc

Agrimoniin

1.5 ± 0.0 0.5 ± 0.0 0.3 ± 0.0 0.8

10.8 ± 0.1 7.7 ± 0.1 8.8 ± 0.5 9.1

nd 0.6 ± 0.0 0.4 ± 0.0 0.3

2.0 ± 0.0 3.1 ± 0.1 1.3 ± 0.1 2.2

1.1 ± 0.0 1.0 ± 0.0 0.6 ± 0.0 0.9

2.7 ± 0.0 0.5 ± 0.0 0.4 ± 0.0 1.2

1.5 ± 0.0 1.4 ± 0.0 1.4 ± 0.1 1.4

0.8 ± 0.0 3.1 ± 0.2 2.9 ± 0.1 2.3

5.9 ± 0.2 1.5 ± 0.4 1.7 ± 0.1 3.0

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

2.0 ± 0.0 0.6 ± 0.0 0.6 ± 0.0 1.1

16.5 ± 0.2 9.7 ± 1.5 12.0 ± 0.3 12.7

nd 0.6 ± 0.1 0.6 ± 0.0 0.4

3.0 ± 0.0 3.5 ± 0.6 1.8 ± 0.0 2.8

1.2 ± 0.0 0.9 ± 0.1 0.6 ± 0.0 0.9

2.7 ± 0.0 0.7 ± 0.0 0.7 ± 0.0 1.3

2.1 ± 0.0 1.9 ± 0.6 2.3 ± 0.1 2.1

0.9 ± 0.1 5.1 ± 0.0 4.8 ± 0.1 3.6

5.7 ± 0.9 2.1 ± 0.2 2.0 ± 0.4 3.3

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

2.6 ± 0.0 1.0 ± 0.0 1.0 ± 0.1 1.5

23.7 ± 0.0 15.9 ± 0.6 16.4 ± 1.5 18.7

nd 1.5 ± 0.1 0.9 ± 0.1 0.8

4.9 ± 0.0 5.5 ± 0.2 2.4 ± 0.2 4.3

1.0 ± 0.0 1.0 ± 0.0 0.7 ± 0.1 0.9

3.0 ± 0.0 0.8 ± 0.0 1.0 ± 0.1 1.6

3.8 ± 0.0 3.5 ± 0.2 3.3 ± 0.3 3.5

2.9 ± 0.1 5.7 ± 0.0 6.8 ± 0.6 5.1

4.6 ± 0.0 1.3 ± 0.6 2.4 ± 0.7 2.8

Jam stored for 3 months at 4 °C Nearly ripe ‘Blink’ 0.5 ± 0.0 ‘Polka’ 0.3 ± 0.0 ‘Senga’ 0.3 ± 0.0 Mean 0.3

3.9 ± 0.0 4.7 ± 0.3 7.4 ± 0.2 5.3

nd 0.4 ± 0.0 0.3 ± 0.0 0.2

0.6 ± 0.0 1.7 ± 0.1 1.0 ± 0.0 1.1

1.6 ± 0.0 0.8 ± 0.0 1.2 ± 0.0 1.2

2.4 ± 0.1 0.5 ± 0.1 1.5 ± 0.0 1.4

1.4 ± 0.0 1.3 ± 0.0 1.4 ± 0.0 1.4

0.5 ± 0.0 2.9 ± 0.0 1.6 ± 0.0 1.7

5.6 ± 0.2 1.4 ± 0.1 3.1 ± 0.2 3.3

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

1.1 ± 0.0 0.5 ± 0.0 0.4 ± 0.0 0.7

8.7 ± 0.2 7.9 ± 0.2 10.0 ± 0.4 8.9

nd 0.5 ± 0.0 0.4 ± 0.0 0.3

1.5 ± 0.0 2.6 ± 0.0 1.5 ± 0.1 1.9

1.6 ± 0.1 0.8 ± 0.1 1.1 ± 0.0 1.2

3.1 ± 0.0 0.8 ± 0.1 1.4 ± 0.0 1.7

2.2 ± 0.0 1.8 ± 0.0 2.1 ± 0.1 2.0

1.1 ± 0.0 6.0 ± 0.5 1.1 ± 0.0 2.8

5.7 ± 0.1 2.1 ± 0.6 2.0 ± 0.0 3.3

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

1.5 ± 0.0 0.7 ± 0.0 0.6 ± 0.0 0.9

13.1 ± 0.0 11.6 ± 0.3 11.7 ± 0.9 12.1

nd 1.1 ± 0.0 0.6 ± 0.0 0.6

2.6 ± 0.0 3.8 ± 0.1 1.7 ± 0.1 2.7

1.8 ± 0.0 0.7 ± 0.1 1.5 ± 0.0 1.3

3.6 ± 0.0 1.1 ± 0.2 1.7 ± 0.0 2.1

3.7 ± 0.0 3.2 ± 0.1 2.9 ± 0.2 3.3

2.7 ± 0.1 1.5 ± 0.2 2.9 ± 0.1 2.4

5.7 ± 0.2 2.5 ± 1.5 2.1 ± 0.2 3.4

Jam stored for 3 months at 20 °C Nearly ripe ‘Blink’ nd ‘Polka’ nd ‘Senga’ nd Mean 0.0

0.3 ± 0.0 1.4 ± 0.0 2.9 ± 0.2 1.5

nd nd 0.2 ± 0.1 0.1

nd 0.3 ± 0.0 0.3 ± 0.0 0.2

1.8 ± 0.1 0.8 ± 0.0 1.3 ± 0.1 1.3

2.5 ± 0.1 0.6 ± 0.1 1.7 ± 0.0 1.6

1.2 ± 0.0 0.9 ± 0.0 1.5 ± 0.1 1.2

0.5 ± 0.0 5.1 ± 0.1 1.0 ± 0.1 2.2

5.7 ± 0.8 2.5 ± 0.1 3.3 ± 0.1 3.8

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

nd 0.2 ± 0.0 nd 0.1

0.6 ± 0.0 2.6 ± 0.1 4.0 ± 0.1 2.4

nd 0.2 ± 0.0 0.2 ± 0.0 0.1

nd 0.5 ± 0.0 0.4 ± 0.0 0.3

1.6 ± 0.0 0.8 ± 0.0 1.1 ± 0.0 1.2

3.5 ± 0.0 1.5 ± 0.1 1.4 ± 0.1 2.1

1.8 ± 0.0 1.8 ± 0.0 2.0 ± 0.0 1.9

0.9 ± 0.0 0.9 ± 0.0 2.8 ± 0.1 1.5

7.3 ± 0.0 2.7 ± 0.1 1.6 ± 0.2 3.9

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

0.2 ± 0.0 0.3 ± 0.0 0.3 ± 0.0 0.2

2.1 ± 0.0 4.6 ± 0.1 5.6 ± 0.0 4.1

nd 0.5 ± 0.0 0.3 ± 0.0 0.3

0.1 ± 0.0 0.9 ± 0.0 0.4 ± 0.0 0.5

1.6 ± 0.0 0.6 ± 0.0 1.4 ± 0.1 1.2

3.5 ± 0.0 1.2 ± 0.1 1.5 ± 0.0 2.1

3.2 ± 0.1 3.2 ± 0.0 2.7 ± 0.0 3.0

2.2 ± 0.0 2.9 ± 0.1 1.6 ± 0.0 2.2

5.2 ± 0.0 1.2 ± 0.0 3.1 ± 0.4 3.2

Jam stored for 6 months at 4 °C Nearly ripe ‘Blink’ 0.2 ± 0.0 ‘Senga’ nd Mean 0.1

2.3 ± 0.0 3.4 ± 0.0 2.9

nd 0.2 ± 0.0 0.1

0.4 ± 0.0 0.5 ± 0.0 0.4

1.6 ± 0.0 1.2 ± 0.0 1.4

2.5 ± 0.0 0.8 ± 0.1 1.6

1.4 ± 0.0 1.7 ± 0.0 1.5

0.5 ± 0.0 2.2 ± 0.1 1.3

6.5 ± 0.1 4.1 ± 0.1 5.3

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

0.6 ± 0.0 0.2 ± 0.0 0.3 ± 0.0 0.4

5.1 ± 0.1 4.4 ± 0.1 6.0 ± 0.0 5.2

nd 0.4 ± 0.0 0.4 ± 0.0 0.2

0.8 ± 0.0 1.2 ± 0.0 0.7 ± 0.0 0.9

1.5 ± 0.4 2.1 ± 0.0 1.1 ± 0.1 1.5

2.9 ± 0.1 2.0 ± 0.1 0.9 ± 0.0 1.9

2.0 ± 0.0 2.0 ± 0.0 2.4 ± 0.1 2.2

0.9 ± 0.0 1.4 ± 0.1 4.0 ± 0.1 2.1

6.0 ± 0.7 4.6 ± 0.2 2.7 ± 0.5 4.5

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

1.1 ± 0.0 0.5 ± 0.0 0.4 ± 0.0 0.7

10.4 ± 0.3 7.7 ± 0.1 7.5 ± 0.1 8.5

nd 0.8 ± 0.0 0.5 ± 0.0 0.4

1.9 ± 0.0 2.2 ± 0.0 0.8 ± 0.0 1.6

1.7 ± 0.2 2.1 ± 0.0 1.1 ± 0.0 1.6

3.4 ± 0.4 2.3 ± 0.0 1.2 ± 0.0 2.3

3.5 ± 0.1 4.3 ± 0.1 3.0 ± 0.0 3.6

2.5 ± 0.1 2.7 ± 0.0 5.0 ± 0.0 3.4

5.2 ± 0.2 4.7 ± 0.1 3.4 ± 0.4 4.4

0.2 ± 0.0 0.3 ± 0.0 0.4 ± 0.0

nd nd nd

nd nd nd

1.1 ± 0.0 1.5 ± 0.0 1.4 ± 0.1

2.6 ± 0.0 1.9 ± 0.0 0.8 ± 0.0

1.3 ± 0.0 1.3 ± 0.0 1.5 ± 0.0

0.6 ± 0.0 0.7 ± 0.1 1.8 ± 0.1

6.0 ± 0.1 4.8 ± 0.1 3.7 ± 0.2

Freshly processed Nearly ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

jam

Jam stored for 6 months at 20 °C Nearly ripe ‘Blink’ nd ‘Polka’ nd ‘Senga’ nd

(continued on next page)

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S.P. Mazur et al. / Food Chemistry 146 (2014) 412–422

Table 4 (continued) Cyd-3-glc

Pg-3-glc

Pg-3-rut

Pg-3-malglc

EAC

Flavonols

Coum-hex

Cinn-Glc

Agrimoniin

Mean

0.0

0.3

0.0

0.0

1.3

1.8

1.4

1.0

4.8

Ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

nd nd nd 0.0

0.5 ± 0.0 0.7 ± 0.0 0.6 ± 0.0 0.6

nd nd nd 0.0

0.0 ± 0.0 0.0 ± 0.0 0.0 ± 0.0 0.0

1.2 ± 0.3 1.4 ± 0.0 1.4 ± 0.0 1.3

3.0 ± 0.1 1.6 ± 0.0 1.0 ± 0.1 1.8

2.2 ± 0.0 1.4 ± 0.0 2.2 ± 0.1 1.9

1.2 ± 0.1 1.2 ± 0.0 3.1 ± 0.0 1.8

5.7 ± 0.6 3.9 ± 0.2 3.8 ± 0.0 4.5

Fully ripe ‘Blink’ ‘Polka’ ‘Senga’ Mean

nd nd nd 0.0

1.3 ± 0.0 1.6 ± 0.0 1.0 ± 0.0 1.3

0.0 ± 0.0 0.2 ± 0.0 nd 0.1

0.0 ± 0.0 0.2 ± 0.0 0.0 ± 0.0 0.1

1.0 ± 0.1 1.7 ± 0.0 1.4 ± 0.1 1.4

3.1 ± 0.0 1.9 ± 0.0 1.1 ± 0.0 2.0

3.5 ± 0.1 2.4 ± 0.0 2.6 ± 0.1 2.9

2.4 ± 0.0 2.3 ± 0.1 4.0 ± 0.1 2.9

5.9 ± 0.1 3.7 ± 0.1 3.4 ± 0.3 4.3

a Abbreviations: cyd, cyanidin; pg, pelargonidin; glc, glucoside; rut, rutinoside; mal, malonyl; EAC, ellagic acid conjugates; coum-hex, coumaroyl hexose; cinn-glu, cinnamoyl glucose.

Table 5 Influence of ripeness, cultivar, storage time and storage temperature on the concentration (mg/100 g FW) of selected phenolic compoundsa in strawberry jams. Cyd-3-glc

Pg-3-glc

Pg-3-rut

Pg-3-malglc

EAC

Flavonols

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄

ns

⁄⁄⁄

⁄⁄

⁄⁄

⁄⁄⁄

⁄⁄⁄

ns

⁄

⁄⁄⁄

ns ns

ns ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

ns

⁄⁄⁄

⁄

⁄⁄⁄

⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄

⁄⁄⁄

⁄

⁄⁄

ns ns

ns ns ns

ns ns ns ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄

⁄

ns ns

ns ns ns

⁄⁄

⁄⁄⁄

ns

ns

⁄⁄

ns ns

⁄⁄⁄

⁄

ns

ns ns ns ns

ns

ns ns

Concentrations (mg/100 g FW)c Ripeness Nearly ripe 0.4c Ripe 0.5b Fully ripe 0.8a

4.8c 7.1b 10.6a

0.2c 0.3b 0.5a

1.0c 1.4b 2.2a

1.2a 1.2a 1.2a

Cultivar ‘Blink’ ‘Polka’ ‘Senga Sengana’

1.0a 0.4b 0.3b

8.4a 6.7c 7.5b

0.0c 0.6a 0.4b

1.5b 2.2a 1.0c

Storage Fresh processed 3 Months 6 Months

1.1a 0.4b 0.2b

13.5a 5.7b 3.1c

0.5a 0.3b 0.2c

Temperature 4 °C 20 °C

0.7a 0.4b

9.5a 5.6b

0.4a 0.2b

Significanceb Ripeness (R) Cultivar (C) Storage time (S) Storage temperature (T) CR CS CT RS RT ST CRS CRT CST RST

⁄

ns

ns ⁄⁄⁄

Coum-hex

Cinn-glc

Agrimoniin

⁄⁄⁄

⁄⁄⁄

ns

ns

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

⁄⁄⁄

ns

ns ns ns ns ns ns ns ns

ns ns ns ns ns ns ns ns

1.5c 1.7b 1.9a

1.4c 2.0b 3.3a

1.8b 2.6b 3.5a

3.8a 3.8a 3.5a

1.4a 1.1b 1.0b

2.9a 1.1b 1.1b

2.3a 2.2a 2.2a

1.4b 3.3a 3.3a

5.7a 2.6b 2.7b

3.0a 1.1b 0.5c

0.9b 1.2a 1.4a

1.4b 1.9a 1.9a

2.4a 2.1b 2.3ab

3.7a 2.1b 2.2b

3.0c 3.5b 4.6a

2.0a 1.1b

1.2a 1.1b

1.7a 1.7a

2.4a 2.2b

2.8a 2.5a

3.6a 3.7a

⁄⁄

a Abbreviations: cyd; cyanidin; pg, pelargonidin; glc, glucoside; rut, rutinoside; mal, malonyl; EAC, ellagic acid conjugates; coum-hex, coumaroyl hexose; cinn-glu, cinnamoyl glucose. b Significance: ⁄p 6 0.05; ⁄⁄p 6 0.01; ⁄⁄⁄p 6 0.001; ns – non significant. c The values are averages. Values in a column for a factor with different letters are different (p 6 0.05) based on Tukey’s comparison test.

hue could be used to predict the TMA content in strawberry jams, or the opposite. The TMA content correlated positively with cinnamoyl glucoside and coumaroyl hexose, which all were present in higher concentrations in more ripe berries. The content of anthocyanins and ascorbic acid in the jams were also positively correlated, probably due to their rapid degradation during storage. No correlations were found between the content of anthocyanins and EAC, flavonols or TP in the samples. This accentuate that other compounds than anthocyanins make the largest contribution to TP in strawberry products, especially in stored products, as previously shown for strawberry purees (Aaby et al., 2007). Ascorbic acid correlated negatively with EAC and flavonols, possibly due to the fact that the latter compounds were presented in higher concentrations

in the jams of ‘Blink’, as distinct from ascorbic acid (Tables 3 and 5). A positive correlation was found between ascorbic acid and cinnamoyl glucose, both present in lowest concentrations in jams made from ‘Blink’.

4. Conclusion Quality parameters and chemical composition of fruits of three strawberry cultivars were significantly affected by ripeness of the fruits. The degradation of phenolic compounds and ascorbic acid during jam processing was generally low compared to the changes occurred during storage. Although the differences in ripeness of the

421

S.P. Mazur et al. / Food Chemistry 146 (2014) 412–422 Table 6 Pearson correlationsa between selected compoundsb and quality attributes in strawberry jams. Cyd-3glc Pg-3-glc Pg-3malglc Pg-3-rut Agrimoniin Cinn-glc Coum-hex EA Flavonols L⁄ Chroma Hue Ascorbic acid TMA TP

Pg-3-glc

Pg-3malglc

Pg-3-rut

Agrimoniin

Cinn-glc

0.89⁄⁄⁄ 0.77⁄⁄⁄

0.88⁄⁄⁄

0.11 0.12 0.12 0.43⁄⁄ 0.06 0.30⁄ 0.11 0.74⁄⁄⁄ 0.58⁄⁄⁄ 0.46⁄⁄

0.47⁄⁄ 0.23 0.38⁄ 0.50⁄⁄⁄ 0.26 0.01 0.26 0.79⁄⁄⁄ 0.73⁄⁄⁄ 0.68⁄⁄⁄

0.63⁄⁄⁄ 0.32⁄ 0.41⁄⁄ 0.43⁄⁄ 0.28 0.14 0.12 0.83⁄⁄⁄ 0.63⁄⁄⁄ 0.67⁄⁄⁄

0.65⁄⁄⁄ 0.56⁄⁄⁄ 0.39⁄⁄ 0.36⁄ 0.53⁄⁄⁄ 0.18 0.46⁄⁄ 0.43⁄⁄ 0.55⁄⁄⁄

0.60⁄⁄⁄ 0.01 0.64⁄⁄⁄ 0.86⁄⁄⁄ 0.26 0.20 0.27 0.51⁄⁄⁄

0.34⁄ 0.47⁄⁄⁄ 0.55⁄⁄⁄ 0.35⁄ 0.25 0.28 0.49⁄⁄⁄

0.89⁄⁄⁄ 0.35⁄

0.99⁄⁄⁄ 0.03

0.92⁄⁄⁄ 0.02

0.51⁄⁄⁄ 0.35⁄

0.25 0.71⁄⁄⁄

0.38⁄ 0.35⁄

Coumhex

0.11 0.27 0.33⁄ 0.35 0.33⁄ 0.06 0.54⁄⁄⁄ 0.21

EAC

Flavonols

L⁄

Chroma

Hue

0.60⁄⁄⁄ 0.26 0.21 0.24 0.54⁄⁄⁄

0.16 0.01 0.04 0.45⁄⁄

0.21 0.30⁄ 0.11

0.59⁄⁄⁄ 0.64⁄⁄⁄

0.47⁄⁄⁄

0.25 0.60⁄⁄⁄

0.02 0.65⁄⁄⁄

0.26 0.35⁄

0.81⁄⁄⁄ 0.17

0.73⁄⁄⁄ 0.18

Ascorbic acid

0.66⁄⁄⁄ 0.32⁄

TMA

0.03

a

Correlation coefficient, R. Level of significance: ⁄p 6 0.05; ⁄⁄p 6 0.01; ⁄⁄⁄p 6 0.001. b Abbreviations: cyd, cyanidin; pg, pelargonidin; glc, glucoside; rut, rutinoside; mal, malonyl; EAC, ellagic acid conjugates; coum-hex, coumaroyl hexose; cinn-glu, cinnamoyl glucose.

fruits were quite small it affected the changes that occurred in the jams during storage. Concentrations of anthocyanins and ascorbic acid decreased the most in jams made from the least ripe fruits. Consequently, colour changed the most, i.e. chroma decreased and hue increased during storage. In addition, stability of anthocyanins and colour was affected by genotype, being the most stable in jams made from ‘Senga Sengana’ and least stable in jams made from ‘Blink’. Our results indicate that fully ripe fruits should be used for processing to obtain a product with high colour stability during storage. Further, stability of phenolic compounds and colour is affected by cultivar. However, it is difficult to predict quality and stability of jams from quality and chemical composition of the fruits, therefore suitability for processing and storage of new cultivars should be tested in stability trials. Acknowledgements This work was supported by the Norwegian Research Council (Project 1810148) and the Norwegian industry partners: Lerum AS, Tine BA, Findus AS, Stabburet AS and Røra AS. The authors wish to thank Mona Ringstad at Nofima AS for excellent guidance and technical assistance with the analyses of ascorbic acid and industry partners for production of jams. The authors also wish to thank Torfinn Torp from the Norwegian Institute for Agricultural and Environmental Research for brilliant guidance with statistical analysis. References Aaby, K., Mazur, S., Nes, A., & Skrede, G. (2012). Phenolic compounds in strawberry (Fragaria  ananassa Duch.) fruits; composition in 27 cultivars and changes during ripening. Food Chemistry, 132, 86–97. Aaby, K., Skrede, G., & Wrolstad, R. E. (2005). Phenolic composition and antioxidant activities in flesh and achenes of strawberries (Fragaria ananassa). Journal of Agricultural and Food Chemistry, 53(10), 4032–4040. Aaby, K., Wrolstad, R. E., Ekeberg, D., & Skrede, G. (2007). Polyphenol composition and antioxidant activity in strawberry purees; impact of achene level and storage. Journal of Agricultural and Food Chemistry, 55(13), 5156–5166. Bøgh-Sørensen, L. (2002). Dry matter in foodstuffs. The vacuum method. In Nordic committee on food analysis. Espoo, Finland, 169 García-Viguera, C., Zafrilla, P., Romero, F., Abellán, P., Artés, F., & Tomás Barberán, F. (1999). Color stability of strawberry jam as affected by cultivar and storage temperature. Journal of Food Science, 64(2), 243–247. Giusti, M. M., & Wrolstad, R. E. (2001). Characterization and measurement of anthocyanins by UV-visible spectroscopy. In R. E. Wrolstad (Ed.), Current protocols in food analytical chemistry. New York: John Wiley & Sons Inc. [Unit F1.2.1–Unit F1.2.13].

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