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Changes in fruit firmness, quality traits and cell wall constituents of two highbush blueberries (Vaccinium corymbosum L.) during postharvest cold storage
Scientia Horticulturae 246 (2019) 557–562
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Changes in fruit firmness, quality traits and cell wall constituents of two highbush blueberries (Vaccinium corymbosum L.) during postharvest cold storage Binghua Liua,b, Kaifang Wanga,b, Xiuge Shua, Jing Lianga,b, Xiaoli Fana, Lei Suna,b, a b
T
⁎
Shandong Academy of Forestry, 250014, Jinan, Shandong, China Economic Forest Products Quality Inspection Test Center of State Forestry Administration (Jinan), 250014, Jinan, Shandong, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Blueberry Cell wall composition Firmness Softening Weight loss
Blueberries are now the second most economically important soft fruit. However, they are highly perishable and susceptible to rapid spoilage. Softening is one of the main reasons for short postharvest life of blueberries. The changes of fruit firmness, weight loss, flavor quality and cell wall composition of Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra were investigated in this study. The results showed that fruit firmness declined concomitantly with the increase of fruit weight loss and water soluble pectin (WSP) content paralleled by a decrease in the content of cellulose (CEL) and hemicellulose (HCEL) during postharvest cold storage at 0 ℃ and 90% relative humidity. Compared with Sierra blueberries, Bluecrop blueberries were much more resistant to postharvest cold storage as manifested by the higher values in fruit flavor quality and firmness which were associated with less weight loss, lower WSP content and higher amount of CEL and HCEL.
1. Introduction Blueberries (Vaccinium spp.), the second most important soft fruit species after strawberry, are highly appreciated for their various human health benefits, unique taste, and nutritional value (Giongo et al., 2013). In particular, blueberries contain high amounts of phenolic compounds, including anthocyanins, flavonols, chlorogenic acid and procyanidins (Wang et al., 2017), and have been illustrated a wide diversity of bioactivities such as antioxidant, antimicrobial, antiproliferative, lifespan-prolonging, anti-inflammatory, carcinogenesis preventive, and cardioprotective activities (Bunea et al., 2013; de Souza et al., 2014; Diaconeasa et al., 2015; Figueira et al., 2016; Folmer et al., 2014). However, blueberries are highly perishable and susceptible to rapid spoilage because of microbial decay, mechanical damage, and moisture and nutritional loss (Hancock et al., 2008; Paniagua et al., 2014). One of the main reasons for short shelf-life is postharvest softening, which may influence not only fruit quality, but also its storage life, transport ability and resistance of postharvest diseases, thereby significantly reducing commercial value of blueberry fruit (Chen et al., 2015). Temperature is the most important environmental factor affecting blueberry quality during postharvest storage. Postharvest storage at 0–5 ℃ and 90–95 % relative humidity (RH) is recommended for
extending the postharvest life of blueberry by delaying senescence and preserving fruit quality of blueberry (Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014). Fruit quality is a consequence of many biochemical processes that result in changes of its intrinsic properties such as color, texture, flavor and aroma, together with the exterior appearance (size, color and shape) and nutritional value (Bianchi et al., 2016). Postharvest changes in blueberry quality during cold storage are determined by diverse physiological, biochemical, physical and pathological processes (Chen et al., 2015; Chiabrando et al., 2009; Giongo et al., 2013; Zhou et al., 2014), and have been reported correlated with a number of factors including fruit firmness, fruit weight loss (WL), total soluble solids (TSS) content and effective acidity (pH) (Chiabrando et al., 2009; Lobos et al., 2014; Saftner et al., 2008). As well as TSS and pH, fruit firmness is one of the most important quality properties that influence acceptability by consumers (Zhang et al., 2010). In blueberries, fruit firmness is strongly associated with the general concept of fruit freshness and quality, and affected by cellular organelles and biochemical constituents, water content, and cell wall compositions (Chiabrando et al., 2009; Saftner et al., 2008; Silva et al., 2005). Changes in firmness of blueberry occur due to changes in the chemistry of the primary cell wall components including water soluble pectin (WSP), cellulose (CEL) and
Abbreviations: CEL, cellulose; HCEL, hemicellulose; RH, relative humidity; TSS, total soluble solid; WL, fruit weight loss; WSP, water-soluble pectin ⁎ Corresponding author at: Shandong Academy of Forestry, 250014, Jinan, Shandong, China. E-mail address: [email protected] (L. Sun). https://doi.org/10.1016/j.scienta.2018.11.042 Received 7 September 2018; Received in revised form 5 November 2018; Accepted 14 November 2018 0304-4238/ © 2018 Published by Elsevier B.V.
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hemicelluloses (HCEL) that occur during growth and development or postharvest storage (Chen et al., 2015, 2017a; Deng et al., 2014; Giongo et al., 2013; Konarska, 2015). Therefore, investigating the postharvest changes in fruit firmness and physicochemical compositions will be beneficial to illustrating the fundamental of postharvest quality changes of blueberry during cold storage. In order to test the hypothesis, the present study was designed to observe the dynamic changes in fruit firmness, quality traits (WL, TSS and pH) and cell wall components (WSP, CEL and HCEL) of two highbush blueberries (Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra) during 50 days of postharvest storage at 0 ℃ and 90% RH, as well as the correlation relationships between fruit firmness and physicochemical compositions.
2.2.3. Total soluble solids (TSS) content and pH After the TPA test, three replicates of ten blueberries each cultivar were grinded and centrifuged (Rotofix 32, Hettich Zentrifugen, Tuttlingen, Germany) at 3000 × g for 10 min at 20 ℃. TSS content was measured with a digital handheld refractometer (AtagoPAL-1, Japan). A drop of the filtered juice was carefully placed into the lens and values were recorded. Calibration was made with deionized water and the lens was rinsed between different samples. The pH was measured with a digital portable electrode pH-meter (JENCO 6010, USA) equipped with temperature probe. Rinse the pH electrode and temperature probe with distilled water and immerse them in the 1:10 (v/v) diluted juice to measure pH. Remove any air bubbles trapped around the probe by shaking or stirring the probe.
2. Materials and methods
2.2.4. Cell wall components Cell wall materials were obtained as ethanol insoluble residue using the methods described by Chen et al. (2017a, 2017b, 2015). Briefly, blueberries (10 g) were ground, extracted by 95% (v/v) ethanol and maintained in boiling water for 30 min. to inactivate enzymes. Then the sample was homogenized after cooling and incubated overnight with 90% (v/v) dimethysulphoxide at 4 ℃ to remove starch. The residues were subsequently washed three times with water, 2:1 (v/v) chloroform-ethanol, and acetone, respectively. The isolated cell wall materials were dried overnight in a vacuum oven at 40 ℃ to get the final weight and then stored over silica gel in a vacuum desiccator for further determination. The cell wall materials was fractionated according to the methods of Chen et al. (2017a, 2017b, 2015) and Li et al. (2006). WSP fraction was obtained by suspending cell wall materials in 50 mM sodium acetate buffer (pH 6.5) for 6 h of shaking, and collecting supernatant by centrifuging at 10,000 × g for 10 min at 4 ℃. The sediment was re-suspended three times in 50 mM sodium acetate buffer (pH 6.5) containing 50 mM EDTA, shaken for 6 h, and centrifuged as above. The residue was re-suspended three times again in 50 mM Na2CO3 containing 2 mM EDTA, shaken and centrifuged as above. The remaining residue was resuspended in 4 mM NaOH containing 100 mM NaBH4, shaken and centrifuged. The supernatant was collected as hemicellulosic fraction and the final residue was cellulosic fraction. The WSP content was measured via m-hydroxydiphenyl method by using galacturonic acid as standard (Paul and Jerome, 1982; Wang et al., 2015). Contents of CEL and HCEL were determined via anthrone method by using glucose as standard (Vicente et al., 2005; Wang et al., 2015).
2.1. Fruit material and storage conditions Fruits of two northern highbush blueberry cultivars (Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra) were hand-harvested from five-year-old blueberry plants in a blueberry farm located in Chentuan town (119°27′N, 35°50′E), Rizhao City, Shandong Province, China, in early June of 2017. All fruits at commercial maturity, as determined by complete blue skin color (100% blue coloration), were packed in commercial vented clamshell containers, and then were placed in a 120 L incubator with ice at the bottom, and then were transported to the laboratory in 4 h for experimental treatment. In the laboratory, the fruits were screened for uniform size and maturity. Defective fruits (crushed, cracked, or immature) were eliminated. For each cultivar, the selected fruits were placed in plastic containers with snap-on lids and each contained one hundred fruits. Ten containers per cultivar. The containers were stored in a temperature-controlled cold room under regular storage conditions: normal atmosphere, 0 ℃, with a relative humidity of 90% that has been recommended for maintaining postharvest storage quality of blueberry fruit (Chiabrando et al., 2009). Samples were taken initially and at 10day intervals for physicochemical determination during storage of 50 days. 2.2. Physicochemical determination 2.2.1. Fruit firmness Fruit firmness of blueberries was obtained from texture profile analysis (TPA) test. Instrumental TPA test as described by Chen and Opara (2013) with a 35 mm diameter stainless probe was performed in a Stable Micro Systems TA-XT Plus texture analyzer equipped with an Acoustic Envelop Detector (AED) device (Stable Micro Systems Ltd., Godalming, UK). Samples were compressed to 75% of their original height at a crosshead speed of 2 mm s−1. Each sample was subjected to a two-cycle compression with 5 s between cycles. Data were collected by using Texture Expert Version 1.17 software. The highest value of force required to compress the sample during the first compression cycle was recorded as fruit firmness of blueberry. Prior to the TPA test, samples were kept for 2 h at room temperature (20 ℃), because firmness of most fruits and vegetables was influenced by increasing temperature (Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014).
2.3. Data analysis The experiments were performed by using a completely randomized design. All the measurements were conducted in triplicate. Data were presented as mean ± standard deviation (SD). Statistical analysis was carried out using the SPSS-13.0 for Windows statistical software package (Standard released version 13.0 for Windows; SPSS Inc., IL, USA). Tukey’s HSD (honestly significant difference) post hoc test (P ≤ 0.05) was performed to test the existence of statistical differences between different treatments. Analyses of two-way variance (ANOVA) were used to evaluate the effects of cultivar and cold storage time. Correlation relationships between firmness and physicochemical parameters were determined by using the Pearson’s correlation coefficients test. 3. Results and discussion
2.2.2. Fruit weight loss (WL) WL was calculated as the percentage difference between the initial and the final weight of the plastic containers containing fruit. Weight loss was calculated according to the following equation: WL (%) = (WI − WF)/WI × 100, where WI and WF are the initial and final sample weight (g), respectively. A digital balance (BSA224S Beijing Sartorius, China) with 0.001 g precision was used for these weight measurements.
3.1. Changes in fruit firmness Fruit firmness is one of the most critical quality indices for blueberry (Angeletti et al., 2010; Chen et al., 2017a, 2015; Chiabrando and Giacalone, 2017; Li et al., 2011; Perkins-Veazie et al., 1994). It is typically used as a measure of eating quality, as well as an estimate of 558
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Table 1 Changes in fruit firmness and fruit weight loss (WL) of two highbush blueberry cultivars during postharvest cold storage. Parameters
Firmness (N)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
ANOVA analyses FC FS FC × S
0 10 20 30 40 50
6.82 6.76 6.53 6.45 5.92 5.63
± ± ± ± ± ±
0.13A, 0.07A, 0.09A, 0.08A, 0.12A, 0.16A,
WL (%) Sierra a
6.27 5.93 5.85 5.54 5.07 4.75
a a ab b b
11.38*** 9.52** 7.46*
± ± ± ± ± ±
Bluecrop 0.11B, 0.13B, 0.12B, 0.10B, 0.13B, 0.08B,
a ab b b b b
— 1.06 1.72 2.43 3.45 4.87
± ± ± ± ±
0.10B, 0.22B, 0.18B, 0.26B, 0.20B,
Sierra
b b ab ab a
— 1.17 1.93 3.02 4.11 5.21
± ± ± ± ±
0.25A, 0.15A, 0.15A, 0.22A, 0.14A,
b b ab ab a
10.55** 17.36*** 6.38*
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: storage time effect; FC × S: cultivar × storage time effect. *, **, and ***, significant at P ≤ 0.05, 0.01, and 0.001, respectively.
Although, there were still many different results of those changes of blueberry during storage under experimental conditions (Angeletti et al., 2010; Chen et al., 2017a, 2015; Giongo et al., 2013; Li et al., 2011; Nunez-Barrios et al., 2005). All the variable firmness and weight loss behavior which were previously observed in blueberries validates the responses obtained under the experiment storage conditions which led to either blueberry softening or firming. The significant differences in firmness and WL and their change extents between different blueberry cultivars during postharvest cold storages were mainly associated with their genetic origin property. Previous researches had shown that fruit texture quality of blueberry was influenced by the Vaccinium species (Giongo et al., 2013; Silva et al., 2005) and cultivar (Chen et al., 2017a; Chiabrando et al., 2009; Hancock et al., 2008; Lobos et al., 2014; Li et al., 2011; Paniagua et al., 2014; Saftner et al., 2008). All the above validated that fruit texture quality of blueberry is a trait under genetic control and it has high heritability (Burgher et al., 2002; Edwards et al., 1974), thus with a high potential impact on breeding programs.
storability and resistance to injury of the product during postharvest handling, storage and marketing (Szczesniak, 2002). In recent years, numerous researches on fruit firmness dynamics of blueberry during fruit growth and development or postharvest storage were reported (Chen et al., 2017a, 2015; Chiabrando et al., 2009; Giongo et al., 2013; Li et al., 2011; Paniagua et al., 2014, 2013), and the results showed that changes in fruit firmness of blueberry during growth, ripening, and postharvest storage have a profound effect on consumer acceptability. In the present study, fruit firmness of Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra during postharvest cold storage were measured by using a texture profile analyzer which helps in quality control and fruit development to quantify desired characteristics (Singh et al., 2013). The results showed that fruit firmness was significantly influenced by cultivar (P ≤ 0.001), storage time (P ≤ 0.01) and cultivar × storage time interaction (P ≤ 0.05). Sierra blueberries were softer than Bluecrop blueberries as manifested by the lower value in firmness of Sierra than that of Bluecrop during the postharvest cold storage times (P ≤ 0.05, Table 1). Increasing storage time resulted in a significant decrease (P ≤ 0.05) in fruit firmness of both blueberry cultivars, and a slower decrease was observed in Bluecrop than that in Sierra (Table 1). After 50 days of cold storage, the firmness of Sierra blueberry decreased rapidly from 6.27 N to 4.75 N, while Bluecrop blueberry decreased slowly from 6.82 N to 5.63 N. In addition, the same reduction trend of firmness was observed in both blueberry cultivars, which decreased slightly in the first 10 days and then decreased rapidly (Table 1). Pervious researches showed that WL of blueberry is the major cause of firmness change during postharvest storage (Chen et al., 2017a, 2017b, 2015; Paniagua et al., 2014, 2013). In this study, WL of Bluecrop and Sierra blueberries was determined and the results shown in Table 1. WL was significantly influenced by cultivar (P ≤ 0.01), storage time (P ≤ 0.001) and cultivar × storage time interaction (P ≤ 0.05). WL of Bluecrop and Sierra blueberries significantly increased with the increasing postharvest storage time (P ≤ 0.05, Table 1). Fruit weight of Sierra lost more sharply than Bluecrop, as manifested by the WL value ranged from 1.17% to 5.21% and from 1.06% to 4.87% for Sierra and Bluecrop, respectively (Table 1). Significant difference of WL was found between the two cultivars, and Sierra had higher value in WL than Bluecrop during the 50 days’ storage (P ≤ 0.05, Table 1). Additionally, the results of Pearson’s correlation analysis in Table 4 showed that WL had significant negative correlation relationship with firmness (R = −0.831, P ≤ 0.001). It suggested that maintaining firmness of blueberries for extended storage period could be achieved by preventing fruit weight loss. Changes in fruit firmness and WL of blueberry under the same storage condition have also been reported in other cultivars (Chiabrando et al., 2009; Lobos et al., 2014; Paniagua et al., 2013).
3.2. Changes in fruit flavor quality Fruit quality is a consequence of many biochemical processes that result in changes of its intrinsic properties (color, texture, flavor and aroma), exterior appearance (size, color and shape) and nutritional value (Bianchi et al., 2016). Postharvest changes of blueberry flavor quality, always determined by fruit TSS and pH, play an important role in consumer satisfaction and influence fruit further consumption (Chiabrando et al., 2009; Lobos et al., 2014; Perkins-Veazie et al., 1994; Saftner et al., 2008). In the present study, TSS content and pH in Bluecrop and Sierra blueberries at different postharvest cold storage times were measured. Two-way ANOVA analysis indicated that storage time had significant effect on TSS content (P ≤ 0.01) and pH (P ≤ 0.05) (Table 2). Increasing storage time resulted an increase in TSS content and pH, and a greater increase was observed in Sierra (ranged from 10.49% to 11.02% and from 3.26 to 4.25, respectively) than those in Bluecrop (ranged from 11.32% to 11.66% and from 3.45 to 4.39, respectively) (Table 2). Since blueberry fruit does not have starch to support soluble sugar synthesis after harvest, the little increase in TSS may be a consequence of cell wall degradation (Cordenunsi et al., 2003). Acidity, determined by pH value, was increased during the first 20 days and then kept in stable level (Table 2) that usually related to good storage quality (Chiabrando et al., 2009). Fruit flavor quality of blueberry is a trait under genetic control (Burgher et al., 2002; Perkins-Veazie et al., 1994), and that has been proved by the significant differences among many different blueberry cultivars (Duan et al., 2011; Duarte et al., 2009; Gündüz et al., 2015; 559
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Table 2 Changes in total soluble solid (TSS) content and pH of two highbush blueberry cultivars during postharvest cold storage. Parameters
TSS content (%)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
0 10 20 30 40 50
10.49 10.76 10.68 10.87 11.02 11.26
ANOVA analyses FC FS FC × S
± ± ± ± ± ±
pH Sierra
0.15B, 0.09B, 0.16B, 0.15B, 0.15B, 0.07B,
b
11.32 11.47 11.56 11.52 11.66 11.87
ab b ab ab a
Bluecrop ± ± ± ± ± ±
0.16A, 0.12A, 0.16A, 0.16A, 0.18A, 0.13A,
b
3.26 3.72 4.05 4.16 4.25 4.24
ab ab ab ab a
16.42*** 10.03** 5.28**
± ± ± ± ± ±
Sierra
0.07B, b 0.08A, ab 0.05B, a 0.01B, a 0.07B, a 0.05B, a
3.45 3.78 4.17 4.31 4.39 4.39
± ± ± ± ± ±
0.04A, 0.05A, 0.03A, 0.05A, 0.05A, 0.03A,
b ab a a a a
11.73*** 7.88* 3.24
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: storage time effect; FC × S: cultivar × storage time effect. *, **, and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively. Table 3 Changes in contents of water-soluble pectin (WSP), cellulose (CEL) and hemicellulose (HCEL) of two highbush blueberry cultivars during postharvest cold storage. Parameters
WSP content (mg g−1)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
ANOVA analyses FC FS FC × S
0 10 20 30 40 50
0.27 0.36 0.39 0.42 0.46 0.48
± ± ± ± ± ±
0.01A, b 0.00A, ab 0.00A, ab 0.01B, ab 0.00A, a 0.01B, a
CEL content (mg g−1) Sierra 0.28 0.38 0.41 0.47 0.49 0.53
Bluecrop
± ± ± ± ± ±
0.01A, 0.00A, 0.01A, 0.01A, 0.01A, 0.01A,
b ab ab a a a
3.62 3.45 3.47 3.26 2.98 2.87
± ± ± ± ± ±
0.06A, 0.07A, 0.11A, 0.05A, 0.07A, 0.12A,
HCEL content (mg g−1) Sierra
a a a ab b b
3.47 3.35 3.02 2.88 2.65 2.38
± ± ± ± ± ±
Bluecrop 0.05A, a 0.15A, a 0.12B, ab 0.13B, ab 0.14B, b 0.10B, b
6.86* 13.02*** 8.54**
3.28 10.59*** 5.18*
1.76 1.45 1.28 1.06 0.98 0.87
± ± ± ± ± ±
Sierra
0.02A, 0.07A, 0.05A, 0.05A, 0.05A, 0.04A,
a ab ab b b b
1.61 1.42 1.15 0.97 0.87 0.74
± ± ± ± ± ±
0.05B, a 0.05A, a 0.02B, ab 0.03A, ab 0.04B, b 0.03B, b
11.37*** 12.25*** 9.97**
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: Storage time effect; FC × S: cultivar × storage time effect. *, **, and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively. Table 4 Linear Pearson’s correlation coefficients (R) between firmness and physicochemical parameters (n = 36) of the two highbush cultivars during postharvest cold storage. Physicochemical parameters
WL
Firmness
−0.831
***
TSS content
pH
−0.792
−0.755
**
WSP content **
−0.821
***
CEL content 0.637
**
HCEL content 0.805***
WL: fruit weight loss, TSS: total soluble solid, WSP: water-soluble pectin, CEL: cellulose, HCEL: hemicellulose. * ** , , and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively.
relationship with firmness (P ≤ 0.01, Table 4). It suggested that good postharvest flavor quality of blueberry can be achieved by maintaining fruit firmness during the postharvest storage. Good fruit storage quality of the two Bluecrop and Sierra blueberries manifested by small firmness loss, low WL (< 2.0%) and pH (< 4.0) during the first 20 days of cold storage time indicates again that the experimental storage condition at 0 ℃ and 90% RH is the optimum conditions recommended for highbush blueberry storage to obtain the maximal postharvest life (Chiabrando and Giacalone, 2017; Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014).
Konarska, 2015; Paniagua et al., 2013; Saftner et al., 2008). In this study, significant effect of cultivar on TSS content and pH was found (P ≤ 0.001, Table 2). Postharvest flavor quality of Sierra was much better than Bluecrop as manifested by the significant higher values in TSS and pH during the storage times (P ≤ 0.05, Table 2), and that is mainly due to the genetic origin property of the two different blueberry cultivars. Changes in fruit flavor quality of the same or different blueberry cultivars under the same postharvest storage condition also have been reported by many previous researches (Chiabrando et al., 2009; Paniagua et al., 2013; Saftner et al., 2008). Although, different changes of these quality parameters under different experimental conditions also have been published (Angeletti et al., 2010; Duan et al., 2011; Duarte et al., 2009; Nunez-Barrios et al., 2005; Paniagua et al., 2014; Saftner et al., 2008). All the variable behavior of flavor quality observed in blueberries validates the responses obtained under the experimental storage conditions which led to either deterioration or shelf-life prolongation of fresh blueberries. Pearson’s correlation analysis indicated that TSS content (R = −0.792) and pH (R = −0.755) had significant negative correlation
3.3. Changes in cell wall constituents Softening is one of the main reasons for fruit high perishability and susceptible spoilage of blueberry during postharvest storage and influence fruit quality, storage life, transport ability and diseases resistance (Chen et al., 2015; Deng et al., 2014; Hancock et al., 2008; Paniagua et al., 2013). Blueberries’ softening, as in peach (Zhang et al., 2010), pear (Chen et al., 2017b), apple (Costa et al., 2012), melon 560
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blueberry showed greater firmness and the process of softening was delayed due to lower WL and WSP content, and higher levels of CEL and HCEL during the postharvest cold storage. There is potential for industry to benefit from the relationship between firmness and physicochemical compositions by minimizing blueberry weight loss (or moisture loss) and cell wall degradation during the postharvest storage as a way to delaying softening and maintaining good quality of fresh blueberries.
(Bianchi et al., 2016), tomato (Saladié et al., 2007; Xie et al., 2017), strawberry (Vicente et al., 2005), and date (Singh et al., 2013) is primarily due to the degration of cell wall components including WSP, CEL and HCEL, leading to the disassembly of the cellulose-hemicellulose network of cell wall structure during fruit development, ripening, and postharvest storage phases (Chen et al., 2017a, 2015; Deng et al., 2014; Giongo et al., 2013; Konarska, 2015; Silva et al., 2005). In the current study, contents of WSP, CEL and HCEL in blueberry was significantly influenced by storage time (P ≤ 0.001, Table 3). WSP content in both cultivars increased with increasing storage time, and the WSP content in Bluecrop increased slower than that in Sierra (Table 3). After 50 days’ postharvest storage at 0 ℃ and 90% RH, WSP content in Bluecrop and Sierra increased from 0.27 mg g−1 to 0.48 mg g−1 and from 0.28 mg g−1 to 0.53 mg g−1, respectively (Table 3). Further comparison showed that Sierra exhibited slightly higher WSP content than Bluecrop during the storage time (P ≤ 0.05, Table 3). Contents of CEL and HCEL in fruits of both blueberry cultivars declined rapidly with increasing storage time, and the contents of CEL and HCEL in Bluecrop blueberries declined much slower than that in Sierra blueberries. In Bluecrop blueberries, the contents of CEL and HCEL reduced from 3.62 mg g−1 to 2.87 mg g−1 and from 1.76 mg g−1 to 0.87 mg g−1, respectively (Table 3). In terms of Sierra blueberries, the contents of CEL and HCEL reduced from 3.47 mg g−1 to 2.38 mg g−1 and from 1.61 mg g−1 to 0.74 mg g−1, respectively (Table 3). Further comparison showed that Bluecrop blueberries displayed higher contents of CEL and HCEL than Sierra blueberries during the storage (P ≤ 0.05, Table 3). Results in this study demonstrated that the degradation of cell wall materials in blueberries of the two highbush cultivars (Bluecrop and Sierra) during postharvest cold storage were characterized by an increase in WSP content and decrease in contents of CEL and HCEL (Table 3) as manifested by the significant positive correlation between hardness and the content of CEL (R = 0.637, P ≤ 0.01, Table 4) and HCEL (R = 0.805, P ≤ 0.001, Table 4) and the significant negative correlation between hardness and WSP content (R = −0.821, P ≤ 0.001, Table 4), which were associated with softening of blueberries during postharvest cold storage (Tables 1 and 2). In the current study, cell wall composition of both cultivars showed sustained increase in WSP content and a continuous decrease in contents of CEL and HCEL (Table 3). Similar results also have been reported in many other fruits species such as peach (Zhang et al., 2010), pear (Chen et al., 2017a,b), apple (Costa et al., 2012), melon (Bianchi et al., 2016), and cherry (Wang et al., 2015), etc. Results from cell wall components analyses showed degradation of cell wall during cold storage supported by the increase of WSP content and the decrease of the contents of CEL and HCEL (Table 3). Low temperature can postpone degradation of cell wall components of blueberries during postharvest cold storage through slowing reduction of CEL and HCEL and increasing production of WSP (Chiabrando and Giacalone, 2017; Chen et al., 2017a, 2015; Deng et al., 2014; Giongo et al., 2013). In addition, due to the higher amount of CEL and HCEL and their slower reduction of Bluecrop blueberries than Sierra blueberries (Table 3), the higher hardness in Bluecrop blueberries was observed during the postharvest cold storage (Table 1). These results showed that Bluecrop blueberries were much more resistant to postharvest cold storage than Sierra blueberries, that also had been manifested by the higher flavor quality of Bluecrop (higher TSS content and S/H) blueberries than Sierra blueberries during postharvest storage (Table 2).
Acknowledgements This research was supported by the Special Fund Project for Forest Scientific Research in the Public Interest (201204402). The authors are grateful to Yang Li for help in revising our English composition and to Wolin Agricultural (Qingdao) co., LTD. for supply of Bluecrop and Sierra blueberries. References Angeletti, P., Castagnasso, H., Miceli, E., Terminiello, L., Concellon, A., Chaves, A., Vicente, A.R., 2010. Effect of preharvest calcium applications on postharvest quality, softening and cell wall degradation of two blueberry (Vaccinium corymbosum) varieties. Postharvest Biol. Technol. 58, 98–103. Bianchi, T., Guerrero, L., Gratacós-Cubarsí, M., Claret, A., Argyris, J., Garcia-Mas, J., Hortós, M., 2016. Textural properties of different melon (Cucumis melon L.) fruit types: sensory and physical-chemical evaluation. Sci. Hortic. 201, 46–56. Bunea, A., Rugină, D., Sconţa, Z., Pop, R.M., Pintea, A., Socaciu, C., Tăbăran, F., Grootaert, C., Struijs, K., VanCamp, J., 2013. Anthocyanin determination in blueberry extracts from various cultivars and their antiproliferative and apoptotic properties in B16-F10 metastatic murine melanoma cells. Phytochem. 95, 436–444. Burgher, K.L., Jamieson, A.R., Lu, X.W., 2002. Genetic relationships among lowbush blueberry genotypes as determined by randomly amplified polymorphic DNA analysis. J. Am. Soc. Hortic. Sci. 127, 98–103. Chen, L., Opara, U.L., 2013. Approaches to analysis and modeling texture in fresh and processed foods-A review. J. Food Eng. 119, 497–507. Chen, H.J., Cao, S.F., Fang, X.J., Mu, H.L., Yang, H.L., Wang, X., Xu, Q.Q., Gao, H.Y., 2015. Changes in fruit firmness, cell wall composition and cell wall degrading enzymes in postharvest blueberries during storage. Sci. Hortic. 188, 44–48. Chen, Y.H., Hung, Y.C., Chen, M.Y., Lin, H.T., 2017a. Effects of acidic electrolyzed oxidizing water on retarding cell wall degradation and delaying softening of blueberries during postharvest storage. LWT–Food Sci. Technol. 84, 650–657. Chen, Y.H., Sun, J.Z., Lin, H.T., Huang, Y.C., Zhang, S., Lin, Y.F., Lin, T., 2017b. Paperbased 1-MCP treatment suppresses cell wall metabolism and delays softening of Huanghua pears during storage. J. Sci. Food Agric. 97, 2547–2552. Chiabrando, V., Giacalone, G., 2017. Shelf-life extention of highbush blueberry using 1methylcyclopropene stored under air and controlled atmosphere. Food Chem. 126, 1812–1816. Chiabrando, V., Giacalonea, G., Rolle, L., 2009. Mechanical behaviour and quality traits of highbush blueberry during postharvest storage. J. Sci. Food Agric. 89, 989–992. Cordenunsi, B.R., Nascimento, J.R.O., Lajolo, F.M., 2003. Physico-chemical changes related to quality of five strawberry fruit cultivars during cool-storage. Food Chem. 83, 167–173. Costa, F., Cappellin, L., Fontanari, M., Longhi, S., Guerra, W., Magnago, P., Gasperi, F., Biasioli, F., 2012. Texture dynamics during postharvest cold storage ripening in apple (Malus × domestica Borkh.). Postharvest Biol. Technol. 69, 54–63. de Souza, V.R., Pereira, P.A.P., Silva, T.L.T., de Oliveira Lima, L.C., Pio, R., Queiroz, F., 2014. Determination of the bioactive compounds, antioxidant activity and chemical composition of Brazilian blackberry, red raspberry, strawberry, blueberry and sweet cherry fruits. Food Chem. 156, 362–368. Deng, J., Shi, Z.J., Li, X.Z., Liu, H.M., 2014. Effects of cold storage and 1-methycyclopropene treatments on ripening and cell wall degrading in rebbiteye blueberry (Vaccinium ashei) fruit. Food Sci. Technol. Int. 75, 1–12. Diaconeasa, Z., Leopold, L., Ruginã, D., Ayvaz, H., Socaciu, C., 2015. Antiproliferative and antioxidant properties of anthocyanin rich extracts from blueberry and blackcurrant juice. Int. J. Mol. Sci. 16, 2352–2365. Duan, J.Y., Wu, R.Y., Strik, B.C., Zhao, Y.Y., 2011. Effect of edible coatings on the quality of fresh blueberries (Duke and Elliott) under commercial storage conditions. Postharvest Biol. Technol. 59, 71–79. Duarte, C., Guerra, M., Daniel, P., Camelo, A.L., Yomm, A., 2009. Quality changes of highbush blueberries fruit stored in CA with different CO2 levels. J. Food Sci. 74, 154–159. Edwards, T.W., Sherman, W.B., Sharpe, R.H., 1974. Evaluation and inheritance of fruit color size, scar, firmness and plant vigor in blueberry. HortScience 9, 20–22. Figueira, M.E., Oliveira, M., Direito, R., Rocha, J., Alves, P., Serra, A.T., Duarte, C., Bronze, R., Fernandes, A., Brites, D., Freitas, M., Fernandes, E., Sepodes, B., 2016. Protective effects of a blueberry extract in acute inflammation and collagen-induced arthritis in the rat. Biomed. Pharmacother. 83, 1191–1202. Folmer, F., Basavaraju, U., Jaspars, M., Hold, G., EI-Omar, E., Dicato, M., Diederich, M., 2014. Anticancer effects of bioactive berry compounds. Phytochem. Rev. 13, 295–322.
4. Conclusions In summary, the present work showed that during fruit softening in blueberries, the decline of fruit firmness accompanying with flavor loss was associated with increased WSP content and WL, and decreased contents in CEL and HCEL. Compared with Sierra blueberry, Bluecrop 561
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Giongo, L., Poncetta, P., Loretti, P., Costa, F., 2013. Texture profiling of blueberries (Vaccinium spp.) during fruit development, ripening and storage. Postharvest Biol. Technol. 76, 34–39. Gündüz, K., Serçe, S., Hancock, J.F., 2015. Variation among highbush and rabbiteye cultivars of blueberry for fruit quality and phytochemical characteristics. J. Food Compos. Anal. 38, 69–79. Hancock, J., Callow, P., Serce, S., Hanson, E., Beaudry, R., 2008. Effect of cultivar, controlled atmosphere storage, and fruit ripeness on the long-term storage of highbush blueberries. HortTechnology 18, 199–205. Konarska, A., 2015. Development of fruit quality traits and comparison of the fruit structure of two Vaccinium corymbosum (L.) cultivars. Sci. Hortic. 194, 79–90. Li, X., Nakagawa, N., Nevins, D.J., Sakurai, N., 2006. Changes in the cell-wall polysaccharides of outer pericarp tissues of kiwifruit during development. Plant Physiol. Biochem. 44, 115–124. Li, C.Y., Luo, J.W., MacLean, D., 2011. A novel instrument to delineate varietal and harvest effects on blueberry fruit texture during storage. J. Sci. Food Agric. 91, 1653–1658. Lobos, G.A., Callow, P., Hancock, J.F., 2014. The effect of delaying harvest date on fruit quality and storage of late highbush blueberry cultivars (Vaccinium corymbosum L.). Postharvest Biol. Technol. 87, 133–139. Nunez-Barrios, A., NeSmith, D.S., Chinnan, M., Prussia, S.E., 2005. Dynamics of rabbiteye blueberry fruit quality in response to harvest method and postharvest handling temperature. J. Small Fruit Rev. 4, 73–81. Paniagua, A.C., East, A.R., Hindmarsh, J.P., Heyes, J.A., 2013. Moisture loss is the major cause of firmness change during postharvest storage of blueberry. Postharvest Biol. Technol. 79, 13–19. Paniagua, A.C., East, A.R., Heyes, J.A., 2014. Interaction of temperature control deficiencies and atmosphere conditions during blueberry storage on quality outcomes. Postharvest Biol. Technol. 95, 50–59. Paul, K.K., Jerome, P.V.B., 1982. Carbohydrate interference and its correction in pectin analysis using the m-hydroxydiphenyl method. J. Food Sci. 47, 756–759. Perkins-Veazie, P., Collins, J.K., Clark, J.R., Magee, J., Substation, S.F., 1994. Postharvest quality of southern highbush blueberries. Science 27, 1254–1255.
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Changes in fruit firmness, quality traits and cell wall constituents of two highbush blueberries (Vaccinium corymbosum L.) during postharvest cold storage Binghua Liua,b, Kaifang Wanga,b, Xiuge Shua, Jing Lianga,b, Xiaoli Fana, Lei Suna,b, a b
T
⁎
Shandong Academy of Forestry, 250014, Jinan, Shandong, China Economic Forest Products Quality Inspection Test Center of State Forestry Administration (Jinan), 250014, Jinan, Shandong, China
A R T I C LE I N FO
A B S T R A C T
Keywords: Blueberry Cell wall composition Firmness Softening Weight loss
Blueberries are now the second most economically important soft fruit. However, they are highly perishable and susceptible to rapid spoilage. Softening is one of the main reasons for short postharvest life of blueberries. The changes of fruit firmness, weight loss, flavor quality and cell wall composition of Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra were investigated in this study. The results showed that fruit firmness declined concomitantly with the increase of fruit weight loss and water soluble pectin (WSP) content paralleled by a decrease in the content of cellulose (CEL) and hemicellulose (HCEL) during postharvest cold storage at 0 ℃ and 90% relative humidity. Compared with Sierra blueberries, Bluecrop blueberries were much more resistant to postharvest cold storage as manifested by the higher values in fruit flavor quality and firmness which were associated with less weight loss, lower WSP content and higher amount of CEL and HCEL.
1. Introduction Blueberries (Vaccinium spp.), the second most important soft fruit species after strawberry, are highly appreciated for their various human health benefits, unique taste, and nutritional value (Giongo et al., 2013). In particular, blueberries contain high amounts of phenolic compounds, including anthocyanins, flavonols, chlorogenic acid and procyanidins (Wang et al., 2017), and have been illustrated a wide diversity of bioactivities such as antioxidant, antimicrobial, antiproliferative, lifespan-prolonging, anti-inflammatory, carcinogenesis preventive, and cardioprotective activities (Bunea et al., 2013; de Souza et al., 2014; Diaconeasa et al., 2015; Figueira et al., 2016; Folmer et al., 2014). However, blueberries are highly perishable and susceptible to rapid spoilage because of microbial decay, mechanical damage, and moisture and nutritional loss (Hancock et al., 2008; Paniagua et al., 2014). One of the main reasons for short shelf-life is postharvest softening, which may influence not only fruit quality, but also its storage life, transport ability and resistance of postharvest diseases, thereby significantly reducing commercial value of blueberry fruit (Chen et al., 2015). Temperature is the most important environmental factor affecting blueberry quality during postharvest storage. Postharvest storage at 0–5 ℃ and 90–95 % relative humidity (RH) is recommended for
extending the postharvest life of blueberry by delaying senescence and preserving fruit quality of blueberry (Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014). Fruit quality is a consequence of many biochemical processes that result in changes of its intrinsic properties such as color, texture, flavor and aroma, together with the exterior appearance (size, color and shape) and nutritional value (Bianchi et al., 2016). Postharvest changes in blueberry quality during cold storage are determined by diverse physiological, biochemical, physical and pathological processes (Chen et al., 2015; Chiabrando et al., 2009; Giongo et al., 2013; Zhou et al., 2014), and have been reported correlated with a number of factors including fruit firmness, fruit weight loss (WL), total soluble solids (TSS) content and effective acidity (pH) (Chiabrando et al., 2009; Lobos et al., 2014; Saftner et al., 2008). As well as TSS and pH, fruit firmness is one of the most important quality properties that influence acceptability by consumers (Zhang et al., 2010). In blueberries, fruit firmness is strongly associated with the general concept of fruit freshness and quality, and affected by cellular organelles and biochemical constituents, water content, and cell wall compositions (Chiabrando et al., 2009; Saftner et al., 2008; Silva et al., 2005). Changes in firmness of blueberry occur due to changes in the chemistry of the primary cell wall components including water soluble pectin (WSP), cellulose (CEL) and
Abbreviations: CEL, cellulose; HCEL, hemicellulose; RH, relative humidity; TSS, total soluble solid; WL, fruit weight loss; WSP, water-soluble pectin ⁎ Corresponding author at: Shandong Academy of Forestry, 250014, Jinan, Shandong, China. E-mail address: [email protected] (L. Sun). https://doi.org/10.1016/j.scienta.2018.11.042 Received 7 September 2018; Received in revised form 5 November 2018; Accepted 14 November 2018 0304-4238/ © 2018 Published by Elsevier B.V.
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hemicelluloses (HCEL) that occur during growth and development or postharvest storage (Chen et al., 2015, 2017a; Deng et al., 2014; Giongo et al., 2013; Konarska, 2015). Therefore, investigating the postharvest changes in fruit firmness and physicochemical compositions will be beneficial to illustrating the fundamental of postharvest quality changes of blueberry during cold storage. In order to test the hypothesis, the present study was designed to observe the dynamic changes in fruit firmness, quality traits (WL, TSS and pH) and cell wall components (WSP, CEL and HCEL) of two highbush blueberries (Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra) during 50 days of postharvest storage at 0 ℃ and 90% RH, as well as the correlation relationships between fruit firmness and physicochemical compositions.
2.2.3. Total soluble solids (TSS) content and pH After the TPA test, three replicates of ten blueberries each cultivar were grinded and centrifuged (Rotofix 32, Hettich Zentrifugen, Tuttlingen, Germany) at 3000 × g for 10 min at 20 ℃. TSS content was measured with a digital handheld refractometer (AtagoPAL-1, Japan). A drop of the filtered juice was carefully placed into the lens and values were recorded. Calibration was made with deionized water and the lens was rinsed between different samples. The pH was measured with a digital portable electrode pH-meter (JENCO 6010, USA) equipped with temperature probe. Rinse the pH electrode and temperature probe with distilled water and immerse them in the 1:10 (v/v) diluted juice to measure pH. Remove any air bubbles trapped around the probe by shaking or stirring the probe.
2. Materials and methods
2.2.4. Cell wall components Cell wall materials were obtained as ethanol insoluble residue using the methods described by Chen et al. (2017a, 2017b, 2015). Briefly, blueberries (10 g) were ground, extracted by 95% (v/v) ethanol and maintained in boiling water for 30 min. to inactivate enzymes. Then the sample was homogenized after cooling and incubated overnight with 90% (v/v) dimethysulphoxide at 4 ℃ to remove starch. The residues were subsequently washed three times with water, 2:1 (v/v) chloroform-ethanol, and acetone, respectively. The isolated cell wall materials were dried overnight in a vacuum oven at 40 ℃ to get the final weight and then stored over silica gel in a vacuum desiccator for further determination. The cell wall materials was fractionated according to the methods of Chen et al. (2017a, 2017b, 2015) and Li et al. (2006). WSP fraction was obtained by suspending cell wall materials in 50 mM sodium acetate buffer (pH 6.5) for 6 h of shaking, and collecting supernatant by centrifuging at 10,000 × g for 10 min at 4 ℃. The sediment was re-suspended three times in 50 mM sodium acetate buffer (pH 6.5) containing 50 mM EDTA, shaken for 6 h, and centrifuged as above. The residue was re-suspended three times again in 50 mM Na2CO3 containing 2 mM EDTA, shaken and centrifuged as above. The remaining residue was resuspended in 4 mM NaOH containing 100 mM NaBH4, shaken and centrifuged. The supernatant was collected as hemicellulosic fraction and the final residue was cellulosic fraction. The WSP content was measured via m-hydroxydiphenyl method by using galacturonic acid as standard (Paul and Jerome, 1982; Wang et al., 2015). Contents of CEL and HCEL were determined via anthrone method by using glucose as standard (Vicente et al., 2005; Wang et al., 2015).
2.1. Fruit material and storage conditions Fruits of two northern highbush blueberry cultivars (Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra) were hand-harvested from five-year-old blueberry plants in a blueberry farm located in Chentuan town (119°27′N, 35°50′E), Rizhao City, Shandong Province, China, in early June of 2017. All fruits at commercial maturity, as determined by complete blue skin color (100% blue coloration), were packed in commercial vented clamshell containers, and then were placed in a 120 L incubator with ice at the bottom, and then were transported to the laboratory in 4 h for experimental treatment. In the laboratory, the fruits were screened for uniform size and maturity. Defective fruits (crushed, cracked, or immature) were eliminated. For each cultivar, the selected fruits were placed in plastic containers with snap-on lids and each contained one hundred fruits. Ten containers per cultivar. The containers were stored in a temperature-controlled cold room under regular storage conditions: normal atmosphere, 0 ℃, with a relative humidity of 90% that has been recommended for maintaining postharvest storage quality of blueberry fruit (Chiabrando et al., 2009). Samples were taken initially and at 10day intervals for physicochemical determination during storage of 50 days. 2.2. Physicochemical determination 2.2.1. Fruit firmness Fruit firmness of blueberries was obtained from texture profile analysis (TPA) test. Instrumental TPA test as described by Chen and Opara (2013) with a 35 mm diameter stainless probe was performed in a Stable Micro Systems TA-XT Plus texture analyzer equipped with an Acoustic Envelop Detector (AED) device (Stable Micro Systems Ltd., Godalming, UK). Samples were compressed to 75% of their original height at a crosshead speed of 2 mm s−1. Each sample was subjected to a two-cycle compression with 5 s between cycles. Data were collected by using Texture Expert Version 1.17 software. The highest value of force required to compress the sample during the first compression cycle was recorded as fruit firmness of blueberry. Prior to the TPA test, samples were kept for 2 h at room temperature (20 ℃), because firmness of most fruits and vegetables was influenced by increasing temperature (Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014).
2.3. Data analysis The experiments were performed by using a completely randomized design. All the measurements were conducted in triplicate. Data were presented as mean ± standard deviation (SD). Statistical analysis was carried out using the SPSS-13.0 for Windows statistical software package (Standard released version 13.0 for Windows; SPSS Inc., IL, USA). Tukey’s HSD (honestly significant difference) post hoc test (P ≤ 0.05) was performed to test the existence of statistical differences between different treatments. Analyses of two-way variance (ANOVA) were used to evaluate the effects of cultivar and cold storage time. Correlation relationships between firmness and physicochemical parameters were determined by using the Pearson’s correlation coefficients test. 3. Results and discussion
2.2.2. Fruit weight loss (WL) WL was calculated as the percentage difference between the initial and the final weight of the plastic containers containing fruit. Weight loss was calculated according to the following equation: WL (%) = (WI − WF)/WI × 100, where WI and WF are the initial and final sample weight (g), respectively. A digital balance (BSA224S Beijing Sartorius, China) with 0.001 g precision was used for these weight measurements.
3.1. Changes in fruit firmness Fruit firmness is one of the most critical quality indices for blueberry (Angeletti et al., 2010; Chen et al., 2017a, 2015; Chiabrando and Giacalone, 2017; Li et al., 2011; Perkins-Veazie et al., 1994). It is typically used as a measure of eating quality, as well as an estimate of 558
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Table 1 Changes in fruit firmness and fruit weight loss (WL) of two highbush blueberry cultivars during postharvest cold storage. Parameters
Firmness (N)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
ANOVA analyses FC FS FC × S
0 10 20 30 40 50
6.82 6.76 6.53 6.45 5.92 5.63
± ± ± ± ± ±
0.13A, 0.07A, 0.09A, 0.08A, 0.12A, 0.16A,
WL (%) Sierra a
6.27 5.93 5.85 5.54 5.07 4.75
a a ab b b
11.38*** 9.52** 7.46*
± ± ± ± ± ±
Bluecrop 0.11B, 0.13B, 0.12B, 0.10B, 0.13B, 0.08B,
a ab b b b b
— 1.06 1.72 2.43 3.45 4.87
± ± ± ± ±
0.10B, 0.22B, 0.18B, 0.26B, 0.20B,
Sierra
b b ab ab a
— 1.17 1.93 3.02 4.11 5.21
± ± ± ± ±
0.25A, 0.15A, 0.15A, 0.22A, 0.14A,
b b ab ab a
10.55** 17.36*** 6.38*
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: storage time effect; FC × S: cultivar × storage time effect. *, **, and ***, significant at P ≤ 0.05, 0.01, and 0.001, respectively.
Although, there were still many different results of those changes of blueberry during storage under experimental conditions (Angeletti et al., 2010; Chen et al., 2017a, 2015; Giongo et al., 2013; Li et al., 2011; Nunez-Barrios et al., 2005). All the variable firmness and weight loss behavior which were previously observed in blueberries validates the responses obtained under the experiment storage conditions which led to either blueberry softening or firming. The significant differences in firmness and WL and their change extents between different blueberry cultivars during postharvest cold storages were mainly associated with their genetic origin property. Previous researches had shown that fruit texture quality of blueberry was influenced by the Vaccinium species (Giongo et al., 2013; Silva et al., 2005) and cultivar (Chen et al., 2017a; Chiabrando et al., 2009; Hancock et al., 2008; Lobos et al., 2014; Li et al., 2011; Paniagua et al., 2014; Saftner et al., 2008). All the above validated that fruit texture quality of blueberry is a trait under genetic control and it has high heritability (Burgher et al., 2002; Edwards et al., 1974), thus with a high potential impact on breeding programs.
storability and resistance to injury of the product during postharvest handling, storage and marketing (Szczesniak, 2002). In recent years, numerous researches on fruit firmness dynamics of blueberry during fruit growth and development or postharvest storage were reported (Chen et al., 2017a, 2015; Chiabrando et al., 2009; Giongo et al., 2013; Li et al., 2011; Paniagua et al., 2014, 2013), and the results showed that changes in fruit firmness of blueberry during growth, ripening, and postharvest storage have a profound effect on consumer acceptability. In the present study, fruit firmness of Vaccinium corymbosum cv. Bluecrop and Vaccinium corymbosum cv. Sierra during postharvest cold storage were measured by using a texture profile analyzer which helps in quality control and fruit development to quantify desired characteristics (Singh et al., 2013). The results showed that fruit firmness was significantly influenced by cultivar (P ≤ 0.001), storage time (P ≤ 0.01) and cultivar × storage time interaction (P ≤ 0.05). Sierra blueberries were softer than Bluecrop blueberries as manifested by the lower value in firmness of Sierra than that of Bluecrop during the postharvest cold storage times (P ≤ 0.05, Table 1). Increasing storage time resulted in a significant decrease (P ≤ 0.05) in fruit firmness of both blueberry cultivars, and a slower decrease was observed in Bluecrop than that in Sierra (Table 1). After 50 days of cold storage, the firmness of Sierra blueberry decreased rapidly from 6.27 N to 4.75 N, while Bluecrop blueberry decreased slowly from 6.82 N to 5.63 N. In addition, the same reduction trend of firmness was observed in both blueberry cultivars, which decreased slightly in the first 10 days and then decreased rapidly (Table 1). Pervious researches showed that WL of blueberry is the major cause of firmness change during postharvest storage (Chen et al., 2017a, 2017b, 2015; Paniagua et al., 2014, 2013). In this study, WL of Bluecrop and Sierra blueberries was determined and the results shown in Table 1. WL was significantly influenced by cultivar (P ≤ 0.01), storage time (P ≤ 0.001) and cultivar × storage time interaction (P ≤ 0.05). WL of Bluecrop and Sierra blueberries significantly increased with the increasing postharvest storage time (P ≤ 0.05, Table 1). Fruit weight of Sierra lost more sharply than Bluecrop, as manifested by the WL value ranged from 1.17% to 5.21% and from 1.06% to 4.87% for Sierra and Bluecrop, respectively (Table 1). Significant difference of WL was found between the two cultivars, and Sierra had higher value in WL than Bluecrop during the 50 days’ storage (P ≤ 0.05, Table 1). Additionally, the results of Pearson’s correlation analysis in Table 4 showed that WL had significant negative correlation relationship with firmness (R = −0.831, P ≤ 0.001). It suggested that maintaining firmness of blueberries for extended storage period could be achieved by preventing fruit weight loss. Changes in fruit firmness and WL of blueberry under the same storage condition have also been reported in other cultivars (Chiabrando et al., 2009; Lobos et al., 2014; Paniagua et al., 2013).
3.2. Changes in fruit flavor quality Fruit quality is a consequence of many biochemical processes that result in changes of its intrinsic properties (color, texture, flavor and aroma), exterior appearance (size, color and shape) and nutritional value (Bianchi et al., 2016). Postharvest changes of blueberry flavor quality, always determined by fruit TSS and pH, play an important role in consumer satisfaction and influence fruit further consumption (Chiabrando et al., 2009; Lobos et al., 2014; Perkins-Veazie et al., 1994; Saftner et al., 2008). In the present study, TSS content and pH in Bluecrop and Sierra blueberries at different postharvest cold storage times were measured. Two-way ANOVA analysis indicated that storage time had significant effect on TSS content (P ≤ 0.01) and pH (P ≤ 0.05) (Table 2). Increasing storage time resulted an increase in TSS content and pH, and a greater increase was observed in Sierra (ranged from 10.49% to 11.02% and from 3.26 to 4.25, respectively) than those in Bluecrop (ranged from 11.32% to 11.66% and from 3.45 to 4.39, respectively) (Table 2). Since blueberry fruit does not have starch to support soluble sugar synthesis after harvest, the little increase in TSS may be a consequence of cell wall degradation (Cordenunsi et al., 2003). Acidity, determined by pH value, was increased during the first 20 days and then kept in stable level (Table 2) that usually related to good storage quality (Chiabrando et al., 2009). Fruit flavor quality of blueberry is a trait under genetic control (Burgher et al., 2002; Perkins-Veazie et al., 1994), and that has been proved by the significant differences among many different blueberry cultivars (Duan et al., 2011; Duarte et al., 2009; Gündüz et al., 2015; 559
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Table 2 Changes in total soluble solid (TSS) content and pH of two highbush blueberry cultivars during postharvest cold storage. Parameters
TSS content (%)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
0 10 20 30 40 50
10.49 10.76 10.68 10.87 11.02 11.26
ANOVA analyses FC FS FC × S
± ± ± ± ± ±
pH Sierra
0.15B, 0.09B, 0.16B, 0.15B, 0.15B, 0.07B,
b
11.32 11.47 11.56 11.52 11.66 11.87
ab b ab ab a
Bluecrop ± ± ± ± ± ±
0.16A, 0.12A, 0.16A, 0.16A, 0.18A, 0.13A,
b
3.26 3.72 4.05 4.16 4.25 4.24
ab ab ab ab a
16.42*** 10.03** 5.28**
± ± ± ± ± ±
Sierra
0.07B, b 0.08A, ab 0.05B, a 0.01B, a 0.07B, a 0.05B, a
3.45 3.78 4.17 4.31 4.39 4.39
± ± ± ± ± ±
0.04A, 0.05A, 0.03A, 0.05A, 0.05A, 0.03A,
b ab a a a a
11.73*** 7.88* 3.24
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: storage time effect; FC × S: cultivar × storage time effect. *, **, and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively. Table 3 Changes in contents of water-soluble pectin (WSP), cellulose (CEL) and hemicellulose (HCEL) of two highbush blueberry cultivars during postharvest cold storage. Parameters
WSP content (mg g−1)
Cultivar
Bluecrop
Storage times (days at 0 ℃)
ANOVA analyses FC FS FC × S
0 10 20 30 40 50
0.27 0.36 0.39 0.42 0.46 0.48
± ± ± ± ± ±
0.01A, b 0.00A, ab 0.00A, ab 0.01B, ab 0.00A, a 0.01B, a
CEL content (mg g−1) Sierra 0.28 0.38 0.41 0.47 0.49 0.53
Bluecrop
± ± ± ± ± ±
0.01A, 0.00A, 0.01A, 0.01A, 0.01A, 0.01A,
b ab ab a a a
3.62 3.45 3.47 3.26 2.98 2.87
± ± ± ± ± ±
0.06A, 0.07A, 0.11A, 0.05A, 0.07A, 0.12A,
HCEL content (mg g−1) Sierra
a a a ab b b
3.47 3.35 3.02 2.88 2.65 2.38
± ± ± ± ± ±
Bluecrop 0.05A, a 0.15A, a 0.12B, ab 0.13B, ab 0.14B, b 0.10B, b
6.86* 13.02*** 8.54**
3.28 10.59*** 5.18*
1.76 1.45 1.28 1.06 0.98 0.87
± ± ± ± ± ±
Sierra
0.02A, 0.07A, 0.05A, 0.05A, 0.05A, 0.04A,
a ab ab b b b
1.61 1.42 1.15 0.97 0.87 0.74
± ± ± ± ± ±
0.05B, a 0.05A, a 0.02B, ab 0.03A, ab 0.04B, b 0.03B, b
11.37*** 12.25*** 9.97**
Values are the means ± standard deviation (SD). Capital superscript letters in the same column are used to compare the cultivar influence. Small case superscript letters in the same row are used to compare the storage time influence. Values followed by the same letter are not significantly different by Tukey’s HSD post hoc test at P ≤ 0.05 level. FC: cultivar effect; FS: Storage time effect; FC × S: cultivar × storage time effect. *, **, and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively. Table 4 Linear Pearson’s correlation coefficients (R) between firmness and physicochemical parameters (n = 36) of the two highbush cultivars during postharvest cold storage. Physicochemical parameters
WL
Firmness
−0.831
***
TSS content
pH
−0.792
−0.755
**
WSP content **
−0.821
***
CEL content 0.637
**
HCEL content 0.805***
WL: fruit weight loss, TSS: total soluble solid, WSP: water-soluble pectin, CEL: cellulose, HCEL: hemicellulose. * ** , , and ***: significant at P ≤ 0.05, 0.01, and 0.001, respectively.
relationship with firmness (P ≤ 0.01, Table 4). It suggested that good postharvest flavor quality of blueberry can be achieved by maintaining fruit firmness during the postharvest storage. Good fruit storage quality of the two Bluecrop and Sierra blueberries manifested by small firmness loss, low WL (< 2.0%) and pH (< 4.0) during the first 20 days of cold storage time indicates again that the experimental storage condition at 0 ℃ and 90% RH is the optimum conditions recommended for highbush blueberry storage to obtain the maximal postharvest life (Chiabrando and Giacalone, 2017; Chiabrando et al., 2009; Paniagua et al., 2014; Zhou et al., 2014).
Konarska, 2015; Paniagua et al., 2013; Saftner et al., 2008). In this study, significant effect of cultivar on TSS content and pH was found (P ≤ 0.001, Table 2). Postharvest flavor quality of Sierra was much better than Bluecrop as manifested by the significant higher values in TSS and pH during the storage times (P ≤ 0.05, Table 2), and that is mainly due to the genetic origin property of the two different blueberry cultivars. Changes in fruit flavor quality of the same or different blueberry cultivars under the same postharvest storage condition also have been reported by many previous researches (Chiabrando et al., 2009; Paniagua et al., 2013; Saftner et al., 2008). Although, different changes of these quality parameters under different experimental conditions also have been published (Angeletti et al., 2010; Duan et al., 2011; Duarte et al., 2009; Nunez-Barrios et al., 2005; Paniagua et al., 2014; Saftner et al., 2008). All the variable behavior of flavor quality observed in blueberries validates the responses obtained under the experimental storage conditions which led to either deterioration or shelf-life prolongation of fresh blueberries. Pearson’s correlation analysis indicated that TSS content (R = −0.792) and pH (R = −0.755) had significant negative correlation
3.3. Changes in cell wall constituents Softening is one of the main reasons for fruit high perishability and susceptible spoilage of blueberry during postharvest storage and influence fruit quality, storage life, transport ability and diseases resistance (Chen et al., 2015; Deng et al., 2014; Hancock et al., 2008; Paniagua et al., 2013). Blueberries’ softening, as in peach (Zhang et al., 2010), pear (Chen et al., 2017b), apple (Costa et al., 2012), melon 560
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blueberry showed greater firmness and the process of softening was delayed due to lower WL and WSP content, and higher levels of CEL and HCEL during the postharvest cold storage. There is potential for industry to benefit from the relationship between firmness and physicochemical compositions by minimizing blueberry weight loss (or moisture loss) and cell wall degradation during the postharvest storage as a way to delaying softening and maintaining good quality of fresh blueberries.
(Bianchi et al., 2016), tomato (Saladié et al., 2007; Xie et al., 2017), strawberry (Vicente et al., 2005), and date (Singh et al., 2013) is primarily due to the degration of cell wall components including WSP, CEL and HCEL, leading to the disassembly of the cellulose-hemicellulose network of cell wall structure during fruit development, ripening, and postharvest storage phases (Chen et al., 2017a, 2015; Deng et al., 2014; Giongo et al., 2013; Konarska, 2015; Silva et al., 2005). In the current study, contents of WSP, CEL and HCEL in blueberry was significantly influenced by storage time (P ≤ 0.001, Table 3). WSP content in both cultivars increased with increasing storage time, and the WSP content in Bluecrop increased slower than that in Sierra (Table 3). After 50 days’ postharvest storage at 0 ℃ and 90% RH, WSP content in Bluecrop and Sierra increased from 0.27 mg g−1 to 0.48 mg g−1 and from 0.28 mg g−1 to 0.53 mg g−1, respectively (Table 3). Further comparison showed that Sierra exhibited slightly higher WSP content than Bluecrop during the storage time (P ≤ 0.05, Table 3). Contents of CEL and HCEL in fruits of both blueberry cultivars declined rapidly with increasing storage time, and the contents of CEL and HCEL in Bluecrop blueberries declined much slower than that in Sierra blueberries. In Bluecrop blueberries, the contents of CEL and HCEL reduced from 3.62 mg g−1 to 2.87 mg g−1 and from 1.76 mg g−1 to 0.87 mg g−1, respectively (Table 3). In terms of Sierra blueberries, the contents of CEL and HCEL reduced from 3.47 mg g−1 to 2.38 mg g−1 and from 1.61 mg g−1 to 0.74 mg g−1, respectively (Table 3). Further comparison showed that Bluecrop blueberries displayed higher contents of CEL and HCEL than Sierra blueberries during the storage (P ≤ 0.05, Table 3). Results in this study demonstrated that the degradation of cell wall materials in blueberries of the two highbush cultivars (Bluecrop and Sierra) during postharvest cold storage were characterized by an increase in WSP content and decrease in contents of CEL and HCEL (Table 3) as manifested by the significant positive correlation between hardness and the content of CEL (R = 0.637, P ≤ 0.01, Table 4) and HCEL (R = 0.805, P ≤ 0.001, Table 4) and the significant negative correlation between hardness and WSP content (R = −0.821, P ≤ 0.001, Table 4), which were associated with softening of blueberries during postharvest cold storage (Tables 1 and 2). In the current study, cell wall composition of both cultivars showed sustained increase in WSP content and a continuous decrease in contents of CEL and HCEL (Table 3). Similar results also have been reported in many other fruits species such as peach (Zhang et al., 2010), pear (Chen et al., 2017a,b), apple (Costa et al., 2012), melon (Bianchi et al., 2016), and cherry (Wang et al., 2015), etc. Results from cell wall components analyses showed degradation of cell wall during cold storage supported by the increase of WSP content and the decrease of the contents of CEL and HCEL (Table 3). Low temperature can postpone degradation of cell wall components of blueberries during postharvest cold storage through slowing reduction of CEL and HCEL and increasing production of WSP (Chiabrando and Giacalone, 2017; Chen et al., 2017a, 2015; Deng et al., 2014; Giongo et al., 2013). In addition, due to the higher amount of CEL and HCEL and their slower reduction of Bluecrop blueberries than Sierra blueberries (Table 3), the higher hardness in Bluecrop blueberries was observed during the postharvest cold storage (Table 1). These results showed that Bluecrop blueberries were much more resistant to postharvest cold storage than Sierra blueberries, that also had been manifested by the higher flavor quality of Bluecrop (higher TSS content and S/H) blueberries than Sierra blueberries during postharvest storage (Table 2).
Acknowledgements This research was supported by the Special Fund Project for Forest Scientific Research in the Public Interest (201204402). The authors are grateful to Yang Li for help in revising our English composition and to Wolin Agricultural (Qingdao) co., LTD. for supply of Bluecrop and Sierra blueberries. References Angeletti, P., Castagnasso, H., Miceli, E., Terminiello, L., Concellon, A., Chaves, A., Vicente, A.R., 2010. Effect of preharvest calcium applications on postharvest quality, softening and cell wall degradation of two blueberry (Vaccinium corymbosum) varieties. Postharvest Biol. Technol. 58, 98–103. Bianchi, T., Guerrero, L., Gratacós-Cubarsí, M., Claret, A., Argyris, J., Garcia-Mas, J., Hortós, M., 2016. Textural properties of different melon (Cucumis melon L.) fruit types: sensory and physical-chemical evaluation. Sci. Hortic. 201, 46–56. Bunea, A., Rugină, D., Sconţa, Z., Pop, R.M., Pintea, A., Socaciu, C., Tăbăran, F., Grootaert, C., Struijs, K., VanCamp, J., 2013. Anthocyanin determination in blueberry extracts from various cultivars and their antiproliferative and apoptotic properties in B16-F10 metastatic murine melanoma cells. Phytochem. 95, 436–444. Burgher, K.L., Jamieson, A.R., Lu, X.W., 2002. Genetic relationships among lowbush blueberry genotypes as determined by randomly amplified polymorphic DNA analysis. J. Am. Soc. Hortic. Sci. 127, 98–103. Chen, L., Opara, U.L., 2013. Approaches to analysis and modeling texture in fresh and processed foods-A review. J. Food Eng. 119, 497–507. Chen, H.J., Cao, S.F., Fang, X.J., Mu, H.L., Yang, H.L., Wang, X., Xu, Q.Q., Gao, H.Y., 2015. Changes in fruit firmness, cell wall composition and cell wall degrading enzymes in postharvest blueberries during storage. Sci. Hortic. 188, 44–48. Chen, Y.H., Hung, Y.C., Chen, M.Y., Lin, H.T., 2017a. Effects of acidic electrolyzed oxidizing water on retarding cell wall degradation and delaying softening of blueberries during postharvest storage. LWT–Food Sci. Technol. 84, 650–657. Chen, Y.H., Sun, J.Z., Lin, H.T., Huang, Y.C., Zhang, S., Lin, Y.F., Lin, T., 2017b. Paperbased 1-MCP treatment suppresses cell wall metabolism and delays softening of Huanghua pears during storage. J. Sci. Food Agric. 97, 2547–2552. Chiabrando, V., Giacalone, G., 2017. Shelf-life extention of highbush blueberry using 1methylcyclopropene stored under air and controlled atmosphere. Food Chem. 126, 1812–1816. Chiabrando, V., Giacalonea, G., Rolle, L., 2009. Mechanical behaviour and quality traits of highbush blueberry during postharvest storage. J. Sci. Food Agric. 89, 989–992. Cordenunsi, B.R., Nascimento, J.R.O., Lajolo, F.M., 2003. Physico-chemical changes related to quality of five strawberry fruit cultivars during cool-storage. Food Chem. 83, 167–173. Costa, F., Cappellin, L., Fontanari, M., Longhi, S., Guerra, W., Magnago, P., Gasperi, F., Biasioli, F., 2012. Texture dynamics during postharvest cold storage ripening in apple (Malus × domestica Borkh.). Postharvest Biol. Technol. 69, 54–63. de Souza, V.R., Pereira, P.A.P., Silva, T.L.T., de Oliveira Lima, L.C., Pio, R., Queiroz, F., 2014. Determination of the bioactive compounds, antioxidant activity and chemical composition of Brazilian blackberry, red raspberry, strawberry, blueberry and sweet cherry fruits. Food Chem. 156, 362–368. Deng, J., Shi, Z.J., Li, X.Z., Liu, H.M., 2014. Effects of cold storage and 1-methycyclopropene treatments on ripening and cell wall degrading in rebbiteye blueberry (Vaccinium ashei) fruit. Food Sci. Technol. Int. 75, 1–12. Diaconeasa, Z., Leopold, L., Ruginã, D., Ayvaz, H., Socaciu, C., 2015. Antiproliferative and antioxidant properties of anthocyanin rich extracts from blueberry and blackcurrant juice. Int. J. Mol. Sci. 16, 2352–2365. Duan, J.Y., Wu, R.Y., Strik, B.C., Zhao, Y.Y., 2011. Effect of edible coatings on the quality of fresh blueberries (Duke and Elliott) under commercial storage conditions. Postharvest Biol. Technol. 59, 71–79. Duarte, C., Guerra, M., Daniel, P., Camelo, A.L., Yomm, A., 2009. Quality changes of highbush blueberries fruit stored in CA with different CO2 levels. J. Food Sci. 74, 154–159. Edwards, T.W., Sherman, W.B., Sharpe, R.H., 1974. Evaluation and inheritance of fruit color size, scar, firmness and plant vigor in blueberry. HortScience 9, 20–22. Figueira, M.E., Oliveira, M., Direito, R., Rocha, J., Alves, P., Serra, A.T., Duarte, C., Bronze, R., Fernandes, A., Brites, D., Freitas, M., Fernandes, E., Sepodes, B., 2016. Protective effects of a blueberry extract in acute inflammation and collagen-induced arthritis in the rat. Biomed. Pharmacother. 83, 1191–1202. Folmer, F., Basavaraju, U., Jaspars, M., Hold, G., EI-Omar, E., Dicato, M., Diederich, M., 2014. Anticancer effects of bioactive berry compounds. Phytochem. Rev. 13, 295–322.
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