•Pea starch/guar gum film incorporated with glycols, sugars, and polyols were developed.•The functional properties of the films were changed according to the type of plasticizer.•FTIR was used to ...study the interactions between the film components.•Monosaccharides showed a great potential to be used as plasticizer.
The influence of different plasticizers (glycols, sugars and polyols) on the moisture sorption, mechanical, physical, optical, and microstructure characteristics of pea starch-guar gum (PSGG) film was studied. All plasticizers formed homogeneous, transparent, and smooth films, while PEG-400 did not produce film with suitable characteristics. Fourier transform infrared (FTIR) spectroscopy results indicated some interaction between plasticizers and the polymers. Scanning electron microscopy (SEM) observations of the films presented surfaces without cracks, breaks, or openings which were indicator of the miscibility and compatibility of employed plasticizers with PSGG films. The results showed that the films containing plasticizers with higher functional groups had lower equilibrium moisture content at aw <0.4. In general, a reduction in tensile strength and Young's modulus and an increase in elongation at break were detected when molecular weight of plasticizers and relative humidity increased in all film formulations. Films plasticized with monosaccharide showed similar mechanical properties to those with sorbitol, but lower solubility and water vapour permeability (WVP), higher transparency and moisture content than the sorbitol-plasticized films. The most noticeable plasticization effect was exerted by following order: glycerol > EG > PG > xylitol > fructose > sorbitol > mannitol > galactose > glucose > sucrose > maltitol.
•‘Golden Delicious’ apples show higher CO2 tolerance than ‘Han Fu’ apple.•PPO activity was associated with CO2 induced browning in ‘Han Fu’ apple.•RAP 2 s and PDCs were correlated to high CO2 ...tolerance in ‘Golden Delicious’ apple.•L-LDHs, PLPs, PALs, PPOs were associated with browning in ‘Han Fu’ apple.
Internal browning is physiological storage disorder in many apples often associated with high CO2 during controlled atmosphere (CA) storage. However the underlying molecular mechanisms leading to internal browning are poorly understood. This study examined changes in the apple transcriptome associated with internal browning related to high CO2 in CA storage by comparing the responses of a CO2 sensitive cultivar ‘Han Fu’ and the CO2 tolerant cultivar ‘Golden Delicious’. The apples were harvested at optimum maturity for long term storage and stored in a CA of 3 % O2 and 6 % CO2 at 4 ℃ for 60 d. The CO2 sensitive ‘Han Fu’ showed severe browning symptoms within 30 d storage in CA, while no internal browning symptoms were detected in ‘Golden Delicious’ even after 60 d storage under the same storage conditions. PPO activity was higher in ‘Han Fu’ apples after 30 d storage. Differences in the expression profile between cultivars were assessed using RNA-sequencing techniques to identify candidate genes associated with internal browning in a cultivar specific manner. The RNA sequencing results showed that higher expression of the related to apetala 2 (RAP 2) and pyruvate decarboxylase (PDC) encoding genes in ‘Golden Delicious’ apples were associated with higher CO2 tolerance in this cultivar. Conversely, the higher expression of key genes from lactate production (lactate dehydrogenase, LDH), lipid catabolic (patatin-like protein, PLP), polyphenol biosynthesis (phenylalanine ammonia-lyase, PAL), polyphenol oxidase (PPO) were associated with the internal browning development in ‘Han Fu’ apple in CA storage condition. A conceptual model elucidating the molecular mechanism of browning development in ‘Han Fu’ and CO2 acclimation in ‘Golden Delicious’ during storage in CA is proposed. The further elucidation of this mechanism will lead to a theory to optimize cultivar breeding in apple.
Fusarium solani-induced quality deterioration in stored sweet potato is poorly characterized and understood. This study examined the effects of F. solani infection in Xinxiang sweet potato roots ...during storage. The results showed that while there were no external symptoms following F. solani infection, upon cutting the roots, the cut surface of the infected root rapidly turned black, whereas the untreated control roots remained unaffected. The metabolites and transcriptive differences between F. solani-infected and control sweet potato roots were investigated with high-performance liquid chromatography, metabolomic analysis, and an Illumina Novaseq platform. The results showed that levels of the toxic ipomeamarone accumulated as high as 2.36 mg/kg DW in tissue after F. solani inoculation and 6 days storage at 28 °C, where the control tissue sample did not accumulate any ipomeamarone. Metabolomic analysis showed that isochlorogenic acid and l-tyrosine significantly increased in the infected tissue and associated with the darkening cut surface of the infected sweet potato. In transcriptomic analysis, a total of 13, 14, and 6 key genes in ipomeamarone, isochlorogenic acid, and l-tyrosine biosynthesis pathways, respectively, were identified. A conceptual model elucidating the physiological and molecular mechanism of F. solani-induced quality deterioration in sweet potato is proposed.
•The PSGG-Sh coatings provided the best performance in extending shelf life.•The bilayer coating resulted in higher perception of off-flavors.•The PSGG-Sh and single layer coatings obtained better ...sensory scores.•The PSGG coatings could be a beneficial substitute to common commercial waxes.
Novel edible composite coatings based on pea starch and guar gum (PSGG), PSGG blended with lipid mixture containing the hydrophobic compounds shellac and oleic acid (PSGG-Sh), and a layer-by-layer (LBL) approach (PSGG as an internal layer and shellac as an external layer), were investigated and compared with a commercial wax (CW) and uncoated fruit on postharvest quality of ‘Valencia’ oranges held for up to four weeks at 20°C and 5°C with an additional storage for 7 d at 20°C. The incorporation of lipid compounds into the PSGG coatings (PSGG-Sh) generally resulted in the best performance in reducing fruit respiration rate, ethylene production, weight and firmness loss, peel pitting, and fruit decay rate of the coated oranges. Fruit coated with PSGG-Sh and a single layer PSGG coatings generally resulted in higher scores for overall flavor and freshness after four weeks at 5°C followed by one week at 20°C than uncoated fruit, as assessed by a sensory panel. Although the LBL coating reduced weight loss and respiration rate with improved firmness retention to a greater extent than the single layer PSGG coating, the bilayer coating also resulted in higher levels of ethanol causing increased perception of off-flavors. Overall results suggested that PSGG-based edible coatings could be a beneficial substitute to common commercial waxes for maintaining quality and storability, as well as extending shelf life of citrus fruit and potentially other fresh horticultural produce.
•Edible films were produced using different pea starch, guar gum and glycerol concentrations by casting method.•The Box–Behnken response surface design (BBD) was an effective tool in evaluating the ...physical and optical properties of biocomposite edible films.•The proportion of the two polysaccharides in the film influenced the physical and optical properties of the films to different extents.•Food and non-food applications of pea starch films were improved with incorporation of guar gum and glycerol.
The influence of process variables (pea starch, guar gum and glycerol) on the viscosity (V), solubility (SOL), moisture content (MC), transparency (TR), Hunter parameters (L, a, and b), total color difference (ΔE), yellowness index (YI), and whiteness index (WI) of the pea starch based edible films was studied using three factors with three level Box–Behnken response surface design. The individual linear effect of pea starch, guar and glycerol was significant (p<0.05) on all the responses. However, a value was only significantly (p<0.05) affected by pea starch and guar gum in a positive and negative linear term, respectively. The effect of interaction of starch×glycerol was also significant (p<0.05) on TR of edible films. Interaction between independent variables starch×guar gum had a significant impact on the b and YI values. The quadratic regression coefficient of pea starch showed a significant effect (p<0.05) on V, MC, L, b, ΔE, YI, and WI; glycerol level on ΔE and WI; and guar gum on ΔE and SOL value. The results were analyzed by Pareto analysis of variance (ANOVA) and the second order polynomial models were developed from the experimental design with reliable and satisfactory fit with the corresponding experimental data and high coefficient of determination (R2) values (>0.93). Three-dimensional response surface plots were established to investigate the relationship between process variables and the responses. The optimized conditions with the goal of maximizing TR and minimizing SOL, YI and MC were 2.5g pea starch, 25% glycerol and 0.3g guar gum. Results revealed that pea starch/guar gum edible films with appropriate physical and optical characteristics can be effectively produced and successfully applied in the food packaging industry.
•Storage of ‘Comte de Parisʼ pineapple fruit at 10 °C reduced internal browning as compared to storage at 25 °C.•Increased the levels of PL, UFA/SFA and IUFA were associated with less internal ...browning in fruit stored at 10 °C.•Accumulations of PA, LPE, and PLAs were correlated with internal browning tolerance in fruit stored at 10 °C.
To uncover the mechanism underlying membrane lipid metabolism of low temperature induced internal browning tolerance in pineapple, membrane phospholipid alterations of harvested ‘Comte de Paris’ winter pineapple fruit stored at either 10 °C or 25 °C was investigated. Fruit stored at 10 °C developed low levels of internal browning as compared to fruit stored at 25 °C and was associated with high contents of phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol, phosphatidylserine, and phosphatidylethanolamine, and low levels of phosphatidic acid. Storage at 10 °C down-regulated the expression levels of phospholipase As. Fruit stored at 10 °C also exhibited high ratio of unsaturated fatty acid to saturated fatty acid and index of unsaturated fatty acid level. These findings suggest that maintenance phospholipid abundance, reduction in phosphatidic acid accumulation and membrane lipid peroxidation may have contributed to the enhanced internal browning tolerance in ‘Comte de Paris’ winter pineapple fruit at low temperature storage.
Six different factors involved in the extraction of catechins from green tea using water were examined for their impact on the yield of catechins and on the efficiency of water use. The best ...temperature and time combination for catechin extraction was at 80°C for 30 min. The yield of catechins was also optimal with a tea particle size of 1 mm, a brewing solution pH <6 and a tea‐to‐water ratio at 50:1 (mL/g). In terms of efficient use of water in a single extraction, a water‐to‐tea ratio of 20:1 (mL/g) gave the best results; 2.5 times less water was used per gram of green tea. At the water‐to‐tea ratio of 20:1 mL/g, the highest yield of catechins per gram of green tea was achieved by extracting the same sample of green tea twice. However, for the most efficient use of water, the best extraction was found to be once at a water‐to‐tea ratio of 12:1 (mL/g) and once at a water‐to‐tea ratio of 8:1 (mL/g). Therefore, all six of the factors investigated had an impact on the yield of catechins extracted from green tea using water and two had an impact on the efficiency of water use.
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