Effect of different packaging materials on the shelf-life of chestnut (Castanea sativa Miller) during short-time storage
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abstract
Chestnuts are a perishable product that loses weight and spoils quickly. Therefore, it is essential to find methods to reduce economic losses. This study aimed to evaluate the effect of four different packaging materials - polyethene packaging" POLY", polyethene packaging with holes "PH", Modified Atmosphere Packaging "MAP", Vacuum bags "VAC-bags" and unpackaged chestnuts "control" - on the shelf-life of chestnuts stored at room temperature during 0, 2, 4 and 6 weeks. Several parameters such as colour, texture, moisture content, water activity, titratable acidity, total soluble solids, starch, amylose, aerobic mesophiles, and moulds and yeasts were determined.
The results showed that the colour, texture, moisture content, water activity, titratable acidity and total soluble solids were little affected by the type of bags used. The starch ranged from 35.2 to 50.4% dry matter (d.m.) without a specific trend, and amylose expressed on the starch basis (25.7 to 45.0%) suggested no remarkable starch functionality changes.
On the contrary, significant differences were observed between bags in weight loss, reducing sugars and microbial counts. The VAC-, MAP-, and POLY-bags showed percentages of weight loss lower than 2%, while the control and PH-bags had values equal to 13.2 and 9.2%, respectively. The highest values of reducing sugars were observed in POLY- and PH-bags, followed by the control, suggesting partial hydrolysis of the starch. Furthermore, VAC- and MAP-bags' application caused a considerable decrease in aerobic mesophiles, moulds and yeasts growth compared to the control during two and four weeks of storag
FCT, Portugal [CIMO: UID/AGR/00690/2019]; Portugal 2020 [Go_ClimCast Project: PDR2020- 1.0.1-FEADER-032060]
This study aimed to evaluate the presence of bioactive antioxidant molecules in chestnut outer shells. For this proposal, several extraction procedures were used, specifically different solvents (water, ethanol:water (80:20) and acetone:water (80:20)) combined with two extraction methods (stirring and ultrasounds (US)) and times of extraction. Several chemical assays were applied to evaluate the flavonoids, hydrolysable and condensed tannins contents, and the antioxidant activity by total reducing capacity, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, and reducing power. Some individual compounds were identified by HPLC-UV detection. Furthermore, the antimicrobial activity of the obtained extracts was screened using different microorganisms, namely Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Enterococcus faecalis) and Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Enterobacter aerogenes, Proteus mirabilis, Klebsiella pneumoniae), as well as fungi (Candida albicans).
The mixture acetone:water (80:20) was the best solvent to extract condensed tannins and flavonoids. It was with this mixture that the best total reducing capacity, (DPPH) radical scavenging activity and reducing power were determined. The highest extraction yield was also obtained with this mixture. Only for the hydrolysable tannins, the most suitable extraction solution was ethanol:water (80:20). The presence of gallic and tannic acids was detected by HPLC-UV.
Concerning the extraction methods, only the extracts obtained by the US exhibited antimicrobial activity. The ethanolic extract showed antimicrobial activity against the Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus, Enterococcus faecalis) and the extracts with acetone:water (80:20) and water showed antimicrobial activity against Proteus mirabilis.
The results of this study demonstrated that the chestnut outer shell is a promising source of bioactive compounds.
