Percorrer por autor "Askri, Firas"
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- Effect of different packaging materials on the shelf-life of chestnut (Castanea sativa Mill)Publication . Askri, Firas; Ramalhosa, Elsa; Pereira, Ermelinda; Oueslati, SouheibChestnuts are very consumed in Portugal and worldwide; however, it is a perishable product that loses weight and spoils quickly. So, it is crucial to find methods to reduce economic losses. Trying to find answers to this problem, the purpose of the present research work was to evaluate the effect of using different packaging materials in chestnuts storage to increase their shelf-life. Two storage assays were performed, one during six-weeks (short-storage), and other during six months (long-storage). In the first assay, different packagings were tested, namely: polyethene packaging ”POLY”, polyethene packaging with holes “PH”, Modified Atmosphere Packaging ”MAP”, Vacuum bags “VAC-bags” and unpackaged chestnuts (“control”). All samples were stored at room temperature during 0, 2, 4 and 6 weeks, to find out the best solution to reduce the industrial losses of chestnuts during their selling process in supermarkets (retail conditions). In the long-storage assay, micro-perforated bags (MP-bags) were used in chestnuts storage in refrigerated industrial chambers for 1, 2, 3 and 6 months. The weight loss, colour, texture, water activity (aw), moisture content, titratable acidity, total soluble solids, reducing sugars, starch, amylose, and microbiological analysis were determined. In the short-storage assay, the colour, texture, moisture content, aw, titratable acidity and total soluble solids were little affected by the type of bags used. Also, the starch ranged from 35.2 to 50.4% dry matter (d.m.) without a specific trend, as well as amylose expressed on the starch basis (25.7 to 45.0%), suggesting no remarkable changes in starch functionality. 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, the application of VAC- and MAP-bags caused a considerable decrease in aerobic mesophils, moulds and yeasts growth compared to the control during two and four weeks of storage. After this period, the counts increased probably due to the appearance of microscopic cracks in the bags, as a result of their excessive expansion. During long-storage, no significant differences were noted in the colour of chestnut kernel between the MP-bags and the control, in the majority of the situations. Furthermore, the texture was also less affected. After six months, the weight loss was much lower in MP-bags (1.9%) than in control (23%). After six months, a significant difference in moisture content was observed between the control and MP-bags (42.7 and 55.2%, respectively), suggesting that the packaged chestnuts retained more the water. Titratable acidity, total soluble solids and starch did not vary significantly between packages. The reducing sugars were significantly influenced by the packaging type and storage time. The highest values were observed in unpackaged chestnuts (control). Along the storage period, some variability, without a definite trend, in the MP-bags, was observed. In control, the contents of reducing sugars increased from 0.09 to 2.06 g glucose/100 g d.m.. For the control and MP-bags, no significant differences in aerobic mesophilic and moulds and yeasts were observed at the end of storage. MP-bags demonstrated to be a promising solution for extending the shelf-life of chestnuts during long storage (6 months) by preserving the nutritional quality of the fruits. The results of the present study showed that the preservation of the chestnuts by the use of a specific type of packaging might have a substantial impact on preserving the colour and texture of the fruits, on preventing the weight loss and microbial growth and on maintaining the moisture content of the fruits.
- Effect of different packaging materials on the shelf-life of chestnut (Castanea sativa Miller) during short-time storagePublication . Askri, Firas; Pereira, Ermelinda; Correia, Paula; Lema, Filipe; Martins, Fátima; Oueslati, Souheib; Droga, Rui; Ramalhosa, ElsaChestnuts 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
- Effect of using microperforated bags on the storage of chestnut (Castanea sativa Mill) for six monthsPublication . Askri, Firas; Pereira, Ermelinda; Correia, Paula; Lema, Filipe; Martins, Fátima; Oueslati, Souheib; Droga, Rui; Ramalhosa, ElsaChestnuts are very consumed worldwide; however, it is a perishable product that loses weight and spoils quickly. So, it is crucial to find methods to reduce economic losses. Thus, the purpose of the present work was to study the effect of using microperforated bags (MP-bags) in long-storage of chestnuts in refrigerated industrial chambers for 1, 2, 3 and 6 months. The weight loss, colour, texture, water activity (aw), moisture content, titratable acidity (TA), total soluble solids (TSS), reducing sugars, starch, amylose, and microbiological analysis were determined. No significant differences were noted in the colour of the chestnut kernel between the MP-bags and the control (unpackaged chestnuts) in most situations. After six months, the weight loss was much lower in MP-bags (1.9%) than in control (23%), and a significant difference in moisture content was observed between both conditions (55.2 and 42.7%, respectively). After six months, TA and TSS varied between packages, while the starch did not. The packaging type and storage time significantly influenced the reducing sugars. The highest values were observed in control. Some variability, without a definite trend in the MP-bags, was observed along the storage period. In control, the contents of reducing sugars increased from 0.09 to 2.06 g glucose/100 g d.m.. No significant differences in aerobic mesophilic and moulds and yeasts were observed for the control and MP-bags at the end of storage. MP-bags demonstrated to be a promising solution for extending the shelf-life of chestnuts by preserving the nutritional quality of the fruits.