تأثیر غلظتهای مختلف چیتوسان بر عمر انبارداری و کیفیت پس از برداشت میوه زغال اخته (Cornus mass L.)
نویسنده مسئول: اسمعیلی، مریم؛
پژوهش های صنایع غذایی زمستان 1398 - شماره 37 علمی-پژوهشی (وزارت علوم)/ISC (14 صفحه - از 139 تا 152)
زمینه مطالعاتی: امروزه کنترل ضایعات پس از برداشت و اولویت دادن به استفاده از روشهای سالم نسبت به استفاده از سموم شیمیایی در پرورش محصولات باغبانی ضروری است. در سالهای اخیر، استفاده از پوششهای خوراکی مانند چیتوسان به منظور کاهش ضایعات پس از برداشت، کاهش سرعت متبولیسم محصول، افزایش عمر انبارمانی و کنترل رشد میکروبی در انواع میوهها رواج پیدا کرده است. هدف: هدف از پژوهش حاضر، تشخیص مناسبترین غلظت چیتوسان در راستای حفظ خاصیت آنتیاکسیدانی محصول زغال اخته، شاخصهای کمی، کیفی و ترکیبهای آنتیاکسیدانی پس از برداشت میوهها بود. روش کار: میوههای سالم و یکنواخت زغال اخته پس از برداشت با غلظت های مختلف چیتوسان (5/0، 1 و 5/1 درصد) بمدت 1 دقیقه تیمار شده و سپس در دمای 1±4 درجه سانتیگراد و به مدت 21 روز انبار شدند. نمونهبرداری جهت مطالعات مختلف بعدی در روزهای 7، 14 و 21 صورت گرفت. نتایج: نتایج آزمایش نشان داد که اثر متقابل زمان و غلظت چیتوسان بر میزان فعالیت آنزیم گایاکولپراکسیداز معنیدار نیست. با این حال تیمار چیتوسان در حفظ میزان اسیدیته قابل تیتراسیون، آنتوسیانین کل، فنل کل، فلاونوئید کل، خاصیت آنتیاکسیدانی و فعالیت آنزیم کاتالاز بیشترین تأثیر را داشت. همچنین فعالیت آنزیمهای پلیفنلاکسیداز و فنیل آلانین آمونیالیاز در غلظت صفر درصد بیشتر بود. نتیجه گیری نهایی: با توجه به نتایج کلی آزمایش، معلوم شد که تیمار ۱ درصد چیتوسان نسبت به سایر غلظتهای آن در حفظ صفات فیزیکوشیمیایی میوههای زغال اخته بهتر عمل نمود.
Introduction: Controlling the postharvest losses and the utilization of safe methods versus chemical compounds is a remarkable priority in the production of horticultural produce. Using techniques to preserve agricultural produce quality dates back to many decades ago (Paliath et al., 2009). This is essential to keep the visual characteristic and quality of products. In some ways, the procedures employed improve the quality and organoleptic properties of the crops. This is end goes to the reduced production charges and the higher incomes (Duan et al., 2007). Postharvest scientists are attempting to employ the materials to cover the fruits and to keep the harvest time quality or even to improve the quality and visual attributes. During the recent years, the application of edible coatings such as chitosan has been increased to reduce the postharvest loses, lowering the respiration rate, shelf life improvement, firmness keeping and for the control of microbial growth rates in fruit crops. Chitosan is an aliphatic organic polymer with a characterized antifungal (Allan and Hadwiger, 1979) property. Furthermore, chitosan coating lowers the respiration rate, prevents microbial growth and delays the fruit ripening by the control of CO2, O2 and ethylene exchange balance (EL Ghaouth et al., 1991). Moreover, low temperature storage intensifies the chitosan keeping qualities on stored fruits. Cornelian cherry fruits contain high amounts of ascorbic acid (vitamin C), organic acids, phenolics,taninns and some other bioactive compounds. Hence, the fruits have considerable nutritional and medicinal benefits effects (Moldovans et al., 2016). Furthermore, the fruits have precious antimicrobial properties (Asadov, 1990). In the present study, we tried to evaluate the effects of different chitosan concentration to keep the antioxidant potential of cornelian cherry and of the quality attributes during postharvest period. Material and methods: Cornus mass L. fruits were harvested from an orchard from northwest of Iran (Hourand country). In advance, the fruits were homogenized for the size, color and shape and were transferred to the Lab. The fruits were treated with 0.5,1 and 1.5 % chitosan solution and distilled water as control for 1 minute. The fruits let too dry at ambient temperature and were stored at 4±1°C for 21 days. TSS, TA and pH were evaluated in fruit juice soon after. Samples were taken during the first, 7, 14 and 21th days after treatment. The fruits were kept at cold storage and immediately the common measurements like pH, TSS and TA were conducted. Then after the fruits were freezed in liquid nitrogen and kept in - 40 °C for further studies. Total phenolics, Flavonoids and anthocyanin were measured by folin- ciocaltea (Gallic acid as standard), flavonoids based on catechin and total anthocyanin by the absorbance difference in divers pH ratios, respectively. DPPH method was employed for the antioxidant potential of fruits. Besides CAT, GPX, PPO and PAL enzymes were quantified as well. The data were analyzed by SAS (ver.9.2) software as CRD with three replications. Excel 2013 was employed for the tables figuration and the means were compared by the Duncan's multiple range test. Results and discussion: ANOVA results revealed that interaction of storage time × chitosan concentration meaningfully (P 2 and O2 alters the TA and pH values. Maturity stage influences TSS values and with ripening progress, TSS was increased (Gunduz et al., 2012). In a similar experiment, with chitosan concentration adding up, TSS increase was slowed down seemingly due to the hydrolytic changes in the starch content and water loss during the storage period (Kays, 1997). Interaction of time and chitosan concentration was statistically influenced (P 2 barrier induced by chitosan which reduces the phenolics oxidation. Moreover, chitosan coating activates PAL enzyme in phenolics biosynthesis (Romanazzi et al., 2017). Total flavonoids were increased by storage time, and by 1% of chitosan treatment. Flavonoids are crucial antioxidants and besides phenolics were increased in the fruits during the storage time and with SA treatment (Dokhanieh et al., 2013). Total anthocyanins followed the same pattern as well. Antioxidant potential of fruits was also impacted by storage time and chitosan as well (P 2 and SA improved the metabolites and antioxidant potential (Dokhanieh et al., 2013; Soleimani-Aghdam et al., 2013). CAT, PPO, GPX and PAL were influenced by the time× chitosan interaction as well. CAT activity was declined during the storage period. But, there was no significant difference between 0, 1 and 1.5% chitosan treatments. Chitosan application improves the selective permeability of membrane for CO2 and O2 exchange and hence reduce the phenolics oxidation. These all reduce the PPO activation and function (Duan et al., 2007). GPX activity was increased during the storage, So, that the highest GPX activity was belonged to the sampling at 21th days. PAL activity was responsive to the interaction of time × chitosan concentration and the enzyme activity was increased in time dependent pattern during the storage. The top data was recorded for the untreated fruits. Conclusions: Cornelian cherry fruitsare rich in antioxidant compounds like phenolics, flavonoids, anthocyanins and ascorbic acid. During the storage period and like other horticultural products (fruits and vegetables), the nutritional and visual quality of cornelian cherry fruits reduces dramatically. Chitosan as an environment-friendly and non-chemical compound preserves the quality attributes of fruits. Over all, in the present experiment, chitosan treated fruits had more antioxidant potential and enzymatic activity than untreated ones. Moreover, chitosan improved the total quantities for phenolics, flavonoids and anthocyanins. DPPH antioxidant potential was improved by chitosan application. Furthermore, CAT, PPO and PAL were correspondingly responded to chitosan treatment in favor of fruits quality. In short, chitosan has a considerable potential to be considered as a good edible coating to improve the postharvest life and quality attributes of cornelian cherry fruits.
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