نوع مقاله : مقاله پژوهشی
نویسندگان
بخش تحقیقات فنی و مهندسی کشاورزی، مرکز تحقیقات و آموزش کشاورزی و منابع طبیعی استان خراسان رضوی، سازمان تحقیقات، آموزش و ترویج کشاورزی، مشهد، ایران.
چکیده
پژوهش حاضر با هدف بررسی تاثیر خشک‌کردن لایه نازک بر ویژگی‌های کمی و کیفی گلبرگ زعفران و همچنین تعیین شرایط بهینة خشک کردن صورت پذیرفت. طراحی آزمایش تجربی خشک کردن گلبرگ زعفران با استفاده از نرم‌افزار سطح پاسخ و طرح مرکب مرکزی محوری انجام گردید. گلبرگ‌ها در دماها (40، 50 و60 درجه سلسیوس) و سرعت‌های هوای متفاوت (7/0، 4/1 و 1/2 متر بر ثانیه) در خشک‌کن لایة نازک خشک شدند و ویژگی‌های کمی و کیفی (میزان ترکیبات فنلی کل، میزان ترکیبات آنتوسیانینی کل، قدرت گیرندگی رادیکال آزاد DPPH، غلظت لازم برای غیر‌فعال کردن50 درصد از رادیکال‌های آزاد DPPH، قدرت احیاءکنندگی آهن سه ظرفیتی و مولفه‌های رنگی L (میزان روشنایی)، a (میزان قرمزی- سبزی) و b (میزان آبی- زردی)) آنها مورد ارزیابی قرار گرفت. پس از تجزیه و تحلیل آماری، دما و سرعت هوای بهینة خشک کردن گلبرگ زعفران با حفظ ویژگی‌های کمی به ترتیب50 درجة سلسیوس و 4/1 متر بر ثانیه تعیین شد. در شرایط بهینه خشک کردن، میزان ترکیبات فنلی کل، میزان ترکیبات آنتوسیانینی کل، قدرت گیرندگی رادیکال آزاد، قدرت احیاءکنندگی آهن سه ظرفیتی و میزان مولفه رنگی a (قرمزی- سبزی) به‌ترتیب 39/46میلی‌گرم بر گرم، 58/1205 میلی‌گرم بر لیتر عصاره، 97/52 درصد و 52/1276 میکرومول آهن П بر لیتر و 13/11 به‌دست آمد که از نظر آماری اختلاف معنی‌داری با نمونة شاهد داشت. خشک کردن گلبرگ در نقطه بهینه نتایج به‌دست آمده را تایید نمود.
کلیدواژه‌ها
عنوان مقاله [English]
Optimazation of thin layer drying conditions of saffron petal using Response Surface methodology
نویسندگان [English]
- Parvin Sharayei
- Hossein Chaji
Department, Khorasan Razavi Agricultural and Natural Resources Research and Education Center, AREEO, Mashhad, Iran.
چکیده [English]
Introduction: Saffron (Crocus sativus) is the most expensive kind of spice in the world while around 400 tons of saffron are estimated to be produced in the current Iranian year (March 2016-17) from 90,000 hectares of land under saffron cultivation across the country. But, high share of producing saffron is exclusively dedicated to produce and dry saffron stigma as whereas their violet color petals are mostly ignored and disposed. Saffron petal is one of the most economical sources of anthocyanin pigments. Attractive colour, functional properties and antioxidant properties of anthocyanins can make them a good substitute for synthetic pigments in the food industry. But, due to high moisture content of petals, 96.36% db, they must be dehydrated immediately to prevent the decay. In the meanwhile, the drying conditions are also too critical to petal sensitive compounds while the method of drying along with drying period and the amount of energy consumed, obviously play a significant role on price and quality of the final product.
Materials and methods: In this study, the optimization of the thin layer drying conditions of saffron petal was investigated using response surface methodology (RSM) and Face Centered Experimental Design (FCED) in order to designate the empirical expriments. Saffron petals were dried at different temperatures (40, 50 and 60◦C) and air velocities (0.7, 1.4 and 2.1 m.s-1) in a thin layer dryer and quantitative and qualitative characteristics of saffron petals (color )L: brightness; a: red – green; and b: blue-yellow, total phenolic compounds (TPC), total anthocyanin components (TAC), scavenging activity of DPPH (RSA), ferric reducing-antioxidant power (FRAP) and minimized 50% of radical-scavenging activity (IC50) contents) were invetigated.
Results & discussions: Maintaining the quality of final dried product as high as possible is a major concern while it is an important aspect to consider for use of phenolic compounds and anthocyanins as antioxidants and colorants in food industry. The results showed that the total phenolic compounds (TPC) and total anthocyanin content (TAC) had a remarkable increase with temperature rise from 40 to 50◦C while more temperature increase brought about sharp drops. But, an increasing trend of variations is observed in parallel with increases in velocity of drying air for each temperature. The rise in anthocyanin and phenolic content is more attributed to much significant reduction in drying duration from 40 to 50◦C in comparison with 50 to 60◦C. It was also observed that total antioxidant activity of dried saffron petals showed the same response as TPC and TAC to temperature rise from 40 to 50◦C. Such behaviour could be explained by the findings of other researchers in which the antioxidant activity has high correlation with anthocyanin content and total phenolic composition of food materials. As a complementary, it can be mentioned that polyphenols in an intermediate stage of oxidation have greater antioxidant power than initially even though this is temporary; furthermore high temperature stabilization procedures may lead to the formation of new compounds with higher antioxidant activity. This is essentially the case of the Maillard reaction, which creates various Maillard reaction products, with markedly higher antioxidant power.
Conclusion: Generally, according to Derringer’s desired function approach, the optimal conditions were 50◦C and 1.4 m.s-1.The experimental values agreed with those predicted values. At this optimum condition, the TPC, TAC, DPPH, FRAP, and a value of the dried saffron petal were found to be 46.39 mg/ g ,1205.58 mg/l, 52.97%, 1276.52 µmol Fe2+/l, and 11.13, respectively. The experimental values were in a good agreement with the predicted values.
کلیدواژه‌ها [English]
- antioxidant properties
- Anthocyanin
- Drying
- Phenolic compound
- saffron petal
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