تاثیر روش نوین خشک کردن لایه نازک زعفران بر ترکیبات موثره و مقایسه با روش‌های مرسوم | The Impact of the New Thin-Layer Drying Technique on the Active Compounds in Saffron and a Comparison with Traditional Drying Methods

Persian. هدف از این پژوهش بررسی استفاده از ماده جاذب رطوبت سلیکاژل بر خشک­کردن زعفران و تاثیر ویژگی­های هوای ورودی به خشک­کن بر شاخص­های کیفی (رنگ، عطر و طعم) زعفران بود. اثرات تیمارهای سرعت هوای ورودی به خشک­کن (2/0، 4/0و 6/0 متر بر ثانیه) و دمای هوای ورودی به خشک­کن (30، 40 و 50 درجه سانتی­گراد)، پس از عبور از لایه ماده جاذب رطوبت، بر کیفیت زعفران بررسی شدند. مقادیر پیکروکروسین، سافرانال و کروسین زعفران خشک شده با این روش با دو روش خشک­کردن متداول زعفران یعنی روش­های اسپانیایی و سایه­خشک (سنتی) مقایسه شدند. نتایج نشان داد هوای ورودی به خشک­کن با دمای °C 30 و سرعت 6/0 متر بر ثانیه، باعث حفظ بیشترین مقادیر سافرانال (2/51) و پیکروکروسین (7/99) در زعفران شد. بیشترین مقدار کروسین (7/235) نیز در دمای °C 50 و سرعت 2/0 متر بر ثانیه اندازه گرفته شد. با توجه به تأثیر یکسان سرعت­های هوای 2/0 ، 4/0 و 6/0 متر بر ثانیه بر کیفیت محصول، سرعت 2/0 متر بر ثانیه به دلیل کاهش مصرف انرژی مناسب­ تشخیص داده شد. استفاده از دمای پایین (º C30) در خشک کردن، محصولی با کیفیت از نظر عطر و طعم ایجاد کرد. برای تولید کروسین (رنگ) بیشتر، نیاز به دمای بالا است. برای این منظور ضرورت دارد در انتهای خشک­کردن زعفران دمای بالاتر (º C50) اعمال گردد. کیفیت زعفران در روش استفاده از ماده جاذب رطوبت مشابه روش سنتی خشک کردن زعفران و نسبت به روش اسپانیایی بالاتر بود.

English. Introduction: Saffron originates from Iran. Due to the country's climatic conditions, it holds a unique significance among other agricultural products. The cultivation and production of saffron increases the export of the country. Saffron crocin is the main water-soluble carotenoid ester. It is a red compound with strong antioxidant power. The aroma of saffron is related to volatile compounds including safranal. The taste of saffron is due to a compound with a bitter taste called picrocrocin. The quality of saffron is related to the concentration of the three main compounds crocin, picrocrocin and safranal. Drying is the most important part of saffron processing, which effects on the physicochemical and sensory quality of saffron and is done in different methods. Moisture absorbent materials cause the transfer of moisture between the absorbent material and the air. The absorbent material, which has low moisture content, draws moisture from the air until it reaches equilibrium. The advantages of moisture-absorbing materials for drying products include low energy consumption and the ability to maintain continuous drying even during non-sunny hours. There is not any research in the field of using moisture absorbing compounds in drying saffron. The purpose of this research was to investigate the effect of the characteristics of the inlet air to drier containing moisture absorbent material on the quality indicators (color, aroma and taste) of saffron.   Materials and Methods: First, the stigmas were separated from the saffron flowers and prepared for drying. Silica gel moisture absorbent material was used in this project. Air with three speeds of 0.2, 0.4 and 0.6 m/s and three temperatures of 30, 40 and 50 degrees Celsius after passing through the layer of moisture absorbing material entered the dryer and their effect on the amount of picrocrocin , safranal and crocin were investigated and the optimal speed and temperature of the inlet air were measured. The effect of drying method on the quality of saffron was investigated.  Saffron was dried using three Spanish methods, traditional and moisture absorbing materials, and the effect of the drying method on the amounts of picrocrocin, safranal and crocin in saffron was investigated.   Results and Discussion: The effects of the speed of the air (0.2, 0.4 and 0.6 m/s) and the temperature of the air (30, 40 and 50 °C) entering the drier with a moisture absorbent material were investigated on the quality indicators of saffron. The amounts of picrocrocin, safranal and crocin of dried saffron by this method were compared with two common methods of drying saffron, such as spanish and traditional methods. The results showed that the air entering to drier with a temperature of 30°C and a speed of 0.6 m/s kept the highest amounts of safranal (51.2) and picrocrocin (99.7) in saffron. Picrocrocin and safranal in saffron as two factors of taste and aroma, play a very important role. These two compounds have a good relationship in its chemical structure. The highest amount of crocin (235.7) was also measured at a temperature of 50 °C and a speed of 0.2 m/s. All of the used air speeds had a similar effect on the quality indicators of saffron.   Conclusion: The use of silica gel moisture absorbent in the process of drying saffron can significantly help in drying saffron with high quality (taste and aroma). It is also possible to recharge the silica gel grains, so using it for drying is economically justified. The speed of 0.2 m/s of air entering to drier was considered due to the reduction of energy consumption. The use of low temperature (30ºC) in drying saffron created a product with a desirable aroma and taste. In order to producing more crocin (color), the higher temperatures were needed. For this purpose, it is necessary to apply a high temperature (50ºC) at the end of drying saffron. The quality of saffron in the method of using a moisture absorbent material was similar to the traditional method for drying saffron and was higher than the spanish method.