نقش دمای انتقال شیشه ای در کنترل تغییرات رنگ و بافت انجیر خشک

نویسنده
فوژان بدیعی
موسسه تحقیقات فنی و مهندسی کشاورزی، سازمان تحقیقات، آموزش و ترویج کشاورزی
10.52547/fsct.18.116.221
چکیده
انجیر تازه میوه ­ای فسادپذیر است که عمر انباری کوتاهی دارد. از اینرو، خشک کردن روشی مناسب برای افزایش ماندگاری انجیر است. تغییر رطوبت انجیر خشک در مدت نگهداری می­ تواند تاثیر نامطلوبی بر بافت و رنگ آن بگذارد. هدف از این تحقیق ارزیابی اثر رطوبت بر ویژگی­ های انجیر خشک با استفاده از دمای انتقال شیشه ­ای(Tg) است. Tg، دمای ذوب بخش بلوری (Tm) و انتالپی ذوب (ΔH) انجیر خشک در رطوبت­­های مختلف با دستگاه گرماسنج پویشی تفاضلی (DSC) اندازه­ گیری شد. دمانگاشت DSC نشان داد که انجیر خشک ساختاری نیمه بلوری دارد. با افزایش رطوبت نمونه ­ها، Tg و Tm کاهش یافت و انتالپی ذوب (ΔH)، با افزایش رطوبت افزایش یافت. نتایج نشان داد که آب پلاستی­ سایزری قوی و مهم برای انجیر خشک است و سفتی بافت را به­ طور معنی­ داری کاهش ­داد. اندازه­ گیری تغییر رنگ بافت انجیر خشک در رطوبت­ های مختلف نشان داد که با افزایش رطوبت، بافت انجیر به ­طور معنی­داری تیره­ شد. برای بررسی تغییر بافت، رنگ و تبلور انجیرخشک در رطوبت­ های مختلف، فاکتور اختلاف دما (ΔT) بین دمای محیط و Tg تعیین شد. با افزایش مقدار ΔT روند کاهش سفتی بافت بیشترشد و مقدار ΔE و میزان تبلور افزایش یافت.
کلیدواژه‌ها
انجیرخشک
دمای انتقال شیشه‌ای
انتالپی ذوب
سفتی بافت
تغییر رنگ

موضوعات

عنوان مقاله English

Role of glass transition temperature in color and textural changes of dried fig

نویسنده English

Fojan Badii
Agricultural Engineering Research Institute (AERI), Agricultural Reseach, Education and Extension Organization (AREEO)
چکیده English

Fresh fig is a highly perishable fruit with a very short storage life. Therefore, drying is the most common method for fig preservation. Changes in water content during storage may lead to undesired physical changes in dried fig which is of great importance in its structure and quality. The objective of this study was to assess the effect of water on the physical properties of dried fig, using glass transition temperature (Tg). Tg, melting temperature (Tm) and the melting enthalpy (ΔH) of dried figs at different moisture contents were measured using differential scanning calorimetry (DSC). DSC thermogram showed that dried fig has a semi-crystalline structure. Tg and Tm decreased while ΔH associated with the melting of the ordered structure increased with increasing moisture content of fig. The results showed that water is a strong plasticizer for dried fig and reduced flesh firmness of fig significantly. Measuring color differences of dried fig at different moisture contents showed that by increasing water, fig flesh became darker significantly. Changes in texture, color and crystallinity of the dried fig as function of moisture were assessed using temperature difference (ΔT) between the fig temperature (T) and Tg. By increasing ΔT, the rate of firmness reduction, ΔE value and the extent of crystallinity increased.

کلیدواژه‌ها English

Dried fig
Glass transition temperature
melting enthalpy
Flesh firmness
color
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