ارزیابی پایداری کشمش های آفتابی، طلایی و تیزابی با بکارگیری ایزوترم جذب رطوبت و نمودار حالت

نوع مقاله : مقاله پژوهشی

نویسندگان

• محسن اسمعیلی ¹
• علی حسن زاده ²

¹ دانشگاه اورمیه

² دانشگاه ارومیه

https://doi.org/10.22067/ifstrj.v8i4.20161

چکیده

ایزوترم جذب رطوبت و نمودار حالت سه نوع کشمش آفتابی، تیزابی و طلایی تهیه شد تا پایداری این محصولات ارزیابی و مقایسه گردد. ایزوترم ها در دماهای C° 15، 25، 35 با بکارگیری روش ایزوپیستیک تعیین و با مدل گب برازش گردید. دماهای گذار شیشه ای محصولات بوسیله گرماسنجی افتراقی (DSC) تعیین و با مدل گوردون تیلور برازش شد. داده های ایزوترم جذب مشخص کرد که در تمامی دماهای مورد بررسی، بیشترین مقدار جذب آب و مقدار رطوبت تک لایه درکشمش تیزابی و کمترین آنها در نمونه کشمش آفتابی وجود دارد. از روی نمودار حالت و رابطه‌ی بین دمای گذار شیشه ای، فعالیت آبی و رطوبت تعادلی، مقادیر فعالیت آبی بحرانی (CWA) و مقدار رطوبت بحرانی (CWC) هریک از محصولات تعیین شد. بر اساس نمودار حالت، CWC (بر اساس وزن خشک) کمتر از 03/0 و مقدار CWA کشمش ها کمتر از 05/0 برآورد گردید.

کلیدواژه‌ها

• کشمش
• پایداری
• ایزوترم جذب
• دمای گذار شیشه ای
• نمودار حالت

عنوان مقاله [English]

Investigating Stability of Sundried, Golden and Sultana Raisins Using Sorption Isotherm and State Diagram

نویسندگان [English]

• Mohsen Esmaiili ¹
• Ali Hassanzadeh ²

¹ Urmia University

² Urmia University

چکیده [English]

The sorption isotherm and state diagram of sundried, golden and sultana raisins were constructed for investigation and comparison of the product stability. The isotherms were measured at 15, 25 and 35 °C using an isopiestic method and the data were modeled with GAB model. Glass transition temperatures of the products were measured by differential scanning calorimetery (DSC) and fitted to Gordon Taylor model. Moisture sorption results indicated that the amount of moisture adsorption and the GAB monolayer moisture contents were the highest in sultana and the lowest in sundried raisins, at all of investigated temperature levels. Critical water activity (CWA) and critical water content (CWC) were estimated from the state diagram and the relationship between water activity, the glass transition and the equilibrium moisture content. According to the state diagram specification, CWC (dry basis) and CWA of raisins were estimated lower than 0.03 and 0.05, respectively.

کلیدواژه‌ها [English]

• Raisin
• Stability
• Sorption isotherm
• Glass transition temperature
• State diagram

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