مطالعه روند خشک‌شدن گوشت میگوی پرورشی در خشک‌کن هوای گرم همرفتی و تغییرات برخی فراسنجه‌های مرتبط با آن

روند خشک‌کردن میگوی پرورشی (litopenaeus vannamei) پوست‌گیری‌شده در یک خشک‌کن هوای گرم همرفتی برای تعیین فراسنجه‌های چروکیدگی، سینتیک خشک‌شدن، جرم حجمی و ضریب انتشار موثر رطوبت مورد مطالعه قرار گرفت. بدین منظور نمونه‌های میگو به شکل ورقه در سه سطح دمای 40، 50 و 60 درجه سلسیوس با سرعت ثابت هوای 1.5 متر بر ثانیه در دستگاه خشک‌کن ساخته‌شده، خشک شدند و وزن و حجم نمونه‌ها طی فرآیند خشک‌شدن، برای مدل‌سازی مورد استفاده قرار گرفتند. از بین مدل‌های تجربی در نظر گرفته‌شده برای چروکیدگی و سینتیک خشک‌کردن، مدل خطی بهترین مدل برای بیان تغییرات چروکیدگی در مقابل تغییرات نسبت رطوبت و مدل توزیع ویبال به‌عنوان بهترین مدل برای بیان تغییرات نسبت رطوبت-زمان انتخاب شد. از یک مدل تجربی وابسته به رطوبت برای بیان تغییرات جرم حجمی ظاهری میگو استفاده شد که با تخمین ضرایب آن، دامنه 3-kg m 1117-1050 به‌دست آمد. افزون بر آن برای بیان اثر محتوای رطوبت و دما بر ضریب انتشار موثر رطوبت میگو یک رابطه آرنیوسی استخراج شد. بر اساس نتایج، تغییرات ضریب انتشار موثر رطوبت میگو در دامنهm^2 s^-1  9-10×0.08 تا m^2 s^-1 9-10×7.39 به‌دست آمد. اثر بسط تعداد جملات قانون دوم فیک بر تغییرات نسبت رطوبت برای معادله ضریب انتشار موثر، مورد مطالعه قرار گرفت و مشخص شد افزایش تعداد‌ جملات بیشتر از 100 جمله اثر قابل‌ملاحظه‌ای در دقت خروجی مدل ندارد و بر همین اساس تعداد صد جمله برای تخمین ضریب انتشار رطوبت توصیه می­‌شود. همچنین برای تعیین این ضریب، اثر چروکیدگی به‌عنوان عامل تاثیرگذار باید لحاظ گردد.

study on drying process of farmed shrimp meat in a hot air convective dryer and variation of some related parameters

introductiondrying shrimp is one of the storage methods that, while increasing the shelf life, leads to the production of a versatile product with various uses, from consumption as snacks to use as one of the main components of foods. drying is preferred over other preservation methods because it offers numerous advantages, including extended shelf life, enhanced microbial stability, convenient consumption, reduced transportation costs, increased value, and product diversity.to accurately model these processes and thus obtain information on factors such as shelf life and energy consumption, it is necessary to determine the product’s initial and final temperatures, its geometry and dimensions, and its thermo-physical characteristics. simulation of different drying processes requires accurate estimation of the effective moisture diffusion coefficient, which is highly dependent on temperature and humidity. its dependence can be shown by an equation with an arrhenius structure as an empirical function of humidity and temperature, or by considering the activation energy.it is necessary to have sufficient knowledge about heat and mass transfer characteristics, such as diffusion or penetration coefficient and the heat transfer coefficient to estimate the final temperature and drying time. this study investigated the drying process of peeled farmed shrimp (litopenaeus vannamei) using a convective hot air dryer. various parameters such as shrinkage and the effective moisture diffusion coefficient were examined.materials and methodsa drying device was built to conduct experimental studies on drying shrimp samples. the experiments were conducted on sliced shrimp meat samples at temperatures of 40, 50, and 60 degrees celsius, with a constant air velocity of 1.5 m/s. the experimental drying models were based on diffusion theory. in these models, it is assumed that the resistance to moisture diffusion occurs from the outer layer of the food. in most cases, fick’s second law was used to describe the phenomenon of moisture penetration.the study used the standard method of immersion in toluene to measure volume changes in the samples. during the drying process, the volume of the samples was measured at 45-minute intervals, and their volume changes were calculated. to measure the moisture content of the samples, each test started by recording the initial weight of the samples using a digital scale with an accuracy of ±0.001 g. during the drying process, the samples were weighed each time their volume was measured.shrinkage during the drying process is commonly modeled by finding a relationship between shrinkage and moisture, using linear and non-linear models. in most cases, effective permeability is defined as a function of humidity and temperature. for this purpose, curve-fitting methods were employed to analyze the data collected from experimental tests. the appropriate function was extracted by incorporating the arrhenius equation, which is applicable to most food items.results and discussionbased on the results of statistical indices, the linear model was the best model for depicting the relationship between shrinkage changes versus moisture ratio changes among the various experimental models evaluated for shrinkage and drying kinetics. similarly, the weibull distribution demonstrated superior performance in expressing variations in moisture ratio over time. a moisture dependent experimental model was used to express the variations in the apparent density of shrimp, resulting in a computed range of 1017-1117 kg m-3. furthermore, an arrhenius equation was derived to express the effect of moisture content and temperature on the effective diffusion coefficient of shrimp. according to the results, the effective diffusion coefficient of shrimp exhibited variations ranging from 0.08 ×10-9 m2 s-1 to 7.39×10-9 m2 s-1. when deriving the effective diffusion coefficient, the impact of the number of terms in fick’s second law on the variation of the moisture ratio was studied. the findings revealed that increasing the number of terms beyond 100 did not significantly affect the model’s outputs.conclusionthe linear model had the highest coefficient of determination (r2) among the evaluated shrinkage models, as well as the lowest root mean square error and sum of square error (sse). this makes it the most optimal model for interpreting shrinkage at the tested temperature levels. the weibull distribution experimental model proved to be the most suitable for expressing changes in the moisture ratio of shrimp meat slices over time within the evaluated temperature range. the arrhenius model accurately predicts changes in the effective diffusion coefficient of shrimp slices with respect to temperature and moisture content within the tested temperature range.