بررسی اثرتعداد لایه‌ها و غلظت‌های مختف پوشش‌های خوراکی کربوکسی‌متیل‌سلولز و کاراگینان بر کارایی فرایند خشک کردن اسمزی سیب زرد لبنانی

در طی فرایند آبگیری اسمز، مواد جامد محلول توسط بافت ماده غذایی جذب شده و اثرات نامطلوبی بر خروج آب، خصوصیات تغذیه ای و حسی می‌گذارد. لذا برای بهبود فرایند اسمز از پوشش های خوراکی استفاده می شود. بهترین شاخص برای ارزیابی یک پوشش، کارایی فرایند (نسبت خروج آب به جذب مواد جامد) است. در این پژوهش از دو پوشش کربوکسی متیل سلولز و کاراگینان در سه غلظت 5/0، 1 و 5/1 درصد، به‌صورت یک لایه و دو لایه، جهت پوشش دهی قطعات مکعبی سیب زرد لبنانی و محلول اسمزی ساکارز با غلظت 30، 45 و 60 % استفاده شد. نتایج نشان داد که نمونه یک بار پوشش داده شده با کاراگینان 1% و تیمار شده در ساکارز 60 % و نمونه های یک و دو لایه پوشش داده شده با کربوکسی متیل سلولز 5/0% بیشترین میزان کارایی فرایند را داشته اند و به‌عنوان تیمارهای برگزیده به‌دست آمدند. این نمونه ها میزان جذب مواد جامد را کاهش داده و تاثیر قابل توجهی بر روی خروج آب نگذاشته اند. همچنین نتایج بیان گر این موضوع است که با افزایش غلظت محلول اسمزی ساکارز از 30 به 60% میزان حذف آب و جذب مواد جامد افزایش می یابد.

Evaluating the influence of number of layers and concentration of carboxymethyl cellulose and carrageenan coating on osmotic dehydration performance of Golden delicious apple

Introduction: Osmotic dehydration involves the partial removal of water by direct contact of a product with a hypertonic medium such as high concentration of sugar, salt or sugarsalt solutions. In this process, food pieces are immersed in a hypertonic solution. The natural membrane of food cells acts as a semipermeable layer so the water moves across the membrane from an area of high water potential (low solute concentration) to an area of low water potential (high solute concentration), meaning the driving force for water removal is the concentration gradient between the solution and the intracellular fluid. During osmotic dehydration, osmotic solute is absorbed by food materials and has undesirable effects on water removal, nutritional and organoleptic properties. Use of coating improves the osmotic processing. Best factor for evaluation of coating material is performance ratio (WL/SG). So a coating should reduce solid uptake without negative effects on water removal.Materials and methods: The apples (Golden delicious) used in this study were purchased from a local market in Mashhad (Iran) and stored at 46°C before processing. The sucrose (99.9%, Fariman sugar company, Iran), carrageenan (kappa type, Negin Khorak Pars Company, Iran), carboxy methyl cellulose (sandros, Japan) and calcium chloride (Dr. Mojallali Lab., Iran) were also used. In this work, apple cubes were single and double coated in three concentrations (0.5, 1 and 1.5% w/w) of carboxy methyl cellulose (CMC) and carrageenan solution and dehydrated osmotically in different concentrations (30, 45 and 60˚ BX) of sucrose solutions. Results and Discussion: The results of this study indicated that increasing coating solution concentration from 0.5% to 1.5% decreased water loss. Also the water loss increased when the number of coating layers and the concentration of osmotic solution increased (from 30 to 60 ˚ BX). Generally, water loss and solids uptake in the samples coated with carrageenan was higher and lower than their CMC counterparts, respectively. The solids uptake in the samples coated with CMC increased by increasing the number of layers, osmotic solution concentration (from 30 to 60˚BX) and coating solution concentration (from 0.5 to 1.5%). The solids uptake increased and decreased with increase in layer number and coating solution concentration (from 0.5% to 1.5%), respectively. Increasing the osmotic solution concentration up to 45 ˚ BX increased solids uptake but, more increasingly did not have a significant effect on it. Finally, it cannot be said strictly that one coating type would facilitate osmotic process or not. It depends on various process factors. Among the 36 treatments studied in this research, the single coated samples with 1% carrageenan treated in 60 ˚ BX sucrose solution and the single and double coated samples with 0.5% CMC treated in 45 ˚ BX sucrose solution were the best, as they had 50% higher performance ratio than control (uncoated) sample.