ارزیابی خصوصیات فیزیکی و شیمیایی زالزالک (crataegus pinnatifida) طی نگهداری در شرایط مختلف و مدل‌سازی تغییرات با مدل‌های سینتیکی

شرایط نگهداری نامناسب منجر به کاهش کیفیت قابل‌توجه زالزالک می‌گردد که بر پذیرش نهایی مصرف‌کننده موثر است. تاکنون پژوهشی مبنی بر بررسی تاثیر شرایط نگهداری بر تغییرات خصوصیات فیزیکی و شیمیایی میوه زالزالک گزارش نشده است. در پژوهش حاضر تغییرات در خصوصیات فیزیکی و شیمیایی مرتبط با کیفیت میوه طی نگهداری زالزالک تحت شرایط مختلف نگهداری (محیط، یخچالی و سردخانه) موردارزیابی قرار گرفت؛ سپس پنچ مدل سینتیکی (مدل‌های درجه صفر، درجه اول، درجه دوم، تبدیل جزء و ویبال) بر داده‌های تجربی برازش گردید و پارامترهای مدل توسط تحلیل رگرسیونی محاسبه گردید. شرایط و زمان نگهداری تاثیر معناداری بر خصوصیات فیزیکی و شیمیایی (به‌غیر از برخی خصوصیات هندسی) داشت و تغییرات قابل‌توجهی در رنگ، سفتی بافت و افت وزن زالزالک رخ داد. سفتی بافت، اسیدیته قابل‌تیتر، ph، شاخص رسیدگی، خصوصیات رنگی (به‌غیر از خصیصه‌های a* و c*) به‌طور معناداری کاهش یافت و افت وزن، میزان مواد جامد محلول و خصیصه‌های a* و c نیز به‌طور معناداری افزایش پیدا نمودند. نتایج نشان داد که مدل‌های سینتیکی درجه اول و ویبال بهترین توصیف را از تغییرات خصوصیات فیزیکی و شیمیایی نشان دادند. وابستگی دمایی کیفیت میوه به شرایط نگهداری به‌طور موفقیت‌آمیزی توسط معادله آرنیوس توصیف گردید. خروجی این پژوهش نتایج مفید و ارزشمندی برای شرایط و نحوه نگهداری زالزالک فراهم می‌آورد.

Evaluation of physicochemical characterization of hawthorn (Crataegus pinnatifida) during various storage conditions and modeling of changes using kinetic models

Introduction: Hawthorn (Crataegus pinnatifida), belonging to the Rosaceae family, consists of small trees and shrubs. The color of the ripe fruit varied from yellow, through green to red and on to dark purple. Most of the species ripen their fruit in early to mid-autumn. Beneficial effects of hawthorn fruit extracts have been confirmed by various studies. Pharmacological data showed that hawthorn fruit and its preparations enhance myocardial contraction and conductivity, protect against ischemia. They have a sedative action, a protective effect against arrhythmia and increase of coronary vessel flow. They have also positive effects on the cardiovascular system. Hawthorn is one of the most widely consumed horticultural products, either in fresh or processed form. It is also an important component of many processed food products because of its excellent flavor, attractive color and high content of many macro- and micro-nutrients. Uncertain storage conditions lead to considerable quality loss in hawthorn fruits, which affect their consumer acceptability. Properties such as color, firmness and moisture provide valuable information for the monitoring of quality changes in postharvest fruits because of their reliability and rapid and easy measurement. These changes are consequences of many biochemical and physiological processes that occur during fruit ripening, such as respiration and transpiration. In addition, these changes depend on the external conditions to which the fruit is exposed. To estimate changes in fruit quality as a function of storage conditions, the evolution of certain quality-indicative properties such as color, firmness or weight can be used to provide related information on the quality grade of the product stored. Kinetic models can be used as tools to describe quantitative physicochemical changes in foods during processing. Kinetic models can be linear or non-linear forms of rate law equations. The rate process of food constituents is usually defined by zero, first or second order kinetics. Method and material: In this study, changes in physicochemical characteristics associated with fruit quality were investigated during various hawthorn fruit storage conditions include: cold (1ºC and RH=90%), refrigerator (10 ºC and RH=85%) and room conditions (25 ºC and RH=60%). Color quality parameters (L*, a*, b*, C*, h* and ΔE), geometrical parameters, weight loss, firmness, total soluble solid (TSS), pH, titratable acidity (TA) and ripening index (RPI) were the measured factors. Different mathematical models were successfully proposed and adjusted to represent the change in physicochemical properties as a function of storage temperature. Among various kinetics model, five models (Zero-order, First-order, Second-order, Fractional conversion and Weibull models) were fitted to experimental data and model parameters in equations were determined by multiple regression analysis. Result and discussion: Storage of hawthorn fruits at different temperature affected their color (L*, a*, b*, C*, h* and ΔE), geometrical, physical (weight loss, firmness) and chemical properties (TSS, pH, TA and RPI). Storage at all conditions had significant impact on the physicochemical parameters analyzed (except some geometrical characteristics). Significant alterations in hawthorn color, firmness and weight loss were observed. The firmness, titratable acidity, pH, ripening index, color characteristics (except a* and C*) decreased while weight loss, total soluble solid, a* and C* increased significantly (p<0.05). Hawthorn stored at low temperatures revealed a delay on quality reduction reactions in terms of color, firmness and weight loss. The results indicated that the First-order and Weibull kinetic models provided the best prediction of the changes in physicochemical parameters. The storage temperature effect was successfully described by the Arrhenius law. Understanding the mechanisms in which these conditions affect the quality changes processes is of great importance because it allows their appropriate modification to maintain quality and maximize storage time. The outcomes of this study provide additional and useful information for hawthorn fruits under various storage conditions.