Influence of lipid based edible coatings and temperature storage on quality of date fruit

  Date palm fruit (Phoenix dactylifera L.) is an important agricultural product of Iran. This fruit is a good source of energy and is rich in nutrients. Amongst several important varieties of dates, Mazafati in terms of marketability and consumption in Iran is placed in first rank. Because of unsuitable storage conditions and packaging types during storage period, fruit quality changes and so the product turns sticky and hard due to syrup exudation and moisture loss. To overcome this problem the application of edible coating is proper assistance. Edible coatings have been widely studied in the last years because of evidence about their beneficial effects on fruits and vegetables. Modification of fruits tissue metabolism by affecting respiration rate, extension of storage life, firmness retention, transportation of antimicrobials, antioxidants, and other preservatives and microbial growth control are the main functional advantages attributed to the use of edible films and coatings. There are different kinds of films and coats which are used such as polysaccharide, protein, lipid and composites. Lipid films have good water vapor barrier properties, due to their low polarity. Also temperature is one of the most important factors, which affect the shelf life and the quality of date fruits. The purpose of this research was to study the effect of lipid based edible coating (glycerylmonoestearate and carnauba wax) and storage temperature on quality of Mzafati date fruit. In this research Mazafati date fruit coated with lipid based coatings (glycerylmonoestearate and carnauba wax) and stored at 4 and 25 C° for 3 months. During this period of storage weight loss, hardness, titratable acidity, total soluble solids (brix), reducing sugars, color (lightness, redness and yellowness) and sensory properties (color, texture, flavor and total acceptance) of date palm fruit were evaluated. The experiments were factorial with a completely randomized design. The edible coating, temperature and storage time were the independent variables. Analysis of variance (ANOVA) was conducted for data using SPSS 21 software. Differences among the mean values were also determined using Tukey test. A significant level was defined as a probability of 0.05. Result showed that the coatings were effective to decrease the weight loss and rate changing titrable acidity and color and protecting sensory properties of the date palm. The coated date fruits had more titratable acidity than the control. Although difference of hardness, titrable acidity, total soluble solids and reducing sugars of the coated date palms not significant but carnauba wax coat was more effective to protect color and sensory properties. Edible coating caused increasing lightness, yellowness and sensory scores of date palm significantly. Increasing of storage temperature increased weight loss and decreased yellowness significantly. Increasing of storage time also caused increasing hardness, redness and decreasing lightness and sensory scores. At the end of storage time least value of weight loss and most value of yellowness (8.13% and -0.841 respectively) were related to 4 C° and glycerylmonoestearate coat also most value of lightness and total acceptance score and least value of redness (17.2, 3.1 and 3.99 respectively) were related to carnauba wax coat. The use of lipid based edible coating and low temperature storage could delay changes in physicochemical and sensory properties of date fruit and increase the shelf life of Mazafati date fruit