Effect of Edible Coating Based on Whey Protein and Zataria multiflora Bioss Extract on the Shelf Life of 'Shah Mive' Pear (Pyrus communis)

The goal of coating development was to improve quality and increase durability of product. Application of edible coatings is a suitable method to maintain quality and reduce from wasting in fresh vegetables and fruits. In this study, durability of pear during 21 days of storage was investigated by using a coating based on whey protein (2.5-5%), Zataria multiflora extract (0-500 mu l) and glycerol (0.375-2.25 g). Zataria multiflora extract was prepared by hydrodistilation. This coating was a solution of concentrated whey protein (85% protein content) in distilled water and glycerol as plasticizer. The pear was coated by immersion at 20 degrees C and after the coating was dried it was put in to a disposable dish without a cap and maintained at 6 degrees C and relative humidity of 78-80% for 21 days. A group of uncoated fruit was used as a control. Some measurements such as weight loss, spoilage evaluation, titratable acidity, and soluble solids were determined weekly. The results were investigated in the form of central composite design and were modeled and analysed by response surface methodology. Soluble solid, titratable acidity and weight loss at the end of storage period were 0.9317, 0.9225, and 0.9067, respectively. The results showed that weight loss and pH (fruit juice) of pear coated by high concentration of whey protein, Zataria multiflora extract and glycerol was less than the other pears. Edible coatings preserved the amount of total soluble solids to a greater amount compared with uncoated fruits. According to variance dissociation tables it was recognized that whey protein was the effective factor in the coating process and the influence of Zataria multiflora extract and glycerol was less than whey. In conclusion 4.99 g of whey protein, 500 mu l of Zataria multiflora Boiss extract and 2.44 g of glycerol per 100 ml of coating solution was optimized coating solution. Achieving a coating with maximum effect on shelf life improvement of pear are: 4.99 g of whey protein, 500 mu l of Zataria multiflora extract and 2.24 g/100 ml water of glycerol.