Determination of the quality properties and storage stability of dried fruits coated using different edible coating solutions

In the thesis, apricot (Prunus armeniaca var. Hacıhaliloğlu), banana (Musa cavendish) and strawberry (Fragaria ananassa var. Festival) samples were coated by dipping in sodium alginate, gluten-soy protein (3: 1), hydroxypropyl methyl cellulose and sodium caseinate solutions and, pre-dried at 40°C to form coating. The samples were then dried with a flow rate of 2.5m / s at 60 °C until the water activity reduced below the target water activity value (aw = 0.65 for apricot, aw = 0.4 for banana and strawberry samples). Physical properties of the dried samples such as dry matter, water activity, shrinkage, rehydration capacity, colour and hardness values were determined. Form the chemical properties of the dried samples, antioxidant activity, ascorbic acid content, aroma profile, total carotenoid content in apricot and banana samples and anthocyanin content in strawberry samples were determined. In addition, sensory analyses were performed to evaluate flavour and colour of the samples, and apricot samples were also evaluated for wrinkling. All physical, chemical and sensory analyses were performed immediately after drying and after 90 and 180 days of storage under 100% nitrogen gas. Apricot, banana and strawberry samples dried faster by coating with sodium alginate and hydroxypropyl methyl cellulose, had higher dry matter content, lower water activity value and less percent shrinkage amount. L*, b*, kroma (C) and hue angle (h °) values of coated and dried apricots and bananas (especially coated with sodium alginate) were found to be higher than the control samples, in other words, the coated and dried samples were less browned. These values also decreased during the storage period. L*, b* and C values of coated and dried apricot and banana samples were significantly higher than those of control samples, especially after 180 days of storage. There was insignificant difference between the L* values of strawberry samples measured immediately after drying, but after 180 days storage, all of the coated samples, especially sodium alginate coated samples, had higher L * values. In addition, a * and C values of the dried strawberries were higher than those of the control samples. Similar to colour results, antioxidant activity, total carotenoid and ascorbic acid contents of coated and dried banana and apricot samples were higher than the control sample. Sodium alginate was more successful in preserving the antioxidant activity, total carotenoid and ascorbic acid amounts of apricots, while hydroxypropyl methyl cellulose was better preserving the carotenoid amount in bananas, and sodium alginate coating was more successful in preserving the antioxidant activity and ascorbic acid content. It was found that antioxidant activity, anthocyanin and ascorbic acid content of strawberry samples were higher especially in samples coated with hydroxypropyl methyl cellulose. The aroma analyses of the apricot, banana and strawberry samples immediately after drying and during storage showed that the total peak areas of the aroma compounds detected in the package headspace of the control sample were larger than those of the coated samples. However, after 180 days, the samples were disintegrated, repackaged, allowed to equilibrate for 30 days and then analysis. In this case, the total amount of aroma of the samples dried by coating with sodium alginate was found to be higher than other samples. The total aroma amounts of the other coated samples were also close to or higher than those of the control sample. This result shows that coatings, particularly coating with sodium alginate, slow down the release of aroma compounds in dried fruits. In the sensory analysis of apricot, banana and strawberry samples immediately after drying, there was small difference between the samples, but after storage, the samples dried by coating with sodium alginate were the most preferred samples both in colour and flavour. According to the results of the research, coating of the apricot, banana and strawberry samples before drying by edible coating was a useful pre-treatment. It was found that coating with sodium alginate protects the colour values, biochemical compounds and aroma components of the samples better than other coating materials. Therefore, it is thought that it may have a potential use in commercial dried fruit production.