Determination of quality characteristics and shelf life of kiwifruit (A. chinensis var. deliciosa 'Hayward') slices by drying them in a heat pump dryer at different water content values
Kiwifruit cultivation area and production are increasing every year in Turkey. With this increase, kiwifruit should be processed and evaluated in different ways other than fresh consumption. In this study, A. chinensis var. deliciosa 'Hayward', almost the only cultivar grown in Turkey, was used. Kiwifruits were harvested at 7-8% Brix and placed in cold storage. Fruits were taken out of cold storage when their Brix value was 12-13, pH 4.32-4.35, firmness 8-9 N and acidity 0.96-1.1%, then pre-treated for drying. Fruits were cut into 9 mm-thick slicess after peeling, and the fruit slices were impregnated with sucrose (60% Brix) by applying osmotic dehydration with vacuum impedance. Then, the kiwifruit slices impregnated with sucrose and not pre-treated were dried in a heat pump dryer at 42°C at a speed of 1 m s‑1 as dried kiwifruit (10-15% water content) and semi-dried kiwifruit (30-35% water content). All dried samples were kept for 12 months and their shelf life was determined. To determine the shelf life, some quality analyses (water content, water activity, L-ascorbic acid content, reducing sugar, total antioxidant activity FRAP-ABTS-DPPH, total phenolic content, surface colour, sensory analysis, and total viable count, total mould/yeast count) were performed. As a result of the analyses, it was determined that the kiwifruit preserved its quality characteristics for 9 months after drying to low water content. Sucrose impregnation in kiwifruit slices reduces its acidic taste, but does not eliminate it completely. On the other hand, it was observed that semi-dried fruits with medium water content preserved their green bright colour, however, pasteurization at high temperatures was required in order to be preserved for a longer time and to prevent microbial growth. In this process, the green colour disappeared, causing browning. Sucrose-impregnated fruits with lower water content (dried kiwifruits) were found suitable and recommended for consumption after sensorial and physical evaluation. Thus, as a result of the study, an alternative method was developed for small fruits sold at lower prices in fresh consumption, to gain added value. However, with the added value to be provided, these drying methods can also be used for larger fruits.
Göksel, Z., Atak, A., Tunçkal, C. and Yemenicioğlu, A. (2022). Determination of quality characteristics and shelf life of kiwifruit (A. chinensis var. deliciosa 'Hayward') slices by drying them in a heat pump dryer at different water content values. Acta Hortic. 1332, 311-320
osmotic dehydration, sucrose impregnation, medium moisture fruits, kiwifruit slices