Effect of Different Method of Drying of Five Varieties Grapes (Vitis vinifera, L.) on the Bunch Stem on Physicochemical, Microbiological, and Sensory Quality.

The influence of the drying technique on certain quality attributes of dried grapes was analysed. Five varieties of grape were used in this study (Bezsemenné, Perlette, Vrboska, Beauty seedless, and Jakubské). All the varieties were dried using four methods: drying at 40 °C, combined drying (70, 65, and 60 °C), drying at 70 °C, and lyophilisation. The quality attributes such as total soluble solids, water activity, content of vitamin C, the colour parameters (L*, a*, b*), and microbiological (colony forming units, moulds, yeasts) and sensory (smoothness, gloss, colour, odour, chewability, juiciness, flavour, and overall impression) analysis were determined, depending on the method of drying. Lyophilised grapes from the Jakubské variety had the highest vitamin C content. They contained 0.58 mg of vitamin C per 100 g of dried grapes. However, no significant differences between varieties in vitamin C content were found. This confirmed concerns about the negative impact on the nutritional quality of dried grapes with increasing temperature. The lowest total count of microorganisms (CFU), moulds, and yeasts were determined after using highest drying temperature (70 °C). Higher CFU values were determined in lyophilised grapes, and then followed by grapes dried at 40 °C. Lyophilised grapes and grapes dried at 40 °C achieved the best sensory rating in general. The final product was intended to have a unique appearance while maintaining the evaluated quality parameters.