Abstract
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.
Highlights
Consumption of grapes and raisins dates to prehistoric times, which is proven by rock paintings from the Mediterranean region [1]
It is generally known in practice that grapes with a high Total soluble solids content (TSS) should be used for the production of high-quality dried raisins
This study examined the impact of drying methods on the quality of five varieties of grape dried at different temperatures or lyophilised on the bunch stem, it could affect processing companies
Summary
Consumption of grapes and raisins dates to prehistoric times, which is proven by rock paintings from the Mediterranean region [1]. It is assumed that the first raisins were produced in the Near. Raisins were valued because they were easy to transport [1,2]. Grapes and products made from grapes are among the most important horticultural products in the world. They are grown on all the inhabited continents on Earth [3,4,5,6]. 75 million tons of grapes are produced every year. 50% of grapes are processed into wine, must, and juice; one third is consumed as fresh fruit; and the rest are dried and processed into other products [5]
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