Vitamin C content in fruits of common raspberry (Rubus ideaus L.) of the variety “Polka” depends on storage methods

Abstract

The content of vitamin C in the fruits of common raspberry (Rubus idaeus L.) variety ‘Polka’, collected in Chernihiv region, was assessed in order to study the influence of different processing and storage methods on the preservation of ascorbic acid. It was found that drying at a temperature of +40°C is the most effective method for preserving vitamin C. Freezing, boiling and treatment with chitosan were also investigated, which turned out to be a promising biopolymer for improving the preservation of freshness of fruits and increasing their nutritional value. The results obtained helped to compare different storage methods and determine the most effective one for preserving the nutritional properties of raspberries. The chitosan treatment method for preserving vitamin C in raspberry fruits is the most effective compared to other methods such as drying, freezing and boiling. Compared to drying, chitosan has a significant advantage, since drying at high temperatures (especially at +60°C) leads to significant losses of vitamin C. While drying at +40°C preserves most of the ascorbic acid, chitosan allows for the preservation of vitamin C at an even higher level, by creating a barrier that slows down oxidative processes and protects against microbiological spoilage. Freezing is also an effective method of preserving vitamin C, as it minimizes the loss of ascorbic acid. However, even when frozen at -17°C, vitamin C is preserved at a lower level than in chitosan-treated fruits. In addition, freezing does not prevent thedevelopment of microorganisms that can cause spoilage during long-term storage. Boiling, in turn, is the most destructive method, since this process causes the greatest loss of vitamin C. When sugar is added during boiling, the loss of ascorbic acid reaches maximum values, which makes this method less effective for preserving the nutritional value of the fruit. Chitosan, as a natural biopolymer, has another significant advantage: due to its antimicrobial properties, it effectively protects the fruit from spoilage, extending its shelf life, while drying and freezing cannot prevent the development of microorganisms. Thus, the chitosan method significantly exceeds other methods in its ability to preserve vitamin C, freshness and nutritional value of raspberry fruits, and also has advantages in terms of safety and environmental friendliness.