Chapter 9 Impact of long-term storage on the quality of frozen pickled sweet peppers

Abstract

Vegetables are produced seasonally; therefore, freezing is one of the main meth- ods of preserving them while maintaining their quality. Both fresh vegetables and semi-finished or ready-to-eat vegetable products are commonly frozen. Such prod- ucts are popular among consumers, as they provide rapid preparation and consump- tion. Vegetables, particularly sweet peppers, are often pickled in marinades with various spices to enhance sensory properties, preserve nutrients, extend shelf life, and expand the range of available products. A promising approach for storing pickled sweet peppers is freezing. In this study, sweet peppers were pickled in a marinade containing the following ingredients: water, sunflower oil, sugar, natural honey, salt, citric acid, and spices (dried dill and parsley, bay leaves, fresh garlic, and allspice). After washing with water, cleaning, and cutting, sweet pepper slices were pickled in the marinade for 12 h at room temperature and subsequently frozen at –20°C. Experimental results showed that during 270 days of frozen storage of pickled sweet peppers, losses of ascorbic acid ranged from 12.0 to 19.8%, carotenoids from 5.8 to 15.1%, dry matter from 0.7 to 4.9%, total sugars from 0.6 to 6.1%. At the same time, the contents of water-soluble pectin, anthocyanins, catechins, and t otal flavonoids increased during storage. Freezing also had a positive effect on the mi- crobiological safety of the product, as the number of microorganisms in the frozen product during storage was lower than that in fresh sweet peppers. The sensory quality of the frozen product, including appearance, color, aroma, taste, and consis- tency, was highly rated by expert evaluators. To bring the product quickly to a ready- to-eat state, microwave thawing is recommended. Pickled sweet peppers thawed using this technique exhibited high sensory quality. However, prolonged storage of the product at room temperature after thawing is not recommended, as it leads to a decrease in ascorbic acid content and an increase in polyphenol oxidase activity and microbial growth. Although the product remained safe for consumption after 24 h of storage at 20°C, the number of microorganisms did not exceed the permissible limits for quick-frozen vegetables (the maximum bacterial and mold counts in the thawed pickled sweet peppers were 48,400 CFU/mm2 and 19.0 CFU/mm2, respectively).