Frozen vegetables and fruits can be healthier than fresh ones, and freezing itself is aimed at extending the life of products that have seasonal production. However, it is important to defrost products correctly so that their taste qualities are preserved, according to the head of the Department of Technology and Organization of Food Production at Novosibirsk State Technical University (NETI) Associate Professor Lada Rozhdestvenskaya and Evgeny Turlo, Associate Professor of the Department of Chemistry and Chemical Technology at NSTU-NETI. Scientists talked about Cook technologies&Freeze and Cook and Chill, about proper defrosting and products that will benefit from cold.
"Some vegetables and fruits can retain most of their nutrients after freezing, so they will be even healthier frozen than fresh ones. This is because freezing helps to preserve vitamins and minerals that are usually lost when storing food fresh. Such products include greens, for example, spinach, parsley, broccoli, green peas, carrots. Of fruits, these are blackberries, raspberries, citrus fruits — lemon, lime, which retain most of their useful properties after freezing," notes Evgeny Turlo.
During freezing, the structures of plant cells and tissues are destroyed, and nutrients come out. So, after freezing parts of a lemon, twenty times more useful substances can be extracted from it, the scientist adds. However, it is worth noting that not all vegetables and fruits retain their nutritional properties equally well after freezing, moreover, freezing is contraindicated for some. These products include cucumbers, tomatoes, lettuce leaves.
Defrosting in warm or hot water will spoil the taste and quality of the products. A sharp temperature drop can lead to cell destruction and the product will "flow," explains Lada Rozhdestvenskaya. The correct approach is slow step—by-step defrosting. Thus, the integrity of the product and its taste qualities are preserved — this applies to meat products and semi-finished products.
"Fruits and vegetables should either be immediately added to the prepared dish and further subjected to heat treatment, or frozen to be included in dishes — for example, frozen puree of berries and fruits as part of desserts or cocktails. Cook technology is based on these principles&Freeze — "cook and freeze" — preparation of semi—finished products of various degrees of readiness followed by deep shock freezing and Cook&Chill - literally: "cooking and cooling", where the distinctive feature is the cooling process. Next, the dishes are regenerated before serving. Cook and Chill cooking is a combined process of cooking a large volume of dishes and cooling them quickly. Thermally processed food is not frozen, but is cooled to +1... + 4 degrees. Moreover, the cooling rate is such that the harmful microflora does not have time to develop. Storing products in such temperature conditions extends their shelf life to at least 5 days, and in some cases up to 21 days before serving," says Lada Rozhdestvenskaya.
According to Evgeny Turlo, it is important that frozen products are stored at a temperature of -18 °C and below and in an airtight package to avoid air ingress, which can cause oxidation and a change in the taste properties of the product.
"Vacuum packaging is ideal for storing products with a smell: cheeses, meat, fish, seafood. It seals the odors, not allowing them to mix with each other. Vacuuming protects the contents from moisture and oxidation, allows you to preserve the flavor of the products, their valuable nutritional properties," adds Lada Rozhdestvenskaya.
