Sous-vide cooking and its effects on antioxidant-rich vegetables

Abstract

The research aims to study optimal conditions for processing plant-based foods using the sous-vide technique, a vacuum -sealed cooking method performed at relatively low and constant temperatures. While sous-vide is typically associated with meat, its use in vegetables is gaining popularity due to its ability to preserve thermolabile vitamins, enhance natural flavours, and ensure even cooking. The method prevents contact with air and minimizes the leaching of nutrients into water, preserving both the nutritional and organoleptic properties of the foods. The focus of this research was to investigate the effects of sous-vide on antioxidant-rich vegetables such as broccoli and carrots, as well as the impact of various food additives on the final product. Instrumental methods were used to analyse the properties of raw and cooked samples, comparing them with traditional cooking techniques. Broccoli and carrots were cooked at 85°C for 25…40 minutes per 100 grams of product and evaluated for changes in antioxidant content, texture, colour, acidity, and sugar retention. Additives such as salt, sugar, and citric acid were tested in solution form (0.2…1%) for their effectiveness in preserving antioxidants and

maintaining the colour of the products. Vegetables were pre-soaked in these solutions for 30 minutes before heat treatment. The sous-vide method was found to maintain more natural sugars and increase acidity in vegetables while preserving the texture and shape better than traditional cooking. Broccoli and carrots, after 25 and 40 minutes of sous-vide cooking, respectively, maintained higher carotenoid levels and better texture than traditionally cooked samples. The results showed that sugar solutions were the most effective in preserving carotenoids in

carrots and chlorophyll in broccoli, while salt and citric acid also contributed to the retention of nutrients. Carrots preserved a bright colour and crunchy texture, salt and citric acid solutions (2 g/l of water) being most effective in preserving lycopene. Broccoli showed significant preservation of chlorophyll (up to 86%) when treated with a sugar solution (10 g/l). Thus, it is recommended to cook broccoli at 85°C for 25 minutes using a sugar solution (10 g/l) to preserve chlorophyll and improve both texture and sweetness. For carrots, to enhance colour and maintain a crisp texture, sous-vide cooking at 85°C for 40 minutes, following pre-treatment with salt or citric acid solutions (2 g/l), is preferable. However, sugar solutions can also be used for carrots, as they demonstrated the highest carotenoid retention among all tested additives. These conditions optimize nutrient retention and sensory qualities, making sous-vide a promising method for processing plant-based foods.