Research on Blanching Pretreatment and Freezing Technology Effect on Selected Vegetables

Abstract

Vegetables present high nutritional content, being rich in vitamins, minerals, dietary fibres, organic acids and antioxidant compounds. However, fresh vegetables are generally harvested seasonally, being available in their fresh form for short periods of time during the year, and are also highly perishable. Therefore, the necessity of preserving them for a longer period of time has been addressed, freezing becoming the main technique used in this scope, due to its ability to maintain the initial quality of the product. The aim of the present study was to determine the properties of several fresh vegetables in different moments during processing for freezing preservation, namely initial moment (fresh form), after blanching pretreatment, after freezing/thawing process. The vegetables that were studied during this study were green peas, green beans, broccoli, asparagus, oyster mushrooms, Agaricus bisporus mushrooms and eggplants. As quality indicators, the following were determined: acidity, aw, colour, total polyphenolic content, antioxidant activity and ascorbic acid content (where applied). The results showed varied values for the monitored parameters. Generally, significant differences were observed during processing, with increasing and decreasing values of the tested parameters depending on the tested sample and applied treatment.