A lab technician told me that freezing raw vegetables from your own garden (such as green broad beans, Brussels sprouts or carrots) creates carcinogenic substances. She stated that all vegetables should therefore be cooked before being frozen.
Is this true? And if so, aren’t many vitamins lost? If I buy frozen vegetables in a store, were they blanched first or were they frozen raw?
Answer
Freezing does not produce any carcinogenic substances.
Vegetables are living products, even after harvest. Biochemical processes in the cells continue as usual, even at deep-freeze temperatures. Enzymes, proteins that catalyze these processes, therefore also remain active. Some of these enzymes can cause taste abnormalities. For example, lipases break down fats into fatty acids, resulting in a soapy taste; lipoxygenases oxidize fats so that the product tastes rancid. To inactivate these enzymes, vegetables must be blanched (= heated briefly to just below boiling point) before freezing. Industrial frozen vegetables are always blanched. Of course there is a certain loss of vitamins, but this is less with industrial frozen vegetables than with products frozen at home because the freezing process is much faster in the first case.
Answered by
Prof. Bart Nicolaï
post-harvest technology, transport phenomena, computational biology, vegetables, fruit, quality, multiscale models, cooling technology, storage, microfluidics
Old Market 13 3000 Leuven
https://www.kuleuven.be/
.