Blanching and long‐term freezing affect various bioactive compounds of vegetables in different ways

Abstract

An extensive study on the effects of blanching/freezing and long-term freezer storage on various bioactive compounds of more than 20 commonly used vegetables was performed. Effects were strongly plant species-dependent. Contents of dietary fibre components either were not affected or increased slightly. Minerals in general were also stable, but some losses of soluble minerals by leaching were observed. Phenolic antioxidants and vitamins were clearly more sensitive. Significant losses (20-30%) of antioxidant activity and total phenolics were detected in many vegetables. A qualitative HPLC profiling method for phenolic antioxidants was developed which proved to be very useful when evaluating the complex behaviour of phenolics during food processing. Up to one-third of vitamin C contents were lost during blanching, and further slight losses were detected during storage. Folic acid turned out to be very sensitive to blanching, with more than half of the vitamin being lost, but was stable during freezer storage. Carotenoids and sterols were not affected by blanching or freezer storage. The usefulness of the applied screening methods for evaluation of the effects of processing on vegetables is shown.

Kinetic evaluation of colour, texture, polyphenols and antioxidant capacity of Irish York cabbage after blanching treatment

“…There was a higher reduction in DPPH RSC up to 6 min, in comparison to the lower temperature range, after which the DPPH RSC remained almost constant. Puupponen-Pimiä et al (2003) measured the AO capacity by the DPPH assay in blanched cauliflower and reported a reduction of 20-30%, which is less than that reported in the present study.…”

Influence of customized cooking methods on the phenolic contents and antioxidant activities of selected species of oyster mushrooms (Pleurotus spp.)

“…In the last few decades, attention on naturally occurring antioxidants in foods has increased because of the adverse effect of synthetic antioxidants and the practice of minimum usage of artificial food additives. Nutritional value or texture of food could be affected or lost during the heat treatments or storage as most of the bioactive compounds and naturally occurring antioxidants are susceptible to heat (Amin and Lee 2005;Puupponen-Pimia et al 2003;Pokorny and Schmidt 2001). Recent studies showed that appropriate cooking methods for different vegetables may maintain the antioxidant properties or improve their nutritional value (Galor et al 2008;Ng et al 2011).…”

Antioxidant potential of spinach, peas and sweet corn in relation to freezing period

“…The recorded decrease of AA level in peas after 10 months of storage (about 26.8%) was not very significant and it was the lowest among all analysed crops. Puupponen-Pimia et al (2003) observed a higher decrease (41.7-55.6%) of AA in peas during 12 months freezing.…”