The effect of cooking on the phytochemical content of vegetables

Abstract

Cooking induces many chemical and physical modifications in foods; among these the phytochemical content can change. Many authors have studied variations in vegetable nutrients after cooking, and great variability in the data has been reported. In this review more than 100 articles from indexed scientific journals were considered in order to assess the effect of cooking on different phytochemical classes. Changes in phytochemicals upon cooking may result from two opposite phenomena: (1) thermal degradation, which reduces their concentration, and (2) a matrix softening effect, which increases the extractability of phytochemicals, resulting in a higher concentration with respect to the raw material. The final effect of cooking on phytochemical concentration depends on the processing parameters, the structure of food matrix, and the chemical nature of the specific compound. Looking at the different cooking procedures it can be concluded that steaming will ensure better preservation/extraction yield of phenols and glucosinolates than do other cooking methods: steamed tissues are not in direct contact with the cooking material (water or oil) so leaching of soluble compounds into water is minimised and, at the same time, thermal degradation is limited. Carotenoids showed a different behaviour; a positive effect on extraction and the solubilisation of carotenes were reported after severe processing.

Seasonal variability of phenolic compounds and antioxidant activity in prickly pear cladodes of Opuntia and Nopalea genres

“…The values found in this work for total phenolics are above those described by Santos-Zea et al (2011) Bensadón et al (2010), is probably related to the effect of temperature-time of drying of the material on the degradation of chemical compounds (Palermo et al, 2014).…”

“…The non-detection of these classes of phytochemical compounds in Opuntia cladodes is probably related to temperature-time damage in the chemical composition of the samples, once the cladodes were dried at 55 °C for 72 hs. Some studies report the effect of temperature-time on the degradation of phytochemical compounds (Palermo et al, 2014).…”

Effect of the intensity of cooking methods on the nutritional and physical properties of potato tubers

“…In summary, a lower core temperature during boiling, a higher temperature and shorter baking time, and a lower microwave power were all beneficial for retaining the TPC in the potato flesh of the cultivars. Palermo, Pellegrini, and Fogliano (2014) suggested that the reduction of TPC after the cooking treatments was attributed to water-soluble phenolics that leach into the water (boiling) and breakdown. Therefore, the phenolic compounds are highly reactive species that undergo several reactions during food processing that are related to the cultivars and cooking conditions.…”

Intake and Profile of Plant Polyphenols in the Diet of the Czech Population

“…Moreover cooking causes a change of polyphenol structure, as well as a change in polyphenol linkage to the plant matter matrix, thereby deteriorating or decreasing polyphenol accessibility in a human body. The bioavailability and bioactivity of plant polyphenols in humans are to be further and more intensively studied [Palermo et al, 2014]. More accurate and interpretable research enabling the development of dietary recommendations regarding the intake of polyphenols is desirable [Balentine et al, 2015].…”