Effects of different cooking techniques on the carotenoids composition, phenolic contents, and antioxidant activity of spinach leaves

Leafy vegetables contain several health-promoting compounds including carotenoids and polyphenols. Different cooking techniques have been shown to affect the composition of these compounds. In this study, spinach leaves were studied using different processing methods i.e., boiling, frying, microwaving, thawing, and sonication. Total phenolic, flavonoid, and anthocyanin contents and DPPH scavenging activity were measured in both treated and control spinach samples. HPLC with DAD was used to study carotenoid contents. It has been found that processing treatments affect the carotenoid contents of spinach and it depends on the type of treatment. The concentration of violaxanthin, lutein, and β-carotene has been increased during boiling and microwave heating while frying has a very adverse effect on these compounds. The amount of lutein increased in all the treatments except in frying. Frying spinach leave kept a higher level of total phenolic or anthocyanin contents than other treatments. Similarly, TFCs have been retained better in thawing than with the other treatments. Similarly, microwave and sonication samples showed the highest %RSA among the studied treatments. In conclusion, the selected treatments can be carefully used to retain the maximum amount of the bioactive compounds.