Effects of Household Cooking on Mineral Composition and Retention in Widespread Italian Vegetables

The process of cooking food can result in alterations to its nutrient composition due to changes in water content and the destruction or loss of certain micronutrients that occur in response to heat. This study examined the impact of diverse cooking techniques, namely grilling, microwave, and steam, on the macronutrients and minerals of vegetables commonly utilized in Italian cuisine (two varieties of zucchini, eggplants, and potatoes).

The proximate composition was determined according to the Association of Official Analytical Chemists (AOAC) methods. The content of the minerals (Ca, K, P, Mg, Na, Fe, Zn, and Mn) was determined via ICP plasma after liquid washing.

Regarding macronutrients, the results revealed a notable difference in the carbohydrate profiles, whereas mineral retention demonstrated considerable heterogeneity. Some minerals, such as Na, Ca, Mn, and Fe, were found to be more prone to significant increases or losses. Moreover, the true retention factor (TR) calculations indicated that microwave cooking resulted in higher retention compared to the other methods for zucchini, while grilling demonstrated higher TR than microwave cooking for eggplants. Potatoes exhibited lower TR values than the other vegetables and their steaming resulted in higher retention than microwave cooking for K, P, Fe, and Zn.

The results confirm the heterogeneous behaviors of minerals in commonly consumed Italian vegetables subjected to different cooking methods. The data underscore the need for additional research to understand the effects of heat treatments on mineral profiles and to determine specific retention factors linked to various cooking techniques. The significant gap between "true" and "apparent" retention factors, caused by changes in water content during cooking, highlight the need for new experimental data to update and enrich the existing literature on this topic.