Effect on the total antioxidant capacity of substituting water with rooibos herbal teas in popular soup recipes

Abstract

Oxidative stress had been linked to the development of certain chronic diseases, but can be delayed or prevented by the consumption of dietary antioxidants. Fruits, vegetables, wholegrains and beverages, such as, teas are the major dietary antioxidant contributors. The majority of South Africans do not consume adequate daily servings of fruits and vegetables, neither sufficient minimally processed grains nor wholegrains. One way to incorporate antioxidants in the South African diet is by adding antioxidant-rich foods or beverages to recipes as ingredients. The objective of this study was to determine the effect on the total antioxidant capacity (TAC) of substituting water with rooibos herbal tea in soup recipe formulations. Rooibos is a proudly South African beverage rich in antioxidants. Soup is a readily available and relatively inexpensive meal item regularly consumed during the winter months in South Africa. Three popularly consumed soups in the City of Cape Town Metropolitan Municipality namely chunky vegetable, butternut and chicken noodle were selected for the experimental study. The water in each of the soup recipe formulations (control) was substituted with fermented and unfermented / “green” rooibos (experimental recipe formulations). The study was of comparative nature as the results (i.e. the TAC as the factor investigated) of three different soup recipe formulations on fluid manipulations of each (with fermented and unfermented rooibos) was compared to the control soup recipe formulations of each (no fluid manipulation). The results (i.e. the TAC) of the three prepared control and experimental soup recipe formulations were also compared to that of the raw soup mixtures of each of the soup recipe formulations to determine the effect of thermal processing on each. The main variable identified in the preparation of the soup recipe formulations that may impact the TAC (the dependent variable) and needed to be controlled was the heat application. Other variables that may influence the results were the soup recipe formulation ingredients, the prepreparation of the raw ingredients, the standing time of ingredients before use and the equipment used. Before determination of the heat applications and the fixed time allocations of the soup recipe formulations to ensure recipe standardisation, the pre-preparation procedures of the raw recipe ingredients were also standardised.