Three soup recipe formulations were used to determine the effect of the substitution of water with rooibos. The total polyphenol content and the carotenoid content, along with the H-ORAC, L-ORAC and TAC were determined for the raw recipe ingredients, the raw control and experimental soup recipe formulations and the correspondent thermally processed control and experimental soup recipe formulations.
There was no similarity or trend in the USDA published polyphenol content and the TAC for the raw soup recipe formulation ingredients utilised in this study and their analysed values. In some cases the published values were far lower or higher compared to the analysis in this study. The only identical value found was for the polyphenol content of the tomato paste. Differences in the phytochemical contents and the TAC of foods occur due to the diverse factors such as the conditions of growth, harvesting, handling, storage, preparation and processing which influence the food value (Kalt, 2005:209).
In all three the raw soup recipe formulations, water or in the case of the experiments, fermented and unfermented rooibos, was the greatest raw single ingredient contributor in relation to the contribution of the other raw ingredients. The fermented and unfermented rooibos did not have the highest polyphenol content, H-ORAC and TAC, but it was the greatest contributor to the raw recipe formulations due to the highest ingredient quantity used in all three soup recipe formulations. The ingredients with the highest polyphenol content and H-ORAC were the herbs, spices and flavourings. The vegetables had a varied polyphenol contents and H-ORAC. Onions had the highest polyphenol content and H-ORAC of all the raw recipe vegetable ingredients. The fermented and unfermented rooibos made no contribution to the L-ORAC of the raw recipe formulations. The H-ORAC of all the raw ingredients was much higher than the L-ORAC. The TAC of the raw ingredients comprised mainly of the H-ORAC of the raw ingredients.
The substitution of water with fermented and unfermented rooibos in all three raw soup recipe formulations resulted in a significant increase in the polyphenol content and H-ORAC. The inclusion of the fermented and unfermented rooibos herbal teas in place of water in the raw soup recipe formulations had little effect on the L-ORAC and carotenoid content of all three raw experimental soup recipe formulations. The TAC of all three raw recipe formulations was also
significantly increased with the substitution of water with fermented and unfermented rooibos as soup ingredients. The null hypothesis stated for the study of no significant difference between the TAC of the raw control soup recipe formulations containing water as the major ingredient (raw combined ingredient soup recipe formulation) and the correspondent raw experimental soup recipe formulations containing fermented and unfermented rooibos herbal teas as the major ingredient, was thus rejected. The liquid (water) substitution with fermented and unfermented rooibos is therefore a worthwhile recipe manipulation to increase the overall TAC of the recipe formulation in particular when the liquid forms part of the whole food to be consumed as with soup. By adding rooibos the nutraceutical properties of the recipes was increased as well, as shown by the increased antioxidant activity. Development and utilisation of foods with functional food characteristics can be used to improve the nutritional status of the population (Ajila et al., 2010:223).
The long-held belief that thermal processing of food decreased and even destroyed the food nutritive value (Dewanto et al., 2002:4959) was not confirmed in this study when using the TAC as index. Thermal processing resulted in a significant increase in the total polyphenol content of all the cooked control versus the raw control soup recipe formulations. The chunky vegetable and butternut experimental soup recipe formulations both increased in total polyphenol content after thermal processing providing for the polyphenol content on thermal processing to be significantly different for the cooked controls and the cooked chunky vegetable and butternut experimental soup recipe formulations compared to the raw soup recipe formulations.
The H-ORAC of all the control soup recipe formulations also increased on thermal processing.
Both the experimental chunky vegetable and butternut soup recipe formulations containing unfermented rooibos also had a significantly increased H-ORAC after being thermally processed compared to the raw experimental soup recipe formulation of each. The H-ORAC of the experimental butternut soup recipe formulation containing fermented rooibos also increased significantly on thermal processing.
Thermal processing caused a significant decrease in the L-ORAC of all the control and experimental soup recipe formulations. Thermal processing had a similar effect on the carotenoid content. The carotenoid content of all the control and experimental soup recipe formulations significantly decreased after thermal processing.
Thermal processing resulted in an increase in the TAC of all three cooked control soup recipe formulations compared to the raw soup recipe formulations. Thermal processing caused a significant increase in the TAC of the chunky vegetable experimental soup recipe formulation
containing unfermented rooibos compared to the raw experimental soup recipe formulation containing unfermented rooibos. The TAC of both the raw experimental butternut soup recipe formulations increased significant on thermal processing. The null hypothesis stated for the study (of no significant difference between the TAC of the raw control and experimental soup recipe formulations respectively containing water and fermented and unfermented rooibos herbal teas as the major ingredients and the correspondent cooked control and experimental soup recipe formulations respectively containing water and fermented and unfermented rooibos herbal teas as the major ingredients) was also rejected for the chunky vegetable and the butternut soup recipe formulations, in particular for the experimental soup recipe formulations, but not for the chicken noodle experimental soup recipe formulations. The H-ORAC of the chicken noodle experimental soup recipe formulations on thermal processing was significantly lower than that of the raw soup mixtures. There was also a significant decrease in the TAC of the chicken noodle experimental soup recipe formulations on thermal processing compared to the TAC of the raw chicken noodle experimental soup recipe formulations. The prolonged heat exposure in the experimental chicken noodle soup recipe formulation possibly caused the decrease in the H- ORAC and TAC. Processing and cooking conditions cause variable losses of antioxidants.
Losses vary widely according to cooking method used and the type of food (Leskova et al., 2006:258)
CHAPTER 7