Antinutrients are not all Bad

In document Compositional and nutritional properties of tef and tef-based food products (Page 189-191)

CHAPTER 6: GENERAL DISCUSSION, CONCLUSIONS AND FUTURE PERSPECTIVES

6.4 Antinutrients are not all Bad

Ever since, overnutrition became the same burden as that of undernutrition in the contemporary society, the previously disadvantageous features of antinutrients are becoming beneficial from health perspectives in one way or another. For example, the presence of PA, PCs and fibers in a plant-based food product were once seen undesirable as antinutrients. However, currently the presence of such compounds is also seen as beneficial. The presence of fiber in a meal is seen as healthy and necessary, the interference of PA in carbohydrate digestibility is becoming desirable as consumers are preferring lower calorie foods. The effect of PA on GI, as observed in part 4.1, i.e. fermented injera which has a higher dry matter content than porridge (not fermented) showed higher eGI. The traditional fermentation process of tef injera eliminates more than 50% of PA as shown in part 2.2, which could indirectly increase starch digestibility, resulting in a higher eGI. This is of course not desirable for diabetic and people on diet control, implying the benefit of the PA when low GI food product is needed. The advantage of PCs as an antioxidant is overweighing their negative image as antinutrients on mineral bioaccessibility/bioavailability and carbohydrate digestibility. In general, the advantage and disadvantage of the presence of a particular antinutrient in a food product is dependent on the intended use of that typical food and the targeted nutrient/health benefits that the consumers are looking for. The current nutrition trend is focusing on individual needs, or personalized nutrition, leading to an increased diversity of food be it through processing or increasing the sources of plant foods.

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From mineral bioavailability perspective, antinutrients are still bad because minerals, specifically Fe and Zn deficiency, are considered as a persisted global burden (Hemery et al., 2018; Nair and Augustine, 2018), particularly in developing countries (Gebreegziabher and Stoecker, 2017; Harika et al., 2017). Tef contains high Fe and Zn content, but their co-existence with mineral chelators such as PA and PCs, could limit their bioaccessibility. The formation of a larger complex of phenolic compound-Fe is a double edge sword that plays a negative role by inhibiting the bioaccessibility of both phenolic compounds and the iron. After fermentation, significant amount of Fe is set free from PA, however, due to the parallel increase of soluble phenolic content in the food matrix, it seems that Fe would be exposed to interact with the soluble phenolic compounds to form bigger complexes thereby reducing the bioaccessibility of iron. On the other hand, depending on the type of phenolic compounds, it is possible that some phenolic compounds could facilitate the bioaccessibility of Fe, by weakly chelating the Fe in the gastrointestinal digestion and make it accessible for absorption in the intestinal phase. Some soluble phenolic compounds can also compete with other potent Fe chelators then reduce the chance of the formation of big insoluble Fe complexes. Hence, the balance of advantage and disadvantage of soluble phenolic compounds in terms of Fe bioaccessibility may depend on the composition and quantity of the phenolic compounds that form soluble and insoluble complexes.

Chapter 3 detailed the effect of fermentation of tef injera on Fe and Zn bioaccessibility in different tef varieties. Only a moderate improvement in the bioaccessibility of Fe and Zn was seen despite the high Fe and Zn contents and more than 50% destruction of PA. However, even a complete destruction of PA may not result in an increase of bioaccessibility of Fe and Zn (Baye et al., 2014). Indeed the PA/mineral mole ratio prediction of mineral bioaccessibility is only little resistant to close scrutinization, specifically in the presence of PCs containing galloyl and catechol groups, compounds also well-known as mineral chelators (Baye et al., 2014; Brune et al., 1991; Gabaza et al., 2017). Therefore, only the elimination of PA may not guarantee an increase in mineral bioaccessibility.

To overcome the inhibition of PCs, it could be important to look into the possibilities of addition of mineral bioavailability enhancers such as ascorbic acid (Cercamondi et al., 2014). It would also be important to prepare or consume tef in mixtures with other foods which have mineral bioaccessibility enhancing properties. In Ethiopia, a plant called moringa (Moringa

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et al., 2016) has been used as a food by particular ethnic groups but now it is becoming popular throughout the country. The optimum enrichment of tef with such plant could be an ideal way to improve the bioaccessibility of iron.

As tef contains the highest Fe, Ca and fairly high Zn contents compared to other cereals, its potential as a source of these minerals should be further studied in terms of bioavailability through manipulations of processes, addition of enhancers or mixing with spices or foods which have a mineral bioavailability enhancing property. The issue of whether the high Fe content of tef is intrinsic or coming from contamination is not yet solved. Considering the importance of Fe in nutrition and the burden of its higher prevalence of deficiency particularly in developing countries, further verification studies on this regard is indispensable.

In document Compositional and nutritional properties of tef and tef-based food products (Page 189-191)