Tannin in Common Beans: Methods of Analysis and Effects on Protein Quality

Abstract

Condensed tannins and related phenols in 13 samples of red Guatamalan common beans (Phaseolus vulgaris) were determined by four chemical assays. The results were highly correlated although the degree of variation among the samples differed greatly according to the assay. In rat feeding trials, tannin content was negatively correlated with net protein ratio, a measure of protein quality, and positively correlated with protein digestibility. Neither correlation was statistically significant due primarily to the low tannin content of the diet. Methionine supplementation not only improves the protein quality but may also play a role in metabolic detoxification of tannin.

Effect of Tea Decoction Given to Rats ad libitum for a Relatively Long Time on Body Weight Gains and Iron, Copper, Zinc, Magnesium Concentrations in Blood, Liver, Duodenum and Spleen

“…The influence of tea decoction on body weight growth is not con firmed by other studies. However, it has been noted that high concentration of tannins re duced growth rate in rats [16]. Also, it has been reported that mice fed with a diet con taining 5 g/100 g tannic acid had decreased mean body weight when compared with mice fed with a control diet [17], Joslyn and Glick [18] reported that feeding tannic acid to rats at 5 g/100 g diet resulted in lower weight gain (about 50% of the control).…”

“…0.0171. and 0.057g/lOOg diet) did not significantly change the body weight [12], On the basis of these findings, our data suggest that the tea decoction which is considered to be an impor tant source of tannins constitutes an impor tant factor able to reduce body weight gains in rats. This effect was not due to the difference in food intakes which were controlled, but it could be related to the influence of tannins from tea decocation on nitrogen and protein digestibility [16], In order to isolate the specific effect of the tea decoction on the trace element retention in the blood and different tissues, all results are given in a constant volume of blood (gg/ ml) and in a constant dry weight of organs (gg/g dry weight) in the two groups.…”

Nutritional value of broad bean seeds. Part 2: Selected biologically active components

“…However, it is known that the ability to inhibit the activity of a-amylases is also attributed to phenolic compounds [2,4]. This study undertook to determine the inhibiting ability of both the named compound groups.…”

“…A favourable influence on health was also shown in the case of a-amylases, i. e., they contribute to the limitation of a postprandial increase in the concentration of glucose in blood, which alleviates the course of insulin-dependent diabetes [3]. Ability to form bonds with enzymes is also shown by phenolic compounds, tannin in particular [2,[4][5][6]. Moreover, these compounds are attributed with numerous medicinal properties which result in many cases from their strong antioxidant properties [7,8].…”

Protein quality of raw and autoclaved cowpeas: Comparison between some insect resistant and susceptible varieties

“…Since legumes are generally deficient in sulphur containing amino acids, any impairment in the digestibility of the protein further serves to accentuate this deficiency [4]. As a complement to this view, even if all heat-labile antinutritional factors in legumes are completely removed, the effects of the heat-stable ones, especially phytic and tannic acids, on protein quality and digestibility are substantial [5,6]. Poor digestibility and biological utilization of legume protein from cooked samples have been directly related to the tannin content of these legumes [7].…”