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Tannins are one of several antinutritional factors present in dry beans and are located mainly in the seed coat or testa. The tannin content of dry beans ranges from 0.0 to 2.0% depending on the bean species and color of the seed coat. Many high tannin bean varieties are of lower nutritional quality than low tannin varieties of beans. Naturally occurring food legume tannins are reported to interact with proteins (both enzyme and nonenzyme proteins) to form tannin‐protein complexes resulting in inactivation of digestive enzymes and protein insolubility. Both in vitro and in vivo studies indicate that bean tannins decrease protein digestibility, either by inactivating digestive enzymes or by reducing the susceptibility of the substrate proteins after forming complexes with tannins and absorbed ionizable iron. Other deleterious effects of tannins include a lowered feed efficiency and growth depression in experimental animals. The antinutritional activity of bean tannins can be reduced by processing (1 or a combination of 2 or more methods), for example dehulling, soaking, cooking and germination. Genetic selection also may help in breeding varieties low in tannins. Potential chemical treatments such as use of tannin complexing agents are discussed.

Hydrogen peroxide is responsible for certain bactericidal effects observed in biological systems, such as growth inhibition of one bacterial species by another and killing of invading microorganisms by activated phagocytic cells. H2O2 might be generated in bacteriological media by their exposure to light and/or oxygen and become an important mediator of toxic effects. H2O2 cytotoxicity is apparently due to its capacity—generally mediated by transition metal ions—to generate more reactive and cytotoxic oxygen species such as the hydroxyl radical, which is a powerful oxidant, and which can initiate oxidation of biomolecules. The conversion of H2O2 into more cytotoxic compounds may be potentiated by reducing agents and by peroxidases. Cells may protect themselves against H2O2 toxicity either by the action of catalases or, in the case of DNA damage, by repairing the damage after it has taken place. Assays for the detection and quantitation of H2O2 in cell cultures include those based on (i) catalase-dependent oxidation of formate to CO2, (ii) generation of fluorescent products due to a H2O2- mediated oxidative reaction, (iii) the loss of fluorescence upon the oxidation of scopoletin, (iv) change in absorbance upon oxidation of phenol red, or (v) formation of complexes with peroxidases. Some possible antimicrobial uses of H2O2 in the food industry are presented.

This study examined the efficacy of UV light for reducing Escherichia coli O157:H7 in unpasteurized cider. Cider containing a mixture of acid-resistant E. coli O157:H7 (6.3 log CFU/ml) was treated using a thin-film UV disinfection unit at 254 nm. Dosages ranged from 9,402 to 61,005 microW-s/cm2. Treatment significantly reduced E. coli O157:H7 (P < or = 0.0001). Mean reduction for all treated samples was 3.81 log CFU/ml. Reduction was also affected by the level of background microflora in cider. Results indicate that UV light is effective for reducing this pathogen in cider. However, with the dosages used in this experiment, additional reduction measures are necessary to achieve the required 5-log reduction.

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