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Barbara Wróblewska, Lucjan Jędrychowski
Institute of Animal Reproduction and Food Research of Polish Academy of Sciences,
Department of Food Enzymes and Allergens,
Tuwima str 10, 10-747 Olsztyn, Poland
INTRODUCTION: Milk has a high nutritive value and bioactive properties. Some people, especially small children, are sensitive to milk protein (a-lactalbumin and b-lactoglobulin). Cow milk allergy is usually the first kind of food allergy in infantis life. Therefore it is necessary to eliminate or reduce allergenic proteins from a diet. Heat treatment of milk usually reduce milk allergenicity, but this approach is not satisfactory. Enzymatic hydrolysis is commonly used in the production of hypoallergenic infant formulas.
AIM: The aim of the study was to lower the level of a-lactalbumin and b-lactoglobulin immunoreactivity after different kinds of modification of cow milk whey proteins.
MATERIALS AND METHODS: Raw cow milk was modified by thermal processes, microwaves and ultrasonification, enzymatic hydrolysis with pepsin, trypsin, chymotrypsin, alcalase and rennin, chemical reaction with acetic and succinic anhydrides and conjugation with polyethylene glycol and bovine serum albumin with the use of glutaraldehyde. Pasteurized milk was exposed to the action of meso- and thermophilic microbiological cultures. Immunoreactive properties of the obtained products were estimated by the ELISA methods. Polyclonal antibodies were obtained through rabbit immunisation with a-la and b-lg. IgG was purified in the presence of Na2SO4. Electrophoretic separation of whey protein on 12% acrylamide gel (SDS-PAGE), capillary electrophoresis (CE), chromatographic separation with the use of the FPLC system with the Bakerbond (WP PEI) ion exchange column were applied in the research.
RESULTS: Immunoreactivity of a-la and b-lg in raw milk was estimated as 100%. The results obtained with ELISA method were compared with these data. Ultrasonification was the most effective method of lowering the immunoreactivity within the termal processes. Residual immunoreactivity was estimated as 0.88%(a-la) and 6.42%(b-lg). The effect of enzymatic reaction with various enzymes was different. After 24 hours of hydrolysis with alcalase, the immunoreactivity of -la decreased to 0.62%. Reaction of 1 g of acetic anhydride to 1 g milk protein decresed the immunoreactivity to 0.01% (a-la), and 0.65% (b-lg). Residual immunoreactivity of adducts obtained from whey protein and polyethylene glycol was rather low 0.08% (a-la), and 0.05% (b-lg). Conjugation of a-la and b-lg with bovine serum albumin was not as much effetcive as the above mentioned one. Reaction of 0.1g BSA with 10 mL of milk allowed obtaining a b-lg to 1.42% and 2.48 % in the immunoreactivity of a-la, respectively. Promising results were obtained after lactic acid fermentation. Of mesophilic cultures the most effective strains were: 10s strain which
decreased residual immunoreactivityof a-la to 0.04%, and 14D strain which decreased b-lg to 0.67%. Among termophilic cultures, bacteria of Lactobacillus delbrueckii ssp. bulgaricus was very effective. Especially the strain S11 allowed decreasing the immunoreactivity of a-la to 0.01%. B-lg was more resistant to the activity of bacteria enzymatic proteases.
CONCLUSION: The obtained results show that there are possibilities to decrease the milk immunoreactivity. Chemical modifications show possibilites of lowering the immunoreactivity, but they can not be applied in human nutrition. The most promising kind of modification is lactic acid fermentation. The obtained products are characterized by good properties, very important for potential consumers.
SENSITIVITY OF FOOD ALLERGENS TO PROTEOLYSIS: IN VIVO AND
IN VITRO APPROACHES
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