Effects Of Four Non-thermal Processing On Conformational Changes And Immunological Property Of Bovine β-lactoglobulin

Milk is very popular food because of its rich protein content and various nutrient compositions, and milk is the main source of food protein for infants. However, it is one of main food that causes allergic reaction, and the incidence rate is as high as7.5%. β-lactoglobulin consist in whey protein, is recognized as a major milk allergen and the content is about50%. Currently, heat treatment is the most widely used in dairy processing technology, and it also has adverse effect on the functionality and nutrients of milk. The emerging non-thermal processing technology could not only achieve the desired effect of thermal processing, but also reduce the number of harmful microorganism in the food, maintaing the original sensory and nutritional quality of the food, and retaining its heat-sensitive ingredient. So it has the incomparable advantage over the thermal processing.This research mainly focused on defining the conformational changes and antigenicity and allergenicity changes of β-lactoglobulin treated with hydrostatic high-pressure, ultrasound, irradiation and pulsed electric field processing, were characterized by SDS-PAGE, ultraviolet absorption spectroscopy, circular dichroism spectroscopy, and fluorescence spectroscopy, respectively. Moreover, antigenicity and allergenicity were evaluated by competitive inhibition ELISA.The main research methods, results and conclusions were shown as follows:1. Bovine β-lactoglobulin was treated with hydrostatic high-pressure in different pressure, and it was shown that the primary and second structure almost had no changes, while tertiary structure was sensitive to pressure and its changes were closely related to the changes of allergenicity of β-lactoglobulin; Moreover, the allergenicity of the treated P-lactoglobulin didn’t change strongly.2. Bovine β-lactoglobulin was treated with ultrasound in different times. It was shown that the primary structure stayed stable after processing, while the second structure had weak changes. Moreover, the conformational changes had little relationship with allergenicity, and the exposure of hydrophobic groups in the tertiary structure reflected the changes of epitopes, indicating that the most of allergenic epitopes were located in internal protein and correlated positively with the exposure of hydrophobic groups. Ultrasound could reduce antigenicity and allergenicity of β-lactoglobulin at10min and30min. 3. Bovine β-lactoglobulin was treated with irradiation in different doses. It was shown that a certain extent of β-lactoglobulin polymers were formed after treatment, and the disordered protein structure, surface hydrophobicity and Trp fluorescence intensity had obvious changes. Irradiation mainly destroyed conformational epitopes of β-lactoglobulin, leading to a sharply decrease of antigenicity and allergenicity. This irradiation had significant influence on conformation and immunological properties of β-lactoglobulin, therefore, it can be one of effective approach to reduce potential allergenicity.4. Bovine β-lactoglobulin was treated with pulsed electric field in different electric intensity and number of pulses, and it was shown that partial degradation of P-lactoglobulin occurred at higher processing condition, In addition, the second and tertiary structure changed significantly, a-helix and random coil occurred mutual transformation, and surface hydropobicity increased with the increasing electric field and pulse numbers. However, this treatment failed to reduce antigenicity and allergenicity.