Spray Drying of beta- Lactoglobulin-Vitamin A and beta-Lactoglobulin-Vitamin D Complexes

Abstract

β- Lactoglobulin (β-LG) is a major whey protein of ruminant species. Its amino-acid sequence and 3-dimensional structure show that it is a lipocalin, a serum retinol binding protein. β-LG has been reported to be able to bind a variety of ligands, many of which are hydrophobic compounds. These compounds include retinol (vitamin A), fatty acids, vitamin D, cholesterol, etc. The importance of the binding property is that it can be implemented to deliver these nutrients using β-LG as a carrier without the presence of the fat in which they normally associate.

In the study, two complexes (β-Lactoglobulin-Vitamin A and β-Lactoglobulin-Vitamin D) were produced through spray drying. During the drying process, heat tends to denature the protein and causes the dissociation of the complex, which can result in low retention of vitamins. Certain sugars, such as lactose, were found to stabilize whey protein during spray drying. The study tested the hypothesis that the addition of lactose into the complexes would yield higher recovery of vitamins from spray drying.

The β-Lactoglobulin-Vitamin A complex was formed by mixing retinyl palmitate with 2% β-LG solution in DI water. Cholecalciferol was mixed with 2% β-LG solution in DI water to form β-Lactoglobulin-Vitamin D complex. Both complexes were incubated at 40°C for 2 hr. Binding of vitamin to β-LG was confirmed by fluorescence quenching of the protein at wavelength 332 nm. Lactose was then added into the above complex solutions at 5:1 weight ratio to the protein. Each mixed complex was then pumped into the spray dryer and powder was collected. The content of vitamins in the powder complexes was determined by HPLC analyses.

The results showed that in the presence of lactose, the spray-dried powder had 4-5 times more retention of vitamin A than without lactose and that the content of vitamin D in the powder complex was 1-2 times greater than without lactose.

The study also used the β-lactoglobulin-vitamin A complex to fortify a lemon lime soda and studied the stability of the vitamin A in the complex under different types of light for a period of seven (7) days. The results demonstrated that both lights and acidity lead to the quick degradation of vitamin A in the beverage.