23-10

H. ZHANG, D. Petterson, and A. R. Fairbrother. Department of Food Science, Beijing Agricultural College, Beijing, 102206, China

Australia sweet lupin -- L. angustifolius is the first true low-alkaloid lupin and the most widespread species grown in Western Australia. Its' protein content (42.57%) is comparable to that of soybean (45.48%) and its amino acid profile is basically similar to that of soybean. Lupin kernels have been used partially or completely to substitute soybean in making milk, milk powder, bean curb and Indonesia tempe etc..

Our objective is to study the possibility of using lupin to make yogurt.

Kjeldahl procedure (AOAC method) and refractometer (Brix 0-20%) determined protein content and total soluble solid (TSS) respectively.

Our results showed that, firstly, Glucono-Delta-Lactone (GDL) solution rather than water should be used to soak lupin kernel in order to improve lupin milk yield, which was measured by protein content and total soluble solid (TSS). Lupin milk (water: lupin=1:6) made from soaking lupin kernel in 0.5% GDL solution for 17 hours produced the highest yield (protein 4.05%; TSS 10.6%). Secondly, lupin protein was very heat-liable; it was easily denatured when being exposed to heat treatment (above 70°C for more than one minute); consequently, the separation was so severe that the lupin milk almost becomes transparent. Thirdly, the mixture of lupin milk enriched with 0.2% pectin and 5% skim milk powder was the least separated and most cloudy sample. Fourthly,the lupin milk mixture mentioned above as fermentation substrate of lactic acid bacteria, specifically, L. burgaricus, S. thermophilus, L. acidophilus and B. bifidus enabled the organisms to produce sufficient acid and coagulate the protein. However, the lupin yogurt prepared in this way had strong "grass" flavor from lupin kernels and lacked typical yogurt flavor and uniform texture.

These results suggest that lupin should be used in conjunction with soybean and other necessary ingredients such as thickeners to produce a desirable yogurt.