Abstract:

The changes in functional properties of soybean protein isolates (SPI) before and after freezing were investigated
to reveal the effect of cryopreservation conditions, namely sample concentration, freezing temperature, freezing time
on functional properties of SPI including water-holding capacity, oil-holding capacity, emulsifying property and texture
property. The results showed that reduced SPI concentration could lead to an initial increase and then a final decrease
in water-holding capacity, oil-holding capacity and emulsifying property. When SPI concentration was 1:12, the waterholding
capacity, oil-holding capacity, emulsion stability, hardness and elasticity achieved maximum levels. When freezing
temperature was －18 ℃, the water-holding capacity, oil-holding capacity, emulsion stability, hardness and elasticity
reached maximum levels; however, when freezing temperature was －20 ℃, the best emulsion stability was observed.
With the prolongation of freezing time, the emulsion stability of SPI gradually decreased, reaching the highest level when
freezing time was 3 days; after 2 days of freezing, the highest water-holding capacity was achieved. Compared with unfrozen
samples, the functional properties of frozen SPI were obviously weakened, indicating poorer water-holding capacity, oilholding
capacity, emulsifying property and texture property.

Key words: cryopreservation, soybean protein isolates, water-holding and oil-holding capacity, emulsifying property, texture property