Development of a method for determining oil absorption capacity in pulse flours and protein materials

Background and objectives The conventional method for determining oil absorption capacity (OAC) in pulse ingredients involves mixing a sample with excess oil, centrifuging the dispersion, and then calculating the amount of oil absorbed. However, there are issues associated with the conventional method such as loss of the less dense materials through oil decanting process and reabsorption of oil by samples after centrifugation. Therefore, the objective of this work was to develop a method that could eliminate those concerns for determining OAC. Findings A method for measuring OAC of flours or protein concentrates/isolates derived from pulses and soybeans was developed. The new method involved mixing 0.5 g sample with 1.5 ml canola oil intermittently for 20 min, centrifuging the inverted sample tubes at 600 xgfor 25 min, and measuring the amount of oil absorbed per gram of dry sample. Comparing to the conventional method, the new method used a lower sample to oil ratio (1:3 g/ml), and each test tubes were centrifuged upside down in an apparatus at a lower centrifugal force (600 xg). A syringe barrel was used in the apparatus to hold a filter paper in place to prevent sample materials from draining out with the excess oil during centrifugation. Test efficiency increased due to combining steps of centrifugation and oil draining in the new method. Differences in OAC values determined by the new method were exhibited from various pulse and soybean materials. Conclusions Amounts of oil absorbed by flours and protein concentrates/isolates from pulses and soybeans could be measured by the new method without accounting for the extra free oil trapped in the samples. The new procedure showed good within-laboratory reproducibility. More samples could be tested with the new method due to its simplified procedure. Flours and protein concentrates/isolates from pulses and soybeans with different OAC values could be separated from each other using the new method. Significance and novelty The method developed was simple and reliable and could be applied to a variety of pulse and soybean ingredients.