New methods for evaluating functional properties of pulses

Foaming properties of pulses

In food applications, foam can be created by trapping air bubbles in a liquid using mechanical energy, usually in the form of mixing. Plant-based protein ingredients that are able to foam can be used to make foods such as mousses, pastries and whipped desserts. Foaming capacity (FC) is a measure of the increase in volume achieved by mixing and foaming stability (FS) measures the change in volume of a foam over a defined period of time. Although FC and FS are two important properties that affect how well a food ingredient performs as a foam, there currently are no widely accepted procedures for measuring them.

We studied a variety of pulse ingredients to develop a standard method for quantifying FC and FS under optimal conditions. Samples of each pulse ingredient were homogenized in distilled water and mixed at different speeds and periods of time (Figures 1 and 2). Foam volume was measured using a graduated cylinder and FC and FS were calculated as a percentage using the following:

• FC (%) = (volume of foam at 1 minute/volume of liquid prior to mixing) x 100
• FS (%) = (volume of foam at 60 minutes/volume of foam at 1 minute) x 100

By measuring the effect of mixing speed and mixing time on FC and FS, we were able to establish the optimum conditions for producing foam. This method is simple, has good within-laboratory reproducibility and can be applied to a variety of pulse ingredients.

Determining seed hardness in pulses

Seed hardness is an important factor affecting the physicochemical and functional properties of pulse flours produced by milling. Currently, the published methods for determining seed hardness are mainly applicable to wheat and procedures for determining the seed hardness of pulses are not readily available. We developed a method for measuring seed hardness using a texture analyzer attached with a round compression plate (Figure 3). A single pulse seed is placed on a platform with its hilum (seed scar) parallel to the compression plate and compressed at a fixed rate and strain. Seed hardness is expressed as the amount of work required to compress a seed and is determined by multiplying the force required (Newtons) by the distance compressed (meters) (Figure 4). We found that this method was objective and could be successfully applied to various pulses.

Other research projects

• In collaboration with Pulse Canada, we are developing a database of pulse protein ingredients produced by wet and dry milling using published or standard testing methods. This will provide consistent results on the composition and functionality of pulse ingredients.
• We are investigating how variety, growing location and growing year affect the chemical composition and functionality of faba beans. The results of this study will support the increased use of pulse ingredients and the marketability of Canadian faba beans.
• In collaboration with the Canadian Grain Commission’s Industry Services, we investigated the impact of wrinkled red lentil seeds on dehulling quality. Our results assisted Industry Services in confirming tolerances for the wrinkled seed grading factor for red lentils.