Pulses in Dairy

Pulse flours have successfully been used as functional ingredients or as the base in dairy-product formulations. These ingredients contribute positively to gel stability, water binding, thickening, and promote overall texture while stimulating and maintaining positive microbial and probiotic growth.

Texture

Several projects have evaluated the advantages of incorporating 10-50g/L of raw and/or roasted lentil and chickpea flours as a thickening agent in yogurt formulations. The addition of these flours adds to the total solids content of the formulation, increasing its viscosity and contributing to the overall texture of yogurt (Haq et al., 2019; Hussein et al., 2020; Sidhu et al. 2020). Even when used to replace skimmed-milk powder, Hussei et al. (2020) reported no significant differences in total solids or physicochemical properties of probiotic yogurt containing 10-30g/L of chickpea flour. The water-binding ability of raw and roasted pulse flours also contributes to the overall texture of yogurt formulations by decreasing its susceptibility to syneresis (Benmeziane et al., 2021; Haq et al. 2019). Siddhu et al (2020) reported a reduction in syneresis susceptibility when increasing the inclusion rate of chickpea flour from 10 to 50g/L.

Syneresis of plain yogurt formulated with 50g/L of lentil flour (Benmeziane et al., 2021)

Water-holding capacity and syneresis susceptibility of yogurt samples formulated with roasted chickpea flour (Siddhu et al. 2020).

Sensory Evaluation and Antioxidant Activity

Sensory evaluation of yogurt formulations containing pulse flours have been preferred by panellists over control formulations, despite detectable increases in the yellowness or greenness of the product associated with pulse seed colour (Benmaziane et al., 2021; Hussein et al., 2020). Hussein et al. (2020) also reported chickpea flour addition to increase levels of total phenolic content and antioxidant activity (measured as DPPH and FRAP) relative to the control in yogurt formulations stored over 21 days.

Probiotic Culture Growth Rates

The effects of pulse flour inclusion on yogurt and probiotic culture growth rates have also been evaluated. Generally, the inclusion of pulse flours resulted in appropriate ranges for pH and titratability acidity over 21-28 days of storage with no inhibitory effects noted (Benmeziane et al. 2021; Hussein et al., 2020; Sidhu et al., 2020). Some studies have even reported possible growth promotion, with higher titratability acidity, acidification rates and bacterial culture levels compared to the control (Hussein et al. 2020; Sidhu et al., 2020). This result was particularly notable for probiotic yogurt preparations in which chickpea/lentil flour inclusion accelerated fermentation and significantly enhanced the concentration of viable probiotics over storage (Agil et al., 2013; Hussein et al. 2020; Zare et al., 2012b). This indicates the potential for pulse flours to serve as a prebiotic to support growth in probiotic yogurt formulations.

For stirred yogurt prepared without probiotics, Zare et al. (2012b) only noted improvements in the acidification rates for samples prepared with Lactobacilli, highlighting the significant effect of starter culture on the preferential utilization of pulse flours during fermentation. This result indicates pulse flours could be used to decrease processing times associated with fermentation with proper selection of starter culture. Agil et al. (2013) reported a preferential consumption of lentil flour by yogurt starter cultures Lactobacillus and Streptococcus, which actually resulted in excess fermentation and curdling when incorporated at high inclusion rates (≥60g/L). However, this effect was not noted at lower inclusion levels, highlighting that consideration should be given to appropriately select the inclusion level of pulse flour based on the starter culture being employed during yogurt production.

The figure below demonstrates the counts for two probiotic culture strains in stirred yogurt samples supplemented with 1-3% chickpea flour (data adapted from Hussein et al., 2020). Over the 3-week duration of refrigerated storage, all samples containing chickpea flour demonstrated higher probiotic counts than control formulation.

Count of probiotic culture B. bifidium in stirred bio-yogurt supplemented with chickpea flour.

Count of probiotic culture B. animalis ssp. lactis and Laddophilius in stirred bio-yogurt supplemented with chickpea flour.

Fig.1. Count of probiotic culture (a) B. bifidion, (b) B. animalis ssp. lactis and Lacidophilus in stirred bio-yogurt supplemented with chickpea flour. (Data adapted from Zare et al., 2012a)