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.
Yogurt, fermented milk, cheese, custards.
Water retention, substitute skim milk powder, thickening agent, increase viscosity, decrease syneresis, faster acidification rate (starter culture dependent), decrease processing times (starter culture dependent), source of fermentable nutrients, support probiotic growth, maintain gel structure.
Nutritionally dense, fully- or partially- substitute animal-based ingredients, clean-label thickener, aligns with consumer trends.
Application: Yogurt
Substitute skim milk powder, thickening agent, increase viscosity, decrease syneresis, faster acidification rate (starter culture dependent), decrease processing times (starter culture dependent), prebiotic function, support 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)
Example Yogurt Formulations
| Treatment | Formulation | Preparation |
|---|---|---|
|
Green lentil flour (Agil et al. 2013) |
50mL homogenized (3.25% fat) milk, 2g lentil flour, with and without 0.5 mL probiotic bacteria | Pasteurized milk stirred at 85°C for 15 minutes and cooled to 42°C followed by the addition of lentil flour, starter culture (Lactobacillus delbrueckii spp. Bulgaricus and Streptococcus salivarius spp. Thermophilus) and probiotic bacteria (L. acidophilus and B. lactis). Samples were allowed to ferment until pH 4.5 followed by cooling and storage at 4°C. |
|
Control (Agil et al. 2013) |
50mL homogenized (3.25% fat) milk, with and without 0.5 mL probiotic bacteria | |
|
Green lentil flour (Benmeziane et al. 2021) |
1L partially skimmed milk, 100g sugar, 50g lentil flour, 1g modified starch, 0.03g lactic ferments | Milk heated between 45-50°C, mixed with other ingredients and pasteurized at 93°C for 5 minutes, then cooled to 45°C. Pasteurized milk was inoculated (Streptococcus thermophilus & Lactobacillus delbrueckii subsp. bulgaricus) and fermented for 2-4h before further cooling and storage at 6°C. |
|
Green lentil flour, roasted (Benmeziane et al. 2021) |
||
|
Control (Benmeziane et al. 2021) |
1L partially skimmed milk, 1g modified starch, 0,03g lactic ferments | |
|
Chickpea flour, roasted (Sidhu et al. 2020) |
250mL milk, 2.5g skim milk powder, 2.5g/6.25g/12.5g chickpea flour | Skim milk powder combined with milk before pasteurized at 80-85°C for 30 min then cooled to 40-42°C. Pasteurized milk was inoculated (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) at the same time as probiotic addition (Lactobacillus acidophilus LA5 and Bifidobacterium BB12) and fermented until a pH of 4.4-4.5 was reached before further cooling and storage at 4°C. |
|
Control (Sidhu et al. 2020) |
250mL milk, 2.5g skim milk powder | |
|
Chickpea flour (Hussein et al. 2020) |
1L raw cow’s milk, 80g sugar, 0/10/20g skimmed milk powder, 30/20/10g chickpea flour | Ingredients combined with milk and mixed before pasteurized at 90°C for 5 min, then cooled to 42°C. Pasteurized milk was inoculated with pre-biotic culture (Bifidobacterium animalis subsp. Lactis and Lactobacillus acidophilus) at 8-log10 CFU/mL an hour before inoculation with yogurt culture (LYOfast at 0.3g/L), then fermented until pH 4.7 before further cooling, stirring and packaging. |
|
Control (Hussein et al. 2020) |
1L raw cow’s milk, 80g sugar, 30g skimmed milk powder | |
|
Chickpea flour (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder, 4g chickpea flour | Skim milk and skim milk powder were combined and stirred for 20 min followed by supplementation of pulse ingredients, additional skim milk powder or left and pasteurized directly by boiling for 1 min. Pasteurized milk was adjusted to pH 6.5 and cooled to 42°C and inoculated with yogurt culture (Yogourmet OR Yogotherm M133) and probiotic culture (Lactobacillus rhamnosus AD200 OR Lactobacillus acidophilus AD200) for 18h while continuously stirred at 100rpm/min. |
|
Lentil flour (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder, 4g lentil flour | |
|
Control A (no solids added) (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder | |
|
Control B (additional solids added) (Zare et al. 2012b) |
200mL skim milk, 9.5g + 4g skim milk powder |
| Treatment | Formulation | Preparation |
|---|---|---|
|
Green lentil flour (Agil et al. 2013) |
50mL homogenized (3.25% fat) milk, 2g lentil flour, with and without 0.5 mL probiotic bacteria | Pasteurized milk stirred at 85°C for 15 minutes and cooled to 42°C followed by the addition of lentil flour, starter culture (Lactobacillus delbrueckii spp. Bulgaricus and Streptococcus salivarius spp. Thermophilus) and probiotic bacteria (L. acidophilus and B. lactis). Samples were allowed to ferment until pH 4.5 followed by cooling and storage at 4°C. |
|
Control (Agil et al. 2013) |
50mL homogenized (3.25% fat) milk, with and without 0.5 mL probiotic bacteria | + |
|
Green lentil flour (Benmeziane et al. 2021) |
1L partially skimmed milk, 100g sugar, 50g lentil flour, 1g modified starch, 0.03g lactic ferments | Milk heated between 45-50°C, mixed with other ingredients and pasteurized at 93°C for 5 minutes, then cooled to 45°C. Pasteurized milk was inoculated (Streptococcus thermophilus & Lactobacillus delbrueckii subsp. bulgaricus) and fermented for 2-4h before further cooling and storage at 6°C. |
|
Green lentil flour, roasted (Benmeziane et al. 2021) |
+ | + |
|
Control (Benmeziane et al. 2021) |
1L partially skimmed milk, 1g modified starch, 0,03g lactic ferments | + |
|
Chickpea flour, roasted (Sidhu et al. 2020) |
250mL milk, 2.5g skim milk powder, 2.5g/6.25g/12.5g chickpea flour | Skim milk powder combined with milk before pasteurized at 80-85°C for 30 min then cooled to 40-42°C. Pasteurized milk was inoculated (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) at the same time as probiotic addition (Lactobacillus acidophilus LA5 and Bifidobacterium BB12) and fermented until a pH of 4.4-4.5 was reached before further cooling and storage at 4°C. |
|
Control (Sidhu et al. 2020) |
250mL milk, 2.5g skim milk powder | + |
|
Chickpea flour (Hussein et al. 2020) |
1L raw cow’s milk, 80g sugar, 0/10/20g skimmed milk powder, 30/20/10g chickpea flour | Ingredients combined with milk and mixed before pasteurized at 90°C for 5 min, then cooled to 42°C. Pasteurized milk was inoculated with pre-biotic culture (Bifidobacterium animalis subsp. Lactis and Lactobacillus acidophilus) at 8-log10 CFU/mL an hour before inoculation with yogurt culture (LYOfast at 0.3g/L), then fermented until pH 4.7 before further cooling, stirring and packaging. |
|
Control (Hussein et al. 2020) |
1L raw cow’s milk, 80g sugar, 30g skimmed milk powder | + |
|
Chickpea flour (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder, 4g chickpea flour | Skim milk and skim milk powder were combined and stirred for 20 min followed by supplementation of pulse ingredients, additional skim milk powder or left and pasteurized directly by boiling for 1 min. Pasteurized milk was adjusted to pH 6.5 and cooled to 42°C and inoculated with yogurt culture (Yogourmet OR Yogotherm M133) and probiotic culture (Lactobacillus rhamnosus AD200 OR Lactobacillus acidophilus AD200) for 18h while continuously stirred at 100rpm/min. |
|
Lentil flour (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder, 4g lentil flour | + |
|
Control A (no solids added) (Zare et al. 2012b) |
200mL skim milk, 9.5g skim milk powder | + |
|
Control B (additional solids added) (Zare et al. 2012b) |
200mL skim milk, 9.5g + 4g skim milk powder | + |
Application: Fermented Milk
Substitute skim milk powder, decrease syneresis, maintain milk gel structure, improve temperature stress stability, increase acidification rate, prebiotic function, support probiotic growth (starter culture and pulse type dependent).
Microbial Viability
Both lentil and faba bean flours have been evaluated for their effects on fermented milk quality at inclusion rates of 1-4% (w/v). Zare et al. (2012a) incorporated 1-3% (w/v) lentil flour into probiotic fermented skim milk samples and compared its performance to similar inclusion rates of skim milk powder. All samples maintained minimum CFU concentrations to allow for a probiotic health claim (per CFIA regulations) based on a 100mL serving size. In another study, (Maselli and Hekmat, 2016) noted conflicting results in which 3% (w/v) lentil flour addition was unable to support microbial viability of fermented skim milk over a 28-day storage period. The authors attributed this to the different strains of L. rhamnosus used in the study, and the differing methods of preparation for fermented milk samples. In beverages produced strictly from lentil, Verni et al (2020) evaluated seven starter strains where all demonstrated the ability to grow and acidify in the beverage medium.
Boudjou et al. (2014) evaluated 4% (w/v) whole faba bean flour inclusion in Kefir with added probiotic cultures. The inclusion of faba flour stimulated microbial growth, where probiotic samples had 6-23% higher viable cell counts than their corresponding controls. These levels remained constant through to the end of a four-week storage period, indicating that faba flour helped to maintain cell viability during storage. Faba bean flour also appeared to be favoured during fermentations as these samples exhibited the lowest pH, highest titratable acidity and doubled the rate of pH reduction. The authors concluded that faba bean supplementation was able to stimulate probiotic growth and act as a prebiotic withstanding storage, which maintained probiotic stability over the life of the Kefir.
Stability
Zare et al. (2012a) found lentil flour increased the acidification rate of fermented milk compared to skim milk powder addition and was able to meet the target pH of 4.5 faster. The pH of 3% supplemented fermented milks were significantly more stable after 14 days of storage, and all lentil flour samples seemingly increased the acidifying ability of lactobacillus over storage. Lentil flour addition also significantly lowered the rate of syneresis relative to control and skim milk powder. This was most effective at higher addition levels. The samples containing 3% lentil flour showed the lowest syneresis compared to all other samples after 14 days. Lentil flour addition also served to stabilize the milk-gel structure over storage, resulting in smallest reductions in G’ and G’’ values over time. This stabilizing effect was also observed when the milk was subject to heating and subsequent cooling stresses, where skim milk supplemented samples exhibited an almost-collapsed gel structure that was otherwise preserved and more stable when lentil flour was added.
Impact on Colour
The addition of lentil flour has been found to increase the darkness and impart more yellowness hues to the fermented milk (Zare at al., 2012a), however at 1-2% lentil flour addition, the samples still had similar lightness values to 2% skim milk and control samples.
Example Fermented Milk Formulations
| Treatment | Preparation |
|---|---|
|
Probiotic Fermented Milk (Zare et al. 2012a) |
Skim milk powder (9.5% (w/v) dissolved in distilled water, stirred for 20 minutes and cooled to 4°C for 24h to create control sample. Treatments included supplementation with 1-3% (w/v) lentil flour or 1-3% (w/v) skim milk powder. Samples were heated to 65-70°C, homogenized for 3 min at 2500 rpm and pasteurized at 90°C for 10 minutes before pH adjusted to 6.5 with NCl and NaOH. Samples were then inoculated with 2x107 CFU/mL of Lactobacillus rhamnosus AD200 and incubated at 37°C until pH 4.5, followed by cooling and storage at 4°C. |
|
Probiotic Fermented Milk (Maselli and Hekmat, 2016) |
Skim milk (0.1% fat) supplemented with 3% (w/v) oat, white rice, barley, quinoa or green lentil flour was autoclaved for 15 min at 15 psi and cooled to 37°C. Samples were then inoculated with 2% (w/v) MRS broth solution containing 10% (w/v) Lactobacillus rhamnosus GR-1. Milk solutions were incubated anaerobically for 24h at 37.5°C prior to cooling and storage at 4°C. |
|
Kefir + Probiotic (Boudjou et al., 2014) |
Freeze-dried starter kefir culture (Lb. lantarum, Lb. rhamnosus, Lactoccocus lactic, L. cremoric and Leuconostoc cremoris) diluted in pasturized, homogenized milk (3.25% fat), stirred at 85°C for 15 min and cooled to 42°C. 4% (v/v) of 6.5 log CFU/mL probiotic culture solution (Lb. acidophilus, B. lactis, or co-culture ) was added to the milk with or without 4% (w/v) whole faba bean flour. Samples were incubated at 42°C until pH 4.2 before cooling and storage at 4°C. |
| Treatment | Preparation |
|---|---|
|
Probiotic Fermented Milk (Zare et al. 2012a) |
Skim milk powder (9.5% (w/v) dissolved in distilled water, stirred for 20 minutes and cooled to 4°C for 24h to create control sample. Treatments included supplementation with 1-3% (w/v) lentil flour or 1-3% (w/v) skim milk powder. Samples were heated to 65-70°C, homogenized for 3 min at 2500 rpm and pasteurized at 90°C for 10 minutes before pH adjusted to 6.5 with NCl and NaOH. Samples were then inoculated with 2x107 CFU/mL of Lactobacillus rhamnosus AD200 and incubated at 37°C until pH 4.5, followed by cooling and storage at 4°C. |
|
Probiotic Fermented Milk (Maselli and Hekmat, 2016) |
Skim milk (0.1% fat) supplemented with 3% (w/v) oat, white rice, barley, quinoa or green lentil flour was autoclaved for 15 min at 15 psi and cooled to 37°C. Samples were then inoculated with 2% (w/v) MRS broth solution containing 10% (w/v) Lactobacillus rhamnosus GR-1. Milk solutions were incubated anaerobically for 24h at 37.5°C prior to cooling and storage at 4°C. |
|
Kefir + Probiotic (Boudjou et al., 2014) |
Freeze-dried starter kefir culture (Lb. lantarum, Lb. rhamnosus, Lactoccocus lactic, L. cremoric and Leuconostoc cremoris) diluted in pasturized, homogenized milk (3.25% fat), stirred at 85°C for 15 min and cooled to 42°C. 4% (v/v) of 6.5 log CFU/mL probiotic culture solution (Lb. acidophilus, B. lactis, or co-culture ) was added to the milk with or without 4% (w/v) whole faba bean flour. Samples were incubated at 42°C until pH 4.2 before cooling and storage at 4°C. |
Application: Custards
Substitute starches, thickening agent.
A study by Aguilar-Raymundo & Velez-Ruiz (2018) evaluated raw and cooked chickpea flour to replace starch in dairy-custard dessert formulations. The addition rate of chickpea flour was calculated based on its proximate composition, so the starch content of the corresponding formulations remained consistent to the control. Chickpea variety and roasting parameters were significant in altering the soluble solids, pH, acidity and syneresis between custards whereas the inclusion rates, which ranged from 8.3-11.3g, did not. Overall, all chickpea flours were able to produce a successful custard with good characteristics in which the chickpea flours contributed positively to the viscoelastic behaviour of the products. The results indicate the importance of understanding the effect of processing and varietal influences when selecting a pulse flour for a custard application.
Example Custard Formulations
| Treatment | Preparation |
|---|---|
|
Dairy Custard Dessert (Aguilar-Raymundo and Velez-Ruiz, 2018) |
Control Formula: 88.98 mL whole milk (3% fat), 6.5g of sucrose, 4.5g starch 0.02g of κ-carrageenan 8.3-11.3g of raw and roasted chickpea flour derived from two varieties were used to replace starch in control formulation. Dry ingredients were dispersed in milk and stirred constantly for 4 min, followed by subsequent heating to 90°C for 5 min. Samples were then cooled to room temperature before storage at 4°C. |
| Treatment | Preparation |
|---|---|
|
Dairy Custard Dessert (Aguilar-Raymundo and Velez-Ruiz, 2018) |
Control Formula: 88.98 mL whole milk (3% fat), 6.5g of sucrose, 4.5g starch 0.02g of κ-carrageenan 8.3-11.3g of raw and roasted chickpea flour derived from two varieties were used to replace starch in control formulation. Dry ingredients were dispersed in milk and stirred constantly for 4 min, followed by subsequent heating to 90°C for 5 min. Samples were then cooled to room temperature before storage at 4°C. |
Brix
Acidity
Syneresis
Brix, acidity and syneresis values for custard formulated with raw (R) and cooked (C) chickpea flour milled from blanco noroeste (BN) and costa 2004 (C4) varieties at 8.3% (1), 9.3% (2), 10.3% (4), and 11.3% (4) inclusion rates. (Data adapted from Aguilar-Raymundo & Velez-Ruiz, 2018).
Application: Cheese
Water retention, increased yield, partial replacement of animal proteins.
Few studies have evaluated the use of pulse flours in conventional, animal-based cheese applications. Moradi et al (2021) prepared a feta cheese product by replacing up to 27% of raw milk in the formulation with a mixture of inulin (3.5% or 7%) and lentil milk (10% or 20%). The pH of the cheese was only affected at the highest inclusion rate of lentil milk, where the addition of lentil milk, prepared from soaked and blended lentil seeds, significantly increased the protein content of the final product. Overall, an inclusion of 10% was recommended due to an otherwise sandy texture at higher levels. Total acceptance of cheese samples decreased with the addition of lentil milk; however, this was alleviated by the addition of inulin which increased firmness and taste scores. Overall, the most acceptable product was made using 10% lentil milk and 3.5% inulin.
Chechetkina et al. (2016) produced a soft cheese from goat milk which incorporated 1-10% extruded chickpea flour after partial whey drainage. Overall, the inclusion of extruded chickpea flour resulted in a weak smell of bean, with homogeneous and moderately dense consistency as well as higher moisture and titratability acidity when analyzed over a 13-day storage period. The increased water retention of cheeses containing 5% extruded chickpea flour resulted in a 12% increase in product yield compared to the control sample with highest sensory scores.
| Soft Cheese Sample | Consistency | Average Sensory Rating (5-point scale) |
|---|---|---|
| Control | Gentle, elastic | 4.8 |
| 1% extruded chickpea flour | Uniform | 3.9 |
| 3% extruded chickpea flour | Moderately dense | 4.5 |
| 5% extruded chickpea flour | Gentle, connected | 5.0 |
| 7% extruded chickpea flour | Friable | 4.4 |
| 10% extruded chickpea flour | Crumbly | 3.7 |
| Soft Cheese Sample | Consistency | Average Sensory Rating (5-point scale) |
|---|---|---|
| Control | Gentle, elastic | 4.8 |
| 1% extruded chickpea flour | Uniform | 3.9 |
| 3% extruded chickpea flour | Moderately dense | 4.5 |
| 5% extruded chickpea flour | Gentle, connected | 5.0 |
| 7% extruded chickpea flour | Friable | 4.4 |
| 10% extruded chickpea flour | Crumbly | 3.7 |
Sensory ratings for soft cheeses formulated with chickpea flour. (Data adapted from Chechetkina et al., 2016)
The Science
How do pulse flours effect the microbial loads in fermented and probiotic products?
Pulse flours have been incorporated into an array of dairy products that utilize microbial cultures in their production. Minimal studies have reported any inhibitory effects on microbial counts where, in fact, many have demonstrated an increased acidification rate, which allows the products to reach optimal pH conditions faster. Authors have attributed the increase in acidification rate to the presence of readily fermentable nutrients in pulse flours in addition to their lower buffering capacity compared to milk for conventional dairy-based products (Zare et al. 2012a).
The stability of probiotics in formulations containing pulse flours has also been demonstrated in which culture counts remained stable and even exceeded those of control formulations withstanding prolonged storage of up to 28 days. Some authors have attributed this to the protein constituents and high oligosaccharide content in pulse flours (particularly raffinose, stachyose, and verbascose) both of which are considered to be easily fermentable and provide a stimulatory effect (Boudjou et al. 2014; Hussein et al., 2020; Zare et al., 2012a). It has been proposed that the antioxidant properties of the carbohydrate components may also help maintain microbial viability (Zare et al., 2012a).
The figure below demonstrates the ability of skim milk powder and lentil flour to enhance the acidification rate of fermented milk, notable after the 8th hour of incubation (data adapted from Zare et al., 2012a). After 12 hours, milks containing lentil flour demonstrated lower pH and were able to reach the target pH of 4.5 significantly earlier than control and skim milk containing samples.
Skim milk powder and lentil flour enhancements to the acidification rate of fermented milk.
Fig. 2. Acidification trend of skim milk (SM) containing L. rhamnosus AD 200 supplemented with 1 to 3% lentil flour (1 LF, 2 LF and 3 LF - treatments) or 1-3% skim milk (1 SM and 3 SM - treatments)
How do pulse flours effect gel stability?
In conventionally fermented dairy products, the acid produced during fermentation lowers the pH near the isoelectric point of casein (pH ~4), which resulted in protein coagulation that forms a gel network. Instability and non-homogeneities in the gelling system resulted in the expulsion of liquid or whey from the network, also known as syneresis. Pulse flour inclusion into dairy systems has been demonstrated to lower the rate of syneresis compared to control formulations. This has been hypothesized to be the result of the greater reduction in pH due to the stimulatory nature of pulse flours on microbial counts, in addition to an increase in protein content and total solids content, which discourages whey separation from the system (Zare et al. 2012a). The presence of carbohydrate components also provided hydrocolloidal properties with the ability to absorb water that may also contribute to stability in the final product (Benmaziane et al., 2021; Zare et al., 2012a).
For example, the figure below demonstrates the effects of 1-3% lentil flour and skim milk powder inclusion on the syneresis of fermented milks (data adapted from Zare et al., 2012a). Not only did lentil flour significantly reduce the rate of syneresis relative to the control formulation, but the lowest lentil flour inclusion level (1%) demonstrated significantly reduced syneresis than all skim milk containing samples (1-3%) at every point of analysis over the 28 days of storage.
Fig. 4. Syneresis in probiotic beverages supplemented with 1-3% lentil flour, 1-3% skim and control sample (no supplementation) during 28 day storage (SM: skim milk, LF: lentil flour), means followed by the same letter are not significantly different (P<0.05)
The enhanced stability of dairy gel networks obtained by pulse-flour inclusion will also have implications on the resulting texture of products. This has typically been demonstrated as an increase in viscosity unless enzymatic hydrolysis has been applied in the yogurt-manufacturing process to break down pulse-flour components. It follows that Zare et al. (2012a) noted an increase in G’ (elasticity) and G’’ (viscosity) values in fermented milk samples containing lentil flour. After subject to temperature stress (incorporating heating and subsequent cooling), all samples exhibited a decrease in G’ and G’’, however, this reduction was not as substantial for samples containing lentil flour, confirming their greater gel stability. For samples containing similar inclusion levels of skim milk powder, the gel structures had almost collapsed when exposed to the same temperature stress conditions.
In the figure below Sidhu et al. (2020) demonstrated the ability of roasted chickpea flour to incrementally increase the viscosity of yogurt formulations relative to the control formulation containing skim milk powder. (Data adapted from Sidhu et al., 2020)
References
Agil, R., Gaget, Al., Gliwa, J., Avis, T. J., Willmore, W. G., & Hosseinian, F. (2013). Lentils enhance probiotic growth in yogurt and provide added benefit of antioxidant protection. LWT-Food Science and Technology, 50, 45-49. http://dx.doi.org/10.1016/j.lwt.2012.07.032.
Aguilar-Raymundo, V. G., & Vélez-Ruiz, J. F. (2018). Physicochemical and Rheological Properties of a Dairy Dessert, Enriched with Chickpea Flour. Foods, 7(2), 25. https://doi.org/10.3390/foods7...;
Benmeziane, F., Raigar, R. K., Ayat, N. E.-H., Aoufi, D., Djermoune-Arkoub, L., & Chala, A. (2021). Lentil (Lens culinaris) flour addition to yogurt: Impact on physicochemical, microbiological and sensory attributes during refrigeration storage and microstructure changes. LWT, 140, 110793. https://doi.org/10.1016/j.lwt....;
Boudjou, S., Zaidi, F., Hosseinian, F., & Oomah, B. D. (2014). Effects of Faba Bean (Vicia faba L.) Flour on Viability of Probiotic Bacteria During Kefir Storage. Journal of Food Research, 3(6), 13. https://doi.org/10.5539/jfr.v3...;
Chechetkina, A., Iakovchenk, N., & Zabodalova, L. (2016). The technology of soft cheese with a vegetable component. Agronomy Research, 14(5), 1562-1572.
Hussein, H., Awad, S., El-Sayed, I., & Ibrahim, A. (2020). Impact of chickpea as prebiotic, antioxidant and thickener agent of stirred bio-yoghurt. Annals of Agricultural Sciences, 65(1), 49–58. https://doi.org/10.1016/j.aoas...;
Maselli, L. & Hekmar, S. (2016). Microbial vitality of probiotic milks supplemented with cereal or pseudocereal grain flours. Journal of Food Research, 5(2) 41-29. doi:10.5539/jfr.v5n2p41
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