Protein composition and nutritional aspects of pea protein fractions obtained by a modified isoelectric precipitation method using fermentation

Pea albumins are promising for their nutritional, biological, and techno-functional properties. However, this fraction is usually discarded in the industry due to its low protein content compared to globulin fraction and the presence of some anti-nutritional compounds. In the present study, we used an alternative method of pea protein extraction based on alkaline solubilization/isoelectric precipitation in which the reduction of pH was achieved by lactic acid fermentation using specific starters instead of mineral acids. Hence, the main objective of this study was to examine the protein profile and the content of anti-nutritional and nutritional active compounds in pea albumin-rich fractions obtained by the isoelectric extraction method without (control) or with fermentation with different lactic acid bacteria (Streptococcus thermophilus, Lactiplantibacillus plantarum, and their co-culture). Different pea cultivars (Cartouche, Ascension, and Assas) were used here for their differences in protein profile. The results revealed a higher total nitrogen content in albumin-rich fraction for fermented samples and, in particular, for co-culture. The majority of total nitrogen was determined as non-protein (~50%), suggesting the degradation of proteins by LAB to small peptides and amino acids, which were solubilized in the soluble fraction (albumin) as confirmed by size exclusion chromatography (SEC-HPLC) analysis. Moreover, the higher antioxidant activity of fermented albumin samples was attributed to the production of small peptides during extraction. Lactic acid fermentation also resulted in a significant reduction of trypsin inhibitor activity, α-galactoside, and phytic acid content of this fraction compared to control

Impact de la fermentation lactique sur la composition des protéines de pois et leur profil aromatique dans une méthode modifiée d'extraction par précipitation isoélectrique

Despite its popularity, pea protein consumption is still limited in industry due to its imperfect functional properties, low solubility and low accepted sensorial profile. However, these properties can be modified through different food processing methods such as extraction. Face with this situation, it has been highlighted the urge to modify and/or hybridize conventional methods in order to develop innovative, cost-effective, green methods for production of protein with respect to the purity and quality of the protein. The purpose of this study was to explore an alternative to the conventional alkaline solubilization/isoelectric precipitation method in which the decrease of pH was achieved by lactic acid fermentation instead of mineral acid addition. To study the feasibility of the method, different commercial starters (i.e. S. thermophilus (S), S. thermophilus and Lactobacillus acidophilus (SL), S. thermophilus, Lactobacillus acidophilus and Bifidobacterium lactis (SLB)) were added to protein extracts obtained from commercial pea flour and the natural acidification up to pH 4.8 led to the precipitation of globulins separated from the soluble fraction (albumins). The results showed a higher content of protein for albumin fraction obtained by fermentation compared to the conventional method. Albumin fraction is usually discarded in industry due to the presence of anti-nutritional compounds. Hence, the second question was to study the effect of the extraction assisted by fermentation on protein profile and nutritional properties of albumin fraction.Different lactic acid bacteria (Streptococcus thermophilus (ST), Lactipluntibacillus plantarum (LP)) and their co-culture were selected for their proteolytic activity and their contribution to organoleptic properties of legume protein. The results supported the idea that fermentation can improve the nutritional quality of albumin fraction (decrease of phytate, trypsin inhibitor, α-galactosides content and improve antoxidant activity) without impairing the protein profile of the globulin fraction. However, tailoring the properties of albumin fraction depended on the strain of lactic acid bacteria. For instance, the highest level of proteolysis and production of peptides was observed for the bacteria in co-culture compared to the mono-cultures. The third part of the study investigated the effect of lactic acid fermentation on aromatic profile of the pea protein fractions. The analysis of volatile compounds and odor active compounds evidenced that the samples obtained by fermentation (depending on the strains) were associated with more pleasant aroma such as fruity, floral and lactic, compared to the samples obtained by conventional acidification. The result represented that alkaline solubilization/isoelectric precipitation method assisted by fermentation is promising for production of legume protein with increased nutritional value, and improved aromatic profile. In the future, it would be interesting to determine the techno-functional properties of pea proteins obtained by this method, and the sensory profile of food including these proteins as ingredients. The industrial application of this method requires further optimization in terms of bacteria selection, cost-effectiveness and scale-up.Malgré sa popularité, la consommation de protéines de pois reste limitée dans l'industrie agroalimentaire en raison de ses propriétés fonctionnelles imparfaites, de sa faible solubilité et de son profil sensoriel mal accepté. Cependant, ces propriétés peuvent être modifiées par différents procédés tels que l'extraction. Face à cette situation, c’est nécessaire de modifier et/ou d'hybrider les méthodes conventionnelles afin de développer des méthodes innovantes, rentables et écologiques pour la production de protéines végétales tout en respectant la pureté et la qualité des protéines. L'objectif de cette étude était d'explorer une alternative à la méthode d’extraction conventionnelle de solubilisation alcaline/précipitation isoélectrique dans laquelle la diminution du pH était obtenue par la fermentation lactique au lieu de l'ajout d'acide minéral. Pour étudier la faisabilité de la méthode, différentes souches commerciales (Streptococcus thermophilus (S), Streptococcus thermophilus et Lactobacillus acidophilus (SL), Streptococcus thermophilus, Lactobacillus acidophilus et Bifidobacterium lactis (SLB)) ont été ajoutées à des extraits de protéines obtenus à partir de farine de pois commerciale. L'acidification naturelle jusqu'à un pH de 4,8 a conduit à la précipitation des globulines qui ont été séparées de la fraction soluble (albumines). Les résultats ont montré une teneur plus élevée en protéines pour la fraction d'albumine obtenue par fermentation par rapport à la méthode conventionnelle. La fraction albumine est généralement éliminée par l'industrie en raison de la présence de composés antinutritionnels. La deuxième question était donc d'étudier l'effet de l'extraction assistée par fermentation sur le profil protéique et les propriétés nutritionnelles de la fraction d'albumine.Différentes bactéries lactiques (Streptococcus thermophilus (ST), Lactipluntibacillus plantarum (LP)) et leur co-culture ont été sélectionnées pour leur activité protéolytique et leur contribution aux propriétés organoleptiques des protéines de légumineuses. Les résultats soutiennent l'idée que la fermentation peut améliorer la qualité nutritionnelle de la fraction d'albumine (diminution des phytates, des inhibiteurs de trypsine, de la teneur en α-galactosides et l’amélioration de l'activité antoxydante) sans altérer le profil protéique de la fraction de globuline. Cependant, l'adaptation des propriétés de la fraction albumine dépend de la souche de bactéries lactiques. Par exemple, le niveau le plus élevé de protéolyse et de production de peptides a été observé pour les bactéries en co-culture par rapport à la mono-culture. La troisième partie de l'étude a porté sur l'effet de la fermentation lactique sur le profil aromatique des fractions de protéines de pois. L'analyse des composés volatiles et des composés odorants actifs a montré que les échantillons obtenus par fermentation (en fonction des souches) étaient associés à des arômes plus agréables tels que fruités, floraux et lactiques, par rapport aux échantillons obtenus par acidification conventionnelle. Les résultats montrent que la solubilisation alcaline/précipitation isoélectrique assistée par fermentation est une méthode prometteuse pour la production de protéines de légumineuses avec une valeur nutritionnelle accrue et un profil aromatique amélioré. À l'avenir, il serait intéressant de déterminer les propriétés techno-fonctionnelles des protéines de pois obtenues par cette méthode, ainsi que le profil sensoriel des aliments contenant ces protéines comme ingrédients. L'application industrielle de cette méthode nécessite une optimisation plus poussée en termes de sélection des bactéries, de rentabilité et de mise à l'échelle

Pea Protein Extraction Assisted by Lactic Fermentation: Impact on Protein Profile and Thermal Properties

International audienceAlthough pea protein has been widely explored, its consumption is still limited by undesirable sensory characteristics and low solubility. All these properties can be modified during protein extraction process. Besides, previous studies showed that lactic acid bacteria (LAB) have a positive effect on legume protein ingredients in terms of flavor and functional properties. Hence, the objective of this work was to explore an alternative extraction method based on alkaline extraction/isoelectric precipitation (AEIEP) resulting in globulin-rich and residual albumin-rich fractions. Here, the decrease in pH was achieved by lactic fermentation instead of mineral acid addition. Different bacteria strains (Streptococcus thermophilus, Lactobacillus acidophilus and Bifidobacterium lactis) have been used alone or in co-culture, and the results were compared with the usual acidification. The extraction assisted by fermentation led to the increase by 20-30% in protein content/yield of the albumin fraction, meaning that the solubility of the extracted pea protein was increased. This result could be explained by the proteolytic activity of bacteria during lactic fermentation. Therefore, the thermal denaturation properties of the isolated protein fractions measured by differential scanning calorimetry could be mainly ascribed to differences in their polypeptide compositions. In particular, higher denaturation enthalpy in globulin fractions after fermentation compared to AEIEP (~15 J/g protein vs. ~13 J/g protein) revealed the relative enrichment of this fraction in pea legumins; a higher part of 7S globulins seemed to be consumed by lactic acid bacteria

Effect of Lactic Acid Fermentation on Legume Protein Properties, a Review

International audienceLegume proteins have a promising future in the food industry due to their nutritional, environmental, and economic benefits. However, their application is still limited due to the presence of antinutritional and allergenic compounds, their poor technological properties, and their unpleasant sensory characteristics. Fermentation has been traditionally applied to counteract these inconveniences. At present, lactic acid fermentation of legumes is attracting the attention of researchers and industry in relation to the development of healthier, tasty, and technologically adapted products. Hence, we aimed to review the literature to shed light on the effect of lactic acid fermentation on legume protein composition and on their nutritional, functional, technological, and sensorial properties. The antimicrobial activity of lactic acid bacteria during legume fermentation was also considered. The heterogenicity of raw material composition (flour, concentrate, and isolate), the diversity of lactic acid bacteria (nutriment requirements, metabolic pathways, and enzyme production), and the numerous possible fermenting conditions (temperature, time, oxygen, and additional nutrients) offer an impressive range of possibilities with regard to fermented legume products. Systematic studies are required in order to determine the specific roles of the different factors. The optimal selection of these criteria will allow one to obtain high-quality fermented legume products. Fermentation is an attractive technology for the development of legume-based products that are able to satisfy consumers’ expectations from a nutritional, functional, technological, and sensory point of view

Identification of volatile and odor‐active compounds in pea protein fractions obtained by a modified extraction method using fermentation

International audienceThis study investigates the aromatic composition of pea albumin and globulin fractions obtained through either fermentation or conventional acidification using hydrochloric acid (control) toward the isoelectric point of pea globulins. Different lactic acid bacteria were used including S. thermophilus (ST), L. plantarum (LP), and their coculture (STLP). The volatile compounds were extracted by solvent‐assisted flavor evaporation technique and quantified by gas chromatography–mass spectrometry (GC‐MS). Odor‐active compounds (OAC) were further characterized by gas chromatography–olfactometry (GC‐O). In total, 96 volatile and 36 OACs were identified by GC‐MS and GC‐O, respectively. The results indicated that the protein fractions obtained by conventional acidification were mainly described by green notes for the presence of different volatile compounds such as hexanal. However, the samples obtained by fermentation had a lower content of these volatile compounds. Moreover, protein fractions obtained by coculture fermentation were described by volatile compounds associated with fruity, floral, and lactic notes. Practical Application The insights from this study on pea protein aroma could find practical use in the food industry to enhance the sensory qualities of plant‐based products. By utilizing fermentation methods and specific lactic acid bacteria combinations, manufacturers may produce pea protein with reduced undesirable green notes, offering consumers food options with improved flavors. This research may contribute to the development of plant‐based foods that not only provide nutritional benefits but also meet consumer preferences for a more appealing taste profile