Food Biotechnology
Rana Tahmasbi; Mahta Mirzaei; Mohammadreza Khani
Abstract
Introduction: Fermented foods, probiotic, prebiotics, and symbiotic, are among the most important groups of functional food that have attracted the attention of researchers during the last years. Proteolytic activity of lactic acid bacteria can lead to the production of peptides in the fermented product. ...
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Introduction: Fermented foods, probiotic, prebiotics, and symbiotic, are among the most important groups of functional food that have attracted the attention of researchers during the last years. Proteolytic activity of lactic acid bacteria can lead to the production of peptides in the fermented product. The produced peptides can exhibit different biological activities such as antioxidant, antihypertensive, etc. that are influenced by the type of protein source, type of bacteria, time and conditions of fermentation process. Fermentation of various cereals such as quinoa seeds with high sugar and protein content by lactic acid bacteria can lead to the production of antioxidant peptides and improving their nutritional properties. Materials and Methods: In this study, the role of Lactobacillus reuteri and Lactobacillus acidophilus and the combination of two bacteria on the progress of fermentation and antioxidant activity of quinoa extract was investigated. The fermentation process was started by separate and simultaneous inoculating of Lactobacillus reuteri and Lactobacillus acidophilus and continued for 72 hours at 37° C. Sampling was performed every 24 hours of fermentation and samples were kept at -20° C for further analysis. The parameters such as pH, acidity, amount of soluble protein, degree of hydrolysis, amount of phenolic compounds and DPPH and ABTS radical scavenging activity were determined. Results and Discussion: Lactobacillus acidophilus showed higher acidification capacity than Lactobacillus reuteri. The amount of acidity in the sample fermented by Lactobacillus acidophilus increased from 0.27 to 1.13 % after 72 hours, while this amount was measured as 0.80 % for sample fermented by Lactobacillus reuteri. The amount of soluble protein and the degree of hydrolysis increased in samples fermented by both species. However, the largest increase was related to the sample fermented by Lactobacillus reuteri, so that the amount of soluble protein increased from 0.72 to 0.88 mg / ml and the value of free amino groups increased from 20.28 to 58.14 µM leucin/ mg protein during 72 hours of fermentation. The DPPH and ABTS radical scavenging activity increased in all fermented samples. The highest antioxidant activity was observed in samples fermented by Lactobacillus reuteri, followed by a combination of two bacteria (50:50) and Lactobacillus acidophilus. The amounts of phenolic compounds increased in all fermented samples. However, the highest increase was related to the sample fermented by Lactobacillus reuteri, so that it increased from 0/73 to 16.21 mg Gallic acid / ml after 72 hours of fermentation. Therefore, the results showed that despite the higher acidifying power of Lactobacillus acidophilus in quinoa extract, but Lactobacillus reuteri exhibited higher proteolytic activity, more ability to produce antioxidant peptides and also release phenolic compounds during the fermentation process.Simultaneous use of the two bacteria did not intensify the proteolytic activity and antioxidant activity of peptides, and the greatest increase in acidity, proteolysis, and antioxidant activity occurred in the first 24 hours of fermentation. Fermented extracts showed higher ABTS radical inhibitory activity than DPPH radical inhibition, indicating the hydrophilic nature of most produced antioxidant compounds. The highest levels of antioxidant activity were observed in samples fermented by Lactobacillus reuteri, a combination of Lactobacillus reuteri and Lactobacillus acidophilus (50:50) and Lactobacillus acidophilus, respectively. The results showed that fermentation by Lactobacillus reutri has the greatest effect on the production of antioxidant peptides and the release of phenolic compounds. The results of this study confirm the effectiveness of fermentation methods on improving the healing properties of quinoa extract and Lactobacillus reuteri was a more effective bacterium in fermentation and production of antioxidant peptides compared to Lactobacillus acidophilus. Simultaneous use of two bacteria did not increase the intensity of fermentation and did not improve the antioxidant activity compared to single use of each bacteria. Finally, the results of this study showed that fermentation of quinoa extract improves its antioxidant properties and has the potential to be used as a fermented beverage.
Food Chemistry
Roxana Alizadeh Firozeh; Mahta Mirzaei; Vajiheh Fadaei Noghani
Abstract
Introduction: Bioactive peptides are protein fragments with 2 to 20 amino acids that have different biological properties depending on the type of amino acids and peptide sequences, including antioxidant, antihypertensive, and antidiabetic. These peptides are inactive in their parent protein sequences ...
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Introduction: Bioactive peptides are protein fragments with 2 to 20 amino acids that have different biological properties depending on the type of amino acids and peptide sequences, including antioxidant, antihypertensive, and antidiabetic. These peptides are inactive in their parent protein sequences but are released during fermentation, enzymatic hydrolysis, or food processing, and exhibit a positive effect on body function and health being. Lentil protein hydrolysate containing antioxidant peptides can be considered as an ingredient of functional foods. One major challenge in using protein hydrolysate in the formulation of functional foods is their stability against the various processes applied to food such as heat and pH treatments. Materials and Methods: In this study, Lentil protein (Lens esculinaris) was hydrolyzed by Alcalase enzyme under controlled conditions (enzyme/substrate ratio of 90 Anson unit (AU)/ kg protein, 55°C, one hour). The intensity of enzymatic hydrolysis was monitored by the OPA method and antioxidant activity was evaluated based on DPPH and ABTS radical scavenging activity. The heat stability of lentil protein hydrolysate was evaluated by heating samples at 37, 50, 75 (for 15 -60 min), and 90°C (for 5 minutes). The pH stability was investigated by exposing the sample at a pH of 2, 5, 7, 9, And 11 for 1 hr and then adjusting on 7. OPA method was also used to evaluate the possible effect of pH and heat treatments on the content of free amino groups. Results and Discussion: The results showed that hydrolysis of Lentil protein by Alcalase under controlled conditions produced antioxidant peptides. Heating at 37, 50, and 75°C for 15 minutes reduced the DPPH radical scavenging activity by 1.25, 4.9, and 10.17% and ABTS radical scavenging activity by 3.8, 6.8, and 9%, respectively. The results of the OPA assay also showed a significant (P<0.05) decrease in the number of free amino groups in protein hydrolysate exposed to heat treatment. With increasing the time of treatment up to 60 minutes, the antioxidant activity decreased more significantly (P<0.05), simultaneously with a decrease in the content of free amino acid groups in the protein hydrolysate sample. So that, after heat treatment at 37, 50, and 75 ° C for 60 minutes, the free amino acid groups reached from 33/66 μM leucin /mg protein to 29.51, 27.59, and 25.68 μM leucin /mg protein and the most decrease in antioxidant activity was measured for samples exposed to 75°C for 60 minutes. It caused a 27.2%, and 29.2% reduction in DPPH and ABTS radical scavenging activity, respectively. Also, exposure to heat treatment at 90°C for 5 minutes caused a 15% and 13% decrease in DPPH and ABTS radical scavenging activity. The results obtained from consideration the antioxidant activity of samples exposed to pH treatment (2, 5, 7, 9, and 11 for 1 hour) showed the highest antioxidant activity of peptides at neutral pH and confirmed that acidic and alkaline conditions caused a significant decrease in antioxidant activity (P<0.05). As exposure to pHs 2 and 11 for one hour led to respectively 16.3 and a 29.2% decrease in DPPH radical scavenging activity and 16 and 18.2% decrease in ABTS radical scavenging activity. The results of the OPA assay also confirmed the role of acidic and basic pH on less exposure of free amino acid groups in protein structure.The results showed the potential of using Alcalase enzyme to hydrolyze Lentil protein and produce antioxidant peptides and the Lentil protein hydrolysate with antioxidant activity exhibited relative stability toward different heat and pH treatments. It was concluded that peptides retained 88% and 76% of antioxidant activity at maximum heat (90 ° C for 5 minutes) and pH treatment ( pH=11, for 1 hour). According to the results of the OPA assay, the observed decrease in antioxidant activity may be due to the changes that happen in protein and peptide structure when are exposed to heat and pH treatments. Altogether, our results showed that Lentil protein hydrolysate can be considered as a potential food ingredient with stable antioxidant activity.
