سعید میردامادی

Protein hydrolysates and bioactive peptides that have health benefits for consumers and protein glycolysis is a well-known strategy for increasing the health benefits and functional qualities of proteins. The subjects of this study were the effects of temperature, pH, and sugar type on the progress of the Mailard reaction in lentil protein hydrolysate, as well as its antioxidant and emulsification capabilities.

The protein isolated from lentil seeds was hydrolyzed enzymatically by alkalase and mixed with glucose and lactose.  Millard reaction occured at temperatures of 60 and 80 ° C and pHs of 6.5 and 11. The reaction progress was tracked over time by measuring the color intensity at 420 nm and the values of free amine groups using OPA method. The ABTS radical scavenging activity  and  emulsification capabilities of the  final products product were analysed.

The results revealed that the reaction of lentil protein hydrolysate with glucose at 60 ° C and pH of 6.5 produced the most deep brown color. The findings of measuring the number of free amine groups also confirmed the results. Lactose sugar products with a lesser browning degree have the greatest effect on increasing antioxidant activity. Overall, the antioxidant activity of lentil protein hydrolyate increased from 24.18 to 60.97%, and its emulsifying function was enhanced.

Overall, the results demonstrated that the Millard interaction between lentil protein hydrolysate proteins and peptides increases its health and functional qualities, and the product has the potential to be exploited in the formulation of functional foods.

Today, the use of Lactobacill strains and their metabolites is the new strategies in control of diabetes and oxidative stress. Therefore, the present study aimed to investigate the antidiabetic and antioxidant properties of metabolites obtained from of Lactobacillus delbrueckii ssp. bulgaricus culture media. The samples were evaluated including cell free supernatant (CFS), cell free extracts (CFE), cell free supernatant of fermented milk (CFS-FM) and bioactive peptides separated from ultrafiltration (3,5,10 kDa). The ability of bacteria in proteolysis of protein of  fermented milk (FM) was evaluated by O-phthaldialdehyde method compared with non-fermented milk (NFM). The antidiabetic activity was measured based on inhibition of α-amylase and α-glucosidase. The antioxidant activity was evaluated by inhibition of 2,2-Diphenyl-1-picrylhydrazyl (DPPH) and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS). The results showed that the sample of CFS-FM inhibited α-amylase (25%) and α-glucosidase (26.6%) enzymes. Among the peptide fractions, fraction  of >10 kDa with higher protein content (13.816 mg (had the highest inhibition of α-amylase (80.64%) and α-glucosidase enzyme (54%) (p<0.05). The inhibitory efficiency ratio (IER) showed that the 3-5 kDa fraction had more inhibitory than other peptide fractions (p<0.05). Also, the CFS and CFE inhibited α-glucosidase enzyme by 50% and 25%, respectively. In case of antioxidant properties, it was observed that the free radicals scavenging of CFS-FM increased compared with NFM (p<0.05). Also, the peptide fractions of 3-5 kDa (80.85%) and >10 kDa (43.63%) had the highest DPPH and ABTS free radicals scavenging. The antioxidant capacity of trolox equivalent from peptide fractions (µmTE/mg protein) showed that the <3 kDa fraction had the highest antioxidant activity (p<0.05). The ability to free radicals scavenging in CFS and CFE was observed. Results indicate the importance of  Lactobacillus delbrueckii as a starter culture and its functional role.

Nowadays, Polysaccharides are used to improve the nutritional and physicochemical properties of dairy products. The identification of natural compounds such as polysaccharides with antidiabetic and antioxidant properties has become important due to the relationship between diabetes and oxidative stress. Therefore, the present study aimed to evaluate the influence of pectin on the antidiabetic and antioxidant activity of milk fermented by lactic acid bacteria (LAB) isolated from traditional Iranian dairy products. Pectin (1%) was added to the samples following milk fermentation by Lactobacillus helveticus and Lactobacillus para-casei strains, and antidiabetic activity was assessed by considering the inhibitory effects on α-amylase and α-glucosidase. The antioxidant activity was determined by evaluating inhibition of 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and hydroxyl radicals. Samples included pectin solution (0.5-3.5 mg/ml and 0.5-10 mg/ml for evaluation of anti-diabetic and antioxidant activity, respectively), whey of fermented and non-fermented milk with (1%) and without pectin. The results indicated the role of  pectin on  inhibition of  α-glucosidase enzyme activity (IC50=2.38 mg/ml), as well as scavenging the DPPH (44.57%), ABTS (28.7%), and Hydroxyl (38.85%) radicals (P<0.05) a concentration of 10 mg/ml. Pectin added to the whey of non-fermented milk sample boosted antioxidant properties and the maximum rate of free radical scavenging activity (35%) was obtained for DPPH radicals. Furthermore, adding pectin to the whey of milk fermented with Lactobacillus helveticus strain improved the activity of the product on inhibition of α-glucosidase enzyme (29%), scavenging of DPPH (41.26 %), ABTS (2.5%), and hydroxyl radicals (7.64%) (P<0.05). The results indicated the potential of pectin to be used in the formulation of beneficial food products due to its ability to improve the antioxidant and anti-diabetic properties of fermented milk products.

The inclination to manufacture beneficial dairy products has increased in recent years, as consumers pay more attention to food products with adequate sensory qualities and health benefits.

The current study looked first at the anti-diabetic efficacy of milk fermented by Lactobacillus delbrueckii, and Lactobacillus helveticus strains isolated from traditional yogurt as well as co-culture of two-strain based on the inhibitory activity of alpha-amylase and alpha-glucosidase enzymes for the production of functional fermented milk. Then, added 1% inulin as an appropriate and applied prebiotic to fermented milk resulting from the combination of two strains and evaluated physicochemical, anti-diabetic, anti-oxidant, proteolysis rate, and population of bacteria during 19 days at 4°C.

The results indicated that milk fermented with two-strain bacterial intercropping had stronger inhibitory activity on alpha-amylase (45%) and alpha-glucosidase (35%) than single strains of Lactobacillus delbrueckii and Lactobacillus helveticus (p<0.05). The addition of inulin increased the inhibitory activity of alpha-amylase (20%) and alpha-glucosidase (33%) at the end of fermentation, respectively. During storage at 4°C, the composition two bacterial strains and inuline significantly increased the population of bacteria, acidity and viscosity and significantly reduced the pH and proteolysis rate of fermented milk. However, there was a decrease in antioxidant and antidiabetic activities.

The results revealed that both bacterial strains in combination with inulin have the capacity to produce functional food.

Mulberry is a fruit that has a considerable acceptance among consumers. The short harvest season and low persistence of this fruit have led to the use of methods such as freezing that have the least effect on phenolic compounds and antioxidant properties and sensory properties of the mulberry. One of the problems of sensory evaluation is the non-parametric results of the answers and the low accuracy of their analysis. Today, methods such as fuzzy logic allow inaccurate parameters to be analyzed by mathematical methods. In the present study, mulberry was stored in a freezer at -18 °C for six months and removed from the freezer at 0, 72 h, one month, two months and six months. After juice making, the sensory evaluation was performed using five-point hedonic method and the data were analyzed using fuzzy logic methodology, while attributes were color, aroma, taste, and feel mouth. Also, pH, acidity, antioxidant activity and total phenol content were evaluated. Sensory evaluation of the samples showed that the freezing of the mulberry increased the overall suitability of the samples in 72 hours and did not show a decrease in sensory properties during 6 months. Panelists assessed the importance of sensory attributes including taste, mouthfeel, fragrance, and color, as well. Although, sensory evaluation did not decrease the sensory of juice, significant decrease of pH (19.83%), increase in acidity (0.31%) and a decrease in antioxidant activity (about 14%) and phenolic compounds (about 21%) during freezing was observed. According to the obtained results, freezing can be suggested as an acceptable method for long storage of mulberry fruit.

The application of probiotic starter cultures in fermented products is expanding in different communities. The genetic variation makes the effects of these bacteria different and unpredictable in different human societies. Therefore, the safety control and evaluation of their non-pathogenicity is of great importance and monitoring centers are required to closely monitor the safety of the bacteria used in food products. In this study, two strains of Lactobacillus isolated from dairy products of Ardabil (Heyran mountain road villages) and Khuzestan province (Behbahan city) in Iran were identified based on the biochemical and molecular properties through sequence analysis of 16S rRNA gene. Then, their safety was examined based on the international guidelines, especially the European :union: standard. The two identified strains included Lactobacillus fermentum (PTCC 1929) and Lactobacillus helveticus (PTCC 1930). The results showed the lack of gelatinase enzyme, inability of blood hemolysis, inability of amino acids decarboxylation and the lack of genes responsible for the invasive characteristics of pathogenic microorganisms including gelE, efaAfm , efaAfs , agg, ace, cylM, cylA, cylB.  In addition, the results showed the sensitivity of both isolates to Penicillin, Ampicillin, Rifampicin and Tetracycline, and their resistance to Kanamycin and Ciprofloxacin. Lactobacillus fermentum was resistant to vancomycin, whereas Lactobacillus helveticus was susceptible to it. Since cases of antibiotic resistance are inherent according to scientific reports, the obtained results confirmed the potential application of these two isolated strains as starter in the fermented dairy products. It also confirmed the necessity of using safety assessment procedures for probiotic bacteria.

The use of protein hydrolysate containing antioxidant peptides in the formulation of functional food has been increasing recently. The types and sequences of amino acids, the type of hydrolyzing enzymes and hydrolysis progress have some important impacts on the properties of protein hydrolysate.

In this research, the effects of pepsin and alcalase enzymes (E/S:1/10) under optimal conditions of each ones, were investigated on the extraction of antioxidant peptides from peanuts protein. Peanut’s oil was extracted using solvent extraction method and protein was precipitated at isoelectric point. The extracted protein was subjected to the pepsin and alcalase enzymes for maximum period of five hours. The progress of hydrolysis was considered every thirty-minutes using Ortho-Phthalaldehyde (OPA) method.

The results indicated that the most hydrolysis occurs after 250 and 90 min of hydrolysis for pepsin and alcalase, respectively and the values of free amino acid groups increased from 167.0 to 263.0 μM leucin/mg protein (for alcalase) and from 415.0 to 517.0 μM leucin/mg protein (for pepsin). Moreover, the antioxidant activity of protein hydrolysate was investigated based on DPPH and ABTS radical scavenging activity. By increasing the degree of hydrolysis, the DPPH and ABTS radical scavenging activity increased simultaneously. The maximum values of DPPH and ABTS free radicals scavenging activity were measured respectively, 5175.0 and 756.0 mMTE/mg proteins (for pepsin) and 3644.0 and 1087.0 mMTE/mg proteins (for alcalase).

The results indicated that the progress of enzymatic hydrolysis of peanut protein by alcalase and pepsin enzymes leads to producing more antioxidant peptides and the final products obtained can be considered as a candidate for producing functional foods.

Lactic acid bacteria have a long history in the production of fermented dairy products. They are of great importance in the production of bioactive peptides and increasing the health effects due to their proteolytic ability. In the present study, the ability of two strains of Lactic acid bacteria were investigated after isolation from Iranian dairy products and were compared in terms of fermentation ability, proteolytic properties, and production of fermented milk with antioxidant and acceptable sensory properties. Two isolated strains, including Lactobacillus fermentum</em> (PTCC 1929) and Lactobacillus helveticus</em> (PTCC1930)  were identified based on the ability of sugar fermentation and 16S rRNA sequence analysis. The results showed that in spite of the better growth of Lactobacillus fermentum</em>bacteria in the first 24 hours, the initial acidification was higher in L. helveticus</em>.  The pH value in the Lactobacillus helveticus</em>sample was less than 4 in the early 24 hours, while this value was achieved after 72 hours in L. fermentum</em>. In the co-culture, the pH reduction steps reached at a minimum level of 3.63 with the initial and secondary acidifications of Lactobacillus helveticus</em>and L. fermentum</em>, respectively. The results showed that, despite the higher proteolysis ability of Lactobacillus helveticus</em>, the antioxidant activity of the sample containing Lactobacillus fermentum</em>was 1.5 to 1.7 times higher. The highest antioxidant activity was observed in all samples at the first 24 hours. Increase in proteolysis did not cause an increase in the production of antioxidant peptides. Milk fermented by Lactobacillus fermentum</em> for</em> 24 hours was significantly lower in taste and acceptability score compared to the other samples (P</em><0.05). In general, the results showed that two strains co-culture has a better ability to produce antioxidant bioactive peptides with a suitable overall acceptance and has the potential for the production of fermented dairy products with healthy properties.