lactobacillus acidophilus

The health benefits of consuming milk and its products, as well as the presence of intestinal microorganisms, have been well known in recent years. It is also known that the optimal balance in the number of microbes in the digestive system depends on nutrition and health. Cheese is one of the dairy products that have played an important role in human nutrition for centuries. Due to its dry matter, fat, and pH higher than other milk products, it can play a more effective role in transferring probiotics. Spirulina algae has a positive effect on increasing the bioavailability of probiotics due to its unique properties (rich in nutrients such as vitamins, minerals such as iron, and digestible and absorbable protein), and it can be used to enrich foods such as dairy products by creating a favorable color. Therefore, this study aimed to investigate the prebiotic effect of Spirulina platensis algal extract on Lactobacillus acidophilus bacteria survival and the physical, chemical, and sensory properties of feta cheese during storage at 4 °C for49 days.

S. platensis extract was purchased, ground, and shaken for 48 h. Afterward, the mixture was strained and the extract was concentrated and dried in a Fore machine. Fresh and whole cow's milk pasteurized at 72 °C for 15 sec was used to produce feta cheese. The milk temperature was raised to 35 °C, and 5 I of milk was poured into sterile containers for cheese preparation. After that, the starter and then calcium chloride were added to the milk samples after 1.5 h. Finally, rennet was added to the milk and stirred slowly for 3-5 min. For better rennet efficiency, 1 m3 was cut and the temperature of the milk was kept at around 35 °C during the clot formation period. The clot was formed after 1 h.The treatments were control, probiotic treatment, probiotic treatment + 0.5% extract, and probiotic treatment + 1% extract. All experiments were repeated three times. The viability of L. acidophilus probiotic, acidity, pH, and percentages of moisture and dry matter, as well as organoleptic properties, including aroma, taste, texture, appearance, and general acceptability, were investigated during cheese storage (49 days). Finally, the mean, standard deviation, and minimum and maximum number of bacterial counts were reported and the trend of changes in the logarithm of the number of bacteria in the 49-day period was analyzed in each group and in each of the study days. All statistical analyses were performed by SPSS20 software at a significance level of p<0.05.

The highest growth of L. acidophilus in the treatments belonged to the probiotic treatment along with 1.5% S. platensis extract, which reached from 8.02 log CFU/g to 10.32 log CFU/g on the 49th (final) day, with an increase of 2 log CFU/g. After that, probiotic treatment with 1% S. platensis extract and probiotic treatment + 0.5% S. platensis extract reached from 7.99 log CFU/g to 9.52 log CFU/g and from 8.01 log CFU/g to 9.22 log CFU/g, respectively. During cheese storage, an increase in acidity and moisture and a decrease in pH were observed due to lactic acid production resulting from lactose sugar fermentation by probiotics. Regarding pH, probiotic treatment + 1.5% of S. platensis extract showed the greatest decrease in cheese (p<0.05). Regarding the acidity, adding 0.5, 1, and 1.5% of S. platensis extract increased the acidity compared to the probiotic treatment, which can be effective in microbial quality and increasing the shelf life of cheese. In the control treatment, there was no significant difference during the storage period (p<0.05). In the control treatment, acidity was 0.71 on day zero, which increased during storage and reached 1.11 by day 49. The addition of 0.5, 1, and 1.55 of the extract increased the acidity compared to the probiotic treatment. The analysis of moisture and dry matter revealed that probiotic treatment + 1.5% S. platensis extract showed the best performance (p<0.05). The examination of organoleptic properties showed no statistically significant differences between the sensory properties studied in the cheese samples (p<0.05), and the sensory scores decreased with an increase in the algal extract concentration.

In general, the present study shows that the addition of S. platensis extract improves the viability of L. acidophilus, increases acidity and moisture, and, accordingly, decreases pH and brix in feta cheese. Therefore, the use of this extract or its additive compounds can be an effective step toward improving food products and consumer health.

The biological activity of probiotics is affected by various environmental factors each of which can influence the performance as well as the growth of probiotics for increasing the health of the consumers. The aim of is to investigate the effect of fructose , dose 0/5,1 ,1/5 and 2 present of the primary culture and temperature of 35 ,38 ,41 and 44 degrees centigrade on the growth and metabolism and metabolism of Lactobacillus acidophilus La5 in sterilized milk ; in order to do this ,the milk fermented with Lactobacillus acidophilus La5 (as the culture ferment ) was used for incubating the milk sample different; incubators were used as the suitable temperatures for the growth of microorganisms. The acidity and the pH of the milk samples were measured during different hours and the total number of microbial counts were and measured at 0 , 4 and 8 h after the incubation. In order to measure the effect of fructose 0/75 % (w/v) added the milk samples, and the resulted sample , together with the control sample , was kept in incubation at 41 degree centigrade ; and then the acidity , pH of Lactobacillus acidophilus La5 was measured and the total number of lactobacillus acidophilus was counted during the above mentioned periods after incubation . Every of above operations was replicate ten times ; then , utilizing statistical tests , were compared with one another during the above mentioned periods. The findings of the study indicated that the total number of bacteria and the amount of acidity in the incubated milk samples at 41 and 44 degrees centigrade were significantly greater than the other temperatures (P<0.05 ). The multiplication rate of the total hours of bacteria in samples containing 2 % of culture ferment during the fourth h of incubation was significantly greater than the other samples ( P<0.05 ); however , this difference in 8 h after the incubation was not significant. Concerning the use of prebiotic fructose, the total number of bacteria in and the acidity in the milk samples containing fructose was significantly greater than the number of control sample ( P<0.05 ). It is concluded from this study that The best alternative temperature for this purpose is an incubation temperature range of 41-44° C as well and if fructose is added to milk , there is a significant effect in enhancing the growth of Lactobacillus acidophilus La5.