Research On Animal Production

Extended Abstract
Background: 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.
Methods: 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.
Results: 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.
Conclusion: 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.