Lactose Content and Selected Quality Parameters of Sheep Milk Fermented Beverages during Storage

Abstract

The aim of the research was to evaluate lactose content and rheological, physical, chemical, and organoleptic parameters during the storage of fermented beverages made from sheep’s milk. The research was carried out on natural, probiotic, and Greek-type yogurts, as well as kefir. The products were made using the thermostat method from the milk of 42 East Frisian sheep in the middle lactation period, in duplicate. Lactose contents, active and titratable acidity, color by the L*a*b*C*h* system, and rheological parameters (hardness, consistency, consistency, and viscosity) were tested, and organoleptic assessments were carried out on the first, seventh, fourteenth, and twenty-first days of storing the drinks at 4 °C. Of all drinks, the highest reduction in lactose after 21 days of storage was found to occur in kefir (52% reduction) and, among the yogurts, in the Greek yogurt (41% reduction). The product with the lowest lactose content, regardless of the storage period, was kefir. This indicates that kefir is more suitable than yogurt for people with partial lactose intolerance. Effects of both inoculation type and beverage storage time were shown to exist for all parameters. It was also found that kefirs suffered deterioration in most rheological parameters and, in general organoleptic evaluation in the final period of storage. Based on our analysis, the optimal storage time for natural yogurts and sheep’s milk kefirs at 4 °C was 21 and 14 days, respectively.

Identification of Potential Bioactive Peptides in Sheep Milk Kefir through Peptidomic Analysis at Different Fermentation Times

“…Thus, pH changed from around 6.70 in non-fermented milk to 3.80 after 48 h fermentation. Similar values have been previously reported for sheep milk kefir which had been fermented for the same time period [19,42,43], although the grains/milk ratio was not the same as in our work, i.e., 5% w/v. Lactic acid increased from an initial value of 0.056 g/L to 1.69 g/L after 48 h, similar to the results obtained by de Lima et al, 2018 [19], but lower than reported in a previous work [44], in which the authors measured around 9 g/L lactic acid.…”

“…Actually, we did not observe a significant reduction in this metabolite, although its hydrolysis by-product D-galactose did clearly increase according to the fermentation time and with a very similar trend to that of lactic acid, indicating that there is a clear relationship between those compounds. The concentration values of lactose that we detected in our samples are quite similar to others already published, in the range of 30-50 g/L fermented product [42,[44][45][46]. Moreover, some studies have demonstrated that relatively low amounts of lactose disappear even after several days or weeks of storage after kefir production [42,45], thus indicating that during fermentation, lactose is not eliminated.…”

“…The concentration values of lactose that we detected in our samples are quite similar to others already published, in the range of 30-50 g/L fermented product [42,[44][45][46]. Moreover, some studies have demonstrated that relatively low amounts of lactose disappear even after several days or weeks of storage after kefir production [42,45], thus indicating that during fermentation, lactose is not eliminated. These cited studies also have shown that D-galactose levels are in a very similar range, i.e., 0.3-0.7 g/L kefir, than those measured in our samples, i.e., 0.57-0.92 g/L of fermented product (0.048 g/L in the non-fermented milk).…”

Analysis of the Influence of Lactiplantibacillus plantarum and Lacticaseibacillus rhamnosus Strains on Changes in the Hexachlorobenzene Content in Fermented Mare Milk during Refrigerated Storage

“…The material for the study was fermented mare milk produced by the thermostat method under laboratory conditions [ 70 , 71 ]. The milk (9.4% dry matter content, pH 6.46, density 1.034 g/mL, 1.15% fat content) was purchased from a horse dairy farm in Kłodzin (Poland).…”

Probiotic Fermented Goat’s and Sheep’s Milk: Effect of Type and Dose of Collagen on Survival of Four Strains of Probiotic Bacteria during Simulated In Vitro Digestion Conditions

“…It is considered a source of functional bioactive peptides involved in processes related to the functioning of the digestive, endocrine, immune, and nervous systems [ 40 ]. Ovine milk products have therapeutic effects and are of great interest to consumers, especially people with limited lactose tolerance [ 41 ].…”