Heat Stability of Buttermilk
Buttermilk prepared on a laboratory scale from raw cream, or on a commercial scale from flash-pasteurized cream (90°C for 1 to 2 s), exhibited a type B heat coagulation time-pH profile (i.e., stability increased as a function of pH). The high heat stability of buttermilk in the pH range of the minimum of a type A milk (pH ∼6.8 to 7.0) appears to be related to differences in the serum phase constituents (i.e., a low calcium and β-Lg concentration and a high nonmicellar κ-CN content). [1]
Application of Ultrafiltered Sweet Buttermilk and Sweet Buttermilk Powder in the Manufacture of Nonfat and Low Fat Yogurts
Nonfat and low fat yogurts are soft, low in solids, and exhibit whey separation unless they are heavily stabilized. In this study, the quality of nonfat (9.55 to 10.39% total solids) and low fat (13.40%) yogurts that had been fortified with ultrafiltered sweet buttermilk or buttermilk powder was compared with that of a control yogurt that had been fortified with nonfat dry milk. The titratable acidity and pH of low fat yogurts were higher than those of nonfat yogurts. Low fat yogurt that had been fortified with ultrafiltered sweet buttermilk had the highest pH and titratable acidity. As shearing speed increased, the apparent viscosity of yogurts decreased, indicating a shear thinning property. At a high shearing speed, shearing time had little effect on the apparent viscosity. Nonfat yogurts with tested ingredients were similar to the control in flavor, appearance, texture, aroma, smoothness, and sourness. At a high level of fortification, ultrafiltered sweet buttermilk lacked typical yogurt flavor but had good appearance. The microstructures of nonfat yogurts were more open than those of low fat yogurts, possibly because of the higher protein contents of the latter. Ultrafiltered sweet buttermilk yielded the densest matrix. The addition of up to 4.8% sweet buttermilk powder to low fat yogurt mixes yielded a soft and smooth product. [2]
Dynamic surface properties of adsorbed protein solutions: BSA, casein and buttermilk
The dynamic surface properties of three widely different protein systems are investigated using different experimental techniques. These techniques are (i) static drop experiments which allow description of the adsorption of proteins at a clean surface, (ii) experiments at a constant rate of dilatation where the area is continuously expanded and a steady state surface tension is obtained, (iii) modulus experiments where a surface in equilibrium is subjected to small periodic disturbances, (iv) stress relaxation experiments which are theoretically similar to moduli experiments, and (v) to a lesser degree, aspiration and sweeping experiments. The results are described by a process involving two steps: (i) diffusion of proteins to the surface and (ii) unfolding of adsorbed protein molecules at the surface. Only native protein molecules are exchangeable, while the unfolded protein molecules are not. From these results the diffusion relaxation times and reaction relaxation times are obtained. [3]
Isolation of Lactic Acid Bacteria from Ewe Milk, Traditional Yoghurt and Sour Buttermilk in Iran
A total of 63 samples including ewe milk, yoghurt and traditional buttermilk were collected from Myaneh and Hashrood (Azarbayjan-e-Sharqi, Iran) and screened for the presence of Lactic Acid Bacteria (LAB). Based on routine cultural characteristic, general morphological and biochemical assay, 77 out of 168 bacterial isolates were identified as LAB. These isolates were examined for the presence of inhibitory activity against other randomly selected LAB isolates. Thirty-three strains showed antagonistic activity against the closely related LAB strains and were further challenged against other gram-positive and gram-negative pathogens including Listeria monocytogenes, Staphylococcus aureus and Salmonella entritidis. Based on their zones of inhibition diameters the isolates showing maximum inhibitory activity against these pathogens were selected for detailed investigations. The selected isolates were identified to species level by 50CHL API system and were challenged to heat, acid and bile salt. Most of the strains were able to survive at different pH ranges, while one strain of Pedicoccus acidilactici and Lactobacillus paracasei were able to tolerate all ranges of pH during 24 h of incubation. In addition, Lactobacillus brevis was found as the most resistant strain being able to resist all concentrates of bile after 4 h. The results indicated the probiotic potential of the isolates, as majority of the selected LAB isolates were capable of resisting high temperatures, acidic pH values and bile concentrations of 0.7%. [4]
Isolation, Characterization, and Identification of Yeasts Associated with Foods from Assiut City, Egypt
The objective of this work was to isolate, characterize physiologically, and identify yeasts associated with foods from Assiut city, Egypt. Fifty-two colonies of yeasts associated with orange, mandarin, tomato, squash, sobia drink, mango juice, sugarcane juice, yogurt and buttermilk samples, collected from Assiut City, Egypt, were isolated. Out of which, Eleven isolates were selected randomly and subjected to morphological, biochemical studies and molecular identification techniques employing sequence of internal transcribed spacer (ITS) regions and partial D1/D2 large-subunit domains of the 26S ribosomal RNA. Identified yeasts were belonged to six genera and species; four species belonged to ascomycetes: Debaryomyces hansenii (five isolates), Saccharomyces cerevisiae (one isolate), Candida tropicalis (one isolate), and Pichia kudriavzevii (one isolate). In addition, two yeasts species belonged to basidiomyces: Rhodotorula mucilaginosa (two isolates), and Trichosporon dulcitum (one isolate). In spite of low frequency of yeasts isolates on the tested food, mango juice and buttermilk showed the higher sources for incidences during this study. [5]
Reference
[1] O’Connell, J.E. and Fox, P.F., 2000. Heat stability of buttermilk. Journal of dairy science, 83(8), pp.1728-1732.
[2] Trachoo, N. and Mistry, V.V., 1998. Application of ultrafiltered sweet buttermilk and sweet buttermilk powder in the manufacture of nonfat and low fat yogurts1. Journal of Dairy Science, 81(12), pp.3163-3171.
[3] Serrien, G., Geeraerts, G., Ghosh, L. and Joos, P., 1992. Dynamic surface properties of adsorbed protein solutions: BSA, casein and buttermilk. Colloids and surfaces, 68(4), pp.219-233.
[4] Iranmanesh, M., Ezzatpanah, H., Mojgani, N., Torshizi, M. A., Aminafshar, M. and Maohamadi, M. (2012) “Isolation of Lactic Acid Bacteria from Ewe Milk, Traditional Yoghurt and Sour Buttermilk in Iran”, European Journal of Nutrition & Food Safety, 2(3), pp. 79-92. Available at: http://www.journalejnfs.com/index.php/EJNFS/article/view/30026 (Accessed: 21November2020).
[5] Khattab, S., Abdel-Hadi, A., Abo-Dahab, N. and Atta, O. (2016) “Isolation, Characterization, and Identification of Yeasts Associated with Foods from Assiut City, Egypt”, Microbiology Research Journal International, 13(1), pp. 1-10. doi: 10.9734/BMRJ/2016/24170.
