The experiments reported in this research paper aimed to track the microbiological load of milk throughout a low-heat skim milk powder (SMP) manufacturing process, from farm bulk tanks to final powder, during mid- and late-lactation (spring and winter, respectively). In the milk powder processing plant studied, low-heat SMP was produced using only the milk supplied by the farms involved in this study. Samples of milk were collected from farm bulk tanks (mid-lactation: 67 farms; late-lactation: 150 farms), collection tankers (CTs), whole milk silo (WMS), skim milk silo (SMS), cream silo (CS) and final SMP. During mid-lactation, the raw milk produced on-farm and transported by the CTs had better microbiological quality than the late-lactation raw milk (e.g., total bacterial count (TBC): 3.60 ± 0.55 and 4.37 ± 0.62 log 10 cfu/ml, respectively). After pasteurisation, reductions in TBC, psychrotrophic (PBC) and proteolytic (PROT) bacterial counts were of lower magnitude in late-lactation than in mid-lactation milk, while thermoduric (LPC—laboratory pasteurisation count) and thermophilic (THERM) bacterial counts were not reduced in both periods. The microbiological quality of the SMP produced was better when using mid-lactation than late-lactation milk (e.g., TBC: 2.36 ± 0.09 and 3.55 ± 0.13 cfu/g, respectively), as mid-lactation raw milk had better quality than late-lactation milk. The bacterial counts of some CTs and of the WMS samples were higher than the upper confidence limit predicted using the bacterial counts measured in the farm milk samples, indicating that the transport conditions or cleaning protocols could have influenced the microbiological load. Therefore, during the different production seasons, appropriate cow management and hygiene practices (on-farm and within the factory) are necessary to control the numbers of different bacterial groups in milk, as those can influence the effectiveness of thermal treatments and consequently affect final product quality.

This review aims to familiarize the reader with research efforts on the cultivation media of lactic acid bacteria (LAB). We have also included a brief discussion on standard ingredients used in LAB media and chemically defined media as related to bacterial growth requirements. Recent research has focused on modifying standard media for the enumeration, differentiation, isolation, and identification of starter cultures and probiotics. Even though large numbers of these media have been developed to serve dairy microbial control, they have failed to provide consistent results. The research consequently points to the need to develop a reliable lactobacilli growth medium for the dairy industry.

In this Research Communication we present a study of the effect of Ca-binding salts on the recovery of milk fat globule membrane (MFGM) from buttermilk. Sodium phosphate buffer was used for the purpose of MFGM recovery from buttermilk for the first time and we showed that 0.1 M buffer at pH 7.2 was the most effective for the recovery of MFGM. The fact of high efficacy of sodium phosphate buffer in recovery of MFGM from buttermilk allowed us to suggest that MFGM in buttermilk is present in association with casein through Ca- bridges formed between phospholipids of MFGM and phosphate groups of casein, primarily with k-casein as the peripheral protein of casein micelles.

The experiments reported in this research paper examine the potential of digestion using acidic enzymes Protease A and Protease M to selectively hydrolyse α-lactalbumin (α-La) whilst leaving β-lactoglobulin (β-Lg) relatively intact. Both enzymes were compared with pepsin hydrolysis since its selectivity to different whey proteins is known. Analysis of the hydrolysis environment showed that the pH and temperature play a significant role in determining the best conditions for achievement of hydrolysis, irrespective of which enzyme was used. Whey protein isolate (WPI) was hydrolysed using pepsin, Acid Protease A and Protease M by randomized hydrolysis conditions. Reversed-phase high performance liquid chromatography was used to analyse residual proteins. Regarding enzyme selectivity under various milieu conditions, all three enzymes showed similarities in the reaction progress and their potential for β-Lg isolation.

The research reported in this Research Communication evaluates the effect of milk acidification on the physicochemical and sensory properties of Licor de Oro (or Gold Liqueur; LO), a traditional alcoholic beverage produced in Chiloé island, Chile, which is made by mixing milk acidified with lemon juice and alcohol at a ratio of 1.0:1.0, along with sugar and other spices. The mixture is stored for a couple of weeks and then filtered to obtain a product with a yellowish-transparent appearance, sweetness and acidic taste, milky and alcoholic notes. The lack of information regarding LO processing, mainly in the amount of acid added to the mixture, leads to products of highly variable quality. Thus, the objective of this study was to evaluate the effect of milk acidification on the physicochemical and sensory properties of LO. Raw milk was acidified using citric acid to six different pH values: 6.7 (control), 6.0, 5.3, 4.6, 3.9 and 3.2. These milk treatments were then used to make LO. A decrease of milk pH led to LO with higher levels of sensorial and titratable acidity. LO obtained at pH 6.7 and 6.0 had higher levels of total protein than other treatments, leading to excessive turbidity. In contrast, treatments made at pH ≤5.3 had a typical transparent appearance of LO. These results suggest that a minimum level of milk acidification is required to obtain LO with desired appearance and composition.

The aim of this work was to evaluate the impact of two factors on the ripening profiles of hard cooked cheeses: (F1) the growth medium for the primary and adjunct cultures, constituted by autochthonous strains: Lactobacillus helveticus 209 (Lh209) and Lactobacillus paracasei 90 (Lp90), respectively, and (F2) the addition of L. paracasei Lp90 as adjunct culture. Four types of cheeses were made: W and M cheeses in which only Lh209 was added after its growth in whey and MRS, respectively; Wa and Ma cheeses in which both strains (Lh209 and Lp90) were added after their growth in whey and MRS, respectively. Physicochemical and microbial composition, proteolysis and profiles of organic acids and volatile compounds were analyzed. According to the methodology of the cultures preparation, W and Wa cheeses showed a higher level of secondary proteolysis and lower level of primary proteolysis (P < 0·05), lower content of citric and acetic acids and higher amount of propionic acid (P < 0·05), in comparison with M and Ma cheeses. The incorporation of Lp90 increased the secondary proteolysis (P < 0·05), decreased the citric acid (P < 0·05), and increased the propionic acid only when was added after their growth in whey (P < 0·05). Both factors significantly modified the percentages of the volatile compounds grouped in chemical families; in addition, for the half of the compounds detected, significant differences were found. Based on the obtained results, the use of Lp90 as an adjunct in hard cooked cheeses, and the preincubation of the cultures in whey are strategies to accelerate the cheese ripening and to enhance the production of some characteristic compounds of this type of cheeses, such as propan-2-one, hexan-2-one, 2- and 3-methyl butanal, heptan-2-ol, acetic and 3-methylbutanoic acids and 3-hydroxy butan-2-one.

We evaluated the effect of in vitro digested milk on mature adipocytes 3T3-L1, paying particular attention to its fatty acid composition, and comparing human (HM), donkey (DM), bovine (BM), ovine (OM), caprine (CM) and formula (FM) milk. Cellular viability, apoptosis, oxidative response and gene expression levels of NF-κB p65, HMGB1, SREBP-1c and FAS were evaluated. Digested milk treatments significantly reduced 3T3-L1 mature adipocytes viability and caspase activity compared with control group, but no significant differences were observed among different sources of digested milk. In all digested milk samples, ROS level was higher than the control, however, the digested human and formula milk showed lower levels of ROS than DM, BM, OM and CM samples. Lower capacity of HM and FM to induce oxidative stress in mature adipocytes was ascribed to the peculiar free fatty acids profile of digested milk samples. All milk treatments elicited a significant over-expression of NF-κB p65 in 3T3-L1 adipocytes compared to the control; the lowest gene expression was found in HM, BM, OM and CM, the highest in FM and an intermediate behavior was shown in DM. All digested milk treatments influenced the gene expression of SRBP-1c with FM and HM showing the highest levels. For FAS expression, BM showed the highest level, OM and CM intermediate and FM, HM and DM the lowest levels, however HM and DM had comparable levels to the control.