Cows' milk generally contains two types of β-casein, A1 and A2 types. Digestion of A1 type can yield the peptide β-casomorphin-7, which is implicated in adverse gastrointestinal effects of milk consumption, some of which resemble those in lactose intolerance. This study aimed to compare the effects of milk containing A1 β-casein with those of milk containing only A2 β-casein on inflammation, symptoms of post-dairy digestive discomfort (PD3), and cognitive processing in subjects with self-reported lactose intolerance.
A RP-HPLC method, developed for the separation and quantification of the most common genetic variants of bovine milk proteins, was successfully applied to the analysis of water buffalo milk. All the most common buffalo casein and whey proteins fractions, as well as their genetic variants, were detected and separated simultaneously in 40 min. Purified buffalo proteins were used as calibration standards and a total of 536 individual milk samples were analysed for protein composition. α(S1)-, α(S2)-, βγ-, and κ-casein were 32.2%, 15.8%, 36.5%, and 15.5%, respectively, of total casein content, whereas content of β-Lactoglobulin was approximately 1.3 times as high as that of α-Lactalbumin. The existence of a polymorphism of κ-casein was demonstrated in Mediterranean water buffalo and α(S1)- and κ-casein genetic variants were successfully detected by RP-HPLC.
Pseudomonas fluorescens grows at low temperature and produces thermo-resistant protease(s) that can destabilize UHT (Ultra High Temperature) milk during its storage. The consequences of contamination of microfiltered milk with 9 strains of P. fluorescens on the stability of the corresponding UHT milk during storage had been investigated in this study. The strains were classified in two groups according to their ability to destabilize UHT milk. For the group of highly destabilizing strains, sedimentations of UHT milks, low values to phosphate test and the presence of aggregates were observed. Zeta potential and hydration of casein micelles decreased, whereas non casein nitrogen (NCN) and non protein nitrogen (NPN) contents increased. The analyses of NCN fraction by liquid chromatography coupled to mass spectrometry indicated that the different casein molecules were hydrolyzed in a similar way for the destabilizing strains suggesting that the same enzyme was implicated. For the group of slightly or not destabilizing strains no visual and biochemical alteration were found. This study showed that destabilization of UHT milk by P. fluorescens was highly variable and strain-dependent.
Samples of fresh skim milk, reconstituted micellar casein, and casein powder were sonicated at 20kHz to investigate the effect of ultrasonication. For fresh skim milk, the average size of the remaining fat globules was reduced by approximately 10nm after 60min of sonication; however, the size of the casein micelles was determined to be unchanged. A small increase in soluble whey protein and a corresponding decrease in viscosity also occurred within the first few minutes of sonication, which could be attributed to the breakup of casein-whey protein aggregates. No measurable changes in free casein content could be detected in ultracentrifuged skim milk samples sonicated for up to 60min. A small, temporary decrease in pH resulted from sonication; however, no measurable change in soluble calcium concentration was observed. Therefore, casein micelles in fresh skim milk were stable during the exposure to ultrasonication. Similar results were obtained for reconstituted micellar casein, whereas larger viscosity changes were observed as whey protein content was increased. Controlled application of ultrasound can be usefully applied to reverse process-induced protein aggregation without affecting the native state of casein micelles.
Many diet regimens were studied for patients with autism spectrum disorder (ASD) over the past few years. Ketogenic diet is gaining attention due to its proven effect on neurological conditions like epilepsy in children. Forty-five children aged 3-8 years diagnosed with ASD based on DSM-5 criteria were enrolled in this study. Patients were equally divided into 3 groups, first group received ketogenic diet as modified Atkins diet (MAD), second group received gluten free casein free (GFCF) diet and the third group received balanced nutrition and served as a control group. All patients were assessed in terms of neurological examination, anthropometric measures, as well as Childhood Autism Rating Scale (CARS), Autism Treatment Evaluation Test (ATEC) scales before and 6 months after starting diet. Both diet groups showed significant improvement in ATEC and CARS scores in comparison to control group, yet ketogenic scored better results in cognition and sociability compared to GFCF diet group. Depending on the parameters measured in our study, modified Atkins diet and gluten free casein free diet regimens may safely improve autistic manifestations and could be recommended for children with ASD. At this stage, this study is a single center study with a small number of patients and a great deal of additional wide-scale prospective studies are however needed to confirm these results.
To obtain information on the safety and efficacy of the gluten-free/casein-free (GFCF) diet, we placed 14 children with autism, age 3-5 years, on the diet for 4-6 weeks and then conducted a double-blind, placebo-controlled challenge study for 12 weeks while continuing the diet, with a 12-week follow-up. Dietary challenges were delivered via weekly snacks that contained gluten, casein, gluten and casein, or placebo. With nutritional counseling, the diet was safe and well-tolerated. However, dietary challenges did not have statistically significant effects on measures of physiologic functioning, behavior problems, or autism symptoms. Although these findings must be interpreted with caution because of the small sample size, the study does not provide evidence to support general use of the GFCF diet.
Nondietary exposure to milk proteins may be a risk for children who do not outgrow milk allergy by school age.
Undefined mesophilic mixed (DL) starter cultures are used in the production of continental cheeses and contain unknown strain mixtures of Lactococcus lactis and leuconostocs. The choice of starter culture affects the taste, aroma and quality of the final product. To gain insight into the diversity of Lactococcus lactis strains in starter cultures, we whole-genome sequenced 95 isolates from three different starter cultures. Pan-genomic analyses, which included 30 publically available complete genomes, grouped the strains into 21 subsp. lactis and 28 subsp. cremoris lineages. Only one of the 95 isolates grouped with previously sequenced strains, and the three starter cultures showed no overlap in lineage distribution. Culture diversity was assessed by targeted amplicon-sequencing using purR, a core gene, and epsD, present in 93 of the 95 starter culture isolates, but absent in most of the reference strains. This allowed unprecedented discrimination of starter culture Lactococcus lactis, and revealed substantial differences between the three starter cultures and compositional shifts during cultivation of cultures in milk.Importance In contemporary cheese production, standardized frozen seed stock starter cultures are used to ensure production stability, reproducibility, and quality control of the product. The dairy industry experiences significant disruption of cheese production due to phage attack and one commonly used countermeasure to phage attack is to employ a starter rotation strategy, in which two or more starters with minimal overlap in phage sensitivity are used alternately. Culture-independent analysis of the lactococcal diversity in complex undefined starter cultures revealed large differences between the three starter cultures, and temporal shifts in lactococcal composition during production of bulk starters. A better understanding of the lactococcal diversity in starter cultures will enable the development of more robust starter cultures, and assist in maintaining the efficiency and stability of the production process by ensuring the presence of key bacteria that are important to the characteristics of the product.
The aim of this work was to check the efficacy of bovine lactoferrin hydrolyzed by pepsin (LFH) to prevent blue discoloration of Mozzarella cheese delaying the growth of the related spoilage bacteria. Among 64 Pseudomonas fluorescens strains, isolated from 105 Mozzarella samples, only ten developed blue discoloration in cold-stored Mozzarella cheese slices. When Mozzarella cheese samples from dairy were treated with LFH and inoculated with a selected P. fluorescens strain, no pigmentation and changes in casein profiles were found up to 14 days of cold storage. In addition, starting from day 5, the count of P. fluorescens spoiling strain was steadily ca. one log cycle lower than that of LFH-free samples. ESI-Orbitrap-based mass spectrometry analyses allowed to reveal the pigment leucoindigoidine only in the blue LFH-free cheese samples indicating that this compound could be considered a chemical marker of this alteration. For the first time, an innovative mild approach, based on the antimicrobial activity of milk protein hydrolysates, for counteracting blue Mozzarella event and controlling psychrotrophic pigmenting pseudomonads, is here reported.
Microbial communities of traditional cheeses are complex and insufficiently characterized. The origin, safety and functional role in cheese making of these microbial communities are still not well understood. Metagenomic analysis of these communities by high throughput shotgun sequencing is a promising approach to characterize their genomic and functional profiles. Such analyses, however, critically depend on the availability of appropriate reference genome databases against which the sequencing reads can be aligned.