Characterization of Queso Fresco during Storage at 4 and 10°C

Abstract Queso Fresco, a popular Hispanic cheese variety, was prepared and its chemical, rheological, textural, functional, and sensory aspects were evaluated during storage at 4 and 10°C to determine changes in quality. Decreases in lactose and pH levels were observed and attributed to activity by spoilage microorganisms. The appearance of volatile compounds derived from lipids indicated that lipolysis was taking place, and some proteolysis was also noted. Minor variations in texture profile, torsion, color, and melt analyses were seen throughout 8 wk of storage. No microstructural changes were observed. A consumer taste panel generally liked laboratory-made and two commercially-made cheeses, and could not distinguish one of the commercial samples from the laboratory sample. The results provide a basis for assessing the quality traits of Queso Fresco during storage

An in vitro analysis of how lactose modifies the gut microbiota structure and function of adults in a donor-independent manner

IntroductionFollowing consumption of milk, lactose, a disaccharide of glucose and galactose, is hydrolyzed and absorbed in the upper gastrointestinal tract. However, hydrolysis and absorption are not always absolute, and some lactose will enter the colon where the gut microbiota is able to hydrolyze lactose and produce metabolic byproducts.MethodsHere, the impact of lactose on the gut microbiota of healthy adults was examined, using a short-term, in vitro strategy where fecal samples harvested from 18 donors were cultured anaerobically with and without lactose. The data were compiled to identify donor-independent responses to lactose treatment.Results and discussionMetagenomic sequencing found that the addition of lactose decreased richness and evenness, while enhancing prevalence of the β-galactosidase gene. Taxonomically, lactose treatment decreased relative abundance of Bacteroidaceae and increased lactic acid bacteria, Lactobacillaceae, Enterococcaceae, and Streptococcaceae, and the probiotic Bifidobacterium. This corresponded with an increased abundance of the lactate utilizers, Veillonellaceae. These structural changes coincided with increased total short-chain fatty acids (SCFAs), specifically acetate, and lactate. These results demonstrated that lactose could mediate the gut microbiota of healthy adults in a donor-independent manner, consistent with other described prebiotics, and provided insight into how dietary milk consumption may promote human health through modifications of the gut microbiome

Application of Humidity-Controlled Dynamic Mechanical Analysis (DMA-RH) to Moisture-Sensitive Edible Casein Films for Use in Food Packaging

Protein-based and other hydrophilic thin films are promising materials for the manufacture of edible food packaging and other food and non-food applications. Calcium caseinate (CaCas) films are highly hygroscopic and physical characterization under broad environmental conditions is critical to application development and film optimization. A new technology, humidity-controlled dynamic mechanical analysis (DMA-RH) was explored to characterize CaCas/glycerol films (3:1 ratio) during isohume temperature (T) ramps and steps, and isothermal RH ramps and steps, to determine their mechanical and moisture-sorption properties during extensive T and RH variations. When RH and/or T increased, CaCas/Gly films became strongly plasticized and underwent several primary and secondary humidity-dependent transition temperatures (or transition humidities); the CaCas/Gly network hypothetically rearranged itself to adapt to the increased water-content and heat-induced molecular mobility. Between 5–40 °C and 20%–61% RH, moisture-sorption was rapid and proportional to humidity between transition points and accelerated greatly during transitions. CaCas/Gly films seemed unsuitable for storage or utilization in warm/humid conditions as they lost their mechanical integrity around Tm ~ 40 °C at 50% RH and Tm decreased greatly with increased RH. However, below Tm, both moisture- and heat-induced structural changes in the films were fully reversible and casein films may withstand a variety of moderate abuse conditions

Two Methods for Increased Specificity and Sensitivity in Loop-Mediated Isothermal Amplification

The technique of loop-mediated isothermal amplification (LAMP) utilizes four (or six) primers targeting six (or eight) regions within a fairly small segment of a genome for amplification, with concentration higher than that used in traditional PCR methods. The high concentrations of primers used leads to an increased likelihood of non-specific amplification induced by primer dimers. In this study, a set of LAMP primers were designed targeting the prfA gene sequence of Listeria monocytogenes, and dimethyl sulfoxide (DMSO) as well as Touchdown LAMP were employed to increase the sensitivity and specificity of the LAMP reactions. The results indicate that the detection limit of this novel LAMP assay with the newly designed primers and additives was 10 fg per reaction, which is ten-fold more sensitive than a commercial Isothermal Amplification Kit and hundred-fold more sensitive than previously reported LAMP assays. This highly sensitive LAMP assay has been shown to detect 11 strains of Listeria monocytogenes, and does not detect other Listeria species (including Listeria innocua and Listeria invanovii), providing some advantages in specificity over commercial Isothermal Amplification Kits and previously reported LAMP assay

Fractionation of Whey Protein Isolate with Supercritical Carbon Dioxide—Process Modeling and Cost Estimation

Abstract: An economical and environmentally friendly whey protein fractionation process was developed using supercritical carbon dioxide (sCO2) as an acid to produce enriched fractions of α-lactalbumin (α-LA) and β-lactoglobulin (β-LG) from a commercial whey protein isolate (WPI) containing 20 % α-LA and 55 % β-LG, through selective precipitation of α-LA. Pilot-scale experiments were performed around the optimal parameter range (T = 60 to 65 °C, P = 8 to 31 MPa, C = 5 to 15 % (w/w) WPI) to quantify the recovery rates of the individual proteins and the compositions of both fractions as a function of processing conditions. Mass balances were calculated in a process flow-sheet to design a large-scale, semi-continuous process model using SuperproDesigner ® software. Total startup and production costs were estimated as a function of processing parameters, product yield and purity. Temperature, T, pressure, P, and concentration, C, showed conflicting effects on equipment costs and the individual precipitation rates of the two proteins, affecting the quantity, quality, and production cost of the fractions considerably. The highest α-LA purity, 61%, with 80 % α-LA recovery in the solid fraction, was obtained at T = 60 °C, C = 5 % WPI, P = 8.3 MPa, with a production cost of $8.65 per kilogram of WPI treated

Ultraviolet and pulsed light technologies in dairy processing

Thermal processes, such as pasteurization and ultra high temperature (UHT) treatment, are traditionally used in dairy processing. The dairy industry is interested in employing nonthermal technologies that have been introduced as an alternative to thermal processing, to improve the quality of milk and dairy products. Another potential application of nonthermal technologies is processing of heat-sensitive dairy ingredients. Of these, high-pressure processing, pulsed electric field processing, ultrasonication and ultraviolet (UV) light technology are commercially successful in improving quality and shelf life of food products. UV rays can be classified as UV-A, UV-B and UV-C based on the emission wavelength. UV technology has been commercialized for water disinfection in breweries and for pasteurization for apple cider in the beverage industry but is not used extensively in the dairy industry. Pulsed light (PL) technology involves the use of high intensity pulsed broad spectrum light that flashes several times per second to destroy microbes