Impact of cryoconcentration on casein micelle size distribution,micelles inter-distance,and flow behavior of skim milk during refrigerated storage

Cryoconcentration combined with a cascade effect was used to concentrate skim milk up to 25.12% total dry matter. Size, shape, and inter-micellar distance of casein micelles were characterized by ZetasizerNano-ZS, transmission electron microscopy, and ImageJ analyses. Flow properties of the cryoconcentrated skim milk were evaluated during 5 weeks of storage under refrigerated condition at 4 °C. Milk color was also evaluated according to the L*, a*, and b* system. The cryoconcentrated skim milk obtained after three cryoconcentration cycles was characterized by a monomodal distribution of its micelles with a tendency to smaller casein micelles. Approximately 60% of the total micellar volume was occupied by the casein micelles with a size of 100–200 nm, less than 18% of the volume with a size of 50–100 nm and only less than 1% was occupied by micelles with a size > 350 nm. This result shows that cryoconcentration changed the distribution of the mean size of the casein micelles to smaller units. No significant difference was observed on the inter-micellar distance. Cryoconcentration significantly improved the color of skim milk by increasing the L* value up to 67 which was similar to that of whole milk. Transition from a Newtonian to a non-Newtonian behavior was observed from the fourth week storage with a slight increase of casein micelle size.Industrial relevanceA concentration procedure of skim milk based on a complete block cryoconcentration technique was proposed. Application of this sub-zero technology permitted the concentration of skim milk total dry matter up to 25%. The casein micelle size was positively affected by moving the major part of the micelles toward the smaller size, whereas the inter-micellar distance was not affected. This new knowledge can be exploited in milk-based products to enhance the product stability. The cryoconcentrated skim milk color was positively affected since its L* value, which represents the milk whiteness, was significantly improved. The flow behavior of the cryoconcentrated milk was of Newtonian type up to 4 weeks of storage at 4 °C. The generated knowledge in this study can be easily used by the milk processing industry in order to make stable milk product with high dry matter content without adding milk powder, which negatively affects the product sensory properties (floury consistency).     

Effects of different osmo‐dehydrofreezing treatments on the volatile compounds,phenolic compounds and physicochemical properties in mango (Mangifera indica L.)

The influences of different osmotic solution pretreatments (sucrose, glucose and maltose with concentration of 45%) on the volatile compounds, phenolic compounds and other physicochemical parameters in frozen mangoes were studied. Volatile and phenolic compounds were measured using SPME/GC‐MS and HPLC method, respectively. The results revealed that compared with untreated frozen mango, some volatile compounds (e.g. alcohols, aldehydes and some terpenes and esters) increased significantly and there were more compounds identified in osmo‐dehydrofrozen samples. These changes positively affected mango aroma and resulted in higher sensory scores for osmo‐dehydrofrozen samples. In addition, data on phenolic compounds showed that dehydrofrozen samples pretreated in glucose and sucrose had higher ρ‐hydroxybenzoic acid and quercetin contents, respectively, while samples pretreated in maltose showed higher ρ‐coumaric acid and sinapic acid contents compared with untreated frozen samples. The current work indicates that osmo‐dehydrofreezing can improve the retention of phenolic and aromatic compounds in frozen mango.     

Controlled transglutaminase treatment in Edam cheese-making

Transglutaminase (TG) has been widely used in the dairy industry to increase product yield. However, it has not been used in the production of ripened cheeses because of the difficulty of controlling TG activity. It was observed that cross-linking of TG in ultrafiltration retentate could be controlled using a protein standardisation step. TG increased the cheese yield 4%, due to an increase in the moisture content of the cheeses. Traditionally, increased cheese moisture reduces hardness of cheese, but this was not observed in the cheese from TG-treated milk. Furthermore, the organoleptic properties of the TG-cheeses did not differ significantly from those of the control cheeses. No differences were observed in the protein profile of the whey fraction as a result of the TG treatment. The protein standardisation process thus makes it possible to use TG in the production of Edam cheese.     

Synergetic effects of high-pressure carbon dioxide and nisin on the inactivation of Escherichia coli and Staphylococcus aureus

Synergetic effects of high-pressure carbon dioxide (HPCD) and nisin on Escherichia coli and Staphylococcus aureus were evaluated. Changes in morphology, interior structure, and membrane permeability were analyzed by scanning and transmission electron microscopy, and flow cytometry. Synergetic effects were found, especially in S. aureus. HPCD alone or with nisin led to morphological and intracellular alterations in both bacteria, but nisin alone led to these damages only in S. aureus. A positive correlation between membrane damage and inactivation was found, but ratios of inactivation were higher, probably because of viable but non-culturable state. Mechanisms were proposed for synergism: for E. coli, outer membrane was damaged first by HPCD, and then HPCD and nisin jointly acted on and destroyed the cytoplasmic membrane, leading to further intracellular damage by HPCD; for S. aureus, HPCD and nisin acted on the cytoplasmic membrane together leading to cell death.Industrial RelevanceEscherichia coli and Staphylococcus aureus are two common microorganisms, which exist widely in the environment and easily contaminate food such as vegetables and dairy products, respectively. Considering heat treatment may destroy some heat-sensitive quality of the products, this study evaluated synergetic effects of high-pressure carbon dioxide (HPCD) combined with the bacteriocin nisin. The investigations provided evidence for potentially combined application of HPCD and nisin to help keep food safe in the industry.     

Recovery and utilization of effluents from meat processing industries

Production of wastes during the processing of meat products is not desirable because it significantly deteriorates the quality of the final product as well as causes some serious health threats if not properly disposed-off. The majority of the waste, in the meat industry is produced during slaughtering. The composition of waste generated by the meat industry depends on species of animals slaughtered. The waste material of the meat processing industry contains plentiful amount of organic compounds due to which its disposal is quite difficult. Efficient utilization of by-products has direct impact on the economy of the country and reduce environmental pollution. Edible meat by-products are claimed to have high nutritional value as compared to the lean meat. Organ meats can be used for human consumption, animal feed production and medicinal purposes after proper treatment and processing. This article provides information regarding the waste material generated by meat processing plants, its health impacts, nutritional status of meat by-products and their utilization.     

Kinetics of Strecker aldehyde formation during thermal and high pressure high temperature processing of carrot puree

Strecker aldehydes have been negatively associated to flavor of heat sterilized plant-based foods. The present study demonstrated the importance of processing conditions (temperature, pressure and time) as a strong means for the control of Strecker aldehyde formation in vegetables purees. A kinetic study was set up (at isothermal and isothermal-isobaric conditions) to quantify the effects of single process parameters on the changes of 3-methylbutanal (3-MB) in carrot puree as a case study. The increase in 3-MB concentrations was best described by an empirical, logistic model. During the isothermal treatment at atmospheric pressure, the maximum reaction rate constant of 3-MB formation was increased as a function of processing temperature. However, the formation rate was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa. Hence, the reduced formation of Strecker aldehydes under high pressure could open a new possibility for process control and optimization of the formation of these compounds.Industrial relevanceHigh pressure high temperature (HPHT) processing is a relatively young technology and its effect on important quality-related chemical reactions is not as well understood as is the case for conventional thermal processing. The present work investigates the impact of processing conditions (e.g. pressure, temperature) on Strecker aldehydes formation, volatiles that have been negatively associated to flavor of heat sterilized plant-based foods. Based on the kinetic study, the formation rate of the Strecker aldehyde (3-methylbutanal) was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa in carrot puree. Considering the fact that these compounds are often linked to off-flavor development, their reduced formation under high pressure could open a new possibility for process control and optimization.     

Cross-linked chitosan polymers as generic adsorbents for simultaneous adsorption of multiple mycotoxins

The primary objective of this study was to synthesize three types of cross-linked chitosan polymers and further investigate their adsorption capability for multiple mycotoxins, including aflatoxin B₁ (AFB₁), ochratoxin A (OTA), zearalenone (ZEN), fumonisin B₁ (FB₁), deoxynivalenol (DON) and T-2 toxin (T2). Among these synthetic adsorbents, cross-linked chitosan-glutaraldehyde complex presented the highest adsorption capability for AFB₁ (73%), OTA (97%), ZEN (94%) and FB₁ (99%), but no obvious adsorption for DON and T2 (<30%). The effect of various incubation conditions (contact time, dosage and pH) was also studied. Subsequently, the experimental data were fitted to Langmuir, Freundlich and Hill models. The best fitting model to describe AFB₁ and FB₁ adsorption was Langmuir model (R² ≥ 0.99), with the theoretical maximum adsorption amounts of 5.67 mg/g for AFB₁ and 15.7 mg/g for FB₁. The Hill model was the best model for OTA and ZEN adsorption (R² > 0.98), with the predicted maximum adsorption amounts were 24.8 mg/g for OTA and 9.18 mg/g for ZEN. In addition, the adsorption capability of adsorbent for the simultaneous presence of multiple mycotoxins was also evaluated in buffer system and simulated gastrointestinal condition. The results indicated that the coexisted multiple mycotoxins didn't affected the adsorption capability of adsorbent, whereas the adsorption amounts of toxins were decreased by some gastrointestinal components. The findings of this research suggest that chitosan–glutaraldehyde complex has the potential to be applied as multitoxin adsorbent material for reducing the combined adverse effect of multiple mycotoxins on humans and animals.     

Metagenomic analysis revealed the individualized shift in ileal microbiome of neonatal calves in response to delaying the first colostrum feeding

The aim of this study was to explore the effect of colostrum feeding time on the ileal microbiome of neonatal calves. In this study, 22 male Holstein calves were randomly assigned to different colostrum feeding time treatments: after birth (at 45 min, n = 7); at 6 h after birth (n = 8); and at 12 h after birth (TRT12h; n = 7). At 51 h after birth, calves were killed and ileum digesta was collected for microbiome analysis using shotgun metagenomic sequencing. Bacteria, archaea, eukaryotes, and viruses were identified from the ileum microbiome. For the bacteriome, Firmicutes and Proteobacteria were the predominant phyla, and Escherichia, Streptococcus, Lactobacillus were the 3 most abundant genera. For the archaeal community, Euryarchaeota and Crenarchaeota were the 2 major phyla, and Methanosarcina, Methanobrevibacter, and Methanocorpusculum were the 3 most abundant genera. In total, 116 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified from the ileal microbiome, with “biosynthesis of vancomycin group antibiotics,” “biosynthesis of ansamycins,” “valine, leucine, and isoleucine biosynthesis,” “ribosome,” and “d-alanine metabolism” as the top 5 functions. When the ileal microbiomes were compared among the 3 treatments, the relative abundance of Enterococcus was higher in TRT12h calves, suggesting that calves may have a higher abundance of opportunistic pathogens when the feeding of colostrum is delayed for 12 h. Moreover, among all KEGG pathways, the enriched “taurine and hypotaurine metabolism” (KO00430) pathway was identified in the ileal microbiome of TRT12h calves; however, future studies are needed to understand the effect on the host. Additionally, 2 distinct ileal microbial profiles were identified across all samples, indicating that that host factors may play a significant role in driving varied microbiome changes in response to colostrum feeding time. Whether such microbiome shifts affect long-term gut function and calf performance warrants future studies.     

A preliminary study of monosaccharide composition and α‐glucosidase inhibitory effect of polysaccharides from pumpkin (Cucurbita moschata) fruit

In this work, crude polysaccharide extracts were extracted from pumpkin (Cucurbita moschata) fruit by hot water. After removal of proteins and purification, polysaccharides of pumpkin fruit (PP1‐1) were subjected to structural identification. Gas chromatography analysis indicated that PP1‐1 comprised of galactose (86.4%), and glucose (13.6%). The molecular weight of PP1‐1 was measured to be 0.87 × 10⁴ Da by gel permeation chromatography. The inhibitory kinetic evaluation showed that it was non‐competitive inhibition of PP1‐1 on the α‐glucosidase‐catalysed hydrolysis of PNPG. The Michaelis–Menten constant (K_m) was 0.106 m , and the inhibitory constants (K_i), 0.435 mg.