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    The effect of variations in cold plasma conditions on the detoxification of Aflatoxin M1 and degradation products
    (Elsevier B.V., 2024-10-16) Nguyen T; Palmer J; Pedley J; Petcu M; Newson HL; Keener K; Flint S
    The aim of this study was to explore the chemical reactive species of different operating gases, and their effect on the degradation of aflatoxin M1 (AFM1) by cold plasma by measuring the reactive species concentration. Helium, at 80, 90 or 95%, was used mixed with oxygen, nitrogen and air. The efficacy of cold plasma on aflatoxin M1 (AFM1) reduction was improved when decreasing the ratio of helium in the gas mixture. The ratio of the gas mixtures changed the cold plasma chemistry believed to be due to the differences in the concentrations of the reactive species. The degradation products of AFM1 after cold plasma treatment using a helium/air gas mixture and the degradation pathway were identified by LCMS. AFM1 was oxidised by reactive species in the cold plasma to produce degradant products with, theoretically, lower toxicity than AFM1.
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    Growth, carcass and meat quality characteristics of Charolais-sired steers and heifers born to Angus-cross-dairy and Angus breeding cows
    (Elsevier Ltd, 2023-07) Coleman LW; Schreurs NM; Kenyon PR; Morris ST; Hickson RE
    Charolais-sired heifers and steers from Angus, Angus × Holstein-Friesian, Angus × Holstein-Friesian-Jersey and Angus × Jersey cows were measured for growth, carcass, and meat quality characteristics. Despite differences in weaning weight and growth rate, the progeny of different breed-crosses did not differ in final live weight or carcass weight (P > 0.05). Carcass and meat quality characteristics did not differ among breed-crosses (P > 0.05), except for fat that was more yellow in progeny from Angus and Angus-cross-Jersey dams. Steers were slaughtered older and had heavier carcasses with greater fat depth and intramuscular fat than heifers. Meat quality differed between the sex classes, with steers having greater pH and shear force, redder meat, and yellower fat than heifers. Angus-cross-dairy cows when crossed with a beef breed sire such as the Charolais will provide progeny for meat production which are competitive to beef breeds for beef finishing and meat production and therefore, a useful mechanism to utilize surplus animals from the dairy industry.
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    Alternative proteins vs animal proteins: The influence of structure and processing on their gastro-small intestinal digestion
    (Elsevier Ltd, 2022-04) Kaur L; Mao B; Beniwal AS; Abhilasha; Kaur R; Chian FM; Singh J
    Background: Digestibility, an indicator of protein bioavailability, is essentially a measure of the susceptibility of a protein towards proteolysis. Proteins with higher digestibility have been linked with better health outcomes. Animal proteins are generally considered to be of better nutritional value than plant proteins not only because they are a good source of essential amino acids but also due to their higher digestibility in the human gastro-intestinal tract. With the recent emergence of alternative food protein sources, which are now processed in a completely new way to design new foods or new versions of the conventional foods, it has become extremely important to understand their digestion characteristics. Scope and approach: This review discusses the factors that affect protein digestibility, including protein source, structure, type of processing, and modification, with a particular focus on the effects of non-protein components present in food matrix. Key findings and conclusions: To obtain the desired functionality, particularly for alternate proteins, numerous physical, chemical, and enzymatic methods for modification have been reported. These modifications may alter structural characteristics of proteins by inducing structural modifications such as protein unfolding, crosslinking, and aggregation. Depending upon the protein reactivity during processing, the susceptibility of proteins towards hydrolysis by digestive enzymes might change, affecting not only the overall protein digestibility but also the rates of release of polypeptides and amino acids. The faster rates of protein digestion have been linked with muscle anabolism, suggesting the need and importance of classifying the new, emerging and alternative protein sources according to their rates of digestion into rapidly (RDP), slowly digestible (SDP) and resistant (RP) proteins. More research needs to be focussed on converting, through processing, the undigestible or RP into RDP or SDP to achieve better health outcomes.
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    Biofilm formation by B. licheniformis isolated from whey protein concentrate 80 powder as a potential source of product contamination : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2018) Md Zain, Siti Norbaizura binti
    This study aimed to examine biofilm formation of Bacillus licheniformis isolated from whey protein concentrate 80 (WPC80) as a potential source of contamination in the manufacture of WPC. Six WPC80 powder samples from one whey processing plant in New Zealand were used in this study. Six Bacillus species including (percentage of isolates in brackets) B. licheniformis (66%), Bacillus cereus/Bacillus thuringiensis (18%), Bacillus subtilis (4%), Bacillus pumilus (4%), Paenibacillus glucanolyticus (2%) and Lactobacillus plantarum (6%) were identified using colony morphologies, biochemical tests, species specific PCR and 16S ribosomal DNA gene sequencing and subsequent analysis using the BLAST and Seqmatch databases. Preliminary screening for biofilm formation by the predominant contaminant, B. licheniformis using a microtitre plate assay with the bacteria grown in laboratory medium tryptic soy broth (TSB) at three different temperatures (30°C, 37°C and 55°C) showed most biofilm formation at 37°C with 9/33 isolates forming strong biofilm. In total 13/33 isolates formed strong biofilm at three different temperatures on the polystyrene microtitre plate surface. Subsequent tests for biofilm formation on stainless steel (SS) showed an increased frequency of biofilm formation with 32/33 strains forming strong biofilm in TSB at 37°C. This demonstrates the limitation of the microtitre plate assay for screening for biofilm formation and suggests that biofilm growth of B. licheniformis favours a SS surface. The attachment and biofilm formation was further investigated using SS coupons and reconstituted whey medium at different concentrations (1%, 5%, and 20%). The best medium for B. licheniformis isolates to form biofilm on SS at its best growth temperature (37°C) was 1% reconstituted WPC80. Interestingly, when 1% reconstituted WPC80 was supplemented with lactose and minerals (mainly calcium and magnesium) to replicate the composition of Mozzarella cheese whey before ultrafiltration (UF), the B. licheniformis biofilm counts increased at least by one log. The production of protease enzyme, extracellular polymeric substances (EPS) and nitrate reduction by B. licheniformis showed the potential of B. licheniformis to influence the quality of dairy products. Biosurfactant production by B. licheniformis identified as lichenysin consisting of lipopeptide was detected and this may influence biofilm formation on SS. The inability of the B. licheniformis isolates to ferment lactose as their major carbon source was confirmed by lactose fermentation tests and shows that B. licheniformis is not ideally suited to a dairy environment. The B. licheniformis vegetative cells were found to be heat resistant with a < log10 reduction at the three temperatures tested; 72oC, 75oC and 80°C during 15 s, 30 s and 60 s heating intervals. In order to thrive in a dairy system, synergistic interactions with other microflora were investigated as a possible mechanism to use lactose that has been broken down by other microflora. Lactobacillus plantarum (L. plantarum), another isolate from the WPC80 samples, has the ability to produce glucose and galactose from lactose. This was grown with each of two B. licheniformis isolates (E30C11 and F30C02) with different abilities to form biofilm. Interestingly this did not enhance the growth of B. licheniformis suggesting that another carbon source, most likely whey protein, must provide the energy source for this bacterium in a whey environment. A review of the WPC80 processing plant showed the UF membranes had the largest surface area (3500 – 7500 m2), providing most potential for biofilm growth. However, UF was run at 10°C, too low for the growth of B. licheniformis which has a minimum growth temperature of 20°C. The hypothesis that sections of the processing plant before the UF step are the sites for B. licheniformis biofilm growth was supported by analysing several samples from the raw whey balance tank, clarifier, thermaliser and separator where 7 B. licheniformis strains were isolated. This shows that B. licheniformis is present at several early stages of WPC processing, with the most likely areas for growth being the certain sections of the clarifier, thermaliser and the separator where temperatures are close to the best growth temperature for this bacterium (37°C). Preventing B. licheniformis contamination of WPC needs to focus on adjusting the conditions in these sections of the processing plant to limit biofilm growth. Keywords: dairy, Bacillus species, L. plantarum, lichenysin, stainless steel, membrane processing plant.
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    Carcass characteristics and meat quality of Hereford sired steers born to beef-cross-dairy and Angus breeding cows.
    (2016-11) Coleman LW; Hickson RE; Schreurs NM; Martin NP; Kenyon PR; Lopez-Villalobos N; Morris ST
    Steers from Angus, Angus×Holstein Friesian, Angus×Holstein Friesian-Jersey and Angus×Jersey cows and a Hereford sire were measured for their carcass and meat quality characteristics. Steers from the Angus×Holstein Friesian cows had a greater final body weight and carcass weight (P<0.05). Steers from Angus×Jersey cows had the lowest carcass weight and dressing-out percentage (P<0.05). There was a greater fat depth over the rump at 12 and 18months of age for the steers from Angus cows (P<0.05) but, not at 24months of age. The steers had similar meat quality characteristics across the breed groups. Steers from Angus×Holstein Friesian and Angus×Jersey cows had a higher ratio of n6 to n3 fatty acids. Using beef-cross-dairy cows to produce steers for meat production does not impact on meat quality. Using Jersey in the breed cross reduced the carcass tissues in the live weight and the potential meat yield.
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    Insights into the Geobacillus stearothermophilus species based on phylogenomic principles.
    (26/06/2017) Burgess SA; Flint SH; Lindsay D; Cox MP; Biggs PJ
    BACKGROUND: The genus Geobacillus comprises bacteria that are Gram positive, thermophilic spore-formers, which are found in a variety of environments from hot-springs, cool soils, to food manufacturing plants, including dairy manufacturing plants. Despite considerable interest in the use of Geobacillus spp. for biotechnological applications, the taxonomy of this genus is unclear, in part because of differences in DNA-DNA hybridization (DDH) similarity values between studies. In addition, it is also difficult to use phenotypic characteristics to define a bacterial species. For example, G. stearothermophilus was traditionally defined as a species that does not utilise lactose, but the ability of dairy strains of G. stearothermophilus to use lactose has now been well established. RESULTS: This study compared the genome sequences of 63 Geobacillus isolates and showed that based on two different genomic approaches (core genome comparisons and average nucleotide identity) the Geobacillus genus could be divided into sixteen taxa for those Geobacillus strains that have genome sequences available thus far. In addition, using Geobacillus stearothermophilus as an example, we show that inclusion of the accessory genome, as well as phenotypic characteristics, is not suitable for defining this species. For example, this is the first study to provide evidence of dairy adaptation in G. stearothermophilus - a phenotypic feature not typically considered standard in this species - by identifying the presence of a putative lac operon in four dairy strains. CONCLUSIONS: The traditional polyphasic approach of combining both genotypic and phenotypic characteristics to define a bacterial species could not be used for G. stearothermophilus where many phenotypic characteristics vary within this taxon. Further evidence of this discordant use of phenotypic traits was provided by analysis of the accessory genome, where the dairy strains contained a putative lac operon. Based on the findings from this study, we recommend that novel bacterial species should be defined using a core genome approach.