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McClure Knudsen posted an update 6 months ago
The cardinal model for the effect of temperature on Geobacillus stearothermophilus ATCC 7953 growth developed by Kakagianni, Gougouli, & Koutsoumanis, 2016 was expanded for the effect of pH and water activity (aw). The effect of pH (range 5.7-8.5) and aw (range 0.985-0.999) on G. stearothermophilus growth rate was studied in tryptone soy broth (TSB) using the Bioscreen C method and further modelled using a Cardinal Model (CM). The estimated values for the cardinal parameters , and were 5.65 ± 0.14, 6.74 ± 0.03, 8.71 ± 0.03, 0.984 ± 0.007 and 0.998 ± 0.001, respectively. The growth behaviour of G. stearothermophilus was investigated in 7 commercial non-refrigerated plant-based milk alternatives under static conditions (62 °C) and the estimated maximum specific growth rates were used to determine the optimum growth rate for each product. The developed model was validated against observed growth of G. stearothermophilus in the 7 products during storage at non-isothermal conditions (testing 4 different temperature profiles). The validation results showed a good performance of the model with overall Bias factor (Bf) = 1.06 and Accuracy factor (Af) = 1.12. SR18662 order The developed model can be used as an effective tool by the food industry in predicting spoilage of plant-based milk alternatives during distribution and storage at retail and domestic levels.The sulfated polysaccharides extracted from Gracilaria chouae using critic acid extraction and water extraction, respectively, and their digestion and fermentation characteristics were compared in vitro and in vivo. The molecular weight of water extracted polysaccharide of G. chouae (WGCP) was 1.73 × 103 kDa while critic acid extracted polysaccharide (CGCP) was 31.5 kDa. During stimulated gastrointestinal digestion in vitro, WGCP and CGCP were lightly degraded. However, the glycemic index (GI) of WGCP and CGCP were 17.7 and 36.12, respectively. After 24 h of fermentation in vitro, the pH values of CGLP in the fecal culture decreased from 6.89 to 4.82, similar to the inulin but significantly (p less then 0.05) lower than those of the WGCP and normal control. In addition, CGCP and inulin showed similar microbial fermentation characteristics according to the microbiome compositions and contents of short-chain fatty acids (SCFAs). Nevertheless, CGCP gavage for four weeks could also promote the growth of microbes producing the SCFAs such as Peptococcus, Roseburia and Butyricicoccus in the cecum of KM mice. The present study suggests that polysaccharides prepared by acid-extraction method could potentially be used as a good source of prebiotics.The effects of ultrasound-assisted thawing (at ultrasonic frequencies of 45, 80 and 100 kHz) and water immersion thawing on gelling and 3D printing properties of silver carp surimi were examined. Ultrasound-assisted thawing (UT) can save 13.5%~40.4% time, and high ultrasonic frequency (80 kHz and 100 kHz) did not cause high thawing loss. Thawing at higher ultrasonic frequency could reduce the damage of the secondary and tertiary structure of myofibrillar proteins. No significant differences were observed for the main relaxation component (T22) and its peak area proportion (P22), and rheological properties, resulting in similar printing performance. After steam heating, cuboid samples in UT-100 kHz group kept the best geometrical shapes and had the highest hardness, springiness, and chewiness. Thus, ultrasound-assisted thawing provides a promising thawing method in food materials of 3D printing.Plant-based aroma chemicals, constituting the essential oils play a great role as the natural flavours and preservatives in the food industries. Many of these metabolites are susceptible to degradation under heat (i.e. thermolabile aroma chemicals) which may influence the organoleptic properties of the end-products e.g. essential oil, oleoresin, dry herb, tea and packaged juice. The current review identified in total 42 thermolabile aroma and/or flavour molecules belonging to monoterpenoids, sesquiterpenoids and phenolics. The probable pathway of their degradation and its promoting conditions were also described. Degradation pathways were categorized into five major classes including oxidation, C-C bond cleavage, elimination, hydrolysis and rearrangement. Numerous evidences were cited in support of the thermosensitivity of these phytochemicals under pyrolytic, thermal heating or gas chromatographic conditions. Various post-harvest processes involved in the manufacturing such as drying and distillation of the crops or thermal treatment of the food-products for storage were highlighted as the root cause of degradation. The influence of thermolabile aroma chemicals to maintain the sensory quality of the end-products such as citrus juices, floral oils and thermally cooked foods was discussed in detail. In the present article, detailed insight into the chemical and sensory aspects of thermosensitive aromas and flavours was provided, covering the period from 1990 up to 2020.Due to their excellent antimicrobial properties, essential oils (EO) have been proposed as potential preservatives for certain kinds of foods, such as dairy products. However, the occurrence of pathogenic populations that are resistant to EOs could pose a health risk. This report seeks to assess the emergence of resistant populations in Listeria monocytogenes EGD-e growth at 37 °C under selective pressure of Thymbra capitata EO (TCO), to characterise their resistance in laboratory media, and to identify their genotypic changes, as well as to evaluate the resistance in skimmed milk. TCO cyclic treatment allowed the isolation of two L. monocytogenes EGD-e resistant strains against the EO LmSTCO by sublethal doses (75 µL/L TCO) and LmLTCO by lethal doses (300 µL/L TCO) after 20 and 30 cycles, respectively. Both strains displayed an increase of the minimum inhibitory and bactericidal concentration against TCO and a higher survival rate after lethal treatments than the wild-type strain (LmWT). Growth kinetics revealed a better adaptation of LmSTCO in presence of TCO, while LmLTCO grew more slowly compared to LmWT, even in the absence of the antimicrobial. Moreover, a slight increase in cross-resistance to antibiotics was observed LmSTCO to β-lactams and LmLTCO to a series of broad-spectrum antibiotics. The genomic study revealed one sole nucleotide change in LmSTCO located in plsC gene codifying an enzyme involved in the production of phosphatidic acid, a precursor in cell membrane synthesis. Five genetic variations were found in LmLTCO among them, the deletion of an ATP-synthesis system involved in slowing bacterial growth. Inhibition and inactivation assays in skimmed milk confirmed the increased resistance of both strains, thereby indicating a safety risk in case these strains emerge in the food chain. These results strongly suggest that the occurrence of such resistances should be taken into account in order to ensure the efficacy of natural antimicrobials in the design of food preservation strategies.
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