Bacteria, mould and yeast spore inactivation studies by scanning electron microscope observations

Rozali, Siti N.M.; Milani, Elham A.; Deed, Rebecca C.; Silva, Filipa

doi:10.1016/j.ijfoodmicro.2017.10.008

Cited by 32 publications

(20 citation statements)

References 33 publications

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“…Thermal processing is a common sterilization method used for the industrial production of food (Silva ). The heat causes damages in bacterial spore cells, and the heated spores’ deformations and damages, and the release of intracellular components (Rozali et al ). However, they still have the ability to germinate after sublethal injury, and their suitability for genetic manipulation are of practical importance for food sterilization processes (Sella et al ).…”

Section: Discussionmentioning

confidence: 99%

Combined propidium monoazide pretreatment with high‐throughput sequencing evaluated the bacterial diversity in chicken skin after thermal treatment

et al. 2019

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Aims The purpose of this experiment was to study the bacterial diversity and predominance of spoilage bacteria in chicken skin at different thermal treatment temperatures (60, 70, 80, 90, 100, 110, 120°C). Method and Results Bacteria in chicken skin was collected, then propidium monoazide treatment to remove the DNA of dead cell, total DNA was extracted by Tiandz Bacterial DNA Kit, and investigated by high‐throughput sequencing of the v3/v4 regions of the 16S rDNA gene. A total of 796 008 high‐quality bacterial sequences were obtained for assessing the microbial diversity of chicken skin from seven thermal treatment group and control group. The results showed that the bacterial diversity in chicken skin at 90°C was lowest. And Acinetobacter (25·88%), Clostridium (20·70%), Bacteroides (13·93%) and Myroides (13·13%) were the main flora at 25°C; The Clostridium was dominant genus of the samples heat‐treated by 60, 70, 80 and 90°C, the proportion of this genus were up to 64·86, 77·42, 52·22 and 87·30% respectively. The Bacillus was the main flora of the samples heat‐treated by 100, 110 and 120°C, and the relative percentages were 39·44, 79·61 and 45·96% respectively. In addition, high‐temperature‐resistant Serratia was found in chicken skin. Conclusions The study revealed that the relationship between thermal treatment temperature and bacterial diversity and dominant spoilage bacteria in chicken skin, which had a strong guiding significance for the control and prediction of micro‐organisms in foods. Significance and Impact of the Study The results of this paper could provide a theoretical basis for meat products containing chicken skin, including the safe use of chicken skin, determination of sterilization process parameters and selection of preservatives for compounding, which has strong practicality in China.

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Section: Discussionmentioning

confidence: 99%

Combined propidium monoazide pretreatment with high‐throughput sequencing evaluated the bacterial diversity in chicken skin after thermal treatment

et al. 2019

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“…Microbial inactivation can occur due to the disruption of cell membranes, protein denaturation and solute loss ( Figure 2 ). Research suggests that microbial inactivation by HPP involves the perforation of the cell membrane, the formation of dimples and swellings or the overall shrinkage of the volume of the cells [ 35 , 39 , 40 ]. The financial feasibility of HPP is also greatly increased by using the shortest possible processing time that still achieves the desired level of pasteurization [ 4 ].…”

Section: Non-thermal Cold Pasteurization Technologies For Wine Preservationmentioning

confidence: 99%

“…It was also concluded that HPP inactivation depends on the type and size of microorganism targeted [ 87 ]. Environmental scanning electron microscopy analysis images of S. cerevisiae spores demonstrated its death after HPP treatment of 600 MPa for 5 min, showing the release of intracellular content and change in the shape and size of the cell [ 40 ]. Lastly, alcohol concentration proved to be an important factor for microbial inactivation, with higher log reductions achieved in wines with alcohol concentrations above 13% v / v [ 10 , 86 , 87 ].…”

Section: Effect Of Pef Hpp and Other Non-thermal Technologies On Microbial Inactivation In Winementioning

confidence: 99%

Emerging Non-Thermal Technologies as Alternative to SO2 for the Production of Wine

Silva

Wyk

2021

Foods

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SO2 is an antioxidant and selective antimicrobial additive, inhibiting the growth of molds in the must during the early stages of wine production, as well as undesirable bacteria and yeasts during fermentation, thus avoiding microbial spoilage during wine production and storage. The addition of SO2 is regulated to a maximum of 150–350 ppm, as this chemical preservative can cause adverse effects in consumers such as allergic reactions. Therefore, the wine industry is interested in finding alternative strategies to reduce SO2 levels, while maintaining wine quality. The use of non-thermal or cold pasteurization technologies for wine preservation was reviewed. The effect of pulsed electric fields (PEF), high pressure processing (HPP), power ultrasound (US), ultraviolet irradiation (UV), high pressure homogenization (HPH), filtration and low electric current (LEC) on wine quality and microbial inactivation was explored and the technologies were compared. PEF and HPP proved to be effective wine pasteurization technologies as they inactivate key wine spoilage yeasts, including Brettanomyces, and bacteria in short periods of time, while retaining the characteristic flavor and aroma of the wine produced. PEF is a promising technology for the beverage industry as it is a continuous process, requiring only microseconds of processing time for the inactivation of undesirable microbes in wines, with commercial scale, higher throughput production potential.

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Section: Hpp As a Nonthermal Food‐processing Technologymentioning

confidence: 99%

“…Prolonged dwell times also resulted in quicker formation of hyphae (within 24 hr) than shorter dwell times, with this thought to be related to the damages induced by longer pressure exposure. In a more recent study, Rozali, Milani, Deed, and Silva (2017) evaluated the impact of high-pressure, at 600 MPa, for 5 min at 25 to 30 • C, on the ultrastructure of N. fischeri ascospores and observed that such treatment teared apart the membranes, with evident leakage of inner cell content. Similar results were obtained by Kalagatur et al (2018), who observed an increase in red fluorescence of Fusarium graminearum spores (after pressure treatments between 100 to 380 MPa for 30 min at 60 • C) with the increase of the pressure level, revealing that this was due to the disintegration of the spore membranes' that allowed the propidium iodide (fluorescent counterstain used to observe death cells) to enter the spore, resulting in the increase of the red fluorescence.…”

Section: Effects Of Pressure On Fungi Spore Ultrastructurementioning

confidence: 99%

Effects of high‐pressure processing on fungi spores: Factors affecting spore germination and inactivation and impact on ultrastructure

Pinto

Moreira

Fidalgo

et al. 2020

Comp Rev Food Sci Food Safe

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Food contamination with heat‐resistant fungi (HRF), and their spores, is a major issue among fruit processors, being frequently found in fruit juices and concentrates, among other products, leading to considerable economic losses and food safety issues. Several strategies were developed to minimize the contamination with HRF, with improvements from harvesting to the final product, including sanitizers and new processing techniques. Considering consumers’ demands for minimally processed, fresh‐like food products, nonthermal food‐processing technologies, such as high‐pressure processing (HPP), among others, are emerging as alternatives to the conventional thermal processing techniques. As no heat is applied to foods, vitamins, proteins, aromas, and taste are better kept when compared to thermal processes. Nevertheless, HPP is only able to destroy pathogenic and spoilage vegetative microorganisms to levels of pertinence for food safety, while bacterial spores remain. Regarding HRF spores (both ascospores and conidiospores), these seem to be more pressure‐sensible than bacterial spores, despite a few cases, such as the ascospores of Byssochlamys spp., Neosartorya spp., and Talaromyces spp. that are resistant to high pressures and high temperatures, requiring the combination of both variables to be inactivated. This review aims to cover the literature available concerning the effects of HPP at room‐like temperatures, and its combination with high temperatures, and high‐pressure cycling, to inactivate fungi spores, including the main factors affecting spores’ resistance to high‐pressure, such as pH, water activity, nutritional composition of the food matrix and ascospore age, as well as the changes in the spore ultrastructure, and the parameters to consider regarding their inactivation by HPP.

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Bacteria, mould and yeast spore inactivation studies by scanning electron microscope observations

Cited by 32 publications

References 33 publications

Combined propidium monoazide pretreatment with high‐throughput sequencing evaluated the bacterial diversity in chicken skin after thermal treatment

Combined propidium monoazide pretreatment with high‐throughput sequencing evaluated the bacterial diversity in chicken skin after thermal treatment

Emerging Non-Thermal Technologies as Alternative to SO2 for the Production of Wine

Effects of high‐pressure processing on fungi spores: Factors affecting spore germination and inactivation and impact on ultrastructure

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