A new decontamination method for Bacillus subtilisin pasteurized milk: Thermosonication treatment

Insights into the microbiota of raw milk from seven breeds animals distributing in Xinjiang China

Owing to its high nutritional content, raw milk contains a rich microbiota. Thus, to study microorganisms present in raw milk available in Xinjiang China, 142 raw milk samples from seven animal breeds (cow, sheep, goat, donkey, horse, camel, and yak) and four regions (Hami, Tarbagatay, Kashgar, and Ili) were analyzed by high-throughput DNA sequencing. These microorganisms were characterized by 10 dominant phyla. Proteobacteria (68.33%) was the major phylum, followed by Firmicutes (18.80%) and Thermi (3.16%). Horse milk contained more Bacteroidetes, sheep milk contained more Gammaproteobacteria, and donkey milk contained more unclassified sequences. Camel and donkey milk contained the highest and lowest bacterial diversity compared with that contained by the remaining milk samples, respectively. Additionally, spoilage microorganisms, including Chryseobacterium, Propionibacterium, and Flavobacterium, and pathogenic bacteria, including Ochrobactrum anthropi and Sphingomonas, were more prevalent in horse and yak milk, whereas probiotic lactic acid bacteria (LAB), such as Leuconostoc, Lactococcus, or Lactobacillus, were more prevalent in goat, donkey, and camel milk. Furthermore, Moraxella was abundantly present in goat, camel, and yak milk, Acinetobacter was more abundant in camel milk, and Pseudomonas was relatively abundant in sheep and donkey milk. Overall, specific harmful microorganisms and probiotic lactic acid bacteria were found in the raw milk samples obtained from different animals, which provided a basis for preventing and controlling the growth of harmful bacteria, as well as investigating probiotic resources in raw milk.

The viable but non-culturable (VBNC) status of Shewanella putrefaciens (S. putrefaciens) with thermosonication (TS) treatment

Although thermosonication (TS) treatment has been widely used in food sterilization, the viable but non-culturable (VBNC) of bacteria with TS treatment has still concerned potential food safety and public health. The molecular mechanism of VBNC status of bacteria with TS treatment is not clearly known. Therefore, in this study, we used Shewanella putrefaciens, which was a common putrefactive bacteria in aquatic products, to study the VBNC state of bacteria with TS treatment. Firstly, our results revealed that S. putrefaciens still could enter the VBNC state after TS treatments: 50 kHz, 300 W, 30 min ultrasonic treatment and 70 °C heating; Subsequently, we found the VBNC state of S. putrefaciens can resist the damage of TS treatment, such as cell wall break, DNA degradation, etc; Finally, four-dimensional data-independent acquisition-based proteomics showed that under VBNC state, S. putrefaciens upregulated functional proteins to resist TS treatment, such as: ribosomal proteins to accelerate the synthesis of stress proteins to counteract TS treatments, ornithine decarboxylase SpeF and MraY to repair TS treatment-induced damage, etc. Meanwhile, S. putrefaciens downregulates metabolic and transport functional proteins such as dehydrogenase to reduce the metabolism. Importantly, among those proteins, the ribosomal transcriptional regulatory protein family, such as rpsB, etc, may be the key proteins for S. putrefaciens entering VBNC state. This finding can provide some new strategies for preventing VBNC status of bacteria with TS treatment, such as: inhibition of key proteins, etc.

Synergistic bactericidal effect and mechanism of ultrasound combined with Lauroyl Arginate Ethyl against Salmonella Typhimurium and its application in the preservation of onions

In the present study, the synergistic bactericidal effect and mechanism of ultrasound (US) combined with Lauroyl Arginate Ethyl (LAE) against Salmonella Typhimurium were investigated. On this basis, the effect of US+LAE treatment on the washing of S. Typhimurium on the surface of onions and on the physical and chemical properties of onion during fresh-cutting and storage were studied. The results showed that treatment with US+LAE could significantly (P < 0.05) reduce the number of S. Typhimurium compared to US and LAE treatments alone, especially the treatment of US+LAE (230 W/cm2, 8 min, 71 μM) reduced S. Typhimurium by 8.82 log CFU/mL. Confocal laser scanning microscopy (CLSM), flow cytometry (FCM), protein and nucleic acid release and N-phenyl-l-naphthylamine (NPN) assays demonstrated that US+LAE disrupted the integrity and permeability of S. Typhimurium cell membranes. Reactive oxygen species (ROS) and malondialdehyde (MDA) assays indicated that US+LAE exacerbated oxidative stress and lipid peroxidation in cell membranes. Field emission scanning electron microscopy (FESEM) demonstrated that US+LAE treatment caused loss of cellular contents and led to cell crumpling and even lost the original cell morphology. US+LAE treatment caused a significant (P < 0.05) decrease in the number of S. Typhimurium on onions, but there was no significant (P > 0.05) effect on the color, hardness, weight and ascorbic acid content of onions. This study elucidated the synergistic antibacterial mechanism of US+LAE and verified the feasibility of bactericidal effect on the surface of onions, providing a theoretical basis for improving the safety of fresh produce in the food industry and to propose a new way to achieve the desired results.

Effects of ohmic heating with different voltages on the quality and microbial diversity of cow milk during thermal treatment and subsequent cold storage

Ohmic heating (OH), an innovative heating technology, presents potential applications in the pasteurization of liquid foods. Therefore, the study was conducted to evaluate the effect of OH at various voltage gradients (10 V/cm, 12.5 V/cm, and 15 V/cm) and water bath (WB) on microbial inactivation, physicochemical and sensory properties and microbial flora of pasteurized milk. Results indicated that OH with higher voltage could effectively inactivate microorganisms in milk, requiring less heating time and energy. Moreover, OH treatment at higher voltages could decelerate lipid oxidation and better maintain the sensory quality and essential amino acids content of milk. Additionally, all treatments significantly altered the microbial community, and during storage, the microbial community in milk treated with 10 V/cm and 12.5 V/cm OH remained relatively stable. OH treatments with voltage gradients exceeding 12.5 V/cm could effectively inactive microorganisms and maintain the quality attributes of milk.

Microbial decontamination assisted by ultrasound-based processing technologies in food and model systems: A review

Ultrasound (US) technology is recognized as one of the emerging technologies that arise from the current trends for improving nutritional and organoleptic properties while providing food safety. However, when applying the US alone, higher power and longer treatment times than conventional thermal treatments are needed to achieve a comparable level of microbial inactivation. This results in risks, damaging food products' composition, structure, or sensory properties, and can lead to higher processing costs. Therefore, the US has often been investigated in combination with other approaches, like heating at mild temperatures and/or treatments at elevated pressure, use of antimicrobial substances, or other emerging technologies (e.g., high-pressure processing, pulsed electric fields, nonthermal plasma, or microwaves). A combination of US with different approaches has been reported to be less energy and time consuming. This manuscript aims to provide a broad review of the microbial inactivation efficacy of US technology in different food matrices and model systems. In particular, emphasis is given to the US in combination with the two most industrially viable physical processes, that is, heating at mild temperatures and/or treatments at elevated pressure, resulting in techniques known as thermosonication, manosonication, and manothermosonication. The available literature is reviewed, and critically discussed, and potential research gaps are identified. Additionally, discussions on the US's inactivation mechanisms and lethal effects are included. Finally, mathematical modeling approaches of microbial inactivation kinetics due to US-based processing technologies are also outlined. Overall, this review focuses only on the uses of the US and its combinations with other processes relevant to microbial food decontamination.

Exploring the Power of Thermosonication: A Comprehensive Review of Its Applications and Impact in the Food Industry

Thermosonication (TS) has been identified as a smart remedy for the shortcomings of heat treatment, which typically requires prolonged exposure to high temperatures. This technique combines moderate heat treatment with acoustic energy to eliminate harmful microorganisms and enzymes in food products. Unlike conventional heat treatment, thermosonication utilizes short holding times, allowing for the preservation of food products’ phytochemical compounds and sensory characteristics. The benefits and challenges of this emerging technology, such as equipment cost, limited availability of data, inconsistent results, high energy consumption, and scale-up challenges, have been assessed, and the design process for using ultrasound in combination with mild thermal treatment has been discussed. TS has proven to be a promising technique for eliminating microorganisms and enzymes without compromising the nutritional or sensory quality of food products. Utilizing natural antimicrobial agents such as ascorbic acid, Nisin, and ε-polylysine (ε-PL) in combination with thermosonication is a promising approach to enhancing the safety and shelf life of food products. Further research is required to enhance the utilization of natural antimicrobial agents and to acquire a more comprehensive comprehension of their impact on the safety and quality of food products.