Nisin:Carboxymethylcellulose polyion complex (PIC) nanoparticles. Preparation and antimicrobial activity.

Nisin is a cationic antimicrobial peptide used as a natural food preservative against gram-positive bacteria. However, nisin is degraded following interaction with food components. Here, we report the first use of Carboxymethylcellulose (CMC), a versatile and affordable food additive, to protect nisin and extend its antimicrobial activity. First, we optimized the methodology by considering the effect of nisin:CMC ratio, pH, and, especially, the degree of substitution of CMC. In particular, we show here how these parameters affected the size, charge, and, notably, the encapsulation efficiency of these nanomaterials. This way, optimized formulations contained over 60 % w/w in nisin while encapsulating ∼90 % of the nisin used. We then show that these new nanomaterials inhibited the growth of Staphylococcus aureus, a major foodborne pathogen, using milk as a representative food matrix. Remarkably, this inhibitory effect was observed with one-tenth of the concentration of nisin currently used in dairy products. We believe that the combination of the affordability of CMC, flexibility and simplicity of preparation, and the ability to inhibit the growth of food pathogens, makes these nisin:CMC PIC nanoparticles an ideal platform to underpin new nisin formulations.

Pre-lab video demonstrations to enhance students' laboratory experience in a first-year chemical engineering class.

The limited capabilities of teaching laboratories, combined with an increasing number of students enrolled in university, require constant augmentation of instructional approaches. By enhancing laboratory demonstrations with digital technology, these structural issues can be addressed while at the same time enhancing student understanding and learning. Our case study focuses on the fermentation lab part of the Reaction Equilibria and Thermodynamics (RET) module, a first-year chemical engineering course at the University of Birmingham. Video demonstrations were used to introduce students to the laboratory set-ups and walk them through each step and technique. The video demonstrations allowed the students to attend the in-person lab sessions having established knowledge and understanding of the processes involved and the outcomes desired, which decreased the burden on the facilities and the staff. A knowledge-based quiz and a student survey conducted at the end of the module showed that the pre-lab videos encouraged more active participation in the laboratory sessions and reinforced learning. Approximately 70% of the students polled in the first survey conducted within this project felt more confident going into the laboratory sessions after watching the pre-lab videos and attempting the knowledge quiz, while 92% of the students polled in the second survey judged the pre-lab video sessions as beneficial to them. Overall, the teaching method has the potential to improve student participation and access, boost confidence and learning, and provided a more structured and flexible approach to laboratory learning outcomes.

Application of supercritical fluid carbon dioxide in improving food shelf-life and safety by inactivating spores: a review.

Extending shelf-life of food, ensuring it is safe for consumers and meeting regulatory standards is the food industry's governing principle. Food safety is an essential aspect of food processing. Spores-forming microbes such as Bacillus spp. and Clostridium spp. are problematic in the food industry because of their ability to form endospores and survive processing conditions. Hence, their germination in food poses a threat to both shelf-life and safety of food. This paper reports on the current state of supercritical fluid carbon dioxide (SF-CO2) application in the inactivation of spores-forming microbes in food. Unlike high hydrostatic pressure and thermal processes which struggle to deactivate and destroy spores, and if they do, it impacts adversely on the food nutritional and quality attributes. This technique is viable to inactivate spores and maintain the foods structural and nutritional characteristics. The mechanisms of inactivation can be grouped into: (1) release of cellular content due to rupture of the cell wall, coat and cortex, and disruption of membranes, (2) degradation of proteins as a result of interaction with permeated and penetrated SF-CO2 and (3) deactivation of enzymatic activities. It was discovered that the synergistic effect of ultrasound another non-thermal technique or addition of co-solvent such as water, hydrogen peroxide and ethanol or antimicrobial peptide greatly enhanced inactivation of spores. This work harmonizes published perspectives on spores' inactivation mechanisms, and will help inform further research into the application of SF-CO2 in the sterilization of food products.

Sous vide processing: a viable approach for the assurance of microbial food safety.

As consumer needs change, innovative food processing techniques are being developed that have minimal impact on food quality and ensure its microbiological safety. Sous vide (SV) is an emerging technology of cooking foods in vacuum pouches at specific temperatures, which results in even heat distribution. Presented here is an overview of the current state of the art in the application of SV techniques for processing and preserving foods. Unlike the conventional thermal food processing approach, the precise nature of the SV method improves food quality, nutrition and shelf-life while destroying microorganisms. Foods processed by SV are usually subjected to temperatures between 50 and 100 °C. Although sufficient for food preparation/processing, its effectiveness in eliminating microbial pathogens, including viruses, parasites, vegetative and spore forms of bacteria, is limited. However, the inactivation of spore-forming microbes can be enhanced by combining the technique with other non-thermal methods that exert negligible impact on the nutritional, flavour and sensory characteristics of foods. In addition to exploring the mechanism of action of SV technology, the challenges related to its implementation in the food industry are also discussed. SV method potential, applications, and impacts on spore-forming microbes and spore inactivation are explored in this review. Through the debate and discussion presented, further research and industrial applications of this food processing method could be guided. © 2022 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Recent Advances in the Application of the Antimicrobial Peptide Nisin in the Inactivation of Spore-Forming Bacteria in Foods.

Conventional thermal and chemical treatments used in food preservation have come under scrutiny by consumers who demand minimally processed foods free from chemical agents but microbiologically safe. As a result, antimicrobial peptides (AMPs) such as bacteriocins and nisin that are ribosomally synthesised by bacteria, more prominently by the lactic acid bacteria (LAB) have appeared as a potent alternative due to their multiple biological activities. They represent a powerful strategy to prevent the development of spore-forming microorganisms in foods. Unlike thermal methods, they are natural without an adverse impact on food organoleptic and nutritional attributes. AMPs such as nisin and bacteriocins are generally effective in eliminating the vegetative forms of spore-forming bacteria compared to the more resilient spore forms. However, in combination with other non-thermal treatments, such as high pressure, supercritical carbon dioxide, electric pulses, a synergistic effect with AMPs such as nisin exists and has been proven to be effective in the inactivation of microbial spores through the disruption of the spore structure and prevention of spore outgrowth. The control of microbial spores in foods is essential in maintaining food safety and extension of shelf-life. Thus, exploration of the mechanisms of action of AMPs such as nisin is critical for their design and effective application in the food industry. This review harmonises information on the mechanisms of bacteria inactivation from published literature and the utilisation of AMPs in the control of microbial spores in food. It highlights future perspectives in research and application in food processing.

COVID-19 pandemic: A review of the global lockdown and its far-reaching effects.

COVID-19, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), was declared a pandemic by the World Health Organization (WHO) on the 11th of March 2020, leading to some form of lockdown across almost all countries of the world. The extent of the global pandemic due to COVID-19 has a significant impact on our lives that must be studied carefully to combat it. This study highlights the impacts of the COVID-19 pandemic lockdown on crucial aspects of daily life globally, including; Food security, Global economy, Education, Tourism, hospitality, sports and leisure, Gender Relation, Domestic Violence/Abuse, Mental Health and Environmental air pollution through a systematic search of the literature. The COVID-19 global lockdown was initiated to stem the spread of the virus and 'flatten the curve' of the pandemic. However, the impact of the lockdown has had far-reaching effects in different strata of life, including; changes in the accessibility and structure of education delivery to students, food insecurity as a result of unavailability and fluctuation in prices, the depression of the global economy, increase in mental health challenges, wellbeing and quality of life amongst others. This review article highlights the impacts of the COVID-19 pandemic lockdown across the globe. As the global lockdown is being lifted in a phased manner in various countries of the world, it is necessary to explore its impacts to understand its consequences comprehensively. This will guide future decisions that will be made in a possible future wave of the COVID-19 pandemic or other global disease outbreak.