Comparing high pressure thermal processing and thermosonication with thermal processing for the inactivation of bacteria, moulds, and yeasts spores in foods

The Effects of Encapsulation on the In Vitro Anti-Clostridial Activity of Olive Mill Wastewater Polyphenolic Extracts: A Promising Strategy to Limit Microbial Growth in Food Systems

Despite the technologies applied to food production, microbial contamination and chemical deterioration are still matters of great concern. In order to limit these phenomena, new natural approaches should be applied. In this context, the present study aimed to assess the antioxidant and anti-Clostridial effects of two different polyphenolic extracts derived from olive mill vegetation water, one liquid (LE) and one encapsulated (EE). The extracts have been preliminary characterized using Liquid Chromatography Quadrupole Time-Of Flight spectrometry. The Oxygen Radical Absorbance Capacity method was used to determine the antioxidant capacity, registering a higher value for EE compared to that for LE (3256 ± 85 and 2446 ± 13 µgTE/g, respectively). The antibacterial activity against C. perfringens, C. botulinum and C. difficile was studied by the agar well diffusion method, MIC and MBC determination and a time-kill test. The results confirm that EE and LE are able to limit microbial growth, albeit with minor effects when the phenolic compounds are encapsulated. Further studies are needed to evaluate the possible application of these extracts in food systems.

Recent innovations and emerging technological advances used to improve quality and process of plant-based milk analogs

The worldwide challenges related to food sustainability are presently more critical than ever before due to the severe consequences of climate change, outbreak of epidemics, and wars. Many consumers are shifting their dietary habits toward consuming more plant-based foods, such as plant milk analogs (PMA) for health, sustainability, and well-being reasons. The PMA market is anticipated to reach US$38 billion within 2024, making them the largest segment in plant-based foods. Nevertheless, using plant matrices to produce PMA has numerous limitations, including, among others, low stability and short shelf life. This review addresses the main obstacles facing quality and safety of PMA formula. Moreover, this literature overview discusses the emerging approaches, e.g., pulsed electric field (PEF), cold atmospheric plasma (CAP), ultrasound (US), ultra-high-pressure homogenization (UHPH), ultraviolet C (UVC) irradiation, ozone (O3), and hurdle technology used in PMA formulations to overcome their common challenges. These emerging technologies have a vast potential at the lab scale to improve physicochemical characteristics, increase stability and extend the shelf-life, decrease food additives, increase nutritional and organoleptic qualities of the end product. Although the PMA fabrication on a large scale using these technologies can be expected in the near future to formulate novel food products that can offer green alternatives to conventional dairy products, further development is still needed for wider commercial applications.

Inactivating Food Microbes by High-Pressure Processing and Combined Nonthermal and Thermal Treatment: A Review

High-pressure processing (HPP) is a mild technology alternative to thermal pasteurization and sterilization of different food products. HPP has emerged to provide enormous benefits to consumers, i.e., mildly processed food and additive-free food. It effectively retains bioactive compounds and extends the shelf life of food commodities by inactivating bacteria, yeast, mold, and virus. The limitation of HPP in inactivating spores can be overcome by using other thermal and nonthermal processing sequentially or simultaneously with HPP. This review summarizes the applications of HPP in the fruits and vegetables, dairy, meat, fish, and poultry sector. It also emphasizes microbial food safety and the effectiveness of HPP in the load reduction of microorganisms. Comprehensive information about the synergistic effect of HPP with different techniques and their effectiveness in ensuring food safety is reported. The summarized data would be handy to interested researchers and industry personnel.

Emerging Trends for Nonthermal Decontamination of Raw and Processed Meat: Ozonation, High-Hydrostatic Pressure and Cold Plasma

Meat may contain natural, spoilage, and pathogenic microorganisms based on the origin and characteristics of its dietary matrix. Several decontamination substances are used during or after meat processing, which include chlorine, organic acids, inorganic phosphates, benzoates, propionates, bacteriocins, or oxidizers. Unfortunately, traditional decontamination methods are often problematic because of their adverse impact on the quality of the raw carcass or processed meat. The extended shelf-life of foods is a response to the pandemic trend, whereby consumers are more likely to choose durable products that can be stored for a longer period between visits to food stores. This includes changing purchasing habits from “just in time” products “for now” to “just in case” products, a trend that will not fade away with the end of the pandemic. To address these concerns, novel carcass-decontamination technologies, such as ozone, high-pressure processing and cold atmospheric plasma, together with active and clean label ingredients, have been investigated for their potential applications in the meat industry. Processing parameters, such as exposure time and processing intensity have been evaluated for each type of matrix to achieve the maximum reduction of spoilage microorganism counts without affecting the physicochemical, organoleptic, and functional characteristics of the meat products. Furthermore, combined impact (hurdle concept) was evaluated to enhance the understanding of decontamination efficiency without undesirable changes in the meat products. Most of these technologies are beneficial as they are cost-effective, chemical-free, eco-friendly, easy to use, and can treat foods in sealed packages, preventing the product from post-process contamination. Interestingly, their synergistic combination with other hurdle approaches can help to substitute the use of chemical food preservatives, which is an aspect that is currently quite desirable in the majority of consumers. Nonetheless, some of these techniques are difficult to store, requiring a large capital investment for their installation, while a lack of certification for industrial utilization is also problematic. In addition, most of them suffer from a lack of sufficient data regarding their mode of action for inactivating microorganisms and extending shelf-life stability, necessitating a need for further research in this area.

Whey Beverage Emulsified System as Carrying Matrix of Fennel Seed Extract Obtained by Supercritical CO2 Extraction: Impact of Thermosonication Processing and Addition of Prebiotic Fibers

Whey beverages that were enriched with fructooligosaccharides (FOS) and xylooligosaccharides (XOS) were used for carrying Foeniculum vulgare extract that was obtained by the supercritical CO₂ extraction technique to produce novel functional products. Fennel-based whey beverages were subjected to thermosonication processing (100, 200, and 300 W at 60 °C for 15 min) to verify the performance of the dairy colloidal system for protecting the bioactive fennel compounds. The impacts of thermosonication processing on the quality attributes of the functional whey beverages were examined according to their droplet size distribution, microstructure, kinetic stability, color parameters, browning index, total phenolic content (TPC), and antioxidant capacity by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2-Azino-bis-(3-ethylbenzothiazoline)-6-sulphonic acid) assays. The enrichment of the whey beverages with FOS and XOS did not affect their kinetic stability. However, the addition of prebiotic dietary fibers contributed to reducing the mean droplet size due to the formation of whey protein–FOS/XOS conjugates. The thermosonication treatments did not promote color changes that were discernible to the human eye. On the other hand, the thermosonication processing reduced the kinetic stability of the beverages. Overall, the colloidal dairy systems preserved the antioxidant capacity of the fennel seed extract, regardless of thermosonication treatment intensity. The whey beverages enriched with FOS and XOS proved to be effective carrying matrices for protecting the lipophilic bioactive fennel compounds.

High-Pressure Processing for Sustainable Food Supply

Sustainable food supply has gained considerable consumer concern due to the high percentage of spoilage microorganisms. Food industries need to expand advanced technologies that can maintain the nutritive content of foods, enhance the bio-availability of bioactive compounds, provide environmental and economic sustainability, and fulfill consumers’ requirements of sensory characteristics. Heat treatment negatively affects food samples’ nutritional and sensory properties as bioactives are sensitive to high-temperature processing. The need arises for non-thermal processes to reduce food losses, and sustainable developments in preservation, nutritional security, and food safety are crucial parameters for the upcoming era. Non-thermal processes have been successfully approved because they increase food quality, reduce water utilization, decrease emissions, improve energy efficiency, assure clean labeling, and utilize by-products from waste food. These processes include pulsed electric field (PEF), sonication, high-pressure processing (HPP), cold plasma, and pulsed light. This review describes the use of HPP in various processes for sustainable food processing. The influence of this technique on microbial, physicochemical, and nutritional properties of foods for sustainable food supply is discussed. This approach also emphasizes the limitations of this emerging technique. HPP has been successfully analyzed to meet the global requirements. A limited global food source must have a balanced approach to the raw content, water, energy, and nutrient content. HPP showed positive results in reducing microbial spoilage and, at the same time, retains the nutritional value. HPP technology meets the essential requirements for sustainable and clean labeled food production. It requires limited resources to produce nutritionally suitable foods for consumers’ health.

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

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.

Applications of novel processing technologies to enhance the safety and bioactivity of milk

Bioactive compounds in food can have high impacts on human health, such as antioxidant, antithrombotic, antitumor, and anti-inflammatory activities. However, many of them are sensitive to thermal treatments incurred during processing, which can reduce their availability and activity. Milk, including ovine, caprine, bovine, and human is a rich source of bioactive compounds, including immunoglobulins, vitamins, and amino acids. However, processing by various novel thermal and non-thermal technologies has different levels of impacts on these compounds, according to the studies reported in the literature, predominantly in the last 10 years. The reported effect of these technologies either covers microbial inactivation or the bioactive composition; however, there is a lack of comprehensive compilation of studies that compare the effect of these technologies on bioactive compounds in milk (especially, caprine and ovine) to microbial inactivation at similar settings. This research gap makes it challenging to conclude on the specific processing parameters that could be optimized to achieve targets of microbial safety and nutritional quality at the same time. This review covers the effect of a wide range of thermal and non-thermal processing technologies including high-pressure processing, pressure-assisted thermal sterilization, pulsed-electric field treatment, cold plasma, microwave-assisted thermal sterilization, ultra-high-pressure homogenization, ultrasonication, irradiation on the bioactive compounds as well as on microbial inactivation in milk. Although a combination of more than one technology could improve the reduction of bacterial contaminants to meet the required food safety standards and retain bioactive compounds, there is still scope for research on these hurdle approaches to simultaneously achieve food safety and bioactivity targets.

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

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.

Modelling inactivation of Staphylococcus spp. on sliced Brazilian dry-cured loin with thermosonication and peracetic acid combined treatment

Ultrasound (US) has a high capacity to increase food safety. Although high and/or moderate temperature in combination with US has been studied, the knowledge about cooling/low temperatures as well as its combined effect with chemical preservation methods is scarce. Therefore, the aim of this study was to describe the inactivation of Staphylococcus spp. (SA) present in the natural microbiota of sliced Brazilian dry-cured loin (Socol, BDL) using US (40 kHz and 5.40 W/g) at 1.6-17.9 kJ/g, temperature (T) between 6.4 and 73.6 °C and peracetic acid (PA) between 5.5 and 274.5 mg/L employing the Central Composite Rotatable Design. The model fully describes how the combination of US, T, and PA affects SA inactivation. In BDL, an increase in US acoustic energy density (kJ/g) allows the reduction of T necessary to inactivate SA because of the occurrence of synergistic effect. However, US applied at low T was inefficient. On the other hand, PA was more efficient at low T, since high T degraded this compound at different rates according to the holding T. Therefore, the data indicates a relation between the technologies used in the combined decontamination of sliced BDL improving dry-cured meat safety.

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

Spores are the most resistant form of microbial cells, thus difficult to inactivate. The pathogenic or food spoilage effects of certain spore-forming microorganisms have been the primary basis of sterilization and pasteurization processes. Thermal sterilization is the most common method to inactivate spores present on medical equipment and foods. High pressure processing (HPP) is an emerging and commercial non-thermal food pasteurization technique. Although previous studies demonstrated the effectiveness of thermal and non-thermal spore inactivation, the in-depth mechanisms of spore inactivation are as yet unclear. Live and dead forms of two food spoilage bacteria, a mould and a yeast were examined using scanning electron microscopy before and after the inactivation treatment. Alicyclobacillus acidoterrestris and Geobacillus stearothermophilus bacteria are indicators of acidic foods pasteurization and sterilization processes, respectively. Neosartorya fischeri is a phyto-pathogenic mould attacking fruits. Saccharomyces cerevisiae is a yeast with various applications for winemaking, brewing, baking and the production of biofuel from crops (e.g. sugar cane). Spores of the four microbial species were thermally inactivated. Spores of S. cerevisiae were observed in the ascus and free form after thermal and HPP treatments. Different forms of damage and cell destruction were observed for each microbial spore. Thermal treatment inactivated bacterial spores of A. acidoterrestris and G. stearothermophilus by attacking the inner core of the spore. The heat first altered the membrane permeability allowing the release of intracellular components. Subsequently, hydration of spores, physicochemical modifications of proteins, flattening and formation of indentations occurred, with subsequent spore death. Regarding N. fischeri, thermal inactivation caused cell destruction and leakage of intracellular components. Both thermal and HPP treatments of S. cerevisiae free spores attacked the inner membrane, altering its permeability, and allowing in final stages the transfer of intracellular components to the outside. The spore destruction caused by thermal treatment was more severe than HPP, as HPP had less effect on the spore core. All injured spores have undergone irreversible volume and shape changes. While some of the leakage of spore contents is visible around the deformed but fully shaped spore, other spores exhibited large indentations and were completely deformed, apparently without any contents inside. This current study contributed to the understanding of spore inactivation by thermal and non-thermal processes.