Pressure–ohmic–thermal sterilization: A feasible approach for the inactivation of Bacillus amyloliquefaciens and Geobacillus stearothermophilus spores

Advancements in Non-Thermal Processing Technologies for Enhancing Safety and Quality of Infant and Baby Food Products: A Review

Breast milk is the main source of nutrition during early life, but both infant formulas (Ifs; up to 12 months) and baby foods (BFs; up to 3 years) are also important for providing essential nutrients. The infant food industry rigorously controls for potential physical, biological, and chemical hazards. Although thermal treatments are commonly used to ensure food safety in IFs and BFs, they can negatively affect sensory qualities, reduce thermosensitive nutrients, and lead to chemical contaminant formation. To address these challenges, non-thermal processing technologies such as high-pressure processing, pulsed electric fields, radio frequency, and ultrasound offer efficient pathogen destruction similar to traditional thermal methods, while reducing the production of key process-induced toxicants such as furan and 5-hydroxymethyl-2-furfural (HMF). These alternative thermal processes aim to overcome the drawbacks of traditional methods while retaining their advantages. This review paper highlights the growing global demand for healthy, sustainable foods, driving food manufacturers to adopt innovative and efficient processing techniques for both IFs and BFs. Based on various studies reviewed for this work, the application of these novel technologies appears to reduce thermal processing intensity, resulting in products with enhanced sensory properties, comparable shelf life, and improved visual appeal compared to conventionally processed products.

Enhancing the growth of thermophilic Bacillus licheniformis YYC4 by low-intensity fixed-frequency continuous ultrasound

The effect of low-intensity fixed-frequency continuous ultrasound (LIFFCU) on the growth of Bacillus licheniformis YYC4 was investigated. The changes in morphology and activity of the organism, contributing to the growth were also explored. Compared with the control, a significant increase (48.95%) in the biomass of B. licheniformis YYC4 (at the logarithmic metaphase) was observed following the LIFFCU (28 kHz, 1.5 h and 120 W (equivalent to power density of 40 W/L)) treatment. SEM images showed that ultrasonication caused sonoporation, resulting in increased membrane permeability, evidenced by increase in cellular membrane potential, electrical conductivity of the culture, extracellular protein and nucleic acid, and intracellular Ca2+ content. Furthermore, LIFFCU action remarkably increased the extracellular protease activity, volatile components of the culture medium, microbial metabolic activity, and spore germination of the strain. Therefore, LIFFCU could be used to efficiently promote the growth of targeted microorganisms.

Effect of Hurdle Approaches Using Conventional and Moderate Thermal Processing Technologies for Microbial Inactivation in Fruit and Vegetable Products

Thermal processing of packaged fruit and vegetable products is targeted at eliminating microbial contaminants (related to spoilage or pathogenicity) and extending shelf life using microbial inactivation or/and by reducing enzymatic activity in the food. The conventional process of thermal processing involves sterilization (canning and retorting) and pasteurization. The parameters used to design the thermal processing regime depend on the time (minutes) required to eliminate a known population of bacteria in a given food matrix under specified conditions. However, due to the effect of thermal exposure on the sensitive nutrients such as vitamins or bioactive compounds present in fruits and vegetables, alternative technologies and their combinations are required to minimize nutrient loss. The novel moderate thermal regimes aim to eliminate bacterial contaminants while retaining nutritional quality. This review focuses on the “thermal” processing regimes for fruit and vegetable products, including conventional sterilization and pasteurization as well as mild to moderate thermal techniques such as pressure-assisted thermal sterilization (PATS), microwave-assisted thermal sterilization (MATS) and pulsed electric field (PEF) in combination with thermal treatment as a hurdle approach or a combined regime.

High Hydrostatic Pressure-Based Combination Strategies for Microbial Inactivation of Food Products: The Cases of Emerging Combination Patterns

The high demand for fresh-like characteristics of vegetables and fruits (V&F) boosts the industrial implementation of high hydrostatic pressure (HHP), due to its capability to simultaneously maintain original organoleptic characteristics and to achieve preservative effect of the food. However, there remains great challenges for assuring complete microbial inactivation only relying on individual HHP treatments, including pressure-resistant strains and regrowth of injured microbes during the storage process. Traditional HHP-assisted thermal processing may compromise the nutrition and functionalities due to accelerated chemical kinetics under high pressure conditions. This work summarizes the recent advances in HHP-based combination strategies for microbial safety, as exemplified by several emerging non-thermally combined patterns with high inactivation efficiencies. Considerations and requirements about future process design and development of HHP-based combination technologies are also given.

Mild processing of seafood-A review

Recent years have shown a tremendous increase in consumer demands for healthy, natural, high-quality convenience foods, especially within the fish and seafood sector. Traditional processing technologies such as drying or extensive heating can cause deterioration of nutrients and sensory quality uncompilable with these demands. This has led to development of many novel processing technologies, which include several mild technologies. The present review highlights the potential of mild thermal, and nonthermal physical, and chemical technologies, either used alone or in combination, to obtain safe seafood products with good shelf life and preference among consumers. Moreover, applications and limitations are discussed to provide a clear view of the potential for future development and applications. Some of the reviewed technologies, or combinations thereof, have shown great potential for non-seafood products, yet data are missing for fish and seafood in general. The present paper visualizes these knowledge gaps and the potential for new technology developments in the seafood sector. Among identified gaps, the combination of mild heating (e.g., sous vide or microwave) with more novel technologies such as pulsed electric field, pulsed light, soluble gas stabilization, cold plasma, or Ohmic heat must be highlighted. However, before industrial applications are available, more research is needed.

Evaluation of infrared assisted freeze drying for strawberry snacks: drying kinetics, energy efficiency and quality attributes

Feasibility of infrared assisted freeze drying (IRAFD) was evaluated for production of the strawberry snacks. Infrared (IR) radiation provided the driving force of ice sublimation during freeze drying (FD). Different IRAFD conditions were tested, including the continuous IRAFD-1.6 kW/m² and IRAFD-1.6 kW/m² at different weight reductions (20%, 40%, and 60%). Conventional FD had a total drying time of 691 ± 19 min, whereas continuous IRAFD significantly reduced the drying time to 309 ± 32 min. Continuous IRAFD also reduced the amount of consumed electrical energy by 42% compared to that of FD. A long duration of IR radiation produced a soft texture in the snacks. Drying kinetics were analyzed using various models, including the Page model, exponential model, and Henderson and Pabis model. The Page model provided the best fit to the experimental drying curve. This study showed the potential of IRAFD in producing value-added fruit snacks with good textural quality and efficient use of energy.

Synergistic Effects of Nisin, Lysozyme, Lactic Acid, and CitricidalTM for Enhancing Pressure-Based Inactivation of Bacillus amyloliquefaciens, Geobacillus stearothermophilus, and Bacillus atrophaeus Endospores

The inactivation of bacterial endospores continues to be the main curtailment for further adoption of high-pressure processing in intrastate, interstate, and global food commerce. The current study investigated the effects of elevated hydrostatic pressure for the inactivation of endospore suspension of three indicator spore-forming bacteria of concern to the food industry. Additionally, the effects of four bacteriocin/bactericidal compounds were studied for augmenting the decontamination efficacy of the treatment. Elevated hydrostatic pressure at 650 MPa and at 50 °C was applied for 0 min (untreated control) and for 3, 7, and 11 min with and without 50K IU of nisin, 224 mg/L lysozyme, 1% lactic acid, and 1% Citricidal^TM. The results were statistically analyzed using Tukey- and Dunnett’s-adjusted ANOVA. Under the condition of our experiments, we observed that a well-designed pressure treatment synergized with mild heat and bacteriocin/bactericidal compounds could reduce up to >4 logs CFU/mL (i.e., >99.99%) of bacterial endospores. Additions of nisin and lysozyme were able, to a great extent, to augment (p < 0.05) the decontamination efficacy of pressure-based treatments against Bacillus amyloliquefaciens and Bacillus atrophaeus, while exhibiting no added benefit (p ≥ 0.05) for reducing endospores of Geobacillus stearothermophilus. The addition of lactic acid, however, was efficacious for augmenting the pressure-based reduction of bacterial endospores of the three microorganisms.

Bacillus spores: a review of their properties and inactivation processing technologies

Many factors determine the resistance properties of a Bacillus spore to heat, chemical and physical processing, including thick proteinaceous coats, peptidoglycan cortex and low water content, high levels of dipicolinic acid (DPA), and divalent cations in the spore core. Recently, attention has been focused on non-thermal inactivation methods based on high pressure, ultrasonic, high voltage electric fields and cold plasmas for inactivating Bacillus spores associated with deterioration in quality and safety. The important chemical sporicides are glutaraldehyde, chorine-releasing agents, peroxygens, and ethylene oxide. Some food-grade antimicrobial agents exhibit sporostatic and sporicidal activities, such as protamine, polylysine, sodium lactate, essential oils. Surfactants with hydrophilic and hydrophobic properties have been reported to have inactivation activity against spores. The combined treatment of physical and chemical treatment such as heating, UHP (ultra high pressure), PEF (pulsed electric field), UV (ultraviolet), IPL (intense pulsed light) and natural antimicrobial agents can act synergistically and effectively to kill Bacillus spores in the food industry.

Infrared Assisted Freeze-Drying (IRAFD) to Produce Shelf-Stable Insect Food from Protaetia brevitarsis (White-Spotted Flower Chafer) Larva

In this study, the potential of infrared assisted freeze-drying (IRAFD) was tested for the production of shelf-stable edible insects: Protaetia brevitarsis larva (larva of white-spotted flower chafer). The IRAFD system was customized using an infrared lamp, K-type thermocouple, controller, and data acquisition system. The infrared lamp provided the sublimation energy for rapid freeze-drying (FD). The IRAFD conditions were continuous IRAFD-5.0 kW/m² and IRAFD-5.0 kW/m² at different weight reduction (WR) (10%, 20%, and 30%). The continuous IRAFD reduced the drying time to 247 min compared to the 2,833 min duration of FD (p<0.05). The electrical energy could be reduced by more than 90% through infrared radiation during FD (p<0.05). The Page model resulted in the best prediction among the tested drying kinetic models. In terms of quality, IRAFD showed significantly lower hardness, chewiness, and higher protein levels than hot air drying and FD (p<0.05). IRAFD better preserved the glutamic acid (6.30–7.29 g/100 g) and proline (3.84–5.54 g/100 g). The external product appearance after IRAFD exhibited more air pockets and volume expansion, which might result in a good consumer appeal. In conclusion, this study reports the potential of IRAFD in producing shelf-stable and value-added edible insects.

Ohmic cooking of instant rice cake soup: energy efficiency and textural qualities

The potential of ohmic heating was investigated to cook instant rice cakes according to electric field strengths (9, 12, 15, 18 V/cm) and cooking times (60, 80, 100, 120 s). Customized ohmic heating system was equipped with ohmic cell, electrodes, thermocouple, proportional-integral-differential controller and data acquisition system. Heating rate significantly increased when electric field strengths increased. Heating rate was 12.1 °C/min at 9 V/cm, and was increased to 38.8 °C/min at 18 V/cm. The energy efficiency was evaluated in terms of system performance coefficient (SPC) energy efficiency. The best SPC energy efficiency was 0.65 at an electrical field strength of 18 V/cm. An electric field strength of 15 V/cm and an 80 s cooking time resulted in the most preferable hardness (7.73 N). Ohmic heating would be applicable to cook instant rice cakes, resulting in good energy efficiency and textural qualities.

Evaluating the Feasibility of Ohmic Cooking for Home Meal Replacement Curry: Analysis of Energy Efficacy and Textural Qualities

The feasibility of ohmic heating was tested for cooking instant home meal replacement (HMR) curry mixture. A curry mixture (curry powder, spam, carrot, potato, and water) was ohmically heated to 100 °C using different electric fields (9, 12, 15, and 18 V/cm). Temperature come-up time to 100 °C of curry soup were 5.27 ± 0.63, 3.15 ± 0.39, 2.28 ± 0.19, and 1.67 ± 0.24 min at the electric fields of 9, 12, 15, and 18 V/cm, respectively. The come-up time was decreased as a function of enhanced electric fields (P < 0.05). In terms of energy efficacy, the highest electric field (18 V/cm) resulted in the most efficient system performance coefficient (SPC), with a score of 0.62. In terms of textural qualities, cooking at 15 V/cm of carrot and potato the hardness was 3.41 ± 0.69 N and 1.04 ± 0.18 N, respectively, that resulted in the ideal level of hardness. Our study proposed the positive feasibility of ohmic heating to cook HMR curry soup.

Inactivation of Microorganisms in Foods by Ohmic Heating: A Review

Ohmic heating (OH) is an alternative food processing technology for effectively inactivating microorganisms that depends on the heat that has been generated when electrical current passes directly through food material. The advantages of OH for microbial inactivation include shorter heating time, more uniform heat distribution inside food, reduced nutrition losses, and higher energy efficiency. This review presents some published information regarding the inactivation of microorganisms by OH, including the major factors that influence the inactivation effectiveness of OH, the inactivation of vegetative cells and spores in foods by OH, the inactivation mechanisms of OH, and the challenges and prospects of OH for food processing. This information will improve the understanding of OH for inactivation of microorganisms and promote the application of OH in the food industry.