Thermal pasteurization of ready-to-eat foods and vegetables: Critical factors for process design and effects on quality

Persistence of crAssBcn phages in conditions of natural inactivation and disinfection process and their potential role as human source tracking markers

Due to their abundance in the human gut, human specificity, and global distribution, some crAss-like phages, including the original p-crAssphage, have been proposed as indicators of human fecal pollution suitable for microbial source tracking (MST). The prevalence of crAss-like phages in water, and consequently their usefulness as MST indicators, is determined by their ability to survive various inactivation and disinfection processes. Recently, we isolated new crAss-like phages (named crAssBcn phages) capable of infecting Bacteroides intestinalis and exhibiting a wide geographical distribution. Here, we assessed the infectivity and DNA integrity of three crAssBcn phages (ΦCrAssBcn6, 10, and 15) and ΦCrAss001, the first crAss-like phage isolated, at different pHs and temperatures, after UV and chlorine treatments, and under natural conditions. Their bacterial host, B. intestinalis and a siphovirus Bacteroides-infecting phage GA17-A were used as controls. Infectious crAssBcn phages remained stable for a month at 4, 22, and 37 °C, and at pH 7, but inactivated when exposed to pH 3. Infective crAssBcn phages decreased by 5 log10 after treatment with 10 ppm of chlorine for 1 min and after UV treatment at a fluence of 5.94 mJ/cm2. However, heat treatment at 60 and 70 °C resulted in only a moderate decrease (<1 log10 and almost 3 log10 units of reduction, respectively). Experiments under natural conditions in outdoor mesocosms revealed that inactivation rates for crAssBcn phages, as for the other microorganisms, were higher in summer (up to 6 log10) than in winter (<4 log10), suggesting a higher incidence of inactivation factors, such as sunlight and temperature, in the warmer months. B. intestinalis was significantly more prone to inactivation than phages in most conditions except for the irradiation treatment. In contrast, crAssBcn phage DNA remained stable, with minimal reduction under most of the tested conditions, except in the summer mesocosm and UV assays.

Recyclable and non-recyclable packaging films with different barrier properties: Effect of processing and storage time on quality of mashed potato and ground carrot

The aim of this study was to evaluate if high barrier recyclable material polyethylene/ethylene vinyl alcohol (PE/EVOH) can be an alternative non-recyclable polyamides (PA)/PE laminate and also if high barrier is required or recyclable PE material with low barrier properties is good enough to maintain the quality of thermally processed mashed potato and ground carrot. The oxygen transmission rate (OTR) of the PA/PE and PE films decreased after heat treatment, while no change was observed for PE/EVOH films. Food contact did not impact the OTR of PA/PE and PE/EVOH films, while the OTR of PE films decreased. The water vapor transmission rate (WVTR) of PA/PE and PE/EVOH films increased after heat treatment. In general, the WVTR of films increased after food contact. The tensile strength of all films was only reduced up to 3-4 weeks of food contact. After 10 weeks, the PE film showed significantly lower hue values and a larger total color difference than the two other films. Light exposure reduced the hue values and increased total color difference after 6 weeks of storage. The odor and flavor of both mashed potatoes and ground carrots were affected by light exposure. The mashed potato showed a slight reduction in freshness-odor for all materials with storage time. For flavor, mashed potato and ground carrot showed similar trends; flavor was scored unacceptable when packaged in PE films after 6 weeks, but when packaged in PA/PE and PE/EVOH films, the flavor was still acceptable after 10 weeks of storage.

Determination of strain variability and kinetics of food-associated microorganisms following ultrasound treatment

Ultrasound is a promising emerging technology known for its antimicrobial efficacy. However, existing studies have not fully addressed the impact of strain variability and inactivation kinetics on US efficacy. Ten strains of Listeria monocytogenes, Lactiplantibacillus plantarum, Saccharomyces cerevisiae and Escherichia coli were exposed to US treatment (26 kHz, 200 mL, 100 % amplitude, 200 W, 65-71 W/cm2) under dynamic conditions to investigate their resistance profile. Furthermore, the inactivation kinetics of selected resistant/sensitive strains were assessed. The result showed significant intra-species variability in resistance (p < 0.05) for the four target microorganisms evaluated in this study. L6 and NCTC 10357 were the most resistant and sensitive L. monocytogenes strains respectively, having a reduction difference of ∼3.4 log CFU/mL. Regarding L. plantarum, FBR04 emerged as the most resistant strain (4.4 log reduction), while E. coli FAM21845, FAM21805 and FAM21843 (∼2 log reduction) emerged as the most resistant strains. On the other hand, the most resistant strains of S. cerevisiae were CBS 1544, AD 1890 and 077.0001 (<1 log reduction) while S. cerevisiae AD 2913, 028.0404 and 028.0315 were the most sensitive (>5 log reduction). The survival curves of most of the strains exhibited an initial phase of insignificant microbial inactivation followed by a relatively fast log-linear inactivation period. The estimated D-value showed that L. monocytogenes strains exhibited higher resistance to US treatment than any other species, while other species displayed comparable resistance. The findings on strain variability resistance and inactivation kinetics following US treatment are essential for food safety and will pave the way for further research on microbial response to US stress, risk assessment and optimisation studies.

Electromagnetic wave-based technology for ready-to-eat foods preservation: a review of applications, challenges and prospects

In recent years, the ready-to-eat foods market has grown significantly due to its high nutritional value and convenience. However, these foods are also at risk of microbial contamination, which poses food safety hazards. Additionally, traditional high-temperature sterilization methods can cause food safety and nutritional health problems such as protein denaturation and lipid oxidation. Therefore, exploring and developing effective sterilization technologies is imperative to ensure food safety and nutritional properties, and protect consumers from potential foodborne diseases. This paper focuses on electromagnetic wave-based pasteurization technologies, including thermal processing technologies such as microwave, radio frequency, and infrared, as well as non-thermal processing technologies like ultraviolet, irradiation, pulsed light, and photodynamic inactivation. Furthermore, it also reviews the antibacterial mechanisms, advantages, disadvantages, and recent applications of these technologies in ready-to-eat foods, and summarizes their limitations and prospects. By comparing the limitations of traditional high-temperature sterilization methods, this paper highlights the significant advantages of these pasteurization techniques in effectively inhibiting microbial growth, slowing lipid oxidation, and preserving food nutrition and flavor. This review may contribute to the industrial application and process optimization of these pasteurization technologies, providing an optimal choice for preserving various types of ready-to-eat foods.

Toward food safety-driven process design: a systematic review and research agenda

Process design strategies are important to prevent or reduce food safety risks in production systems. In this sense, the Codex Alimentarius presents a set of principles for good hygiene practices to guide food producers. However, studies in food safety often focus on analyzing and controlling implemented production processes without a policy of designing them with a preventive logic, leading to resource misallocation and noncompliance. This study aims to gather and analyze techniques, drivers, challenges, and research opportunities for food safety-driven process design. A systematic literature review was carried out following three steps: (i) Data collection, including 52 studies; (ii) Bibliometric analysis; and (iii) Content analysis, identifying techniques, drivers, challenges, and research opportunities. Three main themes in the subject were identified: process assessment models, risk assessment, and whole-chain traceability. Eleven design techniques were identified and compared according to their typology, structure, and coverage of themes addressed by the Codex Alimentarius. There is a gap in techniques addressing employee competence and personal hygiene. We suggest developing a tool encompassing the Codex Alimentarius good hygiene practices themes in process design to guide food safety-driven process development.

Antiviral Activity of Natural Compounds for Food Safety

Gastroenteritis and hepatitis are the most common illnesses resulting from the consumption of food contaminated with human enteric viruses. Several natural compounds have demonstrated antiviral activity against human enteric viruses, such as human norovirus and hepatitis A virus, while little information is available for hepatitis E virus. Many in-vitro studies have evaluated the efficacy of different natural compounds against human enteric viruses or their surrogates. However, only few studies have investigated their antiviral activity in food applications. Among them, green tea extract, grape seed extract and carrageenans have been extensively investigated as antiviral natural compounds to improve food safety. Indeed, these extracts have been studied as sanitizers on food-contact surfaces, in produce washing solutions, as active fractions in antiviral food-packaging materials, and in edible coatings. The most innovative applications of these antiviral natural extracts include the development of coatings to extend the shelf life of berries or their combination with established food technologies for improved processes. This review summarizes existing knowledge in the underexplored field of natural compounds for enhancing the safety of viral-contaminated foods and underscores the research needs to be covered in the near future.

Comprehensive analysis of predominant pathogenic bacteria and viruses in seafood products

Given the growing global demand for seafood, it is imperative to conduct a comprehensive study on the prevalence and persistence patterns of pathogenic bacteria and viruses associated with specific seafood varieties. This assessment thoroughly examines the safety of seafood products, considering the diverse processing methods employed in the industry. The importance of understanding the behavior of foodborne pathogens, such as Salmonella typhimurium, Vibrio parahaemolyticus, Clostridium botulinum, Listeria monocytogenes, human norovirus, and hepatitis A virus, is emphasized by recent cases of gastroenteritis outbreaks linked to contaminated seafood. This analysis examines outbreaks linked to seafood in the United States and globally, with a particular emphasis on the health concerns posed by pathogenic bacteria and viruses to consumers. Ensuring the safety of seafood is crucial since it directly relates to consumer preferences on sustainability, food safety, provenance, and availability. The review focuses on assessing the frequency, growth, and durability of infections that arise during the processing of seafood. It utilizes next-generation sequencing to identify the bacteria responsible for these illnesses. Additionally, it analyzes methods for preventing and intervening of infections while also considering the forthcoming challenges in ensuring the microbiological safety of seafood products. This evaluation emphasizes the significance of the seafood processing industry in promptly responding to evolving consumer preferences by offering current information on seafood hazards and future consumption patterns. To ensure the continuous safety and sustainable future of seafood products, it is crucial to identify and address possible threats.

Mechanistic insights into the adaptive evolvability of spore heat resistance in Bacillus cereus sensu lato

Wet heat treatment is a commonly applied method in the food and medical industries for the inactivation of microorganisms, and bacterial spores in particular. While many studies have delved into the mechanisms underlying wet heat killing and spore resistance, little attention has so far been dedicated to the capacity of spore-forming bacteria to tune their resistance through adaptive evolution. Nevertheless, a recent study from our group revealed that a psychrotrophic strain of the Bacillus cereus sensu lato group (i.e. Bacillus weihenstephanensis LMG 18989) could readily and reproducibly evolve to acquire enhanced spore wet heat resistance without compromising its vegetative cell growth ability at low temperatures. In the current study, we demonstrate that another B. cereus strain (i.e. the mesophilic B. cereus sensu stricto ATCC 14579) can acquire significantly increased spore wet heat resistance as well, and we subjected both the previously and currently obtained mutants to whole genome sequencing. This revealed that five out of six mutants were affected in genes encoding regulators of the spore coat and exosporium pathway (i.e. spoIVFB, sigK and gerE), with three of them being affected in gerE. A synthetically constructed ATCC 14579 ΔgerE mutant likewise yielded spores with increased wet heat resistance, and incurred a compromised spore coat and exosporium. Further investigation revealed significantly increased spore DPA levels and core dehydration as the likely causes for the observed enhanced spore wet heat resistance. Interestingly, deletion of gerE in Bacillus subtilis 168 did not impose increased spore wet heat resistance, underscoring potentially different adaptive evolutionary paths in B. cereus and B. subtilis.

A multidimensional evaluation of the effects of sweetener selection and UV-C treatment on orange juice and pectin-based confectionery gels

BACKGROUND

Consumers are seeking healthier alternatives to traditional confectioneries. They value the use of sugar replacers, more natural ingredients and/or environmentally friendly preservation technologies. UV-C light is considered an emerging alternative to thermal pasteurization that leaves no residue and requires minimal energy. The present study aimed to investigate the effect of novel sweetener combinations and juice UV-C assisted by mild heat treatment (UV-C/H) on the physicochemical, microbiological, morphological, rheological and sensory properties of orange juice pectin-based confectioneries stored at 5 ± 1 °C for 35 days.

RESULTS

For orange juice processing, UV-C/H (pilot-scale Dean-flow reactor; 892 mJ cm-2 ; 50 ± 1 °C) and thermal (T-coil, 80 °C; 6 min) treatments were used. Low-calorie confectionery gels were elaborated using the treated juices, low-methoxyl pectin and various sweetener combinations. UV-C/H and T-coil effectively inactivated juice native microbiota. The proposed formulations, derived from a previous Box-Behnken optimization study, included partial (F1: 3%-sucrose-S + 0.019%-rebaudioside-A-RA) or complete sucrose replacement (F2: 5.5%-erythritol-E + 0.019%-RA), and one control (C:10%-S). In general, the microbiota of the gels prepared with the UV-C/H or T-coil treated juices did not recover during storage. The physicochemical and mechanical parameters of the formulations were significantly influenced by the choice of sweetener and the duration of storage. The gel surface got smoother and had fewer holes when the sucrose level dropped, according to a scanning electron microscopy study. The UV-C/H-treated samples did not differ in acceptability, whereas the measured sensory attributes approached ideal levels. F1 and F2 showed distinctive temporal-dominance-of-sensations profiles, mainly dominated by sweetness and orange taste, respectively. However, consumers perceived sourness and astringency in C during consumption.

CONCLUSION

The present study provides significant evidence in support of the development of confectionery gels F1 and F2 made from fruit juice treated by UV-C light assisted by mild heat and combinations of sucrose-alternative sweeteners. In terms of the properties investigated, these confectionery gels were comparable to, or even outperformed the full-sucrose option. © 2023 Society of Chemical Industry.

Oil addition increases the heat resistance of Clostridium sporogenes spores in braised sauce beef: Perspectives from spore surface characteristics and microstructure

During thermal processing of braised sauce beef, the lipid content of circularly used sauce increased accordingly because of lipid migration from beef to sauce, which may impact the bacterial heat resistance in the products. This study aims to characterize the heat resistance of Clostridium sporogenes spores in braised sauce beef, and investigate the effects of oil on the spore surface characteristics and microstructure. The results indicated that the heat resistance of C. sporogenes spores in beef was significantly higher than that in sauce. Oil addition remarkably enhanced the spore heat resistance in sauce, with D95°C value three times more than that without oil added, and even higher than that in beef. The results of spore surface characteristics indicated that oil addition led to an increase of hydrophobicity and a decrease of zeta potential, which ultimately increased spore heat resistance. Microstructure analysis indicated that exosporium maintenance and cortex expansion induced by oil addition might contribute to the increase of spore heat resistance. This study has sufficiently verified the importance of oil content on the heat resistance of C. sporogenes spores, which should be taken into consideration when developing thermal processes for controlling the spores in food matrices.

Heat inactivation of aqueous viable norovirus and MS2 bacteriophage

AIMS

This study aimed to compare the heat inactivation kinetics of viable human norovirus with the surrogate, MS2 bacteriophage as well as assess the decay of the RNA signal.

METHODS AND RESULTS

Human intestinal enteroids were used to analyze the heat inactivation kinetics of viable human norovirus compared to the surrogate MS2 bacteriophage, which was cultured using a plaque assay. Norovirus decay rates were 0.22 min-1, 0.68 min-1, and 1.11 min-1 for 50°C, 60°C, and 70°C, respectively, and MS2 bacteriophage decay rates were 0.0065 min-1, 0.045 min-1, and 0.16 min-1 for 50°C, 60°C, and 70°C, respectively. Norovirus had significantly higher decay rates than MS2 bacteriophage at all tested temperatures (P = .002-.007). No decrease of RNA titers as measured by reverse transcription-PCR for both human norovirus and MS2 bacteriophage over time was observed, indicating molecular methods do not accurately depict viable human norovirus after heat inactivation and treatment efficiency is underestimated.

CONCLUSIONS

Overall, our data demonstrate that MS2 bacteriophage is a conservative surrogate to measure heat inactivation and potentially overestimates the infectious risk of norovirus. Furthermore, this study corroborates that measuring viral RNA titers, as evaluated by PCR methods, does not correlate with the persistence of viable norovirus under heat inactivation.

Disentangling the contributions of initial heterogeneities and dynamic stress adaptation to nonlinearities in bacterial survival curves

The deviations from log-linearity that are often observed in bacterial survivor curves can be explained using different arguments, both biological and experimental. In this study, we used Bacillus subtilis as a model organism to demonstrate that the generally accepted vitalistic arguments (initial heterogeneities in the stress resistance of the cells in the population) may fail to describe microbial inactivation in some situations. In this sense, we showed how dynamic stress acclimation during an isothermal treatment provides an alternative explanation for survivor curves with an upwards curvature. We also provided an innovative experimental approach based on preadaptation experiments to evaluate which hypothesis is more suitable for the bacterial response. Furthermore, we used our experimental results to define bounds for the possible stress acclimation that may take place during dynamic treatments, concluding that the magnitude of stress acclimation may be larger for dynamic treatments than for isothermal experiments. We also evaluated the contribution of the SigB general stress response system to heat resistance by comparing the heat survival of wt and the ΔsigB mutant. Both strains survived better in 51, 52.5 and 55 °C when cells were pre-adapted at 48 °C than non-pre-adapted cells. However, ΔsigB was less resistant to heat than wt due to the missing SigB general stress system. Although these conclusions were based on B. subtilis as a model organism, this study can be the first step towards the development of a novel methodology able to estimate dynamic effects using only isothermal experiments. This would improve the models developed within the predictive microbiology community, improving our ability to predict microbial inactivation during industrial treatments, which are most often dynamic.

A New Ready-to-Eat Product Based on Enzymatically Peeled 'Hernandina' Clementine Segments and Citrus Syrup

Ready-to-eat fresh fruit have an increasing presence in international markets due to their convenience and health benefits. However, these products are highly perishable and efficient technologies to increase their shelf life are needed. In the present research, different citrus fruit species and cultivars from organic farming were assessed to obtain enzymatically peeled citrus segments. The best results in terms of segment quality were observed for 'Hernandina' clementine, which was chosen to make a new ready-to-eat product based on peeled citrus segments that were packaged in glass jars with a light syrup made of citrus juice and organic sugar cane. Different citrus juice mixtures were assayed and the most appreciated syrup, based on the sensory scores given by panellists, was that containing 50-50 (v/v) of 'Fino' lemon and 'Hernandina' clementine juices. In addition, different pasteurization treatments were assessed for their effects on conserving the safety, nutritional quality and sensory properties of the product during cold storage. The results show that pasteurization treatment at 50 °C for 45 min was sufficient to prevent microbial contamination with mesophilic and psychrophilic aerobic bacteria or yeast and mould and to maintain sensory properties until five weeks of storage at 4 °C. In addition, only a 10% reduction in vitamin C concentrations was observed in fresh-segments or syrup until the end of the storage period, showing that a high bioactive compound content and health benefits were conserved in the new ready-to-eat product after pasteurization and prolonged cold storage.

Processed foods: From their emergence to resilient technologies

Humans need food processing assuring food safety, quality, and functionality to sustain their life. The ongoing debates regarding food processing require rational and scientific data about food processing and processed foods. This study deals with the importance, origins, and history of processing, defining processes and discussing existing food classification systems and provides recommendations for future food process development. Descriptions and comparisons of technologies for food preservation, their resource efficiency, and beneficial aspects in relation to traditional processing are summarized. Possibilities for pretreatments or combination application and related potentials are provided. A consumer-oriented paradigm change is presented using the potential of resilient technologies for food product improvements rather than the traditional adaptation of raw materials to existing processes. Means for food science and technology research toward dietary changes by transparent, gentle, and resource-efficient processes for consumers food preference, acceptance, and needs are provided.

Perspectives on Novel Technologies of Processing and Monitoring the Safety and Quality of Prepared Food Products

With the changes of lifestyles and rapid growth of prepared food industry, prepared fried rice that meets the consumption patterns of contemporary young people has become popular in China. Although prepared fried rice is convenient and nutritious, it has the following concerns in the supply chain: (1) susceptible to contamination by microorganisms; (2) rich in starch and prone to stall; and (3) vegetables in the ingredients have the issues of water loss and discoloration, and meat substances are vulnerable to oxidation and deterioration. As different ingredients are used in prepared fried rice, their food processing and quality monitoring techniques are also different. This paper reviews the key factors that cause changes in the quality of prepared fried rice, and the advantages and limitations of technologies in the processing and monitoring processes. The processing technologies for prepared fried rice include irradiation, high-voltage electric field, microwave, radio frequency, and ohmic heating, while the quality monitoring technologies include Raman spectral imaging, near-infrared spectral imaging, and low-field nuclear magnetic resonance technology. These technologies will serve as the foundation for enhancing the quality and safety of prepared fried rice and are essential to the further development of prepared fried rice in the emerging market.

High-efficiency fungal pathogen intervention for seed protection: new utility of long-chain alkyl gallates as heat-sensitizing agents

Control of food-contaminating fungi, especially pathogens that produce mycotoxins, is problematic since effective method for intervening fungal infection on food crops is often limited. Generally Regarded As Safe (GRAS) chemicals, such as natural compounds or their structural derivatives, can be developed as antimicrobial agents for sustainable food/crop production. This study identified that long-chain alkyl gallates, i.e., octyl-, nonyl-, and decyl gallates (OG (octyl 3,4,5-trihydroxybenzoic acid), NG, DG), can function as heat-sensitizing agents that effectively prevent fungal contamination. Out of twenty-eight candidate compounds and six conventional antifungal agents examined, the heat-sensitizing capacity was unique to the long-chain alkyl gallates, where OG exhibited the highest activity, followed by DG and NG. Since OG is a GRAS compound classified by the United States Food and Drug Administration (FDA), further in vitro antifungal studies were performed using OG. When OG and mild heat (57.5°C) were co-administered for 90 seconds, the treatment achieved > 99.999% fungal death (> 5 log reduction). Application of either treatment alone was significantly less effective at reducing fungal survival. Of note, co-application of OG (3 mM) and mild heat (50°C) for 20 minutes completely prevented the survival of aflatoxigenic Aspergillus flavus contaminating crop seeds (Brassica rapa Pekinensis), while seed germination rate was unaffected. Heat-sensitization was also determined in selected bacterial strains (Escherichia coli, Agrobacterium tumefaciens). Altogether, OG is an effective heat-sensitizing agent for control of microbial pathogens. OG-mediated heat sensitization will improve the efficacy of antimicrobial practices, achieving safe, rapid, and cost-effective pathogen control in agriculture/food industry settings.

Influence of microbial cell morphology and composition on radio frequency heating of simple media at different frequencies

The effect of Listeria monocytogenes, Salmonella Typhimurium, and Saccharomyces cerevisiae on RF heating was studied in sterilized Milli-Q water and saline solution during treatments at 27.0 ± 0.6 MHz and 3.0 ± 0.02 MHz for 30 min. The presence of microorganisms caused a significant increase in temperature (maximum to 54.9 °C), with no significant decrease in cell numbers being observed for any conditions. For both media and frequencies, heating rates followed the order S. Typhimurium ≤ L. monocytogenes ≤ S. cerevisiae, except for heating at 3.0 ± 0.02 MHz in saline solution, where heating rates for S. cerevisiae and S. Typhimurium were equal. Generally, heating rates for microorganisms were significantly higher at 27.0 ± 0.6 MHz than at 3.0 ± 0.02 MHz, except for the S. cerevisiae case. Observed phenomena were probably caused by differences in the cell lipid and peptidoglycan content, with interaction effects with salt being present. This study was the first to investigate the influence of the presence of microorganisms on heating behavior of simple media. On the long term, more research on this topic could lead to finding specific RF frequencies more suitable for the heating of specific media and products for various applications.

The volatile profile of pasteurized leek (Allium ampeloprasum var. porrum) and Brussels sprouts (Brassica oleracea var. gemmifera) (products), as a witness to (bio)chemical reactivity, influenced by pretreatment and successive refrigerated storage

Processing can affect (bio)chemical conversions in vegetables and can act on their volatile properties accordingly. In this study, the integrated effect of pretreatment and pasteurization on the volatile profile of leek and Brussels sprouts and the change of this profile upon refrigerated storage were investigated. Pretreatments were specifically selected to steer biochemical reactivities to different extents. Volatile profiles were analyzed by headspace-solid phase microextraction-gas chromatography-mass spectrometry. For both vegetables, it was observed that different pretreatments prior to a pasteurization step led to diverse volatile profiles. The differences in volatile profiles observed in the different samples were presumably attributed to the different degrees of enzymatic conversions, further conversions of enzymatically formed products and thermally induced reactivities. Interestingly, the observed initial relative differences between volatile profiles of differently pretreated pasteurized samples were still observed after a refrigerated storage of 4 weeks at 4 °C. In conclusion, refrigerated storage only limitedly affected the resulting volatile profile.

Effects of Microwave Pasteurization on the Quality and Shelf-Life of Low-Sodium and Intermediate-Moisture Pacific Saury (Cololabis saira)

The objective of this study was to investigate the effects of microwave pasteurization on the quality and shelf-life of low-sodium and intermediate-moisture Pacific saury. Microwave pasteurization was used to process low-sodium (1.07% ± 0.06%) and intermediate-moisture saury (moisture content 30% ± 2%, water activity 0.810 ± 0.010) to produce high-quality ready-to-eat food stored at room temperature. Retort pasteurization with the same thermal processing level of F₉₀ = 10 min was used for comparison. Results showed that microwave pasteurization had significantly (p < 0.001) shorter processing times (9.23 ± 0.19 min) compared with traditional retort pasteurization (17.43 ± 0.32 min). The cook value (C) and thiobarbituric acid (TBARS) content of microwave-pasteurized saury were significantly lower than that of retort-pasteurized saury (p < 0.05). With more microbial inactivation, microwave pasteurization brought better overall texture than retort processing. After 7 days of storage at 37 °C, the total plate count (TPC) and TBARS of microwave pasteurized saury still met the edible standard, while the TPC of retort pasteurized saury no longer did. These results showed that the combined processing of microwave pasteurization and mild drying (Aw < 0.85) could produce high-quality ready-to-eat saury products. These results indicate a new methodology for producing high-quality products stored at room temperature.

Preserving Ready-to-Eat Meals Using Microwave Technologies for Future Space Programs

The crewed suborbital and space flights launched by private companies over the past three years have rejuvenated public interest in space travel, including space tourism. Ready-to-eat meals (MREs) are the main source of nutrients and energy for space travelers. It is critical that those meals are free of bacterial and viral pathogens and have adequate shelf life. The participation of private companies in space programs will create new opportunities and demand for high-quality and microbiologically safe MREs for future space travels. In this article, we provide a brief review of nutrition and energy requirements for human activities in space. We discuss the general thermal processing requirements for control of bacterial and viral pathogens in MREs and introduce advanced thermal preservation technologies based on microwaves for production of MREs with different shelf-lives under various storage conditions. We also present the latest advancements in the development of polymer packaging materials for quality preservation of thermally stabilized MREs over extended storage. Finally, we recommend future research on issues related to the sensory quality of specially formulated MREs, microbial safety of dried foods that complement high moisture MREs, and food package waste management in future space missions.

The importance of what we cannot observe: Experimental limitations as a source of bias for meta-regression models in predictive microbiology

Meta-regression models have gained in popularity during the last years as a way to create more generic models for Microbial Risk Assessments that also include variability. However, as with most meta-analyses and empirical models, systematic biases in the data can result in inaccurate models. In this article, we define experimental bias as a type of selection bias due to the practical limitations of microbial inactivation experiments. Conditions with extremely high D-values (i.e. slow inactivation) need very long experimental runs to cause significant reductions. On the other hand, when the D-value is extremely low, not enough data points can be gathered before the microbial population is below the detection limit. Consequently, experimental designs favour conditions within a practical experimental range, introducing a selection bias in the D-values. We demonstrate the impact of experimental bias in meta-regression models using numerical simulations. Models fitted to data with experimental bias overestimated the z-value and underestimated variability. We propose a rapid heuristic method to identify experimental bias in datasets, and we propose truncated regression to mitigate its impact in meta-regression models. Both methods were validated using simulated data. Thereafter the procedures were tested by building a meta-regression model for actual data for the inactivation of Bacillus cereus spores. We concluded that the dataset included experimental bias, and that it would cause an overestimation of the microbial resistance at high temperatures (>120 °C) for classical meta-regression models. This effect was mitigated when the model was built using truncated regression. In conclusion, we demonstrate that experimental bias could potentially result in inaccurate models for predictive microbiology. Therefore, checking for experimental bias should be a routine step in meta-regression modelling, and be included in guidelines on data analysis for meta-regression.

Inactivation of Alicyclobacillus acidoterrestris spores, single or composite Escherichia coli and native microbiota in isotonic fruit-flavoured sports drinks processed by UV-C light

Pasteurized sports drinks and other fruit-based beverages are susceptible to deterioration due to thermal processing ineffectiveness to inactivate certain spoilage microorganisms, like Alicyclobacillus acidoterrestris. This represents a major challenge for the beverage industry. The goals of this study were to: i) investigate the UV-C inactivation (annular thin film unit, actinometrical delivered fluence: 795-1270 mJ/cm², 10-15 min, 20 °C, 1.8 L/h, Re_h = 391-1067, recirculation mode operation) and the evolution during refrigerated storage of A. acidoterrestris ATCC 49025 spores and single or composite Escherichia coli ATCC 25922 in isotonic sports drinks (ISDs) made from orange (orange-ISD, UVT% = 81) or orange-banana-mango-kiwi-strawberry-lemon juices (multi-fruit-ISD, UVT% = 91), compared to a turbid orange-tangerine juice (OT juice, UVT% = 40); ii) assess the effect of pH, °Brix, A_254nm, turbidity, colour and particle size of the ISDs and juice on microbial inactivation, iii) evaluate the evolution of native microbiota during cold storage, iv) investigate the Coroller, biphasic, Weibull, and Weibull-plus-tail models' ability to describe microbial inactivation and v) measure 5-hydroxymethylfurfural (HMF) formation. The modified biodosimetry method was used to calculate the germicidal UV-C fluences. Heat pasteurization (T-coil, 80 °C/6 min) was evaluated as the control treatment. UV-C was highly effective at inactivating E. coli as 4.1-5.1 and 4.5-5.6 log reductions were determined in the multi-fruit-ISD and orange-ISD, respectively, barely impacted by the background microbiota. No significant differences were recorded for the inactivation of E. coli in the UV-C and T-coil systems. Whereas, a significantly higher inactivation of A. acidoterrestris spores was achieved by UV-C (3.7-4.0 log reductions), compared to the negligible one achieved by the thermal treatment. Even though E. coli inactivation curves were similar in shape, UV-C was less effective when a cocktail of other E. coli strains was present. In comparison to the OT juice, the ISDs' inactivation kinetics were markedly different in shape, with a rapid decrease in population during the first minutes of treatment. The germicidal fluence (H_{d biod}) corresponding to A. acidoterrestris (19.1 mJ/cm²) was selected as it was higher than the one obtained for E. coli (11.0 mJ/cm²). UV-C induced 2.8- or 1.3 and 2.3- or 0.8 log-reductions of total aerobes or moulds and yeasts in the multi-fruit-ISD and orange-ISD, respectively. Compared to the other models, the Coroller and biphasic models showed a better fit and more accurate parameter estimates. UV-C-induced HMF production was not significant in the ISDs. The current study found that the UV-C treatment was more effective than typical heat pasteurization for inactivating A. acidoterrestris spores in isotonic drinks, following a similar trend for E. coli and native microbiota.

Estimation of Bacteriophage MS2 Inactivation Parameters During Microwave Heating of Frozen Strawberries

Frozen berries have been repeatedly linked to acute gastroenteritis caused by norovirus, the most common cause of foodborne illness in the United States. Many guidelines recommend that frozen berries be microwaved for at least 2 min, but it is unclear if this thermal treatment is effective at inactivating norovirus. The objective of this study was to model the effect of microwave heating at varying power levels on the survival of bacteriophage MS2, a norovirus surrogate, when inoculated onto frozen strawberries. Bacteriophage MS2 was inoculated onto the surface of frozen strawberries with a starting concentration of approximately 10 log PFU/g. Samples (either 3 or 5 whole strawberries) were heated in a 1300-Watt domestic research microwave oven (frequency of 2450 MHz) at power levels of 30, 50, 70, and 100% (full power), for times ranging from 15 to 300 s to determine inactivation. Temperatures at berry surfaces were monitored during heating using fiberoptic thermometry. All experiments were conducted in triplicate. The primary model for thermal inactivation was a log-linear model of logN vs. time. The secondary model was for a D-value decreasing linearly with temperature and an added term that was path-dependent on the thermal history. Parameters in the model were estimated using dynamic temperature history at the surface of the berry, via nonlinear regression using all data simultaneously. The root mean square error was ∼0.5 PFU/g out of a total 6-log reduction. Log reductions of 1.1 ± 0.4, 1.5 ± 0.5, 3.1 ± 0.1, and 3.8 ± 0.2 log PFU/g were observed for 30, 50, 70, and 100% microwave power levels when three berries were heated for 60 s. D-values were 21.4 ± 1.95 s and 10.6 ± 1.1 s at 10 and 60°C, respectively. This work demonstrates an approach to estimate inactivation parameters for viruses from dynamic temperature data during microwave heating. These findings will be useful in predicting the safety effect of microwave heating of berries in the home or food service.

Criteria and methodologies for determining the causes of swelling of canned tomatoes in tinplate containers

This review provides the current laboratory criteria for the detection and evaluation of the possible causes of alteration of non-concentrated industrial derivatives of tomatoes (peeled tomatoes, pulps, purees, sauces, and fillets), packaged in coated or uncoated tinplate cans. We discuss how the product alterations are typically the consequence of technological errors either in the can production, or in the storage process, or in the product sterilization. The described procedures include the quantitative determination of the distribution of gases (H₂ , CO₂ , N₂ , and O₂ ) present in the headspace of the container. The gas composition and ratios can be used as markers to allow easy diagnosis of the causes of microbiologic and/or physical-chemical alterations of the tomatoes, which are usually made evident by swelling of the containers. These tests should be integrated by microbiological analyses aimed at a restricted group of microorganisms, with the chemical analysis of the container and the chemical analysis of the altered product. By way of example, we report the assessment of the causes of alteration in four different case-studies.

A Comprehensive Review of Variability in the Thermal Resistance (D-Values) of Food-Borne Pathogens-A Challenge for Thermal Validation Trials

The thermal processing of food relies heavily on determining the right time and temperature regime required to inactivate bacterial contaminants to an acceptable limit. To design a thermal processing regime with an accurate time and temperature combination, the D-values of targeted microorganisms are either referred to or estimated. The D-value is the time required at a given temperature to reduce the bacterial population by 90%. The D-value can vary depending on various factors such as the food matrix, the bacterial strain, and the conditions it has previously been exposed to; the intrinsic properties of the food (moisture, water activity, fat content, and pH); the method used to expose the microorganism to the thermal treatment either at the laboratory or commercial scale; the approach used to estimate the number of survivors; and the statistical model used for the analysis of the data. This review focused on Bacillus cereus, Cronobacter sakazakii, Escherichia coli, Listeria monocytogenes, and Clostridium perfringens owing to their pathogenicity and the availability of publications on their thermal resistance. The literature indicates a significant variation in D-values reported for the same strain, and it is concluded that when designing thermal processing regimes, the impact of multiple factors on the D-values of a specific microorganism needs to be considered. Further, owing to the complexity of the interactions involved, the effectiveness of regimes derived laboratory data must be confirmed within industrial food processing settings.

High-pressure pasteurization of low-acid chilled ready-to-eat food

The working population growth have created greater consumer demand for ready-to-eat (RTE) foods. Pasteurization is one of the most common preservation methods for commercial production of low-acid RTE cold-chain products. Proper selection of a pasteurization method plays an important role not only in ensuring microbial safety but also in maintaining food quality during storage. Better retention of flavor, color, appearance, and nutritional value of RTE products is one of the reasons for the food industry to adopt novel technologies such as high-pressure processing (HPP) as a substitute or complementary technology for thermal pasteurization. HPP has been used industrially for the pasteurization of high-acid RTE products. Yet, this method is not commonly used for pasteurization of low-acid RTE food products, due primarily to the need of additional heating to thermally inactivate spores, coupled with relatively long treatment times resulting in high processing costs. Practical Application: Food companies would like to adopt novel technologies such as HPP instead of using conventional thermal processes, yet there is a lack of information on spoilage and the shelf-life of pasteurized low-acid RTE foods (by different novel pasteurization methods including HPP) in cold storage. This article provides an overview of the microbial concerns and related regulatory guidelines for the pasteurization of low-acid RTE foods and summarizes the effects of HPP in terms of microbiology (both pathogens and spoilage microorganisms), quality, and shelf-life on low-acid RTE foods. This review also includes the most recent research articles regarding a comparison between HPP pasteurization and thermal pasteurization treatments and the limitations of HPP for low-acid chilled RTE foods.

The Most Probable Curve method - A robust approach to estimate kinetic models from low plate count data resulting in reduced uncertainty

A novel method is proposed for fitting microbial inactivation models to data on liquid media: the Most Probable Curve (MPC) method. It is a multilevel model that makes a separation between the "true" microbial concentration according to the model, the "actual" concentration in the media considering chance, and the actual counts on the plate. It is based on the assumptions that stress resistance is homogeneous within a microbial population, and that there is no aggregation of microbial cells. Under these assumptions, the number of colonies in/on a plate follows a Poisson distribution with expected value depending on the proposed kinetic model, the number of dilutions and the plated volume. The novel method is compared against (non)linear regression based on a normal likelihood distribution (traditional method), Poisson regression and gamma-Poisson regression using data on the inactivation of Listeria monocytogenes. The conclusion is that the traditional method has limitations when the data includes plates with low (or zero) cell counts, which can be mitigated using more complex (discrete) likelihoods. However, Poisson regression uses an unrealistic likelihood function, making it unsuitable for survivor curves with several log-reductions. Gamma-Poisson regression uses a more realistic likelihood function, even though it is based mostly on empirical hypotheses. We conclude that the MPC method can be used reliably, especially when the data includes plates with low or zero counts. Furthermore, it generates a more realistic description of uncertainty, integrating the contribution of the plating error and reducing the uncertainty of the primary model parameters. Consequently, although it increases modelling complexity, the MPC method can be of great interest in predictive microbiology, especially in studies focused on variability analysis.

Exploratory Study for Probiotic Enrichment of a Sea Fennel (Crithmum maritimum L.) Preserve in Brine

Considering the increasing consumer demand for vegan and vegetarian health foods, different vegetables have been already exploited to produce non-dairy probiotic foods. In addition to being rich in bioactive compounds, sea fennel (Crithmum maritimum L.), also known as rock samphire, represents a valuable candidate in the production of probiotic-enriched foods, and, to the authors' knowledge, it has not yet been explored as carrier for probiotics. Hence, the present study was aimed at evaluating the survival of a commercially available probiotic formulation, SYNBIO^®, and Lactiplantibacillus plantarum IMC 509 in an artificially acidified, pasteurized sea fennel preserve in brine during a refrigerated storage of 44 days. Despite slight reductions in the microbial loads, at the end of the storage, both the probiotic formulations showed loads higher than 7.0 Log CFU g^-1 of sea fennel or mL^-1 of brine, above the recommended administration dose to exert beneficial health effects. Thus, acidified sea fennel sprouts in brine represent a potential vehicle for probiotics delivery to humans.

Microbiological safety and stability of novel green sauces made with sea fennel (Crithmum maritimum L.)

Due to consumers' demand for ready-to-eat foods, in the last decades production of sauces has shifted from home-made to commercial practice. Besides to palatability and nutritional value, safety and stability are key issues of industrial sauces. The present study was aimed at evaluating the microbiological stability and safety of industrial-scale prototypes of two novel green sauces made with sea fennel (Crithmum maritimum L.) as the main ingredient. To this end, accelerated shelf-life and microbial challenge tests were performed to assess: (i) the microbiological shelf-stability of the two sauces stabilized by heat treatments commonly applied at industrial scale to inactivate vegetative cells of spoilage microorganisms and pathogens in vegetable preserves (F₈₅⁷=2min or F₉₅⁷=5min); and (ii) the inhibition of Staphylococcus aureus and Bacillus cereus in the sauce with pH = ∼ 4.6 and a_w < 0.92, subjected to mild pasteurization (F₇₅⁷=1or2min). The results overall collected through the accelerated shelf-life tests clearly demonstrated the microbiological shelf-stability during one month of storage at thermal abuse conditions of both the novel sauces assayed; moreover, the microbial challenge tests revealed that both mild heat treatments assayed were able to inactivate S. aureus; in addition, an inhibition of the growth of B. cereus was seen during storage at 37 °C. Results from this study are expected to be useful both from a scientific and technological standpoint, enabling efficient risk-based development of novel acidified food products.

Application of High Hydrostatic Pressure in fresh purple smoothie: Microbial inactivation kinetic modelling and qualitative studies

The inactivation kinetics of Listeria monocytogenes during High Hydrostatic Pressure (HHP) treatments was studied in a purple smoothie based of fresh fruit and vegetables. Pressure intensity studied was 300, 350, 400 and 450 MPa. Untreated samples were used as control. Furthermore, the effects on quality attributes (sensory, total soluble solids content, colour, titratable acidity, pH, vitamin C and total phenolics content) were also monitored. Microbial inactivation was modelled as a function of the HHP intensity using the Geeraerd model. Shoulder and tail effects were observed only for the 300 MPa pressure assayed, supporting a multiple hit kinetic inactivation of critical factors. Increasing the HHP intensity resulted in a faster inactivation with tailing. A strong positive correlation was observed between the pressure level and the inactivation rate (k). Hence, a linear model was used to describe the relationship between both variables. Nevertheless, further data are required to confirm this secondary model. Quality was mostly unaffected by the HHP treatments, except for the vitamin C content, which reported reductions of 26 and 21% after 300 and 350 MPa, respectively. In conclusion, HHP can be a viable technology for processing fruit and vegetable-based smoothies to preserve quality and safety. A pressure of 400 MPa is advisable to ensure an efficient microbial inactivation with the best sensory and nutritional quality retention.

Effect of thermal processing on quality of tender jackfruit in tin-free-steel cans

Thermal processing is the most efficient and economical technique for the long-term preservation of tender jackfruit in ready-to-cook form on a commercial-scale. Although, thermal processing primarily focus on microbiological safety of the product, the associated quality changes need to be examined as it is decisive of consumer acceptance. The present study investigated the effect of two pasteurization (90 and 100 °C) and sterilization temperatures (110 and 121 °C) at different lethality on microbiological, colour, texture, ascorbic acid (AA), total flavonoid (TFC) and phenol (TPC) contents of tender jackfruit processed in tin-free-steel (TFS) cans. Time required for thermal processing was computed from respective heat penetration curve. Thermal processing improved both the TFC and TPC of tender jackfruit, while colour, texture and AA had degraded. Based on microbiological and physicochemical quality analyses, the study adjudged pasteurization at 90 °C for 19 min and sterilization at 121 °C for 8 min as the best temperature-time combination for thermal processing of tender jackfruit in TFS cans.

The Different Response to an Acid Shock of Two Salmonella Strains Marks Their Resistance to Thermal Treatments

Microbial cells respond to sub-lethal stresses with several physiological changes to increase their chance of survival. These changes are of high relevance when combined treatments (hurdle technology) are applied during food production, as the cells surviving the first hurdle may have greater resistance to subsequent treatments than untreated cells. In this study, we analyzed if Salmonella develops increased resistance to thermal treatments after the application of an acid shock. We compared the heat resistance of acid-shocked (pH 4.5 achieved with citric acid) Salmonella cells with that of cells maintained at pH 7 (control cells). Thermal treatments were performed between 57.5 and 65°C. We observed a differential response between the two strains studied. Acid-shocked cells of Salmonella Senftenberg exhibited reduced heat resistance, e.g., for a treatment at 60.0°C and pH 7.0 the time required to reduce the population by 3 log cycles was lowered from 10.75 to 1.98min with respect to control cells. Salmonella Enteritidis showed a different response, with acid-shocked cells having similar resistance than untreated cells (the time required to reduce 3 log cycles at 60.0°C and pH 7.0 was 0.30min for control and 0.31min for acid-shock cells). Based on results by differential plating (with or without adding the maximum non-inhibitory concentration of NaCl to the recovery medium), we hypothesize that the differential response between strains can be associated to sub-lethal damage to the cell membrane of S. Senftenberg caused by the acid shock. These results provide evidence that different strains of the same species can respond differently to an acid shock and highlight the relevance of cross-resistances for microbial risk assessment.

Does the order of presentation of extrinsic and intrinsic quality attributes matter when eliciting willingness to pay?

In this study, we estimate consumers' willingness to pay (WTP) for ready meals preserved using microwave assisted pasteurization systems (MAPS)-a novel pasteurization technology, compared to frozen, ready meals. We conducted a laboratory multi-round experimental auction for two samples of ready meal jambalaya in which appearance and sensory evaluation along with extrinsic information was sequentially disclosed to panelists. Our results suggest that when participants tasted the meals and formed an opinion from the meal itself, the liking of appearance and sensory attributes were the most impactful factors for participants' WTP regardless of other available extrinsic (name of the preservation technology and environmental impacts of each technology) attributes. The words "microwave" and "pasteurization" did not negatively impact the WTP. The order in which intrinsic and extrinsic attributes were evaluated and presented did not impact absolute WTP values, but the order did impact the weight of each attribute type on the WTP. PRACTICAL APPLICATION: The sensory perceptions had a larger effect than the name of the preservation technology and environmental impacts on the willingness to pay (WTP) for ready meals. The order of presented information to panelists did not impact absolute values of WTP. The words "microwave" and "pasteurization" did not have a negative effect on WTP.

Impact of Heating Rates on Alicyclobacillus acidoterrestris Heat Resistance under Non-Isothermal Treatments and Use of Mathematical Modelling to Optimize Orange Juice Processing

Alicyclobacillus acidoterrestris is a spoilage microorganism responsible for relevant product and economic losses in the beverage and juice industry. Spores of this microorganism can survive industrial heat treatments and cause spoilage during posterior storage. Therefore, an effective design of processing treatments requires an accurate understanding of the heat resistance of this microorganism. Considering that industrial treatments are dynamic; this understanding must include how the heat resistance of the microorganism is affected by the heating rate during the heating and cooling phases. The main objective of this study was to establish the effect of heating rates and complex thermal treatments on the inactivation kinetics of A. acidoterrestris. Isothermal experiments between 90 and 105 °C were carried out in a Mastia thermoresistometer, as well as four different dynamic treatments. Although most of the inactivation takes place during the holding phase, our results indicate the relevance of the heating phase for the effectiveness of the treatment. The thermal resistance of A. acidoterrestris is affected by the heating rate during the heating phase. Specifically, higher heating rates resulted in an increased microbial inactivation with respect to the one predicted based on isothermal experiments. These results provide novel information regarding the heat response of this microorganism, which can be valuable for the design of effective heat treatments to improve product safety and stability. Moreover, it highlights the need to incorporate experimental data based on dynamic treatments in process design, as heating rates can have a very significant effect on the thermal resistance of microorganisms.