High pressure processing pretreatment enhanced the thermosonication inactivation of Alicyclobacillus acidoterrestris spores in orange juice

Effects of Thermosonication on the Antioxidant Capacity and Physicochemical, Bioactive, Microbiological, and Sensory Qualities of Blackcurrant Juice

This study investigated the effects of thermosonication (TS) on the quality of blackcurrant juice, along with its physicochemical properties, bioactive compounds, antioxidant capacity, and microbiological and sensory qualities. The treatments included raw juice (RJ), pasteurized juice (90 °C, 1 min, PJ), and thermosonicated juice (480 W, 40 kHz at 40, 50, or 60 °C, for 10, 20, 30, or 40 min, TJ). The results indicated that the effects of pasteurization and thermosonication on the pH, total soluble solids, and titratable acidity of the juice were not significant (p > 0.05). However, the cloudiness, browning index, and viscosity were significantly increased (p < 0.05), and the color properties of the blackcurrant juice were improved. The total phenolic, flavonoid, and anthocyanin contents of TJ (treated at 50 °C for 30 min) were increased by 12.6%, 20.9%, and 40.4%, respectively, and there was a notable decline in ascorbic acid content after the pasteurization treatment, while the loss was minor in all TJ samples compared with RJ. The scavenging ability of 1,1-diphenyl-2-pyridyl and hydroxyl radicals increased to 52.77% and 50.52%, respectively, which were significantly (p < 0.05) higher than those in the RJ and PJ samples. In addition, both pasteurization and thermosonication resulted in a significant (p < 0.05) reduction in microbial counts, while there were no significant (p > 0.05) differences in the sensory parameters compared with the RJ samples. In conclusion, this study suggests that TS is an effective method that can be used as an alternative to pasteurization to improve the quality of blackcurrant juice.

Application and potential of multifrequency ultrasound in juice industry: Comprehensive analysis of inactivation and germination of Alicyclobacillus acidoterrestris spores

The majority of acidic fruits are perishable owing to their high-water activity, which promotes microbial activity, thus exhibiting metabolic functions that cause spoilage. Along with sanitary practices, several treatments are used during processing and/or storage to inhibit the development of undesirable bacteria. To overcome the challenges caused by mild heat treatment, juice manufacturers have recently increased their involvement in developing novel non-thermal processing procedures. Ultrasonication alone or in combination with other hurdle technologies may be used to pasteurize processed fruit juices. Multifrequency ultrasound has gained popularity due to the fact that mono-frequency ultrasound has less impact on bacterial inactivation and bioactive compound enhancement of fruit juice. Here, we present and discuss the fundamental information and technological knowledge of how spoilage bacteria, specifically Alicyclobacillus acidoterrestris, assemble resistant spores and inactivate and germinate dormant spores in response to nutrient germinants and physical treatments such as heat and ultrasound. To the authors' knowledge, no prior review of ultrasonic inactivation and germination of A. acidoterrestris in fruit juice exists. Therefore, this article aims to provide a review of previously published research on the inactivation and germination of A. acidoterrestris in fruit juice by ultrasound and heat.

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.

Bovicin HC5 and nisin reduce cell viability and the thermal resistance of Alicyclobacillus acidoterrestris endospores in fruit juices

BACKGROUND

Alicyclobacillus acidoterrestris is an important thermoacidophilic spore-forming bacterium in fruit-juice deterioration, and alternative non-thermal methods have been investigated to control fruit juice spoilage. This work aimed to evaluate the capacity of bovicin HC5 and nisin to inhibit the growth of vegetative cells and reduce the thermal resistance of endospores of A. acidoterrestris inoculated (10⁷ CFU mL^-1 ) in different fruit juices. The number of viable cells was determined after 12 h incubation at 43 °C in the presence and absence of nisin or bovicin HC5 (10-100 AU mL^-1 ). The exposure time (min) required to kill 90% of the initial population (reduction of one log factor) at 90 ºC (D_90ºC ) was used to assess the thermal resistance of A. acidoterrestris endospores exposed (80 AU mL^-1 ) or non-exposed to the bacteriocins. Additionally, the effect of bovicin and nisin on the morphology and cell structure of A. acidoterrestris was evaluated by atomic force microscopy (AFM).

RESULTS

Bovicin HC5 and nisin were bactericidal against A. acidoterrestris inoculated in fruit juices and reduced the D_90°C values up to 30-fold. AFM topographical images revealed substantial structural changes in the cellular framework of vegetative cells upon treatment with bovicin HC5 or nisin.

CONCLUSIONS

These results emphasize the potential application of lantibiotics as additional hurdles in food processing to control thermoacidophilic spoilage bacteria in fruit juices. © 2022 Society of Chemical Industry.

The Effect of Temperature-Assisted High Hydrostatic Pressure on the Survival of Alicyclobacillus acidoterrestris Inoculated in Orange Juice throughout Storage at Different Isothermal Conditions

The purpose of this work was to investigate the population dynamics of the spores and vegetative cells of A. acidoterrestris in orange juice treated with temperature-assisted HHP and stored in different isothermal conditions. For this reason, the spores of two A. acidoterrestris strains were inoculated in commercial orange juice and subjected to HHP treatment at 600 MPa/60 °C for 5 and 10 min. Inoculated samples were subsequently stored at 4, 12 and 25 °C for 60 days. During storage, the population of A. acidoterrestris was determined before and after heat shock at 80 °C for 10 min in order to estimate the quantity of spores and any remaining vegetative cells on the Bacillus acidoterrestris medium agar. Results showed that spore populations decreased by 3.0–3.5 log cycles directly after HHP treatment. Subsequently, no significant changes were observed throughout storage regardless of temperature and bacterial strain. However, at 25 °C, an increase of 0.5–1.0 log cycles was noticed. For the remaining vegetative cells, the results illustrated that HHP treatment could eliminate them during storage at 4 and 12 °C, whereas at 25 °C inactivation was strain-dependent. Therefore, temperature-assisted HHP treatment could effectively inactivate A. acidoterrestris spores in orange juice and ensure that the inhibitory effect could be maintained throughout storage at low temperatures.

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&amp;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.

Inactivation kinetics of pathogenic bacteria in persimmon using the combination of thermosonication and formic acid

Four models (Baranyi, modified Gompertz, log-logistic and Weibull models) were applied to examine the performance of thermosonication (TS) and formic acid (FA), individually and in combination, at three temperatures (40, 50, and 60°C) for the inactivation of pathogens inoculated on persimmon. Results indicated that all nonlinear kinetic models provided a good fit to data; however, the Baranyi showed the best performance in fitting data. The combined treatment of FA and TS had a higher negative impact on the microbial population compared to each treatment alone. The highest lethal impact was observed at 60 °C and in TS-3%FA treatment, which reduced the initial population of Escherichia coli, Salmonella enterica subsp. enterica, and Listeria monocytogenes (8.1 log CFU/mL) to 2.2, 1.6, and 1.3 log CFU/mL, respectively. Hence, the obtained models can be used to predict the inactivation of pathogens in a food model subjected to the combined treatment of thermosonication and FA.

Fruit Juice Spoilage by Alicyclobacillus: Detection and Control Methods—A Comprehensive Review

Fruit juices have an important place in humans’ healthy diet. They are considered to be shelf stable products due to their low pH that prevents the growth of most bacteria. However thermo-acidophilic endospore forming bacteria of the genus Alicyclobacillus have the potential to cause spoilage of commercially pasteurized fruit juices. The flat sour type spoilage, with absence of gas production but presence of chemical spoilage compounds (mostly guaiacol) and the ability of Alicyclobacillus spores to survive after pasteurization and germinate under favorable conditions make them a major concern for the fruit juice industry worldwide. Their special characteristics and presence in the fruit juice industry has resulted in the development of many isolation and identification methods based on cell detection (plating methods, ELISA, flow cytometry), nucleic acid analysis (PCR, RAPD-PCR, ERIC-PCR, DGGE-PCR, RT-PCR, RFLP-PCR, IMS-PCR, qPCR, and 16S rRNA sequencing) and measurement of their metabolites (HPLC, GC, GC-MS, GC-O, GC-SPME, Electronic nose, and FTIR). Early detection is a big challenge that can reduce economic loss in the industry while the development of control methods targeting the inactivation of Alicyclobacillus is of paramount importance as well. This review includes a discussion of the various chemical (oxidants, natural compounds of microbial, animal and plant origin), physical (thermal pasteurization), and non-thermal (High Hydrostatic Pressure, High Pressure Homogenization, ultrasound, microwaves, UV-C light, irradiation, ohmic heating and Pulse Electric Field) treatments to control Alicyclobacillus growth in order to ensure the quality and the extended shelf life of fruit juices.

Resistance of Eupenicillium javanicum mold spores to the light-emitting diode (LED), LED-assisted thermal and thermal processing in strawberry and apple juices

The use of light-emitting diode (LED) technology for the non-thermal processing of foods is a major topic of interest among various research groups. This study is aimed at inactivating the Eupenicillium javanicum ascospores present in strawberry and apple juices using a combination of a visible LED (vis-LED, 430–630 nm, 216–420 J/cm²) and 90 °C thermal treatment, as well as to compare the findings with the inactivation done using thermal-processes alone. The results showed that violet-blue LEDs within the range of 430 and 460 nm with an energy between 300 and 420 J/cm² were better for the inactivation of E. javanicum ascospores than the green and red LEDs which were within the 550–630 nm region with an energy range from 216 to 264 J/cm². Furthermore, the inactivation process conducted using vis-LED was affected by the juice's soluble solid contents and the calculated D_LED-values were within the range of 116.3 J/cm² to 277.8 J/cm² in juices with a Brix scale value of 10–20°. Finally, the inactivation rate obtained from combining a violet-blue LED with a 90 °C thermal treatment was similar to the rate of using the thermal treatment alone.

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Effect of visible (vis-) LED treatment on inactivation E. javanicum spores was studied.

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Maximum log reduction was obtained with LED in the violet-blue region.

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E. javanicum spores showed higher LED resistance in apple juice than in strawberry juice.

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Soluble solid has an effect on E. javanicum inactivation by vis-LED.

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Similar thermal inactivation rates were observed between vis-LED + heat and heat alone.

Purification and Characterization of Plantaricin YKX and Assessment of Its Inhibitory Activity Against Alicyclobacillus spp

Consumers prefer natural over synthetic chemical preservatives on a food label. Therefore, it is crucial to ensure the safety and efficacy of such natural preservatives. The emergence of heat-resistant spore-forming Alicyclobacillus spp. has been associated with spoilage problems in the fruit juice industry. Herein, a bacteriocin-producing stain YKX was isolated from the traditional pickles in Hanzhong City, China, and it was identified as Lactobacillus plantarum by morphological, biochemical, physiological, and genotypic features. A stable bacteriocin, plantaricin YKX, was isolated, purified, and tested for its efficacy against Alicyclobacillus acidoterrestris. Plantaricin YKX is a 14-amino acid peptide (Lys-Tyr-Gly-Asn-Gly-Leu-Ser-Arg-Ile-Phe-Ser-Ala-Leu-Lys). Its minimal inhibitory concentrations (MICs) against the tested bacterial and fungal strains were ranged from 16 to 64 μg/mL. It is thermostable and active at pH 3-8. The flow cytometry data and microscopic observations suggested that plantaricin YKX can augment cell membrane permeability, induce potassium ion leakage and pore formation, and disrupt cell membranes. It also affects spore germination and guaiacol production of A. acidoterrestris, probably due to upregulation of the luxS gene linked to quorum sensing.

Thermosonication effect on bioactive compounds, enzymes activity, particle size, microbial load, and sensory properties of almond (Prunus dulcis) milk

The object of this research was to appraise the physicochemical characteristics of almond milk and consumer acceptability after the thermosonication (TS) processing. The almond milk was subjected to TS processing (frequency: 40 kHz; power: 600 W; Temperature: 30, 45, and 60 °C; Time: 10, 20, 30, and 40 min) and pasteurization (for 60 s at 90 °C). After treatments, all samples were analyzed for bioactive compounds, antioxidant activities, microbial, enzymatic, and sensory attributes. The results showed a non-significant difference in total soluble solids and pH while TS processing at 45 and 60 °C significantly increased the cloudiness, viscosity, browning index, and color properties. TS processing increased the bioavailability of total phenolic, flavonols, flavonoids, condensed tannin contents, and antioxidant activity as compared to untreated and pasteurized samples. TS processing also significantly reduced the particle size distribution through acoustic cavitation. Microbial inactivation with TS at 60 °C resulted in ≥ 5 log reduction oftotal plate count and ≥ 4 log reduction ofyeast & moldwas achieved. The highest inhibition of lipoxygenase (LOX) and peroxidase (POD) were observed at 60 °C for 30 min. Moreover, the best sensorial properties were observed after TS processing at 60 °C. Thus; TS processing can increase the almond milk quality and safety as a viable substitute for thermal processing.

Recent trends in bacterial decontamination of food products by hurdle technology: A synergistic approach using thermal and non-thermal processing techniques

Researchers are continuously discovering varied technologies for microbial control to ensure worldwide food safety from farm-to-fork. The microbial load and virulence of spoilage causing microorganisms, including bacteria, fungi, yeasts, virus, and protozoa, determines the extent of microbial contamination in a food product. Certain pathogenic microbes can cause food poisoning and foodborne diseases, and adversely affect consumers' health. To erade such food safety-related problems, various traditional and novel food processing methods have been adopted for decades. However, some decontamination techniques bring undesirable changes in food products by affecting their organoleptic and nutritional properties. Combining various thermal and non-thermal food processing methods is an effective way to impart a synergistic effect against food spoilage microorganisms and can be used as an alternative way to combat certain limitations of food processing technologies. The combination of different techniques as hurdles put the microorganisms in a hostile environment and disturbs the homeostasis of microorganisms in food temporarily or permanently. Optimization and globalization of these hurdle combinations is an emerging field in the food processing sector. This review gives an overview of recent inventions in hurdle technology for bacterial decontamination, combining different thermal and non-thermal processing techniques in various food products.

Inactivation Effect of Thymoquinone on Alicyclobacillus acidoterrestris Vegetative Cells, Spores, and Biofilms

Alicyclobacillus acidoterrestris (A. acidoterrestris), a spore-forming bacterium, has become a main challenge and concern for the juices and acid beverage industry across the world due to its thermo-acidophilic characteristic. Thymoquinone (TQ) is one of the active components derived from Nigella sativa seeds. The objective of this study was to investigate antibacterial activity and associated molecular mechanism of TQ against A. acidoterrestris vegetative cells, and to evaluate effects of TQ on A. acidoterrestris spores and biofilms formed on polystyrene and stainless steel surfaces. Minimum inhibitory concentrations of TQ against five tested A. acidoterrestris strains ranged from 32 to 64 μg/mL. TQ could destroy bacterial cell morphology and membrane integrity in a concentration-dependent manner. Field-emission scanning electron microscopy observation showed that TQ caused abnormal morphology of spores and thus exerted a killing effect on spores. Moreover, TQ was effective in inactivating and removing A. acidoterrestris mature biofilms. These findings indicated that TQ is promising as a new alternative to control A. acidoterrestris and thereby reduce associated contamination and deterioration in the juice and acid beverage industry.

Effect of temperature and soluble solid on Bacillus subtilis and Bacillus licheniformis spore inactivation and quality degradation of pineapple juice

Bacillus subtilis and Bacillus licheniformis spores can survive processing temperatures used in the thermal processes of high-acid foods. Therefore, this study investigated the thermal inactivation of B. subtilis and B. licheniformis spores in pineapple juice at different temperatures (85-100°C) and soluble solids (SS, 11-30°Brix). The quality of juices and microbial loads after the thermal treatments during storage at 4 °C for 35 days was then checked. A linear decrease in D-value was observed with increasing temperature of treatment. Furthermore, the D-values determined in pineapple juice were: D_90°C=13.2 ± 0.5 mins, D_95°C = 6.8 ± 0.9 mins and D_100°C = 2.1 ± 1.7 mins for B. subtilis spores, and D_85°C = 16.6 ± 0.4 mins, D_90°C = 7.6 ± 0.5 mins and D_95°C = 3.6 ± 1.5 min, for B. licheniformis. Generally, the susceptibility of the bacteria to soluble solid change was affected by the interaction between temperature, SS and strain. In addition, pasteurization processes of ≥95°C for ≥33.8 mins was needed to ensure a recommended 5-log reduction of B. subtilis spores and limit vitamin C degradation of pineapple juice within three-week of storage at 4 °C.

Effect of thermosonication on quality attributes of hog plum (Spondias mombin L.) juice

The use of thermosonication (TS) technique to preserve the qualities of fruit juice as an alternative to conventional pasteurization has attracted research interest in recent times. In the present study, freshly prepared hog plum juice (control), and the juice samples subjected to pasteurization (90 °C for 60 s) and thermosonication (40 kHz, 400 W at 40, 50 and 60 °C each for 5, 10, 20 and 30 min) were each analyzed for physicochemical, bioactive, microbial and sensory properties. After treatment, no significant changes in pH, total soluble solids and titratable acidity were observed. Notably, TS at 40 and 50 °C significantly (p < 0.05) improved color parameters, cloudiness and browning index. Furthermore, thermosonication increased ascorbic acid (11.40-18.55%), total phenolic content (17.98-18.35%), carotenoids (2.19-4.30%), flavonoids (10-16%) and antioxidant activity (32.52-48.5%) relative to the control. Both treatments significantly reduced the microbial count to non-detectable level after processing, while sensory attributes slightly improved. However, TS treatment at 60 °C decreased most of the quality parameters. Results showed that TS can improve quality, safety and economic potential of hog plum juice as a feasible alternative to pasteurization.

Alicyclobacillus acidoterrestris Strain Variability in the Inactivation Kinetics of Spores in Orange Juice by Temperature-Assisted High Hydrostatic Pressure

In this work, the inactivation kinetics of Alicyclobacillus acidoterrestris spores by temperature-assisted high hydrostatic pressure was assessed by means of the Weibull model. Spores from two A. acidoterrestris strains (a wild-type strain and a reference strain) were inoculated in commercial orange juice and subjected to high pressure levels (500 and 600 MPa) combined with four temperature regimes (25, 45, 60 and 70 °C) for time up to 30 min. Results showed that for a given high-pressure level spore inactivation was higher as temperature progressively increased. Furthermore, the Weibull model consistently produced satisfactory fit to the inactivation data based on the values of the root mean squared error (RMSE < 0.54 log colony-forming units (CFU)/mL) and the coefficient of determination (R2 > 0.90 in most cases). The shape of inactivation curves was concave upward (p < 1) for all temperature/high pressure levels tested, indicating rapid inactivation of the sensitive cells of the bacterium whereas the remaining ones adapted to high hydrostatic pressure (HHP) treatment. The values of the shape (p) and scale (δ) parameters of the Weibull model were dependent on the applied temperature for a given high pressure level and they were further described in a secondary model using first-order fitting curves to provide predictions of the surviving spore population at 55 and 65 °C. Results revealed a systematic over-prediction for the wild-type strain regardless of temperature and high pressure applied, whereas for the reference strain under-prediction was evident after 3 log-cycles reduction of the surviving bacteria spores. Overall, the results obtained indicate that the effectiveness of high hydrostatic pressure against A. acidoterrestris spores is strain-dependent and also underline the need for temperature-assisted HPP for effective spore inactivation during orange juice processing.

Effects of high-pressure processing and thermal pasteurization on quality and microbiological safety of jabuticaba (Myrciaria cauliflora) juice during cold storage

The aims of this study were to investigate the effects of high-pressure processing (HPP) on jabuticaba juice characteristics including microbial levels, phenolic compounds, antioxidant activity, and physicochemical properties during 28 days of storage at 4 °C and to perform a sensory evaluation. Juice samples were pressurized at 200, 400, or 600 MPa for 5 min. During thermal processing, juice was treated in a water bath at 90 °C for 60 s. Elevated aerobic plate counts, coliforms, psychrotrophs and yeasts/molds, were not detected in the HPP-400, HPP-600, or thermal-processed (TP) juices and further cold storage showed at least a shelf life of 28 days at 7 °C. All HPP-treated juice had significantly higher antioxidant capacities, higher total phenolic, flavonoid, and monomeric anthocyanin content, and lower browning degrees, compared with the TP. The soluble solid content, titratable acidity and pH were not significantly different in the HPP-400, HPP-600, and TP after 28 days. The ΔE values were significantly increased in all juice samples. Sensory analysis indicated that the HPP-treated juices had higher acceptance and lower bitter perception. In conclusion, HPP treatments above 400 MPa were effective in ensuring microbiological safety, maintaining the overall quality parameters, extending the shelf life, and achieving consumer acceptance.

Hurdle enhancement of acidic electrolyzed water antimicrobial efficacy on Bacillus cereus spores using ultrasonication

This study evaluated the inactivation effect of ultrasonic treatment combined with acidic electrolyzed water (AEW) on Bacillus cereus spores. AEW treatment reduced the spores by 1.05-1.37 log CFU/mL while the sporicidal effect of ultrasound was minor. More strikingly, simultaneous ultrasonic and AEW treatments for 30 min led to 2.29 log CFU/mL reduction and thus, considered a synergistic effect. Flow cytometry combined with SYTO/PI staining analysis revealed that ultrasound hydrolyzed the cortex while the AEW partially damaged the integrity of the inner membrane. Scanning and transmission electron microscopies were used to characterize the ultrastructural changes. The detachment of the exosporium induced by ultrasound was the most apparent difference compared with the control group, and the electron density of spores appeared to be heterogeneous after treatment with AEW. These results indicated that combining ultrasound with AEW is a promising decontamination technology with potential uses in the food industry and environmental remediation.

Inactivation kinetics of Bacillus cereus spores by Plasma activated water (PAW)

In recent years, plasma activated water has attracted more attention as a new disinfectant. The purpose of this study was to explore impact of variation of different treatment conditions on the inactivation kinetics of Bacillus cereus spores by PAW. All survival curves showed that the number of spores has decreased rapidly at first, followed by tailing results from the reduction inactivation rate. A linear and two nonlinear models (Weibull and Log-logistic model) were fitted to these data, and Log-logistic model fitted the inactivation of the B. cereus spores best. B. cereus spores in 10⁶ CFU/mL was reduced by 1.62-2.96 log CFU/mL by PAW at 55 °C due to the reactive species generated in PAW. Elevated temperature, lower initial spore concentration, lower bovine serum albumin content, and smaller activation volume of PAW considerably enhanced PAW inactivation of B. cereus spores. These results provide an approach to evaluate the inactivation efficacy of different treatment conditions for PAW.

Effects of high hydrostatic pressure on the microbial inactivation and extraction of bioactive compounds from açaí (Euterpe oleracea Martius) pulp

The aim of this study was to investigate the effects of high hydrostatic pressure (HHP) on the inactivation of Lactobacillus fructivorans, on the inactivation of Alicyclobacillus acidoterrestris spores and on the extraction of anthocyanins and total phenolics from açaí pulp. The tested conditions comprised pressures of 400-600 MPa, treatment times of 5-15 min, and temperatures of 25 °C and 65 °C. Results were compared to those of conventional thermal treatments (85 °C/1 min). Regarding A. acidoterrestris spores, applying HHP for 13.5 min, resulted in a value of four-decimal reduction. L. fructivorans presented considerable sensitivity to HHP treatment, achieving inactivation rates above 6.7 log cycles at process conditions at 600 MPa and 65 °C for 5 min. All samples of açaí pulp processed showed absence of thermotolerant coliforms during the 28 days of refrigerated storage (shelf life study). The açaí pulps processed by HHP (600 MPa/5 min/25 °C) had anthocyanin extraction increased by 37% on average. In contrast, conventional thermal treatment reduced anthocyanin content by 16.3%. For phenolic compounds, the process at 600 MPa/5 min/65 °C increases extraction by 10.25%. A combination of HHP treatment and moderate heat (65 °C) was shown to be an alternative to thermal pasteurization, leading to microbiologically safe products while preserving functional compounds.

Effect of Extraction Method and Thermosonication on Apple Juice Quality

This paper presents the results of a study on the influence of juice extraction and thermosonication methods on the content of microorganisms in juices stored under refrigeration and in ambient temperature. It was determined that the type of extraction device used influenced the content of microorganisms in juice. The lowest total content of mesophilic microorganisms was obtained in juice extracted on a piston press, and the highest was obtained using a centrifuge. The additional purpose was to evaluate the influence of ultrasonic treatment on selected parameters of apple juice quality: cloud value, antioxidant activity, total phenolic content, flavonoid content, and anthocyanin content. The ultrasound treatment of juice from the piston press was conducted at two levels of radiated sonic power so as to obtain sublethal and lethal temperatures of the juice. It was demonstrated that only ultrasound treatment within the range of lethal temperatures was sufficient to deactivate microorganisms. It was determined that thermosonication did not influence the deterioration of chemical properties of juices, with the exception of decreased anthocyanin content. The described method enables prolongation of the shelf life of fresh apple juice under refrigeration to 168 hours (7 days).

Differentiation of Fresh and Processed Fruit Juices Using Volatile Composition

In the current study, a comprehensive approach based on headspace solid-phase microextraction (HS-SPME), combined with gas chromatography-quadrupole mass spectrometry (GC-qMS), was used to establish the volatile signature of fresh and processed fruit juices, obtained from the same batch of grapes, red fruits, orange, pear, and apple. This is a powerful tool for evaluating the impact of the production process on the volatomic pattern of fruit juice. A total of 169 volatile organic compounds (VOCs) belonging to different chemical groups were identified. Esters, carbonyl compounds, terpenoids, and alcohols are the major chemical groups in the investigated fruit juices. However, their contribution to the total volatile profile varied. Special attention should be paid to processed fruit juices to avoid the possible deleterious effects associated with the formation of furanic compounds (e.g., heat treatment), since their furanic content was significantly higher in comparison to that of fresh fruit juices. The knowledge obtained in the current study will allow for the introduction of modifications to the process involved in processing juice, which will improve the organoleptic characteristics of processed juices, contributing to a better acceptance by consumers. Furthermore, more assays should be performed to assess the effect of harvests, geography, and agronomy on the volatile profile of juices.

Effect of ultrasonication and thermal and pressure treatments, individually and combined, on inactivation of Bacillus cereus spores

Bacillus cereus spores are a concern to the food industry due to their high resistance to processing and their ability to germinate to vegetative cells under suitable conditions. This research aimed to elucidate the mechanisms of Bacillus cereus spore inactivation under ultrasonication (US) combined with thermal (thermosonication, TS) treatments, with pressure (manosonication, MS) treatments, and with thermal and pressure (manothermosonication, MTS) treatments. Electronic microscopy, dipicolinic acid (DPA) release, and flow cytometric assessments were used to investigate the inactivation effect and understand the inactivation mechanisms. The sporicidal effects of the US and thermal treatment were slight, and the MS and TS also showed little inactivation effect. However, ultrasonication promoted the detachment of the exosporium, thereby reducing the spore's ability to adhere to a surface, while the thermal treatment induced a decrease in the electron density in the nucleoid of bacterium, which retained a relatively intact exosporium and coat. MS caused 92.54% DPA release, which might be due to triggering of the germinant receptors or releasing of ions and Ca²⁺-DPA. In addition, the morphological changes such as core hydration and cortex degradation were significant after treatment with MS. The release of DPA and the morphological changes were responsible for the reduction in thermal resistance. The MTS showed a remarkable inactivation effect of 3.12 log CFU/mL reductions after 30 min of treatment. It was the most effective treatment and exhibited a large fraction of damage. In addition, the MTS had a significant impact on the intracellular structure of the spores, with the coat destroyed and the cortex damaged. These results indicated that ultrasonication combined with thermal and pressure treatments had a significant sporicidal effect on Bacillus cereus spores and could be a promising green sterilization technology.

Three Pillars of Novel Nonthermal Food Technologies: Food Safety, Quality, and Environment

This review gives an overview of the impact of novel nonthermal food technologies on food safety, on quality, and on the environment. It confirms that research in this field is mainly focused on analyzing microbial and/or chemical aspects of food safety. However, recent research shows that in spite of various food safety benefits, some negative (quality oriented) features occur. Finally, this paper shows the necessity of analyzing the environmental dimension of using these technologies.

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.

Applications of ultrasound in processing of liquid foods: A review

Ultrasonic processing of a variety of liquids, drinks and beverages has generated much interest with published literature papers increasing within this area in recent years. Benefits include enhanced emulsification with improved homogenization and fat globule size reduction being recorded. In dairy systems increased creaming rates are observed on sonication in a process known as fractionation. Whilst fruit juices exhibit retention or enhancement of quality parameters whilst increasing levels of bioactive compounds. Sterilization of liquids is a large feature of ultrasonic treatment with microbial activity of a range of fruit juices being monitored over time as increased stability and reduced spoilage is observed. Progress has also been made towards scale up of ultrasonic processes with several examples of batch and continuous processes being studied with reduced processing times and temperatures being quoted as a result of ultrasonic treatment. This short review covers the effect of sonication on liquids and beverages with a specific focus towards dairy and fruit juices and covers emulsification, fractionation, sterilization and some pilot scale initiatives.