Protein-based indicator system for detection of temperature differences in high pressure high temperature processing

Since the kinetics of change of target attributes in high pressure high temperature (HPHT) processing are not only pressure but also clearly temperature dependent, a control of temperature in space and time is indispensible. A tool that can easily detect temperature differences in prototype HPHT vessels during a HPHT process would aid the design of industrial HPHT equipments. In this work, the potential of ovomucoid as extrinsic, isolated, protein-based indicator to detect temperature differences inside a HPHT vessel was assessed. Ovomucoid fulfilled the selection criteria of a candidate indicator for HPHT. Solvent engineering was successfully used to shift the inactivation window of the candidate indicator into the HPHT processing window. Since, the dissociation equilibrium of buffer systems shifts under high pressure and/or under high temperature, a critical evaluation of the effect of a pH-shift of the selected phosphate buffer system in the context of protein-based indicator development was performed. The ovomucoid system inactivation kinetics were characterized under isobaric–isothermal conditions and modeled best by a first order inactivation model. A temperature dependent inactivation at constant pressure could be observed, which creates potential for the detection of temperature differences under HPHT conditions. These integrating properties were unaffected under dynamic, industrially relevant HPHT conditions.     

Comparing the impact of high pressure high temperature and thermal sterilization on the volatile fingerprint of onion,potato, pumpkin and red beet

This work reports the effect of high pressure high temperature (HPHT) processing as compared to thermal processing on the volatile fraction of four, industrially-relevant, vegetables: onion, potato, pumpkin and red beet. The vegetables were selected from different botanical families, edible plant parts and color groups, aiming for investigation of a wide range of chemical reactions. Despite the difference in chemical composition among these vegetables, some remarkable general trends could be found. Firstly, in all vegetables, Strecker degradation products (such as 2- and 3-methylbutanal) were detected at higher levels after HPHT sterilization in comparison to thermally sterilized counterparts. Secondly, HPHT sterilization enhanced oxidative degradation reactions (e.g. unsaturated fatty acids (in pumpkin, red beet and onion) and carotenoids (in pumpkin)). This work demonstrated the power of the untargeted multi-variate fingerprinting approach as a fast screening tool to zoom into relevant reaction pathways out of a complex network of chemical changes and to determine discriminative volatiles which can serve as potential markers.     

Solvent engineering as a tool in enzymatic indicator development for mild high pressure pasteurization processing

When developing an indicator to detect temperature heterogeneities in a high pressure (HP) vessel, the temperature sensitivity and the broadness of the application window have to be weighed against each other. In this study, the potential of a Bacillus amyloliquefaciens α-amylase (BAA)-based indicator for mild pasteurization conditions was evaluated. Solvent engineering was successfully used to reach two objectives: (i) to shift the pressure,temperature-stability of BAA in the HP pasteurization range; (ii) to differentiate the pressure,temperature-range of BAA inactivation from the pressure,temperature-range of inactivation of a previously developed Bacillus subtilis α-amylase (BSA)-based indicator system (1 g/L – 0.05 M MES pH 5.0), towards milder processing conditions. The BAA-system (0.1 g/L – 0.1 M MES pH 5.0) was kinetically calibrated and modeled under static conditions. As these model parameters were inadequate to predict the residual α-amylase activity of BAA under dynamic conditions correctly, parameters were determined under dynamic conditions and subsequently successfully validated on an independent dynamic data set. Based on the kinetic model and parameters valid under dynamic conditions, isorate contour plots for different inactivation levels were constructed, demonstrating clearly the different application windows of the BAA- and BSA-systems.     

Bovine cathepsin D activity under high pressure

The stability and catalytic activity of bovine cathepsin D in Bis-Tris buffer (pH 6.0) in different pressure–temperature domains (0.1–650 MPa, 20–75 °C) were investigated and described with mathematical models. Cathepsin D inactivation followed first-order kinetics at all pressure–temperature conditions tested. The protease was largely pressure stable at room temperature and heat stable at ambient pressure up to 300 MPa and 55 °C, respectively, causing less than 10% inactivation after 10 min treatment. Pressure and temperature act synergistically on the enzyme inactivation under most conditions. However, at 100 MPa a significant stabilisation of the enzyme against temperature-induced inactivation was observed. Pressure drastically inhibited the cleavage of a synthetic substrate by cathepsin D in Bis-Tris buffer (pH 6.0) causing a reduction of the catalytic rate of more than 50% at 100–400 MPa. Maximal substrate cleavage by cathepsin D was identified at 60 °C and ambient pressure conditions after 20 min treatment.     

Mapping temperature uniformity in industrial scale HP equipment using enzymatic pressure–temperature–time indicators

The potential of two previously developed pressure–temperature–time indicators (pTTIs) to detect temperature differences during high pressure (HP) processing was assessed. In a first theoretical approach, numerical integration of pressure, temperature-profiles and kinetic data of inactivation of the pTTIs, Bacillus amyloliquefaciens α-amylase and Bacillus subtilis α-amylase, was applied to translate hypothetical temperature profiles under pressure into indicator read-outs. This resulted in the definition of the application window with regard to initial temperature of the pressure medium (equal to the high pressure wall), the pressure level, build-up rate and holding time. Both indicators showed great potential for use in HP pasteurization processing. Secondly, in an experimental part, the temperature uniformity in a horizontally oriented, industrial scale HP equipment was mapped for the first time, using these indicators. Differences in indicator read-outs were obtained in the radial plane of the HP vessel, and based on the kinetic data of the pTTIs, attributed to temperature differences. Of course, this temperature non-uniformity will only result in process non-uniformity if the temperature dependency of the kinetics of the target attribute (safety, quality) is sufficiently temperature sensitive in the studied pressure, temperature-range.     

The impact of high pressure and temperature on bacterial spores: inactivation mechanisms of Bacillus subtilis above 500 MPa

Abstract: High‐pressure thermal sterilization (HPTS) is an emerging technology to produce shelf stable low acid foods. Pressures below 300 MPa can induce spore germination by triggering germination receptors. Pressures above 500 MPa could directly induce a Ca⁺²‐dipicolinic acid (DPA) release, which triggers the cortex‐lytic enzymes (CLEs). It has been argued that the activated CLEs could be inactivated under HPTS conditions. To test this claim, a wild‐type strain and 2 strains of Bacillus subtilis spores lacking germinant receptors and one of 2 CLEs were treated simultaneously from 550 to 700 MPa and 37 to 80 C (slow compression) and at 60 to 80 C up to 1 GPa (fast compression). Besides, an additional heat treatment to determine the amount of germinated cells, we added TbCl₃ to detect the amount of DPA released from the spore core via fluorescent measurement. After pressure treatment for 120 min at 550 MPa and 37 °C, no inactivation was observed for the wild‐type strain. The amount of released DPA correlated to the amount of germinated spores, but always higher compared to the belonging cell count after pressure treatment. The release of DPA and the increase of heat‐sensitive spores confirm that the inactivation mechanism during HPTS passes through the physiological states: (1) dormancy, (2) activation, and (3) inactivation. As the intensity of treatment increased, inactivation of all spore strains also strongly increased (up to ?5.7 log₁₀), and we found only a slight increase in the inactivation of one of the CLE (sleB). Furthermore, above a certain threshold pressure, temperature became the dominant influence on germination rate. Practical Application: The continuous increase of high‐pressure (HP) research over the last several decades has already generated an impressive number of commercially available HP pasteurized products. Furthermore, research helped to provoke the certification of a pressure‐assisted thermal sterilization process by the U.S. FDA in February 2009. However, this promising sterilization technology has not yet been applied in industrial settings. An improved understanding of spore inactivation mechanisms and the ability to calculate desired inactivation levels will help to make this technology available for pilot studies and commercialization at an industrial scale. Moreover, if the synergy between pressure and elevated temperature on the inactivation rate could be identified, clarification of the underlying inactivation mechanism during HP thermal sterilization could help to further optimize the process of this emerging technology.     

Moderate electric fields can inactivate Escherichia coli at room temperature

The inactivation of Escherichia coli using moderate electric fields (MEF) below 25 °C, was investigated. Keeping the temperature always below 25 °C demonstrated that electric fields are involved in the inactivation of E. coli, without possible synergistic temperature effects. Electric fields above 220 V cm⁻¹ promoted death rates of 3 log₁₀ cycles of E. coli in less than 6 min, and even higher rates at greater electric fields, while presumably overcoming the thermal degradation caused by conventional high temperature treatments. A non-thermal model was proposed that successfully describes the E. coli death kinetics under this treatment. SEM observations of E. coli cells after the exposure to the MEF treatment, revealed changes at the cell membrane level, indicating a possible cause for the cell death rates. These results show that this treatment holds potential for sterilization of thermolabile products (e.g. serum and other physiological fluids, food products), by itself or as a complement of the traditional heat-dependent techniques.     

超高压对酱料食品中微生物指标的影响

由于超高压杀菌技术实现了常温或较低温度下杀菌和灭酶,保证了食品的营养成分和感官特性,因此被认为是一种最有潜力和发展前景的食品加工和保藏新技术。广泛的应用于含液体成分的固态食品或液态食品的杀菌。本实验尝试以酱料食品为样本,研究超高压杀菌技术对半固体膏状调味品的微生物卫生指标的影响,探讨非热力抑菌技术在半固体膏状调味品生产的应用。分别对压力、保压时间、温度进行单因素实验,结果为300MPa为最佳压力,20min为最佳保压时间,32℃为最适温度。     

Combined osmodehydration and high pressure processing on the enzyme stability and antioxidant capacity of a grapefruit jam

A combined osmodehydration process and high pressure treatment (OD–HHP) was developed for grapefruit jam preservation. The inactivation kinetics of pectin methylesterase (PME) and peroxidase (POD) in the osmodehydrated (OD) jam treated by combined thermal (45–75 °C) and high pressure (550–700 MPa) processes were fitted using special cases of first-order kinetics, the fractional conversion and biphasic models and the Weibull distribution function. No complete inactivation was achieved by any combination of temperature and pressure, and 27–40% and 51–70% of PME and POD, respectively, were pressure-stable fractions. Two PME fractions with different pressure stabilities were observed and kinetic models successfully explained that behavior. POD was found to be very baroresistant and only the labile fraction could be inactivated. The extent of enzyme inactivation was lower in the OD jam in comparison with other food matrices showing a protective effect against the high pressure treatment. The antioxidant capacity was not affected by any treatment. The proposed high pressure preservation processing was able to improve the enzymatic stability of jam obtained by osmotic dehydration without affecting the bioactive content.     

Inactivation Kinetics of Geobacillus stearothermophilus Spores in Water Using High-pressure Processing at Elevated Temperatures

ABSTRACT: Establishment of a high-pressure sterilization process requires data on pressure and temperature-dependent inactivation kinetics of target pathogenic, spoilage, or surrogate spore-forming bacteria in the food being tested. The objective of this study was to examine the response of Geobacillus stearothermophilus ATCC10149 spores to various temperature, time, and pressure combination treatments (500 to 700 MPa; 92°C to 111°C, 0.01 to 360 s). The pressure inactivation of spores was characterized at elevated temperatures under isobaric and isothermal conditions during the holding time using a laboratory-scale high-pressure unit. The inactivation kinetics was well described by the log-linear regression model. As expected, the rate of spore inactivation increased with increasing pressure and temperature. Decimal reduction times at constant pressure ( D _T,P values) varied from 29.4 to 108.8 s at 92°C, 17.4 to 76 s at 100°C, and 6.1 to 51.3 s at 111°C within the pressure range of 500 to 700 MPa. The resistance of spores to temperature and pressure was characterized with z_T and z_P values and compared with their resistance to conventional steam heating. The conventional thermal resistance of G. stearothermophilus species did not correlate to the thermal resistance at high pressure. The study provides kinetic data on the effects of pressure and temperature on the inactivation of a heat-resistant bacterial spore species under conditions applicable to the commercial processing of low-acid foods.     

Combined high pressure and temperature induced lethal and sublethal injury of Lactococcus lactis--application of multivariate statistical analysis

It was the aim of this work to determine the combined effects of pressure, temperature, and co-solutes on Lactococcus lactis, and to detect correlations between culture-dependent and culture-independent methods for assessment of cellular viability and sublethal injury. Therefore, the pressure induced inactivation of L. lactis MG 1363 was investigated in buffer and in buffer with 1.5 M sucrose or 4 M NaCl at a pressure range of 0.1 to 500 MPa and a temperature range of 5 to 50 degrees C. The inactivation was characterised by viable cell counts, stress resistant cell counts, membrane integrity, metabolic activity, and the activity of the multi-drug-resistance transport enzyme LmrP. L. lactis was most resistant to pressure application at 20-30 degrees C. Sucrose protected towards inactivation at any temperature, NaCl provided protection at high temperatures only. By using Principal Component Analysis, correlations were detected between viable cell counts and metabolic activity as well as stress resistant cell counts and LmrP activity. In conclusion, the pressure-inactivation of L. lactis is strongly temperature dependent, baroprotection by sucrose occurs at any temperature but the baroprotective effects of NaCl is temperature dependent. Further on, a combination of two experimental methods fully describe lethal and sublethal injury of pressure treated cells. These simplification of data acquisition and model development facilitates the establishment of pressure processes in food technology.     

Kinetics of Strecker aldehyde formation during thermal and high pressure high temperature processing of carrot puree

Strecker aldehydes have been negatively associated to flavor of heat sterilized plant-based foods. The present study demonstrated the importance of processing conditions (temperature, pressure and time) as a strong means for the control of Strecker aldehyde formation in vegetables purees. A kinetic study was set up (at isothermal and isothermal-isobaric conditions) to quantify the effects of single process parameters on the changes of 3-methylbutanal (3-MB) in carrot puree as a case study. The increase in 3-MB concentrations was best described by an empirical, logistic model. During the isothermal treatment at atmospheric pressure, the maximum reaction rate constant of 3-MB formation was increased as a function of processing temperature. However, the formation rate was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa. Hence, the reduced formation of Strecker aldehydes under high pressure could open a new possibility for process control and optimization of the formation of these compounds.Industrial relevanceHigh pressure high temperature (HPHT) processing is a relatively young technology and its effect on important quality-related chemical reactions is not as well understood as is the case for conventional thermal processing. The present work investigates the impact of processing conditions (e.g. pressure, temperature) on Strecker aldehydes formation, volatiles that have been negatively associated to flavor of heat sterilized plant-based foods. Based on the kinetic study, the formation rate of the Strecker aldehyde (3-methylbutanal) was clearly slower at high pressure (600 MPa) compared to the process at 0.1 MPa in carrot puree. Considering the fact that these compounds are often linked to off-flavor development, their reduced formation under high pressure could open a new possibility for process control and optimization.     

超高压杀菌效果及机制研究进展

超高压作为一种新型的食品非热加工技术, 处理过程温度低、对食品营养成分破坏小,能在有效杀菌的同时显著提升加工食品品质,是未来食品加工技术发展的热点方向。近年来,超高压技术被广泛应用于食品加工,并在国内外实现了商业化应用。杀菌作为超高压加工食品过程中最重要的环节,是保证食品安全、延长产品货架期的关键点,因此一直是本领域研究的重点。本文介绍了超高压技术的设备和作用原理, 总结了超高压或超高压联合其他手段对微生物营养体、细菌芽孢、真菌孢子及病毒的杀灭效果和杀菌机制, 归纳了超高压杀菌中存在的杀菌机制不清、缺乏杀菌指示菌以及深休眠芽孢等问题, 以期为进一步完善超高压杀菌理论、推动超高压技术在食品加工中的产业化应用指明方向。     

Environmental factors influencing the inactivation of Cronobacter sakazakii by high hydrostatic pressure

The effect of High Hydrostatic Pressure (HHP) on the survival of Cronobacter sakazakii was investigated. Deviations from linearity were found on the survival curves and the Mafart equation accurately described the kinetics of inactivation. Comparisons between strains and treatments were made based on the time needed for a 5-log₁₀ reduction in viable count. The ability of C. sakazakii to tolerate high pressure was strain-dependent with a 26-fold difference in resistance among four strains tested. Pressure resistance was greatest in the stationary growth phase and at the highest growth temperatures tested (30 and 37 °C). Cells treated in neutral pH buffer were 5-fold more resistant than those treated at pH 4.0, and 8-fold more sensitive than those treated in buffer with sucrose added (a_w = 0.98). Pressure resistance data obtained in buffer at the appropriate pH adequately estimated the resistance of C. sakazakii in chicken and vegetables soups. In contrast, a significant protective effect against high pressure was conferred by rehydrated powdered milk. As expected, treatment efficacy improved as pressure increased. z values of 112, 136 and 156 MPa were obtained for pH 4.0, pH 7.0 and a_w = 0.98 buffers, respectively. Cells with sublethal injury to their outer and cytoplasmic membranes were detected after HHP under all the conditions tested. The lower resistance of C. sakazakii cells when treated in media of pH 4.0 seemed to be due to a decreased barostability of the bacterial envelopes. Conversely, the higher resistance displayed in media of reduced water activity may relate to a higher stability of bacterial envelopes.     

Data mining and fuzzy modelling of high pressure inactivation pathways of Lactococcus lactis

A mathematical model to predict lethal and sublethal pressure effects on Lactococcus lactic was established through combined use of Principal Component Analysis (PCA) and Fuzzy Logic. The model was based on data comprising pressure inactivation kinetics with 64 combinations of the parameters pressure, temperature, pH, and buffer composition, samples were analysed with respect to 5 physiological states describing lethal or sublethal injury of L. lactis, i.e. viable cell counts (CFU), undamaged cell counts (CFUsub), membrane integrity (MI), metabolic activity (MA) and the activity of the membrane bound enzyme LmrP (LmrP).Correlations found by PCA were used to generate a bi-layer fuzzy model using clustering methods and rule oriented statistical analysis as well as the physiological states CFU and LmrP as autonomous output variables. The result of these variables is used to accurately predict dependent output variables MA, CFUsub, and MI taking into account the combined effects of the inactivation process.Industrial relevanceThe study provides a predictive model for the inactivation of an industrially relevant micro-organism. Predictive models are useful for process design on the industrial scale. Further, our model provides information about intermediate steps of high pressure inactivation.     

Effect of high hydrostatic pressure and temperature on carrot peroxidase inactivation

The combined effects of pressure and temperature on the activity of carrot peroxidase (POD) were investigated in the pressure range 0.1–600 MPa and the temperature range 25–45 °C. At lower pressures (<396 MPa), carrot POD stability increased compared to unpressurized samples. Inactivation of 91% was obtained at 600 MPa and 45 °C. High hydrostatic pressure (HHP) combined with temperature treatment enhanced the inactivation of carrot POD. Regeneration of POD activity with the combined HHP and temperature treatments followed first order kinetics at 25, 35 and 40 °C. Regeneration was not observed at 506 MPa and 45 °C. HHP had no significant effect on the loss of vitamin C or on protein content. HHP combined with mild heat treatment was found to be better than the thermal treatment at high temperatures for inactivation of POD in carrot processing.     

Kinetic study of high pressure microbial and enzyme inactivation and selection of pasteurisation conditions for Valencia Orange Juice

Keeping quality of fresh orange juice is highly dependent on pectinolytic enzyme activity and the growth of spoilage microorganisms. The inactivation kinetics of indigenous pectin methylesterase (PME) and of the two more pressure resistant species of spoilage lactic acid bacteria (LAB) Lactobacillus plantarum and L. brevis in freshly squeezed Valencia orange juice under high hydrostatic pressure (100–500 MPa) combined with moderate temperature (20–40 °C) was investigated. PME inactivation followed first order kinetics with a residual PME activity (15%) at all pressure–temperature combinations used. The values of activation energy and activation volume were estimated at each pressure and at each temperature, respectively. Values of 90 kJ/mol and ?30 mL/mol at reference pressure of 300 MPa and reference temperature of 35 °C were estimated respectively. The corresponding z_T and z_P values of LAB inactivation were also estimated at all conditions tested. Values of 19.5 °C and 95 MPa at reference pressure of 300 MPa and reference temperature of 30 °C were estimated respectively for L. plantarum, while the corresponding values for L. brevis were 40 °C and 82 MPa, respectively, at the same reference conditions. Pressure and temperature were found to act synergistically both for PME and LAB inactivation. The PME and LAB inactivation rate constants were expressed as functions of the temperature and pressure process conditions. These functions allow the determination of the pressure/temperature conditions that achieve the target enzyme and microbial inactivation at a selected processing time. The process conditions of 350 MPa at 35 °C for 2 min are proposed as effective for Valencia orange juice cold pasteurisation.     

Headspace components that discriminate between thermal and high pressure high temperature treated green vegetables: Identification and linkage to possible process-induced chemical changes

For the first time in literature, this study compares the process-induced chemical reactions in three industrially relevant green vegetables: broccoli, green pepper and spinach treated with thermal and high pressure high temperature (HPHT) processing. Aiming for a fair comparison, the processing conditions were selected based on the principle of equivalence. A comprehensive integration of MS-based metabolic fingerprinting techniques, advanced data preprocessing and statistical data analysis has been implemented as untargeted/unbiased multiresponse screening tool to uncover changes in the volatile fraction. For all vegetables, thermal processing, compared to HPHT, seems to enhance Maillard and Strecker degradation reaction, triggering the formation of furanic compounds and Strecker aldehydes. In most cases, high pressure seems to accelerate (an)aerobic thermal degradation of unsaturated fatty acids leading to the formation of aliphatic aldehydes and ketones. In addition, both thermal and HPHT processing accelerated the formation of sulfur-containing compounds. This work demonstrated that the approach is effective in identifying and comparing different process-induced chemical changes, adding depth to our perspective in terms of studying a highly complex chemical changes occurring during food processing.     

Thermal and high hydrostatic pressure inactivation of myrosinase from green cabbage: A kinetic study

Myrosinase, a family of enzymes which coexist with glucosinolates in all Brassica vegetables, catalyses the hydrolysis of glucosinolates to yield compounds that can have beneficial effects on human health. In this study, the thermal and pressure inactivation of myrosinase from green cabbage was kinetically investigated. Thermal inactivation started at 35 °C and inactivation kinetics was studied in the temperature range 35-55 °C. Thermal inactivation of green cabbage myrosinase followed the well known consecutive step model. Pressure inactivation started at 300 MPa, even at 10 °C, and the consecutive step model effectively described pressure inactivation in the range 300-450 MPa at 10 °C. The combined effects of applying various pressures and temperatures on myrosinase inactivation kinetics were studied in the ranges 35-50 °C and, 100-400 MPa. The inactivation followed first-order kinetics at all of the applied combinations. This study demonstrates that myrosinase from green cabbage is highly susceptible to both thermal and high pressure processing. Furthermore, it is also noted that myrosinase stability during processing appears to vary widely between different Brassica species.     

Germination and inactivation of Bacillus coagulans and Alicyclobacillus acidoterrestris spores by high hydrostatic pressure treatment in buffer and tomato sauce

Acidothermophilic bacteria like Alicyclobacillus acidoterrestris and Bacillus coagulans can cause spoilage of heat-processed acidic foods because they form spores with very high heat resistance and can grow at low pH. The objective of this work was to study the germination and inactivation of A. acidoterrestris and B. coagulans spores by high hydrostatic pressure (HP) treatment at temperatures up to 60 °C and both at low and neutral pH. In a first experiment, spores suspended in buffers at pH 4.0, 5.0 and 7.0 were processed for 10 min at different pressures (100-800 MPa) at 40 °C. None of these treatments caused any significant inactivation, except perhaps at 800 MPa in pH 4.0 buffer where close to 1 log inactivation of B. coagulans was observed. Spore germination up to about 2 log was observed for both bacteria but occurred mainly in a low pressure window (100-300 MPa) for A. acidoterrestris and only in a high pressure window (600-800 MPa) for B. coagulans. In addition, low pH suppressed germination in A. acidoterrestris, but stimulated it in B. coagulans. In a second series of experiments, spores were treated in tomato sauce of pH 4.2 and 5.0 at 100 - 800 MPa at 25, 40 and 60 °C for 10 min. At 40 °C, results for B. coagulans were similar as in buffer. For A. acidoterrestris, germination levels in tomato sauce were generally higher than in buffer, and showed little difference at low and high pressure. Remarkably, the pH dependence of A. acidoterrestris spore germination was reversed in tomato sauce, with more germination at the lowest pH. Furthermore, HP treatments in the pH 4.2 sauce caused between 1 and 1.5 log inactivation of A. acidoterrestris. Germination of spores in the high pressure window was strongly temperature dependent, whereas germination of A. acidoterrestris in the low pressure window showed little temperature dependence. When HP treatment was conducted at 60 °C, most of the germinated spores were also inactivated. For the pH 4.2 tomato sauce, this resulted in up to 3.5 and 2.0 log inactivation for A. acidoterrestris and B. coagulans respectively. We conclude that HP treatment can induce germination and inactivation of spores from thermoacidophilic bacteria in acidic foods, and may thus be useful to reduce spoilage of such foods caused by these bacteria.