Quantifying the effects of heating temperature, and combined effects of heating medium pH and recovery medium pH on the heat resistance of Salmonella typhimurium

The influence of heating treatment temperature, pH of heating and recovery medium on the survival kinetics of Salmonella typhimurium ATCC 13311 is studied and quantified. From each non-log linear survival curve, Weibull model parameters were estimated. An average shape parameter value of 1.67 was found, which is characteristic of downward concavity curves and is in agreement with values estimated from other S. typhimurium strains. Bigelow type models quantifying the heating temperature, heating and recovery medium pH influences are fitted on scale parameter delta data (time of first decimal reduction), which reflects the bacterial heat resistance. The estimate of z(T) (4.64 degrees C) is in the range of values given in the literature for this species. The influence of pH of the heating medium on the scale parameter (z(pH): 8.25) is lower than that of the recovery pH medium influence (z(')(pH): 3.65).     

Modeling the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7

The objective of this study was to model with logistic regression the growth/no growth interface of different initial inoculation levels (10¹, 10³ and 10⁵ CFU/ml; study 1), or nonadapted vs acid-adapted (study 2) Escherichia coli O157:H7 as influenced by pH, NaCl concentration and incubation temperature. Study 1 was conducted with a mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in tryptic soy broth (TSB). Study 2 was conducted with the same mixture of four E. coli O157:H7 strains grown (35 °C, 24 h) in glucose-free TSB with 1% added glucose (final pH 4.83), or in diluted lactic acid meat decontamination runoff fluids (washings; final pH 4.92), or nonadapted cultures prepared in glucose-free TSB (final pH 6.45), or in water washings (final pH 6.87). Parameters included incubation temperature (10–35 °C), pH (3.52–7.32), and NaCl concentration (0–10% w/v). Growth responses were evaluated for 60 days turbidimetrically (610 nm) every 5 days in 160 (study 1) and 360 (study 2) combinations in quadruplicate samples, with a microplate reader. The lower the initial inoculum the higher were the minimum pH and a_w values permitting growth. Differences in the pH and a_w growth limits among inoculum concentrations increased at 15 and 10 °C. Acid-adapted cultures were able to grow at lower pH than nonadapted cultures, while at temperatures below 25 °C, growth initiation of nonadapted cultures stopped at higher a_w compared to acid-adapted cultures for the whole pH range of 3.52 to 7.32. A comparison with available data indicated that our model for acid-adapted E. coli O157:H7 in different environments may provide representative growth probabilities covering both nonadapted and stress-adapted contaminants.     

Detecting Aspergillus parasiticus in cereals by an enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay (ELISA) was used for the specific detection of Aspergillus parasiticus molds in artificially contaminated corn, rice, wheat and peanut, and also to detect naturally occurring aflatoxigenic molds in the same form cereals. After inoculation of Aspergillus parasiticus in the cereals, the growth of A. parasiticus was monitored by both plate count and ELISA, and the aflatoxin content was measured. Water activity (a_w) affected the fungal growth, aflatoxin production and degradation. The higher a_w level (a_w=0.98 vs. a_w=0.92) resulted in higher fungal growth rates and fungal masses in corn, rice and wheat, and the plate count and ELISA measurements were better correlated, with correlation coefficients of 0.94, 0.93, 0.96 and 0.86, respectively for corn, rice, wheat, and peanuts. Aflatoxin was also both produced sooner and degraded more rapidly at a_w=0.98. Although standard plate counting techniques detected A. parasiticus/A. flavus in 5 out of the 40 cereal samples bought from retail stores, ELISA did not give a positive result in any of them. After moisturization and incubation of these commercial samples at 28°C for 29 days, the incident rates of aflatoxigenic molds increased to 65% and 52% by plate count and ELISA, respectively.     

Survival curves of heated bacterial spores: effect of environmental factors on Weibull parameters

The classical D-value of first order inactivation kinetic is not suitable for quantifying bacterial heat resistance for non-log linear survival curves. One simple model derived from the Weibull cumulative function describes non-log linear kinetics of micro-organisms. The influences of environmental factors on Weibull model parameters, shape parameter "p" and scale parameter "delta", were studied. This paper points out structural correlation between these two parameters. The environmental heating and recovery conditions do not present clear and regular influence on the shape the parameter "p" and could not be described by any model tried. Conversely, the scale parameter "delta" depends on heating temperature and heating and recovery medium pH. The models established to quantify these influences on the classical "D" values could be applied to this parameter "delta". The slight influence of the shape parameter p variation on the goodness of fit of these models can be neglected and the simplified Weibull model with a constant p-value for given microbial population can be applied for canning process calculations.     

Equilibrium sorption isotherms and thermodynamic properties of starch and gluten

A modification of the GAB isotherm (Guggenheim–Anderson–De Boer) is proposed in order to correlate the sorption data for water activities higher than 0.9. The proposed isotherm retains the desirable properties of the GAB isotherm, i.e. good fitting in the range of a_w between 0.05 and 0.80, and also provides a noticeable improvement in the fitting quality for high values of a_w, by introducing a new term with an additional constant. Sorption data for native potato starch and gluten at different temperatures (2°C, 20°C, 40°C and 67°C) were well correlated for the whole a_w range. For starch at 67°C, the values of the constants of the proposed equation do not follow the same tendency obtained for lower temperatures, suggesting that the structure of the material could be changed due to the high temperature. The proposed isotherm can be of interest in the area of drying given that there are few isotherms that accurately represent sorption data at different temperatures in the zone of high a_w. Also, it can be useful to predict other thermodynamic functions. In addition, a new procedure is proposed to determine the isosteric heat by using a second order polynomial for representing the variation of moisture as a function of temperature at a fixed water activity.     

A model of the specific growth rate inhibition by weak acids in yeasts based on energy requirements

Zygosaccharomyces bailii, a spoilage yeast, capable of metabolic activity in food environments with low pH, low a_w and in the presence of weak acid preservatives was chosen for a study on the effect of benzoic acid on growth parameters. In batch cultures, under controlled pH, this food preservative inhibited growth, decreasing the specific growth rate (μ) and the yield coefficient (Y_S) on glucose. Data obtained at pH 3.5, 4.0 and 4.5 showed that this inhibition was exclusively promoted by the undissociated form of the acid since the effect was independent of pH when the concentration of the acid was expressed in this form. Moreover, the relationship between the values for μ and Y_S, provided evidence that the specific consumption rate of glucose (q_S) was not affected by benzoic acid, indicating that the inhibition of growth should be completely explained by a decrease of Y_S. The outcome of parallel experiments performed in continuous culture was that the decrease of Y_S was due to an increase of the maintenance coefficient (m), defined as the fraction of q_S diverted from growth to cope with stress, represented in this case by the presence of the preservative. Based on these results a model was built, assuming that m increased hyperbolically with the concentration of benzoic acid, from zero in the absence of the acid up to q_S when growth was completely inhibited. The concentration of the acid, for which m=q_S/2, is a constant (K_W), and represents a measure of the tolerance for a preservative, in this case benzoic acid. The simple equation μ/μ₀=1+W/K_W predicts the value of μ for a concentration (W) of the preservative, requiring the knowledge of two parameters: the specific growth rate in the absence of the preservative (μ₀) and K_W. The equation fitted very well the data of the effect of benzoic acid on the specific growth rate of Z. bailii, having K_W=0.96 mM benzoic acid. The model was also validated with other spoilage yeasts grown in the presence of benzoic acid in microtiter plates in an automated spectrophotometer. The values obtained for K_W under these conditions confirm Z. bailii as the most tolerant (K_W=2.1 mM) followed by Pichia sp. (K_W=0.78 mM), Saccharomyces cerevisiae (K_W=0.53 mM) and Debaryomyces hansenii (K_W=0.11 mM).     

Characterization of Micrococcaceae isolated from Iberian dry-cured sausages

The populations of Micrococcaceae in different types of Iberian dry-cured sausages from central-west Spain were characterized and their technological and antimicrobial properties determined in order to evaluate their suitability as starter cultures in dry-cured sausage manufacture. Of a total of four hundred strains isolated from two manufacturers, one hundred and sixty-six were selected to evaluate nitrate reductase, proteolytic, lipolytic, and antimicrobial activities, and growth at different values of pH and water activity (a_w). Most of the strains were identified as Staphylococcus except for eight isolates assigned to Kocuria spp. The species most often isolated was Staphylococccus xylosus. Others were, in descending order of abundance, S. aureus, S. lugdunensis, S. saprophyticus, S. sciuri, S. chromogenes, and S. capitis. The distributions of the minority Staphylococcus species were different for the two manufacturers. All the investigated strains were able to grow at pH and a_w greater than 5.0 and 0.85, respectively, the values usually found in Iberian dry-cured sausages. Five S. xylosus strains showed antimicrobial activity against some indicator strains which were investigated. Seven strains with the best properties were pre-selected and tested for their lipolytic and proteolytic activities against pork fat and myofibrillar and sarcoplasmic pork proteins, respectively, and for their low biogenic amines production. Most of the strains showed proteolytic and lipolytic activities, but none produced histamine, tyramine, phenylethylamine, or spermine. Three strains, identified as Staphylococcus xylosus, possess useful properties which make them candidates for testing as starter cultures in pilot processing of Iberian sausages.     

A quasi-chemical model for the growth and death of microorganisms in foods by non-thermal and high-pressure processing

Predictive microbial models generally rely on the growth of bacteria in laboratory broth to approximate the microbial growth kinetics expected to take place in actual foods under identical environmental conditions. Sigmoidal functions such as the Gompertz or logistics equation accurately model the typical microbial growth curve from the lag to the stationary phase and provide the mathematical basis for estimating parameters such as the maximum growth rate (MGR). Stationary phase data can begin to show a decline and make it difficult to discern which data to include in the analysis of the growth curve, a factor that influences the calculated values of the growth parameters. In contradistinction, the quasi-chemical kinetics model provides additional capabilities in microbial modelling and fits growth-death kinetics (all four phases of the microbial lifecycle continuously) for a general set of microorganisms in a variety of actual food substrates. The quasi-chemical model is differential equations (ODEs) that derives from a hypothetical four-step chemical mechanism involving an antagonistic metabolite (quorum sensing) and successfully fits the kinetics of pathogens (Staphylococcus aureus, Escherichia coli and Listeria monocytogenes) in various foods (bread, turkey meat, ham and cheese) as functions of different hurdles (a_w, pH, temperature and anti-microbial lactate). The calculated value of the MGR depends on whether growth-death data or only growth data are used in the fitting procedure. The quasi-chemical kinetics model is also exploited for use with the novel food processing technology of high-pressure processing. The high-pressure inactivation kinetics of E. coli are explored in a model food system over the pressure (P) range of 207–345 MPa (30,000–50,000 psi) and the temperature (T) range of 30–50 °C. In relatively low combinations of P and T, the inactivation curves are non-linear and exhibit a shoulder prior to a more rapid rate of microbial destruction. In the higher P, T regime, the inactivation plots tend to be linear. In all cases, the quasi-chemical model successfully fit the linear and curvi-linear inactivation plots for E. coli in model food systems. The experimental data and the quasi-chemical mathematical model described herein are candidates for inclusion in ComBase, the developing database that combines data and models from the USDA Pathogen Modeling Program and the UK Food MicroModel.     

Effect of temperature and water activity on growth and ochratoxin A production by Australian Aspergillus carbonarius and A. niger isolates on a simulated grape juice medium

The effect of water activity (0.92, 0.95, 0.965 and 0.98) and temperature (15 °C, 25 °C, 30 °C and 35 °C) on growth rate and ochratoxin A (OA) production by five strains of Aspergillus carbonarius and two strains of A. niger isolated from Australian vineyards was characterised on a synthetic grape juice medium. Maximum growth for A. carbonarius occurred at ca 0.965 a_w and 30 °C, and for A. niger, at ca 0.98 a_w and 35 °C. The optimum temperature for OA production was 15 °C and little was produced above 25 °C. The optimum a_w for toxin production was 0.95–0.98 for A. carbonarius and 0.95 for A. niger. Toxin was produced in young colonies after and, typically, did not continue to accumulate the entire surface area of the plate was colonised. Rather, the amount decreased as colonies aged. Trends for growth and OA production were similar among Australian isolates and those from European grapes, as reported in the literature.     

Effect of water activity on inactivation of Listeria monocytogenes and lactate dehydrogenase during high pressure processing

The aim of this study was to investigate the effect of water activity (a_w) on the inactivation of Listeria monocytogenes and lactate dehydrogenase (LDH) during high pressure processing (HPP). For microbial inactivation lyophilized cells of L. monocytogenes 19,115 were left dry or were suspended in 10 ml of 0.1% peptone water, 10 ml of glycerol, or mixtures of glycerol and peptone water. All samples of various a_ws were high pressure (HP) processed at ambient temperature at 600 MPa for 300 s. Following HPP, samples were serially diluted in 0.1% peptone and spread-plated on Tryptic Soy agar supplemented with Yeast Extract. For enzyme inactivation, 4.2 mg of lyophilized LDH was suspended in 2 ml of 100 mM phosphate buffer (pH 7.4), 2 ml of peptone water or glycerol, or in 2 ml mixtures of glycerol and peptone water. A lyophilized sample with no added liquid was also included. All enzyme samples were subjected to HPP as described above. After HPP, LDH was diluted to 0.28 μg/ml in 100 mM phosphate buffer (pH 7.4). LDH activity was assessed by measuring the change in concentration of β-NADH as a function of time. Dynamic light scattering analysis (DLS) was performed to examine the size distribution, polydispersity, and hydrodynamic radius of LDH before and after HPP. No significant difference in CFU/g was observed between lyophilized cells not subjected to HPP and lyophilized cells subjected to 600 MPa for 300 s (P < 0.05). However, lyophilized cells that were suspended in 100% to 60% peptone water showed a ~ 7.5-log₁₀ reduction when subjected to HPP. Survival of L. monocytogenes following HPP significantly increased (P < 0.05) when the peptone water concentration was decreased below 60% (a_w ~ 0.8). DLS results revealed that LDH suspended in buffer underwent aggregation following HPP (600 MPa, 300 s). Inactivation rate constants obtained using a first-order kinetic model indicated that untreated and HP processed lyophilized LDH had similar activities. When LDH was subject to HPP in solutions containing glycerol, enzyme activity decreased as the water content increased (r² = 0.95). Lyophilization completely protected L. monocytogenes and LDH from inactivation by high pressure. Furthermore, enzyme activity and cell survival increased as water activity was decreased. We postulate low a_w results in protein stabilization, which prevents protein denaturation and cell death during HPP.     

Modelling the influence of palmitic, palmitoleic, stearic and oleic acids on apparent heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3

Heat resistance of spores is affected by many factors such as temperature, pH, water activity (aw) and others. Previous studies have reported that free fatty acids can affect the germination and growth of bacterial spores. In this study, we investigated the influence of free fatty acids in heating medium or in recovery medium on the heat resistance of spores of Bacillus cereus NTCC 11145 and Clostridium sporogenes Pasteur 79.3. Four free fatty acids were studied: palmitic, palmitoleic, stearic and oleic acids. During thermal treatments, the impact of these FFA in heating media was generally low, but the presence of free fatty acids in the recovery medium highly decreases bacterial spore apparent heat resistance, particularly with unsaturated fatty acids. A mathematical model was developed to describe and quantify the influence of free fatty acids in recovery media on the D-values. The z′_FFA parameter values which quantify the impact of free fatty acids were determined. The variation of this parameter value according to the free fatty acid type was compared with MIC value variation given in the literature. The model enables the decrease in D-values in the presence of free fatty acids to be estimated. The high concentrations of free fatty acids in liver or canned duck may explain the microbial stability with low sterilization values applied.     

Sorption isotherms and the state diagram for evaluating stability criteria of abalone

Water adsorption isotherms and the state diagram of abalone were developed to further investigate the connection between the two distinct criteria of food stability. The isotherms were measured at 23, 40 and 60 °C using an isopiestic method and they were treated with appropriate models available in the literature. The state diagram was developed using freezing points, as derived by the cooling curve method, and glass transition temperatures were measured by dynamic oscillation on shear. The limited glass transition process of the abalone network necessitated derivation of the mechanical glass transition temperature, since the transition could not be detected using MDSC. Results indicate that there is a considerable discrepancy in the temperature-related stability criteria predicted by the concepts of water activity (a_w) and the glass phenomenon (T_g). In contrast to the progressive deviation between a_w and T_g with increasing molecular weight reported earlier for a homologous family of materials, the effect of rising temperature produces a constant index of comparison between the two concepts.     

Glass transition and water effects on sucrose inversion in noncrystalline carbohydrate food systems

The effects of water and glass transition on the hydrolysis of sucrose by invertase in noncrystalline carbohydrate systems were investigated. Maltodextrin/sucrose (2:1) and maltodextrin/lactose/sucrose (1:1:1) were dissolved in distilled water. Invertase (10 mg/17.2 g) was added. Amorphous samples were produced by freeze-drying the solutions. Sorption isotherms were determined gravimetrically at 24 °C over the 0.113–0.763 a_w, and over 0.239–0.764 a_w, the glass transition, T_g was determined using differential scanning calorimetry (DSC). DSC and water sorption results suggested that samples remained noncrystalline. Sucrose inversion was analysed by monitoring glucose content during storage. Sucrose hydrolysis occurred at significant rates at 0.662 and 0.764 a_w. The rate increase was not related to the apparent glass transition of the systems.     

Taking injuries of surviving bacteria into account for optimising heat treatments

The main assets of early conventional models applied in the field of canned food industries are their simplicity and their robustness. Moreover, a certain standardisation of these models allows the intrinsic quantification of a food process like sterilisation, regardless of the nature of concerned microbial populations. However, a first drawback of conventional models is their monofactorial nature: only temperature is considered for the evaluation of microbial heat resistance. A second limit of early survival models is that conventional estimates of heat resistance are made by recovering heated surviving cells at optimal incubation conditions. However, many investigators observed that culture medium and incubation temperature influence both the ratio of injured cell recovery and estimated heat resistance values. Mafart and Leguérinel [Mafart, P., Leguérinel, I., 1998. Modeling combined effects of temperature and pH on heat resistance of spores by a linear-Bigelow equation. J. Food Sci. 63, 6-8] developed a model describing the heat resistance of spores as a function of temperature and pH which is an extension of the Bigelow equation. A short while later, they added a further term to their model in order to consider the water activity of the heating medium (Gaillard, S., Leguérinel, I., Mafart, P., 1998. Model for combined effects of temperature, pH and water activity on thermal inactivation of Bacillus cereus spores. J. Food Sci. 63, 887-889). From their model, the authors proposed an extension of the concept of biological destruction value (BDV) noted L(T, pH, a(w)), that they called primary BDV. More recently, we developed a second multifactorial model describing the effect of the temperature, the pH and the water activity of the recovery medium on the estimated D-value of heated spores (unpublished). From this new model we propose the concept of secondary BDV noted L'(T, pH, a(w)). We show that, for calculations of heat processes, the effective BDV, M, to be considered is the overall function M = LL'. From another model [Mafart, P., Leguerinel, I., 1997. Modelling the heat stress and the recovery of bacterial spores. Int. J. Food Microbiol. 37, 131-135], it can be shown that the secondary BDV is also the corrective factor to be considered to assess the overall decimal reduction ratio q: q = L'n where n is the conventional decimal reduction ratio without taking into account the effect of environmental factors of the recovery medium on the effective heat resistance of injured spores.     

Effect of the medium characteristics and the heating and cooling rates on the nonisothermal heat resistance of Bacillus sporothermodurans IC4 spores

In recent years, highly thermo-resistant mesophilic spore-forming bacteria belonging to the species Bacillus sporothermodurans have caused non-sterility problems in industrial sterilization processes. The aim of this research was to evaluate the effect of the heating medium characteristics (pH and buffer/food) on the thermal inactivation of B. sporothermodurans spores when exposed to isothermal and non-isothermal heating and cooling treatments and the suitability of non-linear Weibull and Geeraaerd models to predict the survivors of these thermal treatments. Thermal treatments were carried out in pH 3, 5 and 7 McIlvaine buffer and in a courgette soup. Isothermal survival curves showed shoulders that were accurately characterized by means of both models. A clear effect of the pH of the heating medium was observed, decreasing the D₁₂₀ value from pH 7 to pH 3 buffer down to one third. Differences in heat resistance were similar, regardless of the model used and were kept at all temperatures tested. The heat resistance in courgette soup was similar to that shown in pH 7 buffer. When the heat resistance values obtained under isothermal conditions were used to predict the survival in the non-isothermical experiments, the predictions estimated the experimental data quite accurately, both with Weibull and Geeraerd models.     

Relationship between the apparent heat resistance of Bacillus cereus spores and the pH and NaCl concentration of the recovery medium

Conventional heat resistance data, D values, were previously established by other workers at optimal condition for spores outgrowth. However, in canned food conditions of outgrowth are generally suboptimal in term of pH, salt concentration, water activity. The combined effects of pH and NaCl level of the recovery medium for the D value and z(pH) value were studied. Spores of Bacillus cereus were heated at 95 degrees C in phosphate-citrate buffer media at pH 7. Cells were recovered at 25 degrees C in Nutrient Agar with pH ranging from 5 to 7 and 1% to 4% (w/w) NaCl concentration. For each condition D' values (decimal reduction time associated with the recovery media characteristics) were determined. The results show a major influence of the recovery pH on the D' values. This effect is characterised by the z'(pH) values, distance of recovery medium pH from optimum recovery pH* medium (6.7) which leads to a tenfold reduction time of D value. The increase of the salt concentration leads to a slight decrease of D' value. However z'(pH) values are not significantly affected by the salt concentration. A simple three parameter model describing the effects of pH and NaCl concentration of the recovery medium upon the heat resistance of spores is proposed. The interaction between pH and salt concentration is sufficiently low to be neglected by the model.     

Modelling the influence of the sporulation temperature upon the bacterial spore heat resistance, application to heating process calculation

Environmental conditions of sporulation influence bacterial heat resistance. For different Bacillus species a linear Bigelow type relationship between the logarithm of D values determined at constant heating temperature and the temperature of sporulation was observed. The absence of interaction between sporulation and heating temperatures allows the combination of this new relationship with the classical Bigelow model. The parameters zT and zT(spo) of this global model were fitted to different sets of data regarding different Bacillus species: B. cereus, B. subtilis, B. licheniformis, B. coagulans and B. stearothermophilus. The origin of raw products or food process conditions before a heat treatment can lead to warm temperature conditions of sporulation and to a dramatic increase of the heat resistance of the generated spores. In this case, provided that the temperature of sporulation can be assessed, this model can be easily implemented to rectify F values on account of possible increase of thermal resistance of spores and to ensure the sterilisation efficacy.     

Enzymatic synthesis of cocoa butter analog through interesterification of lard and tristearin in supercritical carbon dioxide by lipase

Substrate oil composition, reaction time, acyl donor, temperature, and pressure affected the triacylglycerol (TG) content of cocoa butter analog during the interesterification reaction catalyzed by lipase in a supercritical carbon dioxide (SC-CO₂) system. Among oil sources used to interact with tristearin, the content of 1(3)-palmitoyl-3(1)-stearoyl-2-monoolein (POS) (P, palmitate; O, oleate; S, stearate) and 1-palmitoyl-2, 3-dioleoylglycerol (POO) in analog was most similar to the corresponding TG content of cocoa butter when analog was prepared with lard. The optimized interesterification reaction using lard and tristearin (at a mole ratio of 1.4) as substrates to produce cocoa butter analog in a SC-CO₂ system was at 17 MPa, 50 °C, pH 9, for 3 h with an immobilized lipase, Lipozyme IM-20, from Mucor miehei. The lyophilized enzyme facilitated the production of cocoa butter analog in anhydrous substrates (a_w 0.33). The yield and melting point of the purified cocoa butter analog by a silica column was 63% and 34.5 °C, respectively, when the analog was produced under optimal conditions.     

Role of surface-inoculated Debaryomyces hansenii and Yarrowia lipolytica strains in dried fermented sausage manufacture. Part 1: Evaluation of their effects on microbial evolution, lipolytic and proteolytic patterns

The aim of this work was to study the effects of Debaryomyces hansenii and Yarrowia lipolytica strains, used with lactic acid starter cultures (Lactobacillus plantarum), on the manufacture of dried fermented sausages to understand their role on sausage microbial evolution, lipolytic and proteolytic patterns. The inoculation of the yeast strains did not markedly affect the sausage’s microbial flora. The sausages with the yeast strains showed more marked and earlier water activity (a_w) reductions. Moreover, the surface inoculation of the yeast strains resulted, at the end of ripening, in more pronounced proteolysis and lipolysis. The lipolytic patterns of the products were affected not only by the yeast strain but also by the level of mincing of the meat mixture used.