Microbial modeling of Alicyclobacillus acidoterrestris CRA 7152 growth in orange juice with nisin added

The adaptation time of Alicyclobacillus acidoterrestris CRA 7152 in orange juice was determined as a response to pH (3 to 5.8), temperature (20 to 54 degrees C), soluble solids concentration (degrees Brix; 11 to 19 degrees Brix), and nisin concentration (0 to 70 IU/ml) effects. A four-factor central composite rotational design was used. Viable microorganisms were enumerated by plating on K medium (pH 3.7). Two primary models were used to represent growth and adaptation time. A second-order polynomial model was applied to analyze the effects of factors. Results showed that the Baranyi and Roberts model was better than the modified Gompertz model, considering the determination coefficient (R-2) for experimental data description. Inhibition of bacteria can be obtained through several studied combinations for at least 47 days of storage. The shortest period of adaptation was observed between 37 to 45 degrees C, with pHs between 4 and 5, yet the longest periods of adaptation could be obtained around 20 degrees C with pHs close to 3.0. Statistical analysis of the quadratic model showed that the adaptation time increased as temperature or pH decreased, and as nisin concentration or soluble solids increased. The model showed that adaptation time has a minimum value for juice without nisin added, with 13.5% soluble solids, pH 5.0, and incubated at 43.8 degrees C. The statistical parameters that validated this model were an R-2 of 0.816, a bias factor of 0.96, and an accuracy factor of 1.14. Manipulation of more than one factor, as well as the use of an antimicrobial agent, can be an alternative to preventing the development of A. acidoterrestris in orange juice, thus contributing to increased orange juice shelf life.6981904191

Thermal death kinetics of B-Stearothermophilus spores in sugarcane must

Thermal death kinetic parameters for Bacillus stearothermophilusspores were evaluated in sugarcane must (21.5 degrees Brix, pH = 6.14) at temperatures ranging from 98 to 130C, using the thermal-death-time tube method and survivors count. Resulting survival curves showed strong nonlinearity and different shapes according to heating temperature. The 98 and 110C curves showed an initial shoulder or thermal lag and were adjusted to the logistic model. At the temperature range of 120-125C, the two-term exponential model for population with heterogeneous heat resistance was fitted, and at 130C, the classic linear model was suitable. It was shown that rate constants are influenced by temperature according to two irreconcilable methods: the Arrhenius and the Bigelow methods. Activation energy (E-a) obtained was 249.52 kJ/mol while thermal resistance parameter (z-value) calculated from E-a and the Bigelow method were 11.48 and 9.19C, respectively. Thermal death kinetic constant, k values, varied from 0.019 to 13.63/min.30562563

Biological validation of tomato pulp continuous heat process

This research validated the commercial process applied to tomato pulp (pH 4.3 and 8 Brix) packed in Tetra Brik packages. Spores of Bacillus coagulans and Neosartorya fischeri were selected as targets. The heat resistance of both microorganisms, tested independently, was compared. The redesigned thermal processes were carried out in a aseptic processing and tested by indirect inoculation and retrieval with spores immobilized in alginate/tomato balls. The results showed that processes for 30 s at 115C or greater did not allow the survival of heat-resistant molds. For bacterial spores, processes for 30 s at 109C or greater showed no survivors. Although, 30 s at 115C will control both types of spoilage spores, concern for possible C. botulinum growth attributed to metabiosis in product with varying initial populations of molds and residual oxygen content dictated, a process recommendation of 60 s at 126C for safety reasons.27644946

Thermal degradation kinetics of sucrose, glucose and fructose in sugarcane must for bioethanol production

Thermal degradation of sugars contained in sugarcane must (21.5 degrees Brix, pH 6.14) was evaluated at temperatures of 110, 120, 130 and 140C, using the thermal-death-time tube method, determining remaining sugars by high-pressure liquid chromatography. The study analyzed thermal degradation kinetics of both the total reducing sugars (TRS) and glucose and fructose individually. All curves of remaining sugars presented strong nonlinearity, with initial shoulder and final tail adjusted by an extended logistic model that was adapted for two species for TRS, and a simple logistic model for the monosaccharides. It was shown that rate constants are influenced by temperature according to two irreconcilable methods: the Arrhenius and the Bigelow methods. Obtained activation energies for fructose and glucose were quite coincident, 140.37 and 140.23 kJ/mol, respectively. Thermal resistance parameters were 21.59 and 21.61C, respectively. Comparison of the rate constants revealed that fructose degraded approximately 9-10 times faster than glucose.29546247

Quality of Mango Nectar Processed by High-Pressure Homogenization with Optimized Heat Treatment

This work aimed to evaluate the effect of high-pressure homogenization (HPH) with heat shock on Aspergillus niger, vitamin C, and color of mango nectar. The nectar was processed at 200 MPa followed by heat shock, which was optimized by response surface methodology by using mango nectar ratio (45 to 70), heat time (10 to 20), and temperature (60 to 85 degrees C) as variables. The color of mango nectar and vitamin C retention were evaluated at the optimized treatments, that is, 200 MPa + 61.5 degrees C/20 min or 73.5 degrees C/10 min. The mathematical model indicates that heat shock time and temperature showed a positive effect in the mould inactivation, whereas increasing ratio resulted in a protective effect on A. niger. The optimized treatments did not increase the retention of vitamin C, but had positive effect for the nectar color, in particular for samples treated at 200 MPa + 61.5 degrees C/20 min. Practical Application The results obtained in this study show that the conidia can be inactivated by applying HPH with heat shock, particularly to apply HPH as an option to pasteurize fruit nectar for industries.762M106M11

Inactivation of Aspergillus niger in Mango Nectar by High-Pressure Homogenization Combined with Heat Shock

This research evaluated the inactivation of a heat-resistant Aspergillus niger conidia in mango nectar by high-pressure homogenization (HPH) combined with heat shock. A. niger were inoculated in mango nectar (106 conidia mL(-1)) and subjected to HPH (300 to 100 MPa) and heat shock (80 degrees C for 5 to 20 min) before or after HPH. Processes were evaluated according to number of decimal reductions reached by each isolated or combined process. Scanning electron microscopy was performed to observe conidia wall after pressure treatment. Pressures below 150 MPa did not inactivate A. niger while pressures of 200 and 300 MPa resulted in 2 and more than 6 log reductions, respectively. D(80 degrees C) of A. niger was determined as 5.03 min. A heat shock of 80 degrees C/15 min, reaching 3 decimal conidia reductions, was applied before or after a 200 MPa pressure treatment to improve the decimal reduction to 5 log cycles. Results indicated that HPH inactivated A. niger in mango nectar at 300 MPa (> 6.24 log cycles) and that, with pressure (200 MPa) combined with post heat shock, it was possible to obtain the same decimal reduction, showing a synergistic effect. On the other hand, pre heat shock associated with HPH resulted in an additive effect. The observation of A. niger conidia treated by HPH at 100 and 200 MPa by scanning electron microscopy indicated that HPH promoted intense cell wall damage, which can sensitize the conidia to post heat shock and possibly explain the synergistic effect observed. Practical Application: The results obtained in this paper are relevant to elucidate the mechanism of conidia inactivation in order to develop the application of HPH as an alternative pasteurization process for the fruit nectar industry.749M509M51

MODELING THE GROWTH LIMIT OF ALICYCLOBACILLUS ACIDOTERRESTRIS CRA7152 IN APPLE JUICE: EFFECT OF PH, BRIX, TEMPERATURE AND NISIN CONCENTRATION

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The logistic regression model was used to describe the temperature effect (25 to 50C), pH(3.5 to 5.5), soluble solids concentration (11 to 19) and nisin concentration (0 to 70 IU/mL) on the growth probability of Alicyclobacillus acidoterrestris CRA 7152 in apple juice. The model concordance was 97.3%, indicating a good fit of the observed data. The results showed that with pH 3.7 the growth probabilities were small (<10(-5)) for nisin concentrations above 50 IU/mL. At 0.05 growth probability, minimum values of pH were established between 3.8 and 4.6 to inhibit the growth with the nisin synergistic action in concentration of 0 and 20 IU/mL, respectively, when the juice is incubated at 30C. The logistic model obtained can provide data to be used in quality control and at processes development. PRACTICAL APPLICATIONS This work applied predictive microbiology to develop a logistic model that can be used to reduce the recontamination of apple juice. The model obtained can be immediately used to food quality control, quality management, risk assessment and management, hazard analysis by control critical point, good manufacturing practices and cost reducing by allowing the prediction. The results also show that nisin plays an important role in the control of apple juice contamination by Alicyclobacillus acidoterrestris and it can be used in combination with pH, soluble solids concentration and temperature.354509517Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP

Use of a logistic model to assess spoilage by Byssochlamys fulva in clarified apple juice

The percentage P (%) of spoiled bottles (n = 40) of clarified apple juice due to Byssochlamys fulva, was modeled by using a logistic model: P = P(max)/1 + exp(k(tau-iota)) where P(max) (%) the maximum percentage of spoiled bottles, k (h(-1)) slope parameter and T (h) the time for P = P(max)/2. Bottles of pasteurized apple juice were inoculated with B.fulva IOC 4518 ascospores for low and high initial loads, 4.8 +/- 23 ascospores/100 mL and 19.3 +/- 4.6 ascospores/100 mL respectively and incubated at 21 degrees C and 30 degrees C. P(max) was not significantly different from 100% except for a low initial load at 21 degrees C. Model parameters were estimated with a good accuracy, RMSE in the range 3.89-7.50. Then the model was used to determine the time for 10% bottles spoiled, t(10%). This time was greater at low initial loads, 57.4 and 104 h at 30 and 21 degrees C respectively, than at high initial loads 23.9 and 75.1 h at 30 and 21 degrees C respectively. This study demonstrated that even at a very low initial contamination, clarified apple juice can be easily spoiled by B.fulva highlighting the importance of controlling critical control steps of fruit juice processing (i.e., fruit washing, juice filtration and pasteurization). (C) 2009 Elsevier B.V. All rights reserved.1374170029930