جستجوی مقالات مرتبط با کلیدواژه "pasteurization" در نشریات گروه "صنایع غذایی"

Today, the desire to use ozone as a strong antimicrobial compound, cost-effective, and eco-friendly innovation, has increased to increase the shelf life of food products. This study was conducted in order to evaluate the chemical and microbial properties of thermally pasteurized skim milk treated with pressurized ozone injection at concentrations of zero, 1.5, 5, and 10 ppm. The chemical, microbial and sensory characteristics of the treated milk samples were evaluated on days 0, 4, 7 and 15 of storage in the refrigerator. The total viable count (TVC) in the treated samples with ozone compared to the control had a noticeable decrease in all storage days. The highest antimicrobial effect was observed on the 15th day of storage with 10 ppm ozone and the lowest effect was observed on the 4th day with 1.5 ppm ozone. However, there was no significant difference in pH (6.8-6.88) and acidity (0.16-0.18) between treated and control samples. Although the peroxide number (PV) in the treated samples and the control samples was higher than the standard, but its reduction was evident in the treated samples compared to the control samples. Also, by comparing the sensory characteristics among the samples, no significant differences were observed. In general, treatments with 5 and 10 ppm ozone had the best efficiency in increasing the shelf life of pasteurized milk. According to the results, ozone can be used as an auxiliary method to increase the effectiveness of thermal processes in pasteurization and increase the shelf life of milk.

In recent years, cold plasma is one of the expected alternatives for post-harvest treatments and post-harvest management of products. A surface discharge plasma system was used for investigating the destruction time of Bacillus cereus, Bacillus coagulans, Bacillus stearothermophilus, and Clostridium botulinum in bottled milk. The simulation was performed by COMSOL a3.5 software for a two-dimensional geometry. The collected experimental data were simulated in COMSOL software. The k factor of microorganism deactivation data was used to validate the simulated data. Results showed that the production of reactive oxygen species during plasma treatment increases with time and extends to the entire container. The concentration of reactive oxygen species (at the output of the plasma probe) at the beginning of the production was high, and at the end when they leave the free surface of the milk, the concentration decreased. Increasing the initial temperature of milk sample, from 50 to 80℃, can cause significant changes in the amount of ozone from 125 mol/m3 to 266 mol/m3, respectively (p <0.05). However, voltage changes in these two temperatures did not show a significant effect on ozone concentration. Also, immediately upon the initiation of plasma treatment, plasma destruction begins where the concentration of active species is higher. It is shown that among the four studied bacteria, Bacillus stearothermophilus has the highest resistance against cold plasma, and after that other bacteria have shown similar resistance. Finally, it can be concluded that the deep plasma treatment in bottle can make it possible to overcome the surface limitation of cold plasma treatment.

Cold plasma is a non-thermal technology and a suitable alternative to conventional thermal methods used in the food industry, which, with its antimicrobial properties, increases the shelf life of food products without negatively affecting their quality. The purpose of this research is to investigate the physicochemical, microbial and sensory properties of red grape juice pasteurized by cold plasma method (under plasma irradiation with voltage of 20, 40 and 60 kV for a period of 1, 2, 3 and 4 min and air gas) and compare it with thermal pasteurization (95°C for 5 seconds). The results showed that the effect of treatment on physicochemical properties (acidity, pH and Brix), bioactive compounds (anthocyanin, total phenol and vitamin C), color properties (components a*, b* and L*), microbial load (mold and yeast, aerobic bacteria and coliform) and sensory characteristics (taste, smell and overall acceptance) of red grape juice pasteurized by cold plasma method was significant (p≤0.05) so that with increasing amount voltage from 20 to 60 kv and time from 1 to 4 min, in grape juice pasteurized by cold plasma method, the amount of acidity, brix, color components a* and b* increased significantly (p≤0.05) and the amount pH, bioactive compounds (anthocyanin, total phenol and vitamin C), the amount of color of L* component, the amount of microbial load (mold and yeast, aerobic bacteria and coliform) decreased significantly (p≤0.05). Also, by increasing the time from 1 to 4 min, the smell score and overall acceptance decreased, and by increasing the voltage from 20 to 60 kV and the time from 1 to 4 min, the taste score decreased. Since the physicochemical, color, microbial and sensory changes of red grape juice pasteurized by cold plasma method in the conditions of 40 kv, 4 min time and air gas were less than thermal pasteurization method and more acceptable for consumption, it was introduced as a superior treatment.

Egg contamination by Salmonella enteritidis is one of the most important causes of foodborne gastroenteritis throughout the world and the common method which can be used to inactivate this bacteria is pasteurization. In this study, the pasteurization of intact egg was mathematically modelled using a CFD technique. The results were compared with experimental data and it was found that the model could reasonably forecast the temperature of egg during pasteurization (R2>0.98). The model showed that in order to predict the temperature variation of the slowest heating zone (SHZ) with higher accuracy, it is necessary to to incorporate the influence of natural convection currents induced by the hot eggshell walls in the pasteurization process. Results indicated that the SHZ keeps moving during pasteurization and eventually stays in a region that is about 25% of the egg height from the bottom after 300 s of heating. These results also show that the time required to reduce the Salmonella enteritidis population in cold point of eggs to 5D is approximately 28 minutes. This model could serve as an important tool in better understanding of the pasteurization process, choosing the best process parameters and facilitate process optimization of intact egg pasteurization towards industrial implementation

Tomato (Solanum lycopersicum) is the second most important horticultural crops next to potato, with an estimated world production of over 120 million tons per year. Iran has always been among the top tomato producing countries in the world due to the diverse topography and climactic conditions prevailing in different parts of Iran. Tomato paste is one of the most important tomato products originates from tomato juice in which water is removed by evaporation and thermal processing plays a key role in the successful production process (Singh and Headman, 2014). Since it can guarantee safety and extend shelf life of the product. Although several emerging technologies such as ohmic heating, microwave heating, and non-thermal processing techniques such as pulsed electric fields and high pressure processing, have been developed for food preservation, Conventional thermal processing (pasteurization and sterilization) is still widely used in the Iranian food industry. However, the challenges of accurately determining both optimal operating conditions and developing a control system for industrial pasteurization process to prevent either under- or overprocessing are significant (Chen and Ramaswamy, 2007). Mathematical modeling and simulation is one of the most commonly used methods to gain a better understanding the process. Modeling can provide insights into complex processes, shorten the design cycle and optimize the process as a function of various variables at lower cost and time. Different mathematical methods for solving heat conduction problems have been proposed, but numerical methods are more useful, especially when such problems cannot be handled by the exact analysis because of nonlinearities, complex geometries, and complicated boundary conditions (Incropera and De Witt, 1990). Among the numerical methods developed so far, finite difference and finite element techniques have been widely used to analyze heat transfer phenomena in cylindrical cans of food. Although many researchers have tried to develop mathematical models based on numerical methods for predicting temperatures in tomato products during thermal processing, such as (Bichier et al., 1995), (Nicolai et al., 1998), (Tattiyakul et al., 2002) and (Plazl et al., 2006), there is not much research available on the subject of thermal processing of tomato paste in Iran. In this study, the efficiency of two different modeling approaches (finite difference vs. finite element) for predicting temperature of tomato paste during pasteurization process were compared. The developed model allows to reduce energy consumption during operations while high-quality products are also produced in a short time.

Experiments were run with batches of 400 g of tomato paste (pH = 4.1 and 28°Brix) in cylindrical cans (211×400) and hot water was used as the heating medium. The chemical analysis of tomato paste sample (Brix, pH salt, moisture, fat and protein) was performed in the first step and the thermal properties of the tomato paste product including thermal conductivity, specific heat and density were determined based on the sample chemical composition and structures model. Temperature changes at various positions in the container were checked with a data logger (Testo, Germany) coupled with computer and thermocouples type-K (at 2 min intervals). The cylindrical can was immersed in a vertical position in the water bath and the temperature recording was started. After finishing the heating time, the can was cooled in another water bath (20ºC). The data were used to validate the developed model. In the next step, 2D heat transfer model was developed in a cylindrical can by using the numerical solution of the Fourier second law with two different methods. 1) Finite difference (explicit scheme) and finite element methods. Computer simulation is done using MATLAB R2009a software (Math works, Inc., Natick, MA, USA) and COMSOL Multiphysic, Ver. 4.0. Finally, in order to evaluate the best model, two criteria, coefficient of determination (R2) and root mean squared error (RMSE) were used.

The results showed that, by placing the sample in the bath, the surface temperature rises rapidly, while the temperature in the center is much slower. In addition, as can be expected, increasing hot water temperature enhanced the heating rate considerably due to the larger temperature gradient between the center and surface of the can at the higher temperatures. The models have been verified by comparing results with two analytical solutions and validated against experimental data. The statistical analysis results showed that the finite element model developed by COMSOL software can predicted temperature more accurate than finite difference model and may be more useful. The reason for this difference between the results of two numerical methods can be attributed to the consideration of a layer of air-steam mixture on the top of the can (head space) in the finite element method which increases the accuracy of the model in temperature prediction. After validation, the developed model was used to determine the cold spot location of the tomato paste can. Results also showed that the cold point was a stationary point and located at the radial center at a height of 60% of the can height from the bottom (Tattiyakul et al., 2002). Two simulations were conducted at two different head space volume (6 and 12% of total can height) to determine the importance of head space volume on cold point location. Results showed that there was no significant difference in the location and temperature of the cold spot in two simulations (Khakbaz Heshmati et al., 2014).

In this study, the pasteurization process of tomato paste (Brix=28) is investigated by two different numerical methods (finite difference& finite element). The results were compared with experimental data and it was found that the predicted temperature by finite element model is more accurate than finite difference method. Although it is generally believed that the coldest point for a solid product will be at the geometric center of the cylinder, our results indicated that the slowest cooling point was located at a height of 60% of the can height from the bottom. The developed model can predict temperature in tomato paste with different degree of concentration (brix) or different thermal processing conditions and with minor modifications, the model may be used to design and control the process of industrial pasteurization for various solid products. In addition, the results of this study is expected to be a significant contribution for further optimization studies.

In this research, the effect of different thermal processes of milk, pasteurization) 63°C for 30 min, 74°C for 15 s, 95°C for 5 min) and sterilization (120°C for 15 min and 140°C for 2-4 s), on the selective physicochemical, sensory and microbial properties of probiotic yoghurt was investigated during cold storage for 21 days. Results showed that during storage time, syneresis decreased and acidity and redox potential increased (p<0.01). By increasing the severity of thermal processing, the decline in syneresis and redox potential (p<0.01) and the increase in acidity and viability of Lactobacillus acidophilus (p<0.05) and Bifidobacterium lactis was observed (p>0.05). Finally, regarding to the highest sensory evaluation and probiotic bacteria viability, the yoghurt sample produced from milk treated at 140°C for 2-4 s was selected as the best sample.

The purpose of this study was to investigate the effect of ultrasonic processing on the microbial and physicochemical properties of sourcherry juice.The effect of pasteurization in comparison with ultrasound was investigated at 25 and 60 °C for 4, 8, 12 minutes with 24.4, 42.7, 61 μm at a frequency of 20 kHz. Pasteurization and treatment of 12 min, 42.7μm amplitued, 60° C, 8 and 12 min, 61 μm, 60° C and 12 min, 61 μm, 25 ° C caused a complete destruction of aerobic bacteria. Except for the 4 minute at 60 ° C treatment, total coliforms were completely destroyed in other treatments.Molds were completely eliminated in other treatments, except for 4 minutes, the temperature of 25 ° C, 24.4 micrometers. Except for the 4 minute at 60 ° C treatment, total coliforms were completely destroyed in other treatments.Molds were completely eliminated in other treatments, except for 4 minutes, the temperature of 25 ° C, 24.4 μm. Yeasts were eliminated in all heat treatments and sonication at 25° C in maximum time and amplitued. By increasing the amplitude of ultrasound, temperature and treatment time had a negative effect on anthocyanin content and phenolic content but did not have a significant effect on antioxidant content.According to the combined results, medium amplitude at 60 ° C can be the most effective treatment in preserving quality traits and providing microbial trait in sourcherry juice.

Heating of milk for the purpose of removing the bacterial pathogens should be done for the shortest time, and sufficient pasteurization must be ensured. The limitation of the classical methods of pasteurization is due to the high sensitivity of the milk to coagulation by the application of high temperature, which sometimes prevents the proper process and causes problems such as milk clotting and the formation of non-washable layers (milk stones) on the interior surface of the pasteurization tubes. These layers prevent the sufficient heat transfer and the adequacy of the pasteurization of the next inlet milk, and as a result, the mentioned milk contains high levels of microbial contamination that will be hazardous to consumers. Therefore, the aim is to find a suitable pasteurization method that does not have the above-mentioned disadvantages and also the milk obtained from the pasteurization process will have a higher quality. Therefore, in this research, the inductive electromagnetic flow heat was used for pasteurization of the milk. In this method, the milk container acts as the second coil of the electromagnetic current (transformer) and allows direct flow of electricity in the milk. In the preparatory steps of the project (stages 1 to 3), whose results are not mentioned in this article, milk pasteurized was done by induction heating in an attempt to modify, revise, and refine the usual classical process. In order to obtain the best conditions for milk pasteurization by the induction method, the effect of four different factors were investigated, namely three diameters of the test vessel (23, 17 and 12 cm), three electrical conductivities (350, 1000 and 1600 watts), three temperatures (72, 75 And 84 ° C), three storage periods at pasteurization stage (15, 20 and 30 seconds) and three replications; Where 243 samples were selected in a completely randomized factorial experiment design. And the tested samples were categorized based on 1) the lowest percentage of residual microbial load, 2) the minimum time spent for pasteurization, and (3) the least Energy consumption for pasteurization. Three selected samples in the third stage of the previous project were prepared using the standard method in this study with the correct mixing at a certain temperature and used for the organoleptic test by the taste Group during the following steps. 1) Selection of 10 panelists. 2) Explaining the method and providing relevant questionnaires; 3) Checking and assuring the qualification of the panelists for evaluation (no smoking, medication, etc.); 4) explaining the evaluation method to the testers. Then, the physical and organoleptic characteristics of the produced samples were determined by the panelist group using a grading method based on the color, aroma, taste, texture, consistency and concentration of the samples. In the samples pasteurized using the induction pasteurization method with 1600 W power transmission intensity, 30 seconds holding time, temperature of 84 ° C and 23 cm cross section of the container, desirable organoleptic and physical properties were obtained compared to the other samples and the control (pasteurized under conventional conditions). So, there was a significant difference between consistency, concentration, and aroma and customer
satisfaction in two treatments at the level of 5% confidence and for the color attribute at 1% level due to the high speed of heat transfer in milk. The induction method of pasteurization is superior to the HTST method in favor of the production of desirable organoleptic properties, and is a very good substitute for the classic method of the factory under the same conditions.

Production of pasteurized liquid egg is a new technology in Iran. The main objective of egg pasteurization is manufacture of a safe product microbiologically, but lack of control of process causes remarkable irreparable damage to its properties such as emulsifying and it leads to financial loss, so protection of egg quality is a basic factor during pasteurization. Egg yolk with certain pasteurization conditions was produced and used as emulsifier for production of oil in water emulsion (30%) based on Box-Behnken design of experiments. Rheological properties were studied using Rheometer, particle size distribution by laser light scattering technique, and emulsion stability index according to turbidity measurement. Impact of temperature, NaCl and pressure on studied factors were evaluated by response surface methodology, and quadratic polynomial model was obtained for each response .To summarize, temperature increasing in lack of salt resulted in decrease of emulsifying characteristic of yolk due to denaturation of its proteins. NaCl retains the emulsifying of egg yolk as a result of protection against adverse effect of temperature during pasteurization. Following this further, homogenization pressure improves the emulsifying of egg yolk by uniformity of particle size and consistency. According to our findings, the results of available models are useful to estimate the impact of pasteurization conditions on responses in order to increase the quality of pasteurized liquid egg yolk.

Effects of Lepidium perfoliatum seed gum (LPSG) concentration (0, 0.3 and 0.6 wt%) and different processing treatments (freezing, pasteurization and sterilization) on physical and stability of oil-in- water emulsion prepared by whey protein (6 wt%) was investigated. For this purpose, particle size distribution, creaming index, microscopic characteristics, viscosity and flow behavior of emulsions were studied. Results showed that thermal processing increased the particle size of dispersed phase. Results also showed that the damage of membrane surface at high temperature such as sterilization was higher than other temperatures. At low Lepidium perfoliatum seed gum concentration, the emulsions were somewhat more resistant to thermal processes. However, at higher gum concentrations (0.3 and 0.6%), thermal processing did not have a negative effect on the emulsion stability. The viscosity and consistency coefficients also increased with increasing gum concentration. Shear thinning behavior for emulsions at all thermal treatments were also observed. Therefore, adding LPSG to the emulsion could increase its stability to the thermal processing.

Milk as a unique source of elements is important in bone formation and its growth. In addition, it contains valuable proteins, minerals and vitamins. Considering the nutritional importance of this food and its role in personal health, microbial quality status of pasteurized milk was studied. In this research, microbiological quality of 60 pasteurized milk samples collected from western part of Tehran was evaluated by enumeration of aerobic mesophilic microorganisms, coliforms and detection of Escherichia coli. According to Iran's National Standard limits, aerobic mesophilic microorganisms and coliforms counts must not exceed 7.5×104 CFU/ml and 10 MPN/ml in pasteurized milk, respectively. Besides, Escherichia coli must be absent. Eighty five percent of the samples had satisfactory qualities. Escherichia coli was not isolated from any sample. The aerobic mesophilic microorganisms and coliforms counts were not in accordance with Iran's National Standard limits in 5% and 10.3% of the studied samples. Aerobic mesophilic microorganisms and coliforms average counts were 1.8×104 CFU/ml and 1.1 MPN/ml in the studied samples, respectively. The results confirmed satisfactory microbial quality of studied pasteurized milk samples.

Traditionally, pot (Kope) cheese produced from raw milk in the Northwestern provinces of country and nowadays some of the Kope cheese producers have been used of plastic or metal container as a pot. The aim of this study was to determine the effect of pasteurization and packaging on the physicochemical and sensory properties of Kope cheeses during 120 days of ripening. The results revealed that before filling of cheese in pot and plastic container, pasteurized cheeses had higher salt and pH, and pasteurization process increased acidity in pot cheese and pH in cheese which ripened in plastic container at 120th day of ripening. Although usage of pot as a container increased pH, total solid, salt, ash, fat, protein and also overall taste, where plastic container increased acidity and lipolysis of cheese.

Lighvan cheese has large market acceptability due to its excellent sensory atributes. Since Lighvan cheese is made of raw sheep milk that was always warring for health with respect of pathogenic bacteria such as brucella, Listeria monocytogenes and others pathogens. The present research was done to, produced cheese from pasteurized sheep milk by adding microbial starter culture of lactobacillus casei and lactobacillus plantarum isolated from Lighvan cheese were used as starter in cheese for producing Lighvan special aroma and taste. In this reaserch the physicochemical and sensory properties of the white brine cheese made of pasteurized sheep milk using lactobacillus and plantarum was studied. Results revealed type of that treatment, ripening time and their interactions had significant (P < 0.05) increase and decrease effects on the physicochemical properties such as ash, dry matter, pH, acidity, fat, protein, lipolysis content. Pasteurization for cheese samples on day 60 ripening 41% had less dry matter than control samples had not been pasteurized. The rate of lipolysis pasteurized treatments cheese was 15 meq/100g oil. Ash samples pasteurized at about % 0/5, most of the samples had not been pasteurized. Pasteurization treatment with Lactobacillus plantarum strains have the highest of soluble nitrogen to total nitrogen was among treatments. Sensory assessment of cheese samples showed the highest sensory scores obtained from pasteurized cheese made with starter lactobacillus plantarum at the end of 60 day of ripening. It can be concluded that, while reducing the amount of chemical properties of pasteurized cheeses such as dry matter, but the risk of pathogenic bacteria were eliminated. According to sensory evaluation and physicochemical results obtained can be said of Lactobacillus plantarum strains isolated from Lighvan cheese capable of can be used as a starter in the pasteurized cheeses for flavor and desirability to consumers than Lactobacillus casei strain.