Thermal Sterilization Process Research Articles

Formation mechanism and stability of egg white fluid gels under ultrahigh-pressure homogenization pretreatment and synergistic heating effect

The thermal sterilization process of protein beverages inevitably leads to the formation of insoluble thermal aggregates, greatly reducing the texture and taste of protein beverages. In this study, homogenized egg white (HEW) was obtained by ultrahigh-high-pressure (UHP) homogenization pretreatment of egg white (EW), and then a special egg white fluid gel (EWFG) was prepared by water bath heating. The results showed that the optimal conditions for preparing EWFG were three cycles at 20 MPa homogenizing pressure and heating in a water bath at 72℃ for 10 min. Under these conditions, the EWFG was a milky-white homogeneous liquid with an average particle size of about 560 nm. Measurements of the physicochemical properties of HEW and EWFG showed that the UHP homogenization treatment reduced the viscosity of HEW, decreased the particle size of protein aggregates, and increased the zeta potential, which altered the interactions of proteins during the subsequent heating process and facilitated the formation of homogeneous and dispersed EWFG. EWFG showed good stability at pH 6–10 and in low-concentration saline and medium-concentration sucrose solutions. The EWFG obtained by the present treatment is more suitable for factory-scale production and has great potential for protein beverage applications.

The Performance Analysis of a Novel Sterilizable Trombe Wall Based on the Combined Effect of Heat and UV Light

A Trombe wall is a widely applied heating system that has a single function. An interesting thing is that both the solar heat and UV light received by a Trombe wall have an air sterilization effect. Here, the air sterilization and thermal performances of a Trombe wall in different cities were investigated based on an established heat and mass transfer model. The main results were as follows: (1) UV dose accumulation and high temperature were the most important factors that affect the UV and thermal sterilization performance, respectively. The Trombe wall had the thermal characteristics of high accumulation of UV doses in the morning and afternoon and a high temperature level at noon, which was a good match with the UV and thermal sterilization process. (2) A typical sterilization process in a Trombe wall was divided into three areas: the UV inactivation area, UV and thermal inactivation area and UV inactivation area. (3) The weather conditions played an important role in the sterilization performance. UV sterilization was dominant in cloudy weather, and thermal sterilization was dominant in sunny weather. (4) In Nanjing, Shanghai, Xining and Guangzhou, the average daily clean air volumes in heating months were 39.4, 33.5, 32.2 and 39.8 m3/m2, respectively. (5) When the wall height increased from 1.5 m to 3.5 m, the average daily clean air volume in heating months increased from 31.7 to 43.6 m3/m2.

Evaluating the influence of high-temperature sterilization and pasteurization on volatile organic compounds in tomato stewed beef brisket: An analysis using gas chromatography-ion mobility spectrometry and multivariate statistical visualization

Thermal Sterilization processes, while essential for ensuring food safety, can potentially compromise the organoleptic qualities and flavor profiles of prepared dishes. The present research endeavors to conduct an investigation into the discrepancies of different sterilization methodologies on the volatile organic compounds (VOCs) present in Tomato Stewed Beef Brisket (TSBB). Employing gas chromatography-ion mobility spectrometry (GC-IMS) and the relative odor activity value (ROAV), this study analyzed Untreated (US), Pasteurized (PS), and High-temperature sterilized (HTSS) TSBB samples. A total of 59 VOCs were identified, with aldehydes (37.2%), ketones (22.0%), and esters (17.5%) being the major contributors to the characteristic VOCs of TSBB.Principal component analysis (PCA) revealed significant distinctions between the US and HTSS. Furthermore, orthogonal partial least squares discriminant analysis (OPLS-DA) and partial least squares discriminant analysis (PLS-DA) collectively elucidated the discrepancies of VOCs from different thermal sterilization processes. The ROAV results indicated the presence of 21, 23, and 24 essential VOCs (ROAV>1) in the US, PS, and HTSS groups, respectively. Notably, High-temperature Sterilization significantly increased the aldehyde content, while Pasteurization augmented the ester content, specifically ethyl acetate-D and butyl acrylate-M. Overall, the findings indicate that High-temperature Sterilization exerted the most profound negative impact on the flavor profile of TSBB.This study provides a theoretical reference and practical basis for selecting the optimal sterilization process for prepared dishes, thereby contributing to the preservation of desirable organoleptic qualities and establishing a methodological framework for examining discrepancies in volatile organic compounds arising from divergent sterilization processes of TSBB.

Simulation and optimization of the thermal sterilization process of puree cans using the production of chestnut puree as an example.

In the production process of puree cans such as chestnuts cans, it is easy to browning due to excessive heating, which causes a lot of waste every year. The heat and mass transfer model of Chinese Chestnut Puree was established through the finite element method. The model simulated the change process of the temperature field, heat flow velocity field and F value during the production of Chinese Chestnut Puree. After comparing and confirming the effectiveness of the model through the thermal penetration test, the model was used to adjust and optimize the production process. For #9121 cans, the two-stage sterilization method was adopted. Through the sterilization method at 10-65-48-14/118-110°C, a sterilization effect equivalent to that of the original process at 10-86-24/121°C was achieved, the browning problem of the product was alleviated, and the product quality was improved. This practice can also provide a reference for canning enterprises to adjust their production processes in the future.

Mathematical modeling to estimate furan formation in thermally processed foods: A preliminary analysis considering carrots as a model food

Mathematical modeling of furan formation can be a powerful tool for the design and optimization of thermal processes for furan minimization under real operation conditions. This research aimed to develop a simple mathematical model based on the dependence of furan kinetic formation on temperature to estimate the furan concentration using the temperature-time profiles measured at the surface and at the center in thermally processed food using carrots as a model food but also that can be extended to furan prediction in real system. The furan prediction model was developed by coupling kinetic and Arrhenius models and validated by the thermal profiles obtained from retorting jarred carrots at different temperatures. The results showed that the furan concentration fit first-order kinetics ( R 2 -values>0.960), showing a dependence on temperature. The furan concentration in the retorted carrot varied between 8.54 ± 0.33 ng of furan/g of carrot and 19.46 ± 0.98 ng of furan/g of carrot depending on the process temperature. The furan prediction model compared with the experimentally quantified model presented an error between −6.95% and +11.21%. The simple furan prediction model developed in this study provides an adequate approximation of the furan concentration at the end of the thermal food processing but more importantly, the model could be used by the food processor to predict furan concentration in a real system, and as a tool to optimize the thermal sterilization process to minimize furan concentrations under real operation conditions. • Furan concentration was mathematically estimated from food temperature profiles. • Errors below 11% were obtained by comparing model with experimental values. • The model can be used by food processors to estimate furan in baby food recipes.

CFD Analysis of Can Heating Process

In this work, the thermal sterilization process in food cans has been analyzed using Computational Fluid Dynamics (CFD). STAR CCM+ software has been used in order to develop a numerical model to study the heating process of standard and the recently proposed toroidal shaped cans. The model has been validated comparing the results with the ones obtained experimentally and numerically that can be found in the literature. A good agreement between the obtained numerical results and the experimental ones has been obtained. The results also agree with other numerical models previously developed in the literature. Once the model has been validated, taking advance of the possibility to easily introduce movement in the simulations, new variables have been analyzed in the system using this model, such as rotational movement of the can. The model developed has been used to study the efficiency of the sterilization process with the two types of cans by means of calculating the temperature inside the systems and calculating the F0 parameter. It can be seen that the efficiency of the sterilization process is better in the toroidal cans. It has been also checked that CFD models can be very helpful in analyzing the temperature profiles inside the cans and making sure that the correct temperature has been obtained inside the can and the sterilization process has been correctly carried out.

Thermo resistant antioxidants from photoautotrophic microorganisms: screening and characterization.

The demand for natural antioxidants to be used in food industry is increasing, as synthetic antioxidants are toxic and have high production costs. Specifically, food processing and preservation require antioxidants resistant to thermal sterilization processes. In this study, twenty-five strains among microalgae and cyanobacteria were screened as antioxidants producers. The species Enallax sp., Synechococcus bigranulatus and Galdieria sulphuraria showed the highest content of chlorophyll a and total carotenoids. In vitro stability and antioxidant activity of the ethanolic extracts were performed. The results revealed that pigments present in the extracts, obtained from the previously mentioned species, were stable at room temperature and exhibited in vitro free radical scavenging potential with IC50 values of 0.099 ± 0.001, 0.048 ± 0.001 and 0.13 ± 0.02mg mL-1, respectively. Biocompatibility assay showed that the extracts were not toxic on immortalized cell lines. The antioxidant activity was also tested on a cell-based model by measuring intracellular ROS levels after sodium arsenite treatment. Noteworthy, extracts were able to exert the same protective effect, before and after the pasteurization process. Results clearly indicate the feasibility of obtaining biologically active and thermostable antioxidants from microalgae. Green solvents can be used to obtain thermo-resistant antioxidants from cyanobacteria and microalgae which can be used in the food industry. Thus, the substitution of synthetic pigments with natural ones is now practicable.

Estimation of Sterilization Value using General Method and Ball Formula for Beef Rendang in Retort Pouch

The existence of a ready-to-eat meal with a long shelf life is essential, particularly for emergency food and military diet, as well as for alternative food for modern society. Rendang is a well-known Indonesian traditional food which may be packaged in a retort bag by employing a sterilization process. The sterilization value of Rendang is presently still limited. This study aimed to estimate sterilization value or heat sufficiency (F0) using the General Method and the Ball Formula Method. The estimated value was then compared with the value obtained from the experiment. It was further used to predict process time (Pt) to minimize the need for trial optimization on the product. The thermal sterilization process was carried out using a horizontal retort with a pressure of 1.3 bar for 40 minutes. The results showed that the F0 values predicted were in a close agreement with the observed (experimental) values. F0 values were 5.88, 5.17, and 5.91 minutes for the General Method, Formula Method, and the observation, respectively. The Pt values of Beef Rendang in a retort bag with F0 values of 4, 5, 8, 10, and 12 minutes were 25, 27, 31, 34, and 36 minutes for retort temperature of 123°C, respectively. Whereas for a retort temperature of 121°C, the Pt values were 28, 30, 36, 39, and 42 minutes, respectively. In conclusion, both the General Method and Ball Formula are accurate to estimate the sterilization value of Beef Rendang packaged in Retort Pouch.

Designing thinner wall ethylene-vinyl alcohol copolymer and polypropylene-based semi-rigid trays for microwave-assisted thermal sterilization and pasteurization processes

Abstract The goal of this research was to design a thinner wall tray for microwave-assisted thermal processing technologies. Three-layer (PP//EVOH//PP) sheets of different EVOH- and PP-layer thicknesses were coextruded. The sheets were then thermoformed into 8-oz trays with dimensions of 150 × 100 × 50 mm (L × W×D). Trays were filled with model foods and subjected to conventional and microwave-assisted pasteurization and sterilization processes. Barrier and mechanical properties were assessed before and after processing. Oxygen ingress, weight loss, and color kinetics were measured over a storage period of 3–6 months at 7, 23, and 37 °C. The newly-designed trays showed comparable or better performance in terms of O2 ingress and weight loss, with a 24 % reduction in wall thickness. Therefore, thinner EVOH and PP-based trays hold promise for use in microwave-assisted sterilization and pasteurization processes. This will result in a reduced carbon footprint and provide more economical alternatives to other forms of packaging that are currently available.

Evaluating the use of preservatives on the shelf life of tender coconut water

Tender coconut water is a sweet, delicious and refreshing natural beverage. The sugar and mineral constituents attributes to the pleasant taste of tender coconut water. Due to the presence of sugars and a number of plant enzymes, tender coconut water has a strong tendency to undergo biochemical changes and spoilage, once the nut is harvested from the tree. Furthermore, coconut as a whole is bulky and perishable without proper packaging, which challenges the task of transportation of tender coconut water over a long distance. So, an attempt has been made to extend its shelf life in bottles, which will lead to easy transport and easy to serve. Design of the process was developed by considering the dependent variables (microbial population, sensory attributes) and independent variables (time, temperature, preservatives). The preservatives used for this study include potassium sorbate and sodium benzoate. During thermal sterilization process the flavour components were destroyed and palatability was not good and hence in-bottle sterilization was adopted in this study to retain the flavours and preserve tender coconut water. It was found that the tender coconut water preserved by the treatments T11 (Potassium Sorbate (@ 300 ppm) at 80 °C for 180 s) in the in-bottle sterilization had a shelf life of 3 months and T27 (sodium benzoate (@ 350 ppm) at 80 °C for 180 s) in the in-bottle sterilization was acceptable with the maximum shelf life of 1 month. By adopting this preservation technique, tender coconut water could be effectively stored and used for 70 days under refrigerated condition (4 °C).

Impact of thermal sterilization on the physicochemical-sensory characteristics of Californian-style black olives and its assessment using an electronic tongue

The effect of thermal sterilization processes on the physicochemical parameters and sensory characteristics of Californian-style black olives, from ‘Hojiblanca’ and ‘Manzanilla Cacereña’ brine solutions, were evaluated. Two-way ANOVA showed that ‘Hojiblanca’ olives had a lower phenols content and defect intensity and that increasing the sterilization period resulted in a decrease in total phenols and an increase of the cooked defect. The impact of thermal sterilization was further evaluated using a potentiometric electronic tongue, which was capable of discriminating the different sterilization treatments (repeated K-fold cross-validation sensitivity: 89.0 ± 15.0% to 97.0 ± 6.0%). Moreover, multiple regressions allowed the prediction of phenols (R2 ≥ 0.95 ± 0.03) and the intensity of the defect (R2 ≥ 0.95 ± 0.04). These results point out the feasibility of the electronic tongue as an analytical tool for monitoring the effects of thermal sterilization treatments. Furthermore, the satisfactory results obtained for the brine solutions may foresee a practical non-destructive method for indirect quality assessment of table olives.

Comparative studies on the stabilization of Flos Sophorae Immaturus beverages by various hydrocolloids

The effects of microcrystalline cellulose (MCC), gellan gum (GG) and mixed emulsifiers on physical stability of cloudy Flos sophorae immaturus (FSI) beverages were studied. The physical stability of FSI beverages characterized by particle size, microstructure, rheological properties, suspension stability index and backscattered light intensity. It occurred an irreversible phase separation during thermal sterilization process in the original FSI beverage. The beverage adding MCC had large (the volume weighted mean diamete [d43]~36 μm) but non-coalesced particles after thermal sterilization step, showing MCC could protect the particles against the coalescence. Moreover, when MCC and GG were added to FSI beverage, the suspension stability index increased, and the particle size and the change of backscattered light intensity (△BS) decreased. Mixed emulsifiers not only enhance the viscosity of beverage but also influence the properties of beverage interface, leading to greater absolute value of zeta potential which rose to 45.5 mV. In the existence of MCC, GG, and mixed emulsifiers, the system displayed greater stability than others. This study provided some suggestions for the industrial production of cloudy beverages with low viscosity and good stability.

Action mechanism of pulsed magnetic field against E. coli O157:H7 and its application in vegetable juice

Compared with traditional thermal sterilization process, pulsed magnetic field (PMF) is a non-thermal sterilization technology with superior advantages of maintaining the nutrition and flavor of food. But little is known about its antimicrobial mechanism. To explore its antimicrobial mechanism, the variation of cell membrane, intracellular biological macromolecules and respiratory metabolism of E. coli O157: H7 after PMF treatment, were investigated. The results showed that PMF could cause cell membrane damage and increase cell membrane permeability, reducing the content of three intracellular macromolecules (protein, ATP and DNA), as well as exhibiting inhibition for ATPase activity. The inhibition rate and superposition rate test confirmed the pathway that affecting the respiratory metabolism of E. coli O157:H7 treated with PMF was hexose monophophate pathway (HMP), via reducing the activity of key enzyme glucose-6-phosphate dehydrogenase in HMP. Besides, PMF also exhibited superior antibacterial effect on E. coli O157:H7 when it was applied in vegetable juices.

Novel processing methods: updates on acidified vegetables thermal processing

Conventional thermal processing of low acid foods experiences significant quality loses due to intense thermal processing schedules. Even though relative improvement in quality of canned foods achieved through modification of processing and packaging methods, due to required high lethality, commercial thermal sterilization process are still heat and energy intensive. Combined use of product pH (pH < 4.6) reduction with use of novel thermal processing methods contributed for better quality retention of thermally processed vegetables with reduced cost of production. Novel pH reduction methods like use of vacuum or high pressure assisted infusion allow uniform and instantaneous pH modification of high acid vegetables. In addition to this, use of novel thermal processing methods like microwave, radiofrequency, ohmic heating and high pressure assisted temperature processing permit uniform and short duration treatments for better quality retention, process efficiency and cost reduction.

Dielectric properties of rice model food systems relevant to microwave sterilization process

Abstract Model foods as chemical marker carriers are needed to evaluate the heating patterns and location of hot and cold spots in developing microwave assisted thermal sterilization (MATS) processes. Previous research on model food development has been conducted for high moisture foods, with limited data on medium moisture foods (20–60% water). This research aimed to determine the dielectric properties (dielectric constants and loss factors) and penetration depths of rice grain (RG) and rice flour gel (RFG) model foods with moisture contents between 50 to 60% (wet basis) and of cooked rice (CR) over a frequency range of 300–3000 MHz at temperatures from 20 to 121 °C. The dielectric properties of rice models with 0% salt and 0.5% d -ribose closely matched the properties of CR; this indicated that rice model foods could be used to emulate CR for heating pattern and cold/hot spot detection in the development of MATS processes at 915 MHz and 2450 MHz. Therefore, rice model foods developed in this research could be useful in the future for the food companies, in order to visualizing the heating pattern and determining the location of cold and hot spots during MATS process of medium moisture foods, such as rice, pasta or macaroni used as main ingredient in ready-to-eat meal products.

Thermal pasteurization process evaluation using mashed potato model food with Maillard reaction products

Model foods with Maillard reaction product formation have been utilized to evaluate thermal sterilization processes, but these models are not optimal for pasteurization. Model foods for pasteurization applications have been developed, but studies on temperature sensitivity and validation are limited. The goal of this research was to assess the temperature sensitivity of chemical marker and color formation in mashed potato model foods and conduct validation testing using a microwave-assisted pasteurization system (MAPS) and conventional, hot water methods. Reaction kinetics were determined for chemical marker M-2 (4-hydroxy-5-methyl-3(2H)-furanone) and color formation (L* and a* values). Results showed that the thermal resistance constants (z-values) were 20.6–24.0 °C for M-2, 20.8–28.8 °C for L* value, and 10.3–25.6 °C for a* value. Correlation analysis between M-2, L*, and a* values and thermal lethality and cook value showed that model foods were most relevant for pasteurization process quality evaluation. Thermal treatment equivalent at the cold spot was approximately 11 min at 90 °C for all pasteurization processes. Model foods pasteurized in MAPS had less color change than those from hot water processes, implying the less severe MAPS process yielded better quality. Model foods and image analysis techniques used in this study could be helpful quality evaluation tools for pasteurization processes.

Prediction of temperature distribution in a horizontal high pressure food processing vessel and its impact on process uniformity

The temperature distributions in HPP vessels should be of particular concern for pressure assisted thermal sterilization (PATS) processes because in PATS temperature plays a major role in microbial inactivation. Numerical simulations were carried out to predict thermal transport in a horizontal HPP vessel with and without insulation. The results showed that the temperature of water added to compensate for the compression of water in the pressure vessel and the addition of insulation on the inner surface of vessel had significant impact on the temperature distribution and on the predicted inactivation of Clostridium botulinum spores. It was concluded that adding insulation to the vessel lead to higher temperature levels but more non-uniform temperature distribution as compared with without insulation. It was also observed that the water added to compensate for compression did not impact the flow pattern in the vessel significantly due to low inlet velocity but the temperature of added water had a significant impact on the temperature and Clostridium botulinum spore inactivation distributions. The temperature distribution was close to uniform when the temperature of the inlet water was the same as the initial temperature for the process. Practical applications The results obtained from this research will be useful in the evaluation of process performance in terms of process validation and process filing with regulatory agencies to develop guidelines for producing high pressure processed foods using PATS, which are safe to consume. The results will also be important for food processors and equipment manufacturers to understand the effects of non-uniform thermal treatment on foods processed using PATS.

Use of the Nanofitin Alternative Scaffold as a GFP-Ready Fusion Tag.

With the continuous diversification of recombinant DNA technologies, the possibilities for new tailor-made protein engineering have extended on an on-going basis. Among these strategies, the use of the green fluorescent protein (GFP) as a fusion domain has been widely adopted for cellular imaging and protein localization. Following the lead of the direct head-to-tail fusion of GFP, we proposed to provide additional features to recombinant proteins by genetic fusion of artificially derived binders. Thus, we reported a GFP-ready fusion tag consisting of a small and robust fusion-friendly anti-GFP Nanofitin binding domain as a proof-of-concept. While limiting steric effects on the carrier, the GFP-ready tag allows the capture of GFP or its blue (BFP), cyan (CFP) and yellow (YFP) alternatives. Here, we described the generation of the GFP-ready tag from the selection of a Nanofitin variant binding to the GFP and its spectral variants with a nanomolar affinity, while displaying a remarkable folding stability, as demonstrated by its full resistance upon thermal sterilization process or the full chemical synthesis of Nanofitins. To illustrate the potential of the Nanofitin-based tag as a fusion partner, we compared the expression level in Escherichia coli and activity profile of recombinant human tumor necrosis factor alpha (TNFα) constructs, fused to a SUMO or GFP-ready tag. Very similar expression levels were found with the two fusion technologies. Both domains of the GFP-ready tagged TNFα were proved fully active in ELISA and interferometry binding assays, allowing the simultaneous capture by an anti-TNFα antibody and binding to the GFP, and its spectral mutants. The GFP-ready tag was also shown inert in a L929 cell based assay, demonstrating the potent TNFα mediated apoptosis induction by the GFP-ready tagged TNFα. Eventually, we proposed the GFP-ready tag as a versatile capture and labeling system in addition to expected applications of anti-GFP Nanofitins (as illustrated with previously described state-of-the-art anti-GFP binders applied to living cells and in vitro applications). Through a single fusion domain, the GFP-ready tagged proteins benefit from subsequent customization within a wide range of fluorescence spectra upon indirect binding of a chosen GFP variant.

Impact of pH, freeze–thaw and thermal sterilization on physicochemical stability of walnut beverage emulsion

The effects of environment stresses on the stability of walnut emulsion were investigated. The physical stability of walnut emulsion was characterized by droplet size, zeta potential and chemical stability of walnut oil in the emulsion was evaluated by determining the peroxide concentration during the storage. The results showed that emulsion in the presence of xanthan gum and mixed emulsifiers exhibited better stability after 4 freeze–thaw cycles. At pH 3–10, the mixed emulsifiers could improve the stability through their absorption on the oil–water interface. However, xanthan gum couldn’t protect the droplets against the aggregation in high acid environment, but greatly enhanced the physical stability at pH 6–10. During the thermal sterilization process, the physical stability of walnut emulsion was decreased with a rise of sterilization temperature and the extension of sterilization time. The sterilization temperature above 121°C and time over 25min led to the poor physical and oxidative stability.

EPR examination of free radicals thermally formed in vaselinum flavum

Abstract The popular pharmaceutical base used in pharmacy – vaselinum flavum – was studied by an X-band (9.3 GHz) EPR spectrometer in the range of microwave power of 2.2–70 mW. The samples were sterilized in hot air oven at temperatures: 160°C (120 min), 170°C (60 min), and 180°C (30 min). The aim of this work was to determine properties and free radical concentrations in vaselinum flavum thermally sterilized at different conditions. The changes in free radical system in vaselinum flavum during storage were analyzed. Free radicals were found in all the heated samples. The lowest free radical concentration was obtained for vaselinum flavum heated at 180°C for 30 min; so these parameters are proposed for the thermal sterilization of this pharmaceutical base. Interactions with oxygen decreased free radical concentration in vaselinum flavum during storage. Strong quenching of free radicals in vaselinum flavum was observed after 2 days for the samples sterilized at temperatures 160 and 180°C. Such an effect for vaselinum flavum heated at temperature 170°C was observed later, 13 days after sterilization. Fast spin-lattice relaxation processes exist in thermally sterilized vaselinum flavum. The EPR lines of heated vaselinum flavum were homogeneously broadened. EPR spectroscopy and its use for examining the thermal sterilization process in pharmacy was confirmed.