Sterilization Temperature Research Articles

Effect of steam sterilization and biocompatibility studies of hyaluronic acid hydrogel for viscosupplementation

Intra-articular injection of hyaluronic acid (HA) hydrogel is one of the treatment methods recommended for osteoarthritis (OA). Here HA hydrogel (2000 kDa) has been developed, sterilized by steam sterilization and the important properties required for viscosupplementation such as equilibrium swelling, enzymatic degradation, carbazole assay and rheology analysis has been compared before and after steam sterilization. The effect of steam sterilization was studied by varying the temperature and time of sterilization and a suitable temperature and time such as 118 ₀C for 5 min was optimized. It was found that the optimized sterilization condition does not affect the material properties of HA hydrogel except equilibrium swelling. The stability of the steam sterilized hydrogel was evaluated for 3 months at two different conditions (5 ₀C and 25 ₀C at 60% RH) and it was found that 5 ₀C at 60% RH is the suitable condition of storage. The safety profiles of the HA hydrogel was checked by cytotoxicity analysis, intracutaneous reactivity, acute toxicity studies and found to be biocompatible. Hence It was found the HA hydrogel developed is highly biocompatible, retain its properties after sterilization and is stable upto 3 months when stored at 5 ₀C at 60% RH.

Measurement of Equilibration Time of Dry Goods Loads in Autoclaves.

The equilibration time of an autoclave is defined as the period of time that elapses between the attainment of the sterilization temperature at the reference measurement point of the autoclave chamber and the attainment of the sterilization temperature at all measurement probes within the dry goods load placed within the autoclave during a sterilization cycle.The equilibration time is an indicator of the ability of the autoclave to remove air from and to subsequently sterilize the dry goods load placed within the autoclave chamber. Therefore, the equilibration time is an indicator of the performance of an autoclave. Periodic measurements of the equilibration time and evaluation of the equilibration time data can assure continued performance of the autoclave.For autoclaves that support biopharmaceutical manufacturing plants, the equilibration time is generally measured by placing heat penetration probes within the dry goods load items placed within the autoclave during a sterilization cycle. However, measurement of the equilibration time in this fashion yields results that are highly variable and difficult to replicate.This paper presents a study that attempts to understand the impact of the following autoclave variables on the consistent measurement of the equilibration time and on the reduction of the equilibration time: type of dry goods load item placed inside the autoclave, location of the heat penetration probe placed within the dry goods load item, location of the dry goods load item inside the autoclave chamber, orientation of the dry goods load item inside the autoclave chamber, number of coils of the tubing elements of a dry goods load item, total thermal mass of the dry goods load items placed inside the autoclave, temperature of the dry goods load items at the start of the sterilization cycle, presence of residual moisture in the dry goods load items at the start of the sterilization cycle, number of steam and vacuum pulses used for preconditioning in the autoclave recipe, depth of the steam and vacuum pulses used for preconditioning in the autoclave recipe, and hold time of the steam and vacuum pulses used for preconditioning in the autoclave recipe.The focus of this paper is on tests performed to evaluate these variables followed by analysis and interpretation of the test data to identify key variables that have the highest impact on the measurement of the equilibration time. The conclusion of this paper presents a process to achieve shorter equilibration times in autoclaves through control of the key variables identified.LAY ABSTRACT: The equilibration time is an indicator of the performance of an autoclave. Periodic measurements of the equilibration time and evaluation of the equilibration time data of an autoclave can assure continued performance of said autoclave.This paper presents a study performed to develop a general guideline for consistent measurement of the equilibration time of an autoclave through identification and control of key sources of variability that impact the measurement. The focus of this paper is the testing and data analysis performed to identify these key sources of variability observed in a typical autoclave load sterilized through a typical autoclave cycle in a biopharmaceutical manufacturing plant. The conclusion of this paper presents a process to achieve shorter equilibration times in autoclaves through control of the key variables identified.

Enhanced Duration of Truffle Sauce Preservation due to Addition of Linoleic Acid

Food products based on truffles such as truffle sauces are commonly sterilized by autoclaving. With the aim of reducing sterilization durations and temperatures and therefore minimizing the formation of new molecules while maintaining sterile conditions, natural molecules with bacteriostatic action can be added. This work takes into account molecular variations in a truffle sauce with linoleic and stearic acids added at various temperatures and durations of sterilization. As controls, the sterilized truffle sauces, not additives, were taken. The SPME/GC has always detected changes in the composition of the headspace but more significant at longer durations. An increase in temperature leads to the transformation of an important fraction of total alcohol into total aldehydes. Bacteriological tests were performed on total aerobic bacteria and Clostridium spp. The total bacterial load, even if low, is instead present in the controls for all temperature/duration combinations. Linoleic acid is more effective than stearic acid and contributes with a concentration of 10% (w/w) to a decisive reduction of the total bacterial load at 10′/121°C and 3′/130°C. The nutritional value of truffle sauces can be increased by adding nutraceuticals, and amongst these, linoleic acid could be a valid candidate.

Developing a sterilization processing and a grading system to produce a uniform quality of sterilized whole corn (Zea mays L. var. ceratina)

In this study, a grading system for ears of corn was developed to design sterilization process of the ear of corn using fuzzy c-mean (FCM) clustering. Three grades (A, B, and C) of corn found by FCM (the m-value and the c-value were 1.15 and 3, respectively) were used to design the sterilization process of the ear of corn. The heat transfer simulation model was successfully developed to determine the locations of the cold point for the three different grades of corn during sterilization (RMSE = 0.104 °C). Among the 3 different temperature used in this study (111.1, 121.1, and 131.1 °C), 121.1 °C found to be the optimum sterilization temperature based on the analysis of texture properties of corn. The heating time to reach the target F0-value (5 min) for grades A, B, and C was 61, 49, and 36 min, respectively. When the longest heating time (61 min) was applied, the quality of the overheated corn (grades B and C) was significantly decreased (p < 0.05), whereas the quality of the corn at the optimum sterilization condition for each grade showed no significant difference. The heat transfer simulation model was successfully combined with the grading system developed by FCM to optimize the sterilization process of packaged whole corn. The texture properties and sensory attributes of sterilized corn were improved by applying the optimum sterilization processes which was adjusted based on the size and weight of corn ears.

Validation of an Autoclave Procedure for Sterilization of Mouse (Mus musculus) Carcasses.

The sterilization of potentially infectious animal carcasses is an important biologic safety issue in animal facilities operating as infection or quarantine barriers. However, the literature lacks a validated protocol. Here we describe the validation of an autoclave program suitable for daily use in a small rodent biocontainment unit. We evaluated several procedures for processing mouse carcasses in a standard autoclave. Heat sensors and biologic indicators were implanted inside the peritoneal cavity of dead mice, which were loaded at various densities into IVC cages or metal boxes. Heat sensors revealed broad differences in temperature inside carcasses compared with the autoclave chamber. Achieving the appropriate sterilization temperature was considerably prolonged in carcasses compared with typical laboratory waste material. We show that for 5 cadavers placed well separated inside an IVC, a modified program for mouse cage sterilization using 134 °C for 15 min is suitable. To sterilize approximately 1 kg of carcasses in autoclavable boxes, a period of 6 h is required to reach an effective temperature of 121 °C for 60 min at the center of the waste by using an autoclave program for liquids. In conclusion, we here validated 2 protocols for the sterilization of potentially infectious mouse carcasses, to ensure the application of efficacious procedures.

Combination of vegetable-fruit formulation composition for obtaining high quality products

We have investigated a change in the active acidity of blended products made from vegetable and fruit raw materials. A possibility has been proven to control active acidity through the introduction to formulations of canned foods fruits with a high content of titrated acidity. Apricot, gooseberry, cherry plum, black currant are characterized by a high content of titratable acidity, thus they could replace in the formulations of canned products the organic acids obtained artificially. It is possible to use zucchini, pumpkin, carrot and beet to produce natural organic purees, juices, compotes, sauces, natural canned vegetable food with a regulated active acidity not higher than 3.9 pH units. To achieve this level of active acidity in canned products, the mass share of titratable acidity should be brought to 0.55‒0.60 %. The canned food products manufactured using a given technique are microbiologically stable and safe when employing the sterilization temperature of 100 °C for 20‒25 minutes; they have a high organic estimate; they efficiently preserve ascorbic acid. The pumpkin puree demonstrated active acidity of 5.6 pH units. In the blended pumpkin and apricot puree, gooseberry and cherry plum puree, the active acidity decreased to 3.80‒3.84 pH units following the introduction of the calculated formulation amount of a fruit part into compositions, from 11.3 to 28.1 %, the content of ascorbic acid increased by 1.6‒2.6 times. The content of ascorbic acid in a pumpkin and black currant puree, at the regulated active acidity of 3.86 pH units, increased to 30.6 mg/100 g, by 7.6 times. A similar trend was observed for the blended purees made from carrot and table beet. The vegetable-fruit purees and sauces, manufactured in line with a given technique, are characterized by excellent organoleptic quality estimation, 26.3‒29.3 points. Canned foods from vegetable raw materials with a controlled level of active acidity, due to their fruit part, are natural products with an elevated content of ascorbic acid. The combination could be used for the manufacture of organic products from the appropriate raw materials, thereby retaining their high quality.

COMPLEX TECHNOLOGICAL AND BIOLOGICAL RESEARCH OF SOLUTIONS FOR PERITONEAL DIALYSIS

Objective: The purpose of our work was to conduct technological, analytical, and biological investigations and stability studies of peritoneal dialysis (PD) solutions containing glucose and sodium lactate in single-chamber containers.Methods: Different formulations of PD solutions were prepared and sterilized at a temperature of 121 °C during 15 m. UV-spectrophotometric determination was performed using purified water as a blank. The spectra of the solutions were run in the range of 220 to 400 nm for the identification of an absorption maximum (λmax) and measuring the absorbance at 228-230 nm and λmaxbefore and after heat sterilization. λmax of the most PD solutions after sterilization was found in the range of 273 to 281 nm. The potentiometric determination was done for pH measuring PD solutions before and after sterilization. Alternative analytical procedure of direct argent metric method was employed for fast measuring content of chloride ions. Viability of Vero cells was evaluated using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test, neutral red (NR) uptake assay, and sulforhodamine B (SRB) test.Results: The results showed that the absorbance of the most laboratory batches of PD solutions augments significantly with increasing an autoclave heating time to the sterilization temperature and time of its cooling after sterilization. The longer these parameters, the higher is the absorbance at 228-230 and 273-281 nm indicating 3,4-dideoxyglucoson-3-en (3,4-DGE) and 5-hydroxymethylfurfural (5-HMF) contents, respectively. Glucose degradation is practically absent at short terms of heating and cooling an autoclave while sterilized samples are preserved sterile. Stability studies showed a significant decrease in the absorbance at 228-230 nm during storage with the achievement of a nadir and the following weak increase; an elevation or decrease in the absorption maximum; a substantial decline in the pH of the solution after sterilization and an insignificant pH decrease during storage. The viability of kidney cells was the highest in the SRB test and the lowest one was in the MTT test.Conclusion: The influence of sterilization regimes on the quality of conventional PD solutions and their stability during storage were studied. The highest cytotoxicity was detected in the MTT test, and the lowest one was done in the SRB test, indicating the largest vulnerability of mitochondria under the influence of PD solutions compared to the membranes permeability, functioning of kidney cell lysosomes and the ability of cells to synthesize proteins. Our studies could be useful in the context of planning development of PD solutions with the purpose of authorization and domestic manufacture of these solutions in low-and-middle-income countries.

PENGARUH WAKTU DAN SUHU STERILISASI TERHADAP KANDUNGAN PROKSIMAT IKAN BANDENG (Chanos chanos) KALENG

This study aims to determine the exact combination of time and temperature of sterilization to the proximate content of canned milkfish. Where the time combination used are 60 minutes, 75 minutes, and 90 minutes. Combination of temperature used are 110OC, 115 OC, and 120 OC. This research was conducted from Januari – Juni 2017 in two locations, namely in the Workshop Teaching Factory SUPM Bone dan BPPMHP Makassar. Sampling taken from canned milkfish randomly in each treatment. The data were analyzed by using ANOVA statistical analysis and next the significant parameter were tested using Tuckey and then explained by using table. The research results that the combination of temperature and time of sterilization had a significant effect on the quality of canned milkfish. Where temperature treatment 110 OC and time of 75 minutes has the best proximate content (best nutrition).

Zinc oxide phytase nanocomposites as contributory tools to improved thermostability and shelflife

The current study suggests the utility of ZnO nanoparticles to increase the thermotolerance of phytase enzymes; thereby aiding their effective utilization to provide better phosphate uptake when applied in animal feeds. Microbial isolates with predominant phytase activity were isolated from industrial wastewater to obtain a promising thermotolerant isolate of Penicillium decumbens. The purified phytase showed activities at mash preparatory temperature (32.59 ± 0.045 Uml−1 min−1 at 55 °C), animal feed pelletising temperature (37.83 ± 0.127 Uml−1 min−1 at 80 °C) and steam sterilization temperature (18.56 ± 0.027 Uml−1 min−1 at 100 °C) of animal feeds as per standard phytase assays. The supplementation of ZnO nanoparticles found to increase thermostability of phytase from 18.56 Uml−1 min−1 to 30.5 Uml−1 min−1 at 100 °C. The antibacterial role of the nanocomposites was checked against human pathogens to obtain satisfactory results against standard antibiotics. Thus the incorporation of ZnO nanoparticles in combination with phytase provided a dual benefit of increasing its thermostability and antimicrobial property thereby increasing its shelflife.

Effect of different sterilization methods on physicochemical and microbiological properties of rice wine

The present study investigated the effect of three different sterilization methods (high hydrostatic pressure sterilization, ultraviolet sterilization, and ultra-high temperature sterilization) on changes of physicochemical and microbiological properties of rice wine Makgeolli during the preservation at 15 °C for 20 weeks. The results indicated that pH, titratable acidity, color, contents of reducing sugar and alcohol were not significantly varied between different sterilization methods but microbial counts and sensory evaluation were exhibited the significant differences. The microbial counts of the sterilized Makgeolli were significantly lower than that in unsterilized one after 20 weeks of storage. Sensory profiles were markedly dependent on the sterilization methods. This work inferred, the high hydrostatic pressure treatment as the suitable method of sterilization for improving the shelf life of rice wine Makgeolli.

Optimization of palm fruit sterilization by microwave irradiation using response surface methodology

This study reported optimization of palm fruit sterilization process by microwave irradiation. The results of fractional factorial experiments showed no significant external factors affecting temperature of microwave sterilization (MS). Response surface methodology (RSM) was employed and model equation of MS of palm fruit was built. Response surface plots and their corresponding contour plots were analyzed as well as solving model equation. The optimum process parameters for lipase reduction were obtained from MS of 1 kg palm fruit at microwave power of 486 Watt and heating time of 14 minutes. The experimental results showed reduction of lipase activity in the present work under MS treatment. The adequacy of the model equation for predicting the optimum response value was verified by validation data (P>0.15).

Acrylamide Production in Autoclaved Rodent Feed.

Sterilization of rodent feed by steam autoclaving is a common practice in many research institutions. Often we only consider the beneficial effects of this process-the reduction of microbial contamination-and forget that the high temperatures and pressures can have negative effects on diet quality. The purpose of our study was to assess both the physical and chemical changes to a standard rodent feed autoclaved at multiple sterilization temperatures and the effects of the treated diets on mice. Pelleted NIH31 rodent feed was autoclaved at 4 sterilization temperatures (230, 250, 260, and 270 °F). Feed pellet hardness and the acrylamide concentrations of the diets were tested and compared with irradiated NIH31 feed. Study diets were fed to mice for 28 d, after which tissue samples were collected for analysis of acrylamide, glycidamide (the active metabolite of acrylamide), and genotoxicity. Both feed pellet hardness and acrylamide concentration increased with increasing sterilization temperatures; however, neither affected feed intake or body weight gain. Plasma acrylamide and glycidamide were significantly elevated only in mice fed NIH31 diet autoclaved at 270 °F compared with the irradiated feed, whereas urine acrylamide and glycidamide metabolites were significantly elevated in most autoclaved diets. Liver DNA adducts, which correlate with genotoxicity, were significantly elevated in all autoclaved diets compared with the irradiated diet. Institutions that autoclave their animal diets should carefully consider the temperatures necessary to achieve feed sterilization and the type of studies in which these autoclaved diets are used.

Application of direct steam injection system to minimize browning of white radish (Raphanus sativus) broth during sterilization

Direct steam injection (DSI) was applied to minimize the quality changes of white radish (Raphanus sativus) broth during sterilization. This study compared the degree of browning of white radish broth from a retort sterilization system and a DSI system. The quality changes after thermal treatments, such as retorting and DSI, were evaluated by Lab color values, the browning index (BI) and sensory evaluation. As the volume of the retort pouch increased, the thermal processing time increased. Significant increases of a and b values, color difference and BI were observed. Unlike the retort sterilization, the DSI treatment showed no significant differences in color properties of the radish broth with a wide range of sterilization temperature. The highest sensory score among the DSI treated samples was observed at the lowest sterilization temperature (125°C). The results demonstrated that the DSI treatment showed a higher stability in the quality associated with the browning reaction, such as the color indices and BI because the DSI process rapidly increased the temperature of the radish broth by transferring the latent heat of steam to the fluid. Keywords: direct steam injection (DSI), retort, sterilization, quality, browning, white radish broth, sensory evaluation DOI: 10.25165/j.ijabe.20171006.3350 Citation: Ham T H, Yoon W B. Application of direct steam injection system to minimize browning of white radish (Raphanus sativus) broth during sterilization. Int J Agric & Biol Eng, 2017; 10(6): 210–220.

Flash autoclave settings may influence eradication but not presence of well-established biofilms on orthopaedic implant material.

Flash autoclaving is one of the most frequently utilized methods of sterilizing devices, implants or other materials. For a number of decades, it has been common practice for surgeons to remove implantable devices, flash autoclave and then reimplant them in a patient. Data have not yet indicated the potential for biofilms to survive or remain on the surface of orthopaedic-relevant materials following flash autoclave. In this study, monomicrobial and polymicrobial biofilms were grown on the surface of clinically relevant titanium materials and exposed to flash autoclave settings that included varying times and temperatures. Data indicated that when the sterilization and control temperatures of an autoclave were the same, biofilms were able to survive flash autoclaving that was performed for a short duration. Higher temperature and increased duration rendered biofilms non-viable, but none of the autoclave settings had the ability to remove or disperse the presence of biofilms from the titanium surfaces. These findings may be beneficial for facilities, clinics, or hospitals to consider if biofilms are suspected to be present on materials or devices, in particular implants that have had associated infection and are considered for re-implantation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1543-1550, 2018.

Low temperature gamma sterilization of a bioresorbable polymer, PLGA

Medical devices destined for insertion into the body must be sterilised before implantation to prevent infection or other complications. Emerging biomaterials, for example bioresorbable polymers, can experience changes in their properties due to standard industrial sterilization processes. Gamma irradiation is one of the most reliable, large scale sterilization methods, however it can induce chain scission, cross-linking or oxidation reactions in polymers. sterilization at low temperature or in an inert atmosphere has been reported to reduce the negative effects of gamma irradiation. The aim of this study was to investigate the impact of low temperature sterilization (at −80°C) when compared to sterilization at ambient temperature (25°C) both in inert atmospheric conditions of nitrogen gas, on poly(lactide co-glycolide) (PLGA).PLGA was irradiated at −80 and 25°C at 40kGy in a nitrogen atmosphere. Samples were characterised using differential scanning calorimetry (DSC), tensile test, Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy and gel permeation chromatography (GPC).The results showed that the molecular weight was significantly reduced as was the glass transition temperature, an indication of chain scission. FTIR showed small changes in chemical structure in the methyl and carbonyl groups after irradiation. Glass transition temperature was significantly different between irradiation at −80°C and irradiation at 25°C, however this was a difference of only 1°C. Ultimately, the results indicate that the sterilization temperature used does not affect PLGA when carried out in a nitrogen atmosphere.

Investigating steam penetration using thermometric methods in dental handpieces with narrow internal lumens during sterilizing processes with non-vacuum or vacuum processes

Dental handpieces are required to be sterilized between patient use. Vacuum steam sterilization processes with fractionated pre/post-vacuum phases or unique cycles for specified medical devices are required for hollow instruments with internal lumens to assure successful air removal. Entrapped air will compromise achievement of required sterilization conditions. Many countries and professional organizations still advocate non-vacuum sterilization processes for these devices. To investigate non-vacuum downward/gravity displacement, type-N steam sterilization of dental handpieces, using thermometric methods to measure time to achieve sterilization temperature at different handpiece locations. Measurements at different positions within air turbines were undertaken with thermocouples and data loggers. Two examples of widely used UK benchtop steam sterilizers were tested: a non-vacuum benchtop sterilizer (Little Sister 3; Eschmann, Lancing, UK) and a vacuum benchtop sterilizer (Lisa; W&H, Bürmoos, Austria). Each sterilizer cycle was completed with three handpieces and each cycle in triplicate. A total of 140 measurements inside dental handpiece lumens were recorded. The non-vacuum process failed (time range: 0-150s) to reliably achieve sterilization temperatures within the time limit specified by the international standard (15s equilibration time). The measurement point at the base of the handpiece failed in all test runs (N=9) to meet the standard. No failures were detected with the vacuum steam sterilization type B process with fractionated pre-vacuum and post-vacuum phases. Non-vacuum downward/gravity displacement, type-N steam sterilization processes are unreliable in achieving sterilization conditions inside dental handpieces, and the base of the handpiece is the site most likely to fail.

β-Carotene from Yeasts Enhances Laccase Production of Pleurotus eryngii var. ferulae in Co-culture.

Laccase is widely used in several industrial applications and co-culture is a common method for enhancing laccase production in submerged fermentation. In this study, the co-culture of four yeasts with Pleurotus eryngii var. ferulae was found to enhance laccase production. An analysis of sterilization temperatures and extraction conditions revealed that the stimulatory compound in yeasts was temperature-sensitive, and that it was fat-soluble. An LC-MS analysis revealed that the possible stimulatory compound for laccase production in the four yeast extracts was β-carotene. Moreover, the addition of 4 mg β-carotene to 150 mL of P. eryngii var. ferulae culture broth improved laccase production by 2.2-fold compared with the control (i.e., a monoculture), and was similar to laccase production in co-culture. In addition, the enhanced laccase production was accompanied by an increase of lac gene transcription, which was 6.2-time higher than the control on the fifth day. Therefore, it was concluded that β-carotene from the co-cultured yeasts enhanced laccase production in P. eryngii var. ferulae, and strains that produce β-carotene could be selected to enhance fungal laccase production in a co-culture. Alternatively, β-carotene or crude extracts of β-carotene could be used to induce high laccase production in large scale.

Natural fibre envelope for cross-linked and non-cross-linked hydrogel-drug conjugates: Innovative design for oral drug delivery

Recent years have witnessed growing demand for cost-effective natural bioproducts for therapeutic applications. In this work, cardamom husk was processed and turned into a protective shield for the hydrogel-drug conjugate. The seedless cardamom husk comprises of crude fibers and offers effective protection to the encapsulated hydrogel-drug matrix against degradation. Sodium alginate (SA) and gelatin were the biodegradable polymers utilized, while naproxen sodium (hydrophilic) and piperine (hydrophobic) were used as model drugs. The polymer-drug blend encased in this husk was engineered to give a long hour, zero-order release kinetics for both types of drugs. The hydrogel-drug conjugate was carefully optimized to achieve a controlled release with minimal or no use of cross-linkers. The viscosity of sodium alginate was used in such a way that the synthesis of a cross-linker free hydrogel-drug blend can be a reality. The husk was also found to be stable near sterilization temperatures. This research not only focusses on an available resource in nature but also showcases the role of modern methodology to convert this resource (cardamom husk) into a protective shield for a polymeric blend carrying drug molecules.

Arginine prevents thermal aggregation of hen egg white proteins

The control of aggregation and solubilization of hen egg white protein (HEWP) is an important issue for industrial applications of one of the most familiar food protein sources. Here, we investigated the effects of edible amino acids on heat-induced aggregation of HEWP. The addition of 0.6M arginine (Arg) completely suppressed the formation of insoluble aggregates of 1mgmL−1 HEWP following heat treatment, even at 90°C for 20min. In contrast, lysine (Lys), glycine (Gly), and sodium chloride (NaCl) did little to suppress the aggregation of HEWP under the same conditions. SDS-PAGE indicated that Arg suppresses the thermal aggregation of almost all types of HEWP at 1mgmL−1. However, Arg did not suppress the thermal aggregation of HEWP at concentrations ≥10mgmL−1 and prompted the formation of aggregates. Transmission electron micrographs revealed a high-density structure of unfolded proteins in the presence of Arg. These results indicate that Arg exerts a greater suppressive effect on a protein mixture, such as HEWP, than on a single model protein. These observations may propose Arg as a safe and reasonable additive to HEWP for the elimination of microorganisms by allowing an increase in sterilization temperature.

Application of non-enzymatic browning of fructose for heating pattern determination in microwave assisted thermal pasteurization system

Various model foods and chemical markers have been used for the heating pattern determination in microwave processing at sterilization temperatures (110–130 °C). These chemical marker systems have slow reaction rates and are not useful at pasteurization temperatures (70–90 °C). In this study, non-enzymatic browning of fructose under alkaline conditions is investigated for its suitability to be used in the heating pattern determination for microwave assisted thermal pasteurization. Kinetics of browning of fructose in the mashed potato model food were studied. The model food samples were heated in a water bath at 60 °C, 70 °C, 80 °C and 90 °C for different time intervals and the browning kinetics were studied by spectrophotometric measurements at 420 nm. Reaction rate kinetics were fit to a linear first order kinetic model. Application of this model food to determine the heating pattern in the microwave assisted thermal pasteurization system was demonstrated. Dielectric properties of the mashed potato were measured to determine its suitability as a model food. Sucrose and salt were used as effective additives for the adjustment of the dielectric constants and loss factor respectively of the mashed potato. This system offers advantages of being cost-effective, opaque, homogeneous and easy to handle and thus provides an excellent system to locate the hot and cold spots of the food products.