Minimal Heat Treatment Research Articles

МОЛЕКУЛЯРНА КУХНЯ ЯК ІННОВАЦІЙНА РЕСТОРАННА ТЕХНОЛОГІЯ

The article examines molecular cuisine as an innovative restaurant technology and a scientific approach to food, primarily from the point of view of the chemical composition, properties and transformations of the ingredients used in cooking. Molecular cuisine as an innovative direction in cooking that combines science and gastronomy to create unusual dishes using advanced technologies and methods. . The main idea of molecular cuisine is to change the physical and chemical properties of ingredients to achieve new taste and texture sensations. The basic principles and techniques of molecular cuisine include: spherification (a technique in which a liquid is turned into balls resembling caviar; this is achieved due to the use of sodium and calcium alginate), gelation (involves the use of various gelling agents such as agar-agar or gelatin, to create gel structures), emulsification (the process of mixing two mutually insoluble liquids to create foam-type emulsions and air textures), lyophilization (the process of removing water from the product at low temperatures and under vacuum, which allows you to preserve the texture and taste of the ingredients), nitrogenation (the use of liquid nitrogen for instant freezing of products, which allows you to create unexpected textures and effects). Molecular cuisine allows you to create unique flavor combinations and textures that cannot be achieved with traditional cooking methods. Dishes created using molecular techniques often look like works of art, making them visually appealing to guests. The use of natural ingredients and minimal heat treatment allows you to preserve more nutrients in dishes. An important applied direction of molecular gastronomy is the study of the relationship between food, its sensory perception and increasing the degree of consumer satisfaction, which can create wide opportunities for improving nutrition and, therefore, people's health.. An important positive aspect of the application of molecular gastronomy is, of course, the popularization of food science and public education in terms of traditional ways of cooking, as well as innovative approaches to food processing.

High-Pressure Processing Helps Meet the Escherichia coli O157:H7 and Shiga Toxin–Producing E. coli (STEC) Performance Standards for Beef Summer Sausage

The United States Department of Agriculture–Food Safety Inspection Service (USDA-FSIS) performance standards require that manufacturers of fermented beef sausages validate their processes to achieve a 5-log reduction of Escherichia coli O157:H7 and Shiga toxin–producing E. coli (STEC). Most processors rely on rapid fermentation to a low pH and a mild heat treatment to achieve the lethality performance standard. However, this process alters the sensorial characteristics of traditional fermented sausages. An alternative method to achieve lethality using high-pressure processing (HPP) during the manufacture of summer sausage with higher pH (5.0) and minimal heat treatment was evaluated. Sausages inoculated with circa 9.1 log CFU/g of E. coli O157:H7 and 8.9 log CFU/g of STEC were fermented to target pH values of 4.6 or 5.0. Subsequently, fermented sausages were heated to endpoint temperatures of 54.4°C, 48.9°C, or 43.3°C to the total process treatments of (1) Process A: pH 4.6 and 54.4°C, simulated cold air chilling, (2) Process B: pH 5.0 and 54.4°C, simulated cold air chilling, (3) Process C: pH 5.0 and 54.4°C, ice bath chilling, (4) Process D: pH 5.0 and 48.9°C, ice bath chilling, and (5) Process E: pH 5.0 and 43.3°C, ice bath chilling. After processing, the product was subjected to HPP (586 MPa; 4°C±2°C) for hold times of 1, 150, or 300 s and a nontreated (no HPP) control. All treatments subjected to HPP for 150 and 300 s reduced (P≤0.05) E. coli (O157:H7 and STEC) populations by>5.0 log CFU/g and >7.5 logCFU/g, respectively. The use of HPP allows for the production of more mild beef summer sausage (pH 5.0 and a mild thermal treatment of 43.3°C) while still achieving USDA-FSIS performance standards for lethality.

Low-Loss Dielectric Ink for Printed Radio Frequency and Microwave Devices.

Direct write printing is restricted by the lack of dielectric materials that can be printed with high resolution and offer dissipation factors at radio frequency (RF) within the range of commercial RF laminates. Herein, we outline the development of dielectric materials with dielectric loss below 0.006 in X and Ku frequency bands (8.2-18 GHz), the range required for radio frequency and microwave applications. The described materials were designed for printability and processability, specifically a prolonged viscosity below 1000 cps and a robust cure procedure, which requires minimal heat treatment. In the first stage of this work, nonpolar ring-opening metathesis polymerization (ROMP) is demonstrated at room temperature in an open-air environment with a low-viscosity monomer, 5-vinyl-2-norbornene, using the second-generation Grubbs catalyst (G-II). Differential scanning calorimetry (DSC) was used to study how the catalyst activity is increased with heating at various stages in the reaction, which is then used as a strategy to cure the material after printing. The resulting cured poly(5-vinyl-2-norbornene) material is then characterized for dielectric and mechanical performance before and after a secondary heat treatment, which mimics processing procedures to incorporate subsequent printed conductor layers for multilayer applications. After the secondary heat treatment, the material exhibits a 55.0% reduction in the coefficient of thermal expansion (CTE), an increase in glass-transition temperature (Tg) from 32.4 to 46.1 °C, and an increased 25 °C storage modulus from 428 to 1031 MPa while demonstrating a minimal change in dielectric loss. Lastly, samples of the developed dielectric material are printed with silver overtop to demonstrate how the material can be effectively incorporated into fully printed, multilayer RF applications.

Shelf Life Extension of Functional Enriched Sugarcane Juice using Ohmic Heating

The present study investigates the development of functional enriched sugarcane juice processed through ohmic heating. Currently, ready to drink functional enriched sugarcane juice with extended shelf life is not available in markets. As conventional heat processing methods reduce the taste, color, and flavor of juices, functional enriched sugarcane juice blended with amla and lemon juice extracts was developed with extended shelf life processed with minimal heat treatment by utilizing ohmic heating - a novel food processing technology. Ohmic Heating (OH) is an alternative thermal treatment as it causes volumetric heating of the sample with a short processing time and it causes minimum discoloration and maintains the nutritive value of the food. The preliminary trials were carried out to optimize the levels of sugarcane juice, amla juice and lemon juice for acceptable sensory attributes on 9 point hedonic scale. Response Surface Methodology (RSM) was used to determine the combinations of the experiment. The independent variables considered were sugarcane juice, amla juice and lemon juice. The responses considered were sensory Volume xxx | Issue xxxx | 2 attributes such as color, flavor, taste and overall acceptability. The optimum levels of sugarcane juice, amla juice and lemon juice were 91.998 mL, 4.720 mL, and 3.282 mL, respectively. The optimum levels were blended for the development of functionally enriched sugarcane juice. The standardized juice was processed using ohmic heating with two different treatments, viz., 50 °C (T1) and 60 °C (T2), for 3 minutes at 25 V/cm. The processed juice was collected in sterile glass bottles and stored at 5 ˚C for conducting storage studies at regular intervals. Microbial and sensory parameters of the untreated, control (pasteurized), and ohmic heated juice were analyzed using one-way analysis of variance (ANOVA). No significant difference (p>0.05) was observed in sensory immediately after ohmic processing when compared to control samples but showed a highly significant difference (p<0.01) in sensory during the storage period. There was a high significant difference (p<0.01) in the total plate count of ohmic heated samples compared to control and during the storage period. No coliform was found in all ohmic heated and control samples. Yeast and mold were present in the untreated sample, but after ohmic heating, no growth was observed. Hence highest microbial reduction was observed in ohmic heating treatment T2 than T1 and control, and the shelf life also extended up to 4 weeks

Combined Effect of Microencapsulated Horseradish Juice and High-Pressure Treatment on Pork Quality During Storage

Abstract High-pressure processing (HPP) is well suited to combine consumer demand for meat products with minimal heat treatment without compromising product safety. In turn, herbs have antioxidant and antimicrobial properties. The aim of this study was to evaluate the application of hurdle technology combining microencapsulated horseradish root and leaf juice with HPP (300 MPa; 15 min) for extending of the raw pork meat shelf life. Water activity (aw), pH, colour, hardness, and micro-biological parameters of meat were evaluated during 21-day storage. Total plate count (TPC) in HPP treated samples was significantly smaller (p < 0.05) compared to untreated samples during storage until the day 14. On day 21, the TPC in processed samples was still slightly lower, however, at this point significance was not established between samples. Water activity dynamics in the HPP-treated microencapsulated pork meat samples differed significantly from other samples. Hardness decreased during storage, but no significant differences were found between samples. The L* values and pH of the meat were not significantly influenced by the added microencapsulated juice, but by high pressure treatment. Treatment with microencapsulated horseradish juice had a positive effect on the TPC and aw of the meat sample.

Formation of rheological characteristics of vegetable and fruit smoothies to ensure their quality

The rheological feature of vegetable-fruit smoothies is a non-stratified, partially heterogeneous texture that fits seamlessly into the concept of a smoothie as a healthy food drink with minimal heat treatment, containing a large number of biologically active substances, primarily vitamins, provitamins, polyphenol substances, as well as dietary fiber - the so-called “superfood”, the effectiveness of which has been proven in vitro. At the same time, the stability of such drinks is a serious technological problem requiring new approaches to the solution. The aim of the study was to study the possibility of using the amylolytic enzyme preparation Termamil 2XL to achieve the stability of the rheological characteristics of the pumpkin-sea buckthorn smoothie, which together provide a stable texture of the drink. It is shown that the use of coarse pumpkin pulp does not allow to achieve the desired result in terms of stable rheological characteristics, since the smoothing separation begins almost immediately after preparation. The possibility of using enzymatic hydrolysis of pumpkin starch, which causes a stable framework due to starch grains in tissue cells, has been established to stabilize the rheological properties of fruit and vegetable smoothies and increase the consumer characteristics of the drink. It is proved that the use of the enzyme preparation Termamil 2XL in a dosage of 0.04% and a treatment time of 60 minutes leads to the production of a stable pseudoplastic fluid with a homogeneous structure and a maximum separation of the liquid phase not exceeding 3% within 24 hours.

Relationship and correlation between antioxidant content and capacity, processing method and fruit colour of cactus pear fruit

Cactus pear fruit is a valuable source of antioxidants and could be an important functional ingredient in foods. Cultivars differ in fruit colour, which may indicate the presence of specific antioxidants. There is increased interest for cactus pear-derived products due to their potential nutraceutical effects, and determining antioxidant potential in processed foods is an important measure to ascertain the quality of a processed product. The aim of the study was to determine the relationship of fruit processing method and colour with antioxidant content and activity in fresh and processed cactus pear fruit. Antioxidant components (ascorbic acid, phenolic compounds, carotenes and betalains) and antioxidant activity (radical scavenging activity towards 2,2′-diphenyl-1-picrylhydrazyl and iron chelating capacity) were determined in fresh and processed (juiced, dried, preserved and chutney) fruits from four different coloured cultivars (purple, green, orange and pink). The highest antioxidant content and potential was found in purple (O. robusta cv Robusta) fruit products, attributed to the highest levels of betalains (1140.4 mg kg−1). Orange fruit (O. ficus-indica) products had the second highest levels, attributed to ascorbic acid and phenolics. Betalains were highly retained in all processed products, while ascorbic acid was mostly retained in the processed products that involved minimal heat treatment. Carotene and phenolic compounds became more available for extraction during processing and showed higher levels after processing. Principal component analysis makes it possible to identify fruit colours of fresh and processed products, which were mostly associated with a specific antioxidant. In the PCA biplot, PC1 (47.93%) and PC2 (21.93%) explained 69.15% of the total variation: a processing method rather than colour-correlated products in terms of antioxidant content and potential. PCA indicated that fresh purple fruit was correlated with chelating activity and betalains, while orange fruit was clustered with phenolics, ascorbic acid, carotene and DPPH. For the processed fruit products, most were clustered together with chelating activity, DPPH and the antioxidants. Orange and pink dried products had high ascorbic acid, phenolics, carotene and DPPH values, while dried and fresh purple fruit had high betalain content and chelating activity.

Thermodynamic description of graphitizable carbons and the irreversible graphitization process

The present paper develops a thermodynamic model for the calculation of the Gibbs energy of graphitizable carbons near the graphitization temperature threshold of 2550K. The graphitization threshold is the minimal heat treatment temperature for the establishment of true graphitic ordering in a graphitizable carbon. The present model represents the structure of graphitizable carbons with a simplified cluster approach. In the model, two distinct clusters share the totality of the carbon atoms in the material: Oberlin's Local Molecular Orientation clusters (LMOs) and mesoscale grain boundary clusters (mGBs). The ability of a carbon material to graphitize is proportional to the size of the LMOs (larger LMOs = more graphitizable). Strongly graphitizing carbons have a large average size for their LMOs. Thus, for these carbons, the fraction of carbon atoms in mGBs can be neglected relative to the one in LMOs. In a LMO, two phases are present in pseudo-thermodynamic equilibrium: the intercrystalline matter phase (IMP) and the coke crystallite phase (CCP). If the average crystallite diameter (La) of the CCP is sufficiently large, the model assumes that the number of carbon atoms in the IMP relative to the CCP is negligible. The paper presents an additive scheme to calculate the Gibbs energy of carbon atoms in a graphitizable carbon based on the present cluster description. The current Gibbs energy model accounts for the contribution of intercrystalline matter removal by the irreversible densification of LMOs up to the graphitization temperature threshold of 2550K.

High Pressure Processing Effects on All Beef Summer Sausage Quality

ObjectivesSummer sausages are currently fermented to a lower pH (≤ 4.6) and mildly heat treated to temperatures of ≥ 54.4°C to meet USDA FSIS performance standards for E. coli O157:H7. Alternatives such as high pressure processing (HPP) may allow for processing with greater pH and lower temperatures while still meeting performance standards, however, the effect of HPP and different processing parameters on sausage quality is not known. The objective of this project was to evaluate HPP in combination with greater pH and minimal heat treatment for their effects on sausage quality.Materials and MethodsThree replicates of all-beef summer sausage products (11% fat) were produced following: (i) pH 4.6, 54.4°C with a traditional smoke house and cooler chill (T); (ii) pH 5.0, 54.4°C T; (iii) pH 5.0, 54.4°C with ice bath chilling (RC); (iv) pH 5.0, 48.9°C RC; and (v) pH 5.0, 43.3°C RC. After chilling, sausages were sliced (3.1 mm), vacuum packaged, transported to a commercial HPP processor, and subjected to HPP at 586 MPa for 0, 1, 150, or 300 s. Post HPP sausages were evaluated for proximate analysis (n = 9), lipid oxidation (n = 9), objective color (n = 9), texture profile analysis (n = 15; hardness, springiness, cohesiveness, gumminess, and chewiness), and sensory characteristics (n = 9) including firmness, cohesion, springiness, and gumminess using trained panelists. Data were analyzed using Proc Mixed (SAS v9.4; SAS Inst. Inc., Cary, NC), as a completely randomized split plot design. The raw sausage chubs were considered the whole plot to which cooking treatments were applied, and the cooked chubs were the split plot, to which HPP times were applied.ResultsThe fat content of the sausages was similar (P = 0.17) among all treatments. There was no difference for moisture:protein attributed to final pH/cooking endpoint or HPP time (P > 0.63), nor was there a difference for lipid oxidation due to pH/cooking endpoint (P = 0.45) or HPP (P = 0.69). Objective color measurements showed that fermentation of summer sausage to pH 4.6, heated to 54.4°C, and traditionally chilled was lighter in color (greater L*; P < 0.01) than all other pH/cooking endpoint combinations which were similar (P > 0.17). Additionally, treatment (i) was less red (lower a*; P < 0.01) than all other treatments while (iv) and (v) exhibited the greatest redness (P < 0.01). Samples became less red and had more fading as HPP time increased (P < 0.05), however, the differences were small in magnitude. Texture profile and sensory characteristic analysis were in agreement and showed that as cooking intensity increased so did the hardness of the sausage (P < 0.01). Similar trends were noted between sensory characteristics and texture profile analysis, with a positive correlation between cooking intensity and the springiness, cohesiveness, and gumminess of the sausage products. High pressure processing also had an effect on springiness and gumminess (P < 0.05), however sensory panelists were unable to detect differences (P > 0.46) for these same attributes.ConclusionHigh pressure processing at 586 MPa for up to 300 s can be used as an alternate method for manufacturing beef summer sausages with marginal impacts on final product quality. Further research needs to be conducted to evaluate the efficacy of the process in reducing E. coli O157:H7 and other STEC population using this alternate summer sausage manufacturing process.

The isolation and identification of Pantoea dispersa strain JFS as a non-pathogenic surrogate for Salmonella Typhimurium phage type 42 in flour

Salmonella is a common pathogen which has been the cause of foodborne illness outbreaks implicating a variety of commodities, including low-moisture foods such as flour. Salmonella costs more than any other pathogen in the United States in terms of health care expenses and time of lost work. Heat treatment can be used to reduce Salmonella and other pathogens in flour to safe levels. However, in low-moisture foods, process times must be increased to achieve adequate lethality, possibly resulting in changes in the flour's functionality such as changes in the gluten quality, vitamin content, and the level of starch gelatinization. There is a need to determine the minimal heat treatment required to achieve desired lethality in flour and other low-moisture foods, with the goal of retaining the flour's functionality. Currently there is no published data about a nonpathogenic bacterial surrogate for Salmonella in flour. In this study, a surrogate, which closely matches the thermal death rate of Salmonella in flour, has been isolated. The surrogate was identified following an evaluation of thermal death curves of ten different strains of bacteria isolated from heat-treated flour and two nonpathogenic surrogates used in other commodities. Flour samples were inoculated with Salmonella or one of the twelve bacterial isolates, and then subjected to heat (70, 75, and 80°C) for 12–60min. The heat tolerance for each organism was determined by plating out at least four different time points for each temperature and comparing the death curve to those from Salmonella. The death curve from Pantoea dispersa was not statistically different (p<0.05) than the death curve of Salmonella. This strain of P. dispersa (strain JFS) can be used as a conservative, slightly more heat resistant, surrogate for Salmonella. It can be used to verify the combination of heat and time necessary to kill Salmonella in flour using a commercial heat-treatment process.

Fungicidal effect of bacteriocins harvested from Bacillus spp.

Aims: This study investigated the ability of bacteriocins isolated from Bacillus spp. (Bacillus species) to inhibit four different yeast isolates obtained from common food products (nono, yoghurt, ogi and cheese) commonly consumed by Nigerians with minimal heat treatment. Methodology and results: Forty-five Bacillus spp. was isolated and identified from common food products using cultural, morphological, physiological and biochemical characteristics. These isolates were tested for antimicrobial activity against Salmonella enteritidis (3), Micrococcus luteus (1) and Staphylococcus aureus (2). Eight bacteriocin producing strains were identified from an over- night broth culture centrifugated at 3500 revolutions for five minutes. Fungicidal effects of these bacteriocins were tested against four yeast strains using the Agar Well Diffusion method. The bacteriocins produced wide zones of inhibition ranging from 5.9±0.000 to 24.00±0.000 mm against the 4 yeast strains tested. There was a significant difference (at p<0.05) between the yeast organisms and the bacteriocins from the Bacillus spp. Conclusion, significance and impact of study: The study reveals the antifungal property of bacteriocins from Bacillus spp. and serves therefore as a base for further studies in its use in the control of diseases and extension of shelf-life of products prone to fungi contamination.

EFFECTS OF BLANCHING TIME ON ANTI OXIDANT (VITAMIN C) STATUS IN SOME FRESH VEGETABLES (CARROT, CABBAGE, AND GREEN BEANS)

This study evaluated the effects of different blanching times on antioxidant (vitamin C) content in selected vegetables (carrot, cabbage, and green beans). Vitamin C in extracts of the raw samples and the blanched (2min, 5min and 10min) were colorimetrically determined at 520nm. The 10min blanching time had the greatest effect on the Vitamin C content in all the vegetables, most especially cabbage. Concentrations of the antioxidant decreased as the blanching time increased, that is, vitamin C concentrations were in the order: Raw>2min> 5min>10min. Raw carrot, cabbage and green beans have decreased from their initial concentrations by 13.46%, 32.43% and 10.77% respectively after 10min blanched. Minimal heat treatment and for through the blanching period of less than ten minutes is recommended to prevent major lost of the antioxidant and other nutritive components in the vegetables. KEYWORDS: Blanching time, antioxidant and vegetable

Effect of ultra high pressure processing on immuno-modulatory activities of the fruits of Rubus coreanus Miquel

Abstract In this study, the most optimal extraction conditions as regards to the immuno-modulatory activity of Rubus coreanus were determined to be 500 MPa with water at 60 °C for 15 min (HPE15). The extraction yield under these conditions was estimated to be 17.3%, which was higher than the yield obtained from the conventional extraction process (13.9%) with water at 100 °C (NE100). For most cases, the extract obtained under a high pressure of 500 MPa for 15 min HPE15 contained higher concentrations of the three main phenolic compounds relative to the conventional extraction procedure; catechin — 5.48 mg/L vs. 3.11 mg/L, caffeic acid — 12.34 mg/L vs. 10.14 mg/L and ferulic acid — 6.94 mg/L vs. 2.59 mg/L. It was found that the high amounts of bioactive components in HPE15 had a stronger beneficial effect on the growth of human B cell (> 20%) and NK cell (> 15%). In addition, the secretion of cytokines, IL-6 (> 10%) and TNF-α (> 12%), and NO- (> 20%) production from macrophages treated with the HPE15 extract was also higher than when the cells were treated with NE100. Based on these combined findings, we concluded that the immuno-modulatory activities of the HPE15 could be enhanced by simultaneous responses of high concentrations of key active components and their synergistic effects. These results clearly proved that high pressure treatment over the appropriate extraction time could effectively destroy the cell membrane and allow the solvents to easily penetrate into the cytoplasm, which can result in the large release of immuno-modulatory active components with less heat damage. Industrial relevance High pressure processing has been used for preservation purposes with no or minimal heat treatment where high temperature processing should be avoided. But, this process has not much studied yet on extracting useful compounds which are sensitive to heat from many food resources including medicinal plants even though this technology has many other advantages including a high yield and rapid extraction time within one hour without the need for thermal energy as well as with few impurities. Therefore, the results from this work about analyzing the ultra high pressure extraction process could definitely contribute to wide ranges of food industries for improving extraction yields correlated to their biological activities, which can expand this technology to process various natural resources having much nutritive and functional values as well as to overcome the mechanical limitations of manufacturing ultra high pressure extraction machines.

Effect of different blanching times on antioxidant properties in selected cruciferous vegetables

AbstractThis study aimed to evaluate the effect of different blanching times on the antioxidant properties (antioxidant and free radical scavenging activities) and phenolic content of selected cruciferous vegetables. The study revealed that a 10‐min blanching time had a significant effect (p &lt; 0.05) on the antioxidant properties and phenolic content of all the vegetables except for cabbage and mustard cabbage. The loss of antioxidant activity was highest in Chinese cabbage (40%) after 15 min of blanching, followed by cabbage (27%), Chinese white cabbage (19%), mustard cabbage (9%) and red cabbage (4%). Red cabbage had lost a total of 40% scavenging activity after 15 min of blanching followed by Chinese cabbage (38%), cabbage (36%), mustard cabbage (23%) and Chinese white cabbage (11%). Only Chinese cabbage showed an increase (p &lt; 0.05) in total phenolic content after 15 min of blanching compared with other vegetables. Minimal heat treatment through blanching process is recommended to prevent the major loss of antioxidant properties and phenolic content in selected cruciferous vegetables. Copyright © 2005 Society of Chemical Industry

A predictive model that describes the effect of prolonged heating at 70 to 90 degrees C and subsequent incubation at refrigeration temperatures on growth from spores and toxigenesis by nonproteolytic Clostridium botulinum in the presence of lysozyme.

Refrigerated processed foods of extended durability such as cook-chill and sous-vide foods rely on a minimal heat treatment at 70 to 95 degrees C and then storage at a refrigeration temperature for safety and preservation. These foods are not sterile and are intended to have an extended shelf life, often up to 42 days. The principal microbiological hazard in foods of this type is growth of and toxin production by nonproteolytic Clostridium botulinum. Lysozyme has been shown to increase the measured heat resistance of nonproteolytic C. botulinum spores. However, the heat treatment guidelines for prevention of risk of botulism in these products have not taken into consideration the effect of lysozyme, which can be present in many foods. In order to assess the botulism hazard, the effect of heat treatments at 70, 75, 80, 85, and 90 degrees C combined with refrigerated storage for up to 90 days on growth from 10(6) spores of nonproteolytic C. botulinum (types B, E, and F) in an anaerobic meat medium containing 2,400 U of lysozyme per ml (50 microg per ml) was studied. Provided that the storage temperature was no higher than 8 degrees C, the following heat treatments each prevented growth and toxin production during 90 days; 70 degrees C for >/=2,545 min, 75 degrees C for >/=463 min, 80 degrees C for >/=230 min, 85 degrees C for >/=84 min, and 90 degrees C for >/=33.5 min. A factorial experimental design allowed development of a predictive model that described the incubation time required before the first sample showed growth, as a function of heating temperature (70 to 90 degrees C), period of heat treatment (up to 2,545 min), and incubation temperature (5 to 25 degrees C). Predictions from the model provided a valid description of the data used to generate the model and agreed with observations made previously.

THERMAL DEATH PARAMETERS of ORANGE JUICE and EFFECT of MINIMAL HEAT TREATMENT and CARBON DIOXIDE ON SHELF-LIFE

Freshly squeezed, refrigerated orange juice has a relatively short shelf-life, which could be extended by minimal processing. D and z values of orange juice microflora were obtained using the capillary method, as well as a plate heat exchanger. the effect of low levels of CO2 on the shelf-life of the juice was also evaluated. the D60 value of typical orange juice flora was about 5 s and the z was 4–5C. A combination of minimal heat treatment (15 s at 60C) and 6 mM CO2 extended the storage life of orange juice to 35 days at 4C. Carbon dioxide flushed into a 10% headspace of 350 ml jars resulted in 6 mM dissolved CO2 in the juice at 4C. This level of CO2 extended the shelf-life of unpasteurized juice to 25 days at 4C and 10 days at 10C, as compared to 17 and 5 days without CO2, respectively. No significant difference in organoleptic evaluations was found between minimally heat treated juices with or without CO2 and fresh untreated juices without CO2 during the first week of storage.

The separation of beta-glucanases produced by Cytophaga johnsonii and their role in the lysis of yeast cell walls.

1. When Cytophaga johnsonii was grown in the presence of suitable inducers the culture fluid was capable of lysing thiol-treated yeast cell walls in vitro. 2. Autoclaved or alkali-extracted cells, isolated cell walls and glucan preparations made from them were effective inducers, but living yeast cells or cells killed by minimal heat treatment were not. 3. Chromatographic fractionation of lytic culture fluids showed the presence of two types of endo-beta-(1-->3)-glucanase and several beta-(1-->6)-glucanases; the latter may be induced separately by growing the myxo-bacterium in the presence of lutean. 4. Extensive solubilization of yeast cell walls was obtained only with preparations of one of these glucanases, an endo-beta-(1-->3)-glucanase producing as end products mainly oligosaccharides having five or more residues. Lysis by the other endo-beta-(1-->3)-glucanase was incomplete. 5. The beta-(1-->6)-glucanases produced a uniform thinning of the cell walls, and mannan-peptide was found in the solution. 6. These results, and the actions of the enzyme preparations on a variety of wall-derived preparations made from baker's yeast, are discussed in the light of present conceptions of yeast cell-wall structure.