Thermal inactivation kinetics of Salmonella and Campylobacter in chicken livers

Salmonella and Campylobacter are major foodborne pathogens that cause outbreaks associated with contaminated chicken liver. Proper cooking is necessary to avoid the risk of illness to consumers. This study tested the thermal inactivation of a 4-strain Salmonella cocktail and a 3-strain Campylobacter cocktail in chicken livers separately at temperatures ranging from 55.0 to 62.5°C. Inoculated livers were sealed in aluminum cells and immersed in a water bath. The decimal reduction time (D-values) of Salmonella in chicken livers were 9.01, 2.36, 0.82, and 0.23 min at 55.0, 57.5, 60.0, and 62.5°C, respectively. The D-values of Campylobacter ranged from 2.22 min at 55.0°C to 0.19 min at 60.0°C. Salmonella and Campylobacter had similar z-values in chicken livers of 4.8 and 4.6°C, respectively. Chicken livers can be heated to internal temperatures of 70.0 to 73.9°C for at least 1.6 to 0.2 s to achieve a 7-log reduction of Salmonella. Validation tests demonstrated that heating chicken livers to internal temperatures of 70.0 to 73.9°C for 2 to 0 s resulted in a reduction of Salmonella exceeding 7 logs. Collectively, these data show that Salmonella exhibits higher heat resistance than Campylobacter in chicken livers. Therefore, Salmonella could be considered as the target pathogen when designing thermal treatments or cooking instructions for liver products. These findings will aid in designing effective thermal processing for both industrial and home cooking to eliminate Salmonella and Campylobacter, ensuring consumer safety when consuming chicken liver products.

Recycling Functional Fillers from Waste Tires for Tailored Polystyrene Composites: Mechanical, Fire Retarding, Electromagnetic Field Shielding, and Acoustic Insulation Properties-A Short Review

Polymer waste is currently a big and challenging issue throughout the world. Waste tires represent an important source of polymer waste. Therefore, it is highly desirable to recycle functional fillers from waste tires to develop composite materials for advanced applications. The primary theme of this review involves an overview of developing polystyrene (PS) composites using materials from recycled tires as fillers; waste tire recycling in terms of ground tire rubbers, carbon black, and textile fibers; surface treatments of the fillers to optimize various composite properties; and the mechanical, fire retarding, acoustic, and electromagnetic field (EMI) shielding performances of PS composite materials. The development of composite materials from polystyrene and recycled waste tires provides a novel avenue to achieve reductions in carbon emission goals and closed-loop plastic recycling, which is of significance in the development of circular economics and an environmentally friendly society.

Theoretical reasons for rapid heating of vegetable oils by microwaves

Water and high-moisture foods are readily heated in microwaves due to their relatively high dielectric loss factors. Vegetable oil, on the other hand, has a much smaller loss factor (about 1/100th that of water), and is generally believed to be unsuitable for microwave heating. In this study, we conducted experiments to compare heating rates between vegetable oil and pure water in a 2450 MHz microwave oven. We found that the vegetable oil samples were heated rapidly in microwaves, and even faster (1.4-2.0 times) than the water samples. To provide a theoretical explanation, we developed a 3-D computer simulation model. The simulation revealed an approximately 10-fold stronger electric field in oil compared to water, resulting in a similar amount of microwave power being absorbed by the oil and water samples. As the absorbed microwave power was converted into thermal energy, the oil samples were heated faster due to their smaller specific heat (1/2 that of water). But we also found that when the dimensions of oil are smaller than half the microwave wavelength, oil is heated slower than water due to the absence of hot spot areas. This study provides a theoretical explanation for microwave heating of vegetable oils and demonstrates opportunities for utilizing microwave energy to electrify industrial heating of vegetable oils.

Antimicrobial activity of gamma-poly (glutamic acid), a preservative coating for cherries

We investigated the minimum inhibitory concentration (MIC), antibacterial activity, and preservation ability of four molar masses of γ-polyglutamic acid (PGA) against Escherichia coli, Bacillus subtilis, and yeast. The antibacterial mechanism was determined based on the cell structure, membrane permeability, and microscopic morphology of the microorganisms. We then measured the weight loss, decay rate, total acid, catalase activity, peroxidase activity, and malondialdehyde content toward the possible use of PGA as a preservative coating for cherries. When the molar mass was greater than 700 kDa, the MIC for Escherichia coli and Bacillus subtilis was less than 2.5 mg/mL. The mechanism of action of the four molar masses of PGA was different with respect to the three microbial species, but a higher molar mass of PGA corresponded to stronger inhibition against the microbes. PGA of 2000 kDa molar mass damaged the microbial cellular structure, resulting in excretion of alkaline phosphatase, but PGA of 1.5 kDa molar mass affected the membrane permeability and the amount of soluble sugar. Scanning electron microscopy indicated the inhibitory effect of PGA. The antibacterial mechanism of PGA was related to the molar mass of PGA and the microbial membrane structure. Compared with the control, a PGA coating effectively inhibit the spoilage rate, delay the ripening, and prolong the shelf life of cherries.

Glass transitions in frozen systems as influenced by molecular weight of food components

Freezing is a frequently used way to expand the storage life of foods with high water content. Under suitable cooling rates, frozen systems attain a condition of maximum freeze concentration, which is characterized by the glass transition temperature (T_g '), end point of freezing or onset of melting (T_m '), and concentration of solids (X_s ') in the maximum-freeze-concentrated matrix. The value of T_g ', T_m ', and X_s ' depends on the chemical composition of frozen system. Below T_g ', the rates of deteriorative reactions are significantly reduced. In this article, the data for T_g ', T_m ', and X_s ' of different frozen systems including sugars, starches, proteins, and food are collected and compiled. The trends in T_g ' and T_m ' data of food are investigated using molecular weight (MW) of food components. The T_g ' and T_m ' of most starches (increased by 2.46% to 87.3% and 10.8% to 85.0%) and some protein-rich foods (increased by 5.00% to 53.4% and 25.0% to 52.9%) were higher than the maximum values of sugar-rich foods. Both T_g ' and T_m ' values increased with increasing MW of solids in frozen food, reaching an asymptotic value. Moreover, there were exponential relationships between T_g ' or T_m ' values and MW for sugar and starch-rich foods taken together. Some studies found that frozen storage below T_g ' maintains the higher quality of food that was achieved by fast freezing. However, other studies found that there was no significant difference in the quality of frozen foods between storage temperature below and above T_g '. Therefore, storage below T_g ' is not the only factor for predicting the stability of frozen foods.

High-pressure pasteurization of low-acid chilled ready-to-eat food

The working population growth have created greater consumer demand for ready-to-eat (RTE) foods. Pasteurization is one of the most common preservation methods for commercial production of low-acid RTE cold-chain products. Proper selection of a pasteurization method plays an important role not only in ensuring microbial safety but also in maintaining food quality during storage. Better retention of flavor, color, appearance, and nutritional value of RTE products is one of the reasons for the food industry to adopt novel technologies such as high-pressure processing (HPP) as a substitute or complementary technology for thermal pasteurization. HPP has been used industrially for the pasteurization of high-acid RTE products. Yet, this method is not commonly used for pasteurization of low-acid RTE food products, due primarily to the need of additional heating to thermally inactivate spores, coupled with relatively long treatment times resulting in high processing costs. Practical Application: Food companies would like to adopt novel technologies such as HPP instead of using conventional thermal processes, yet there is a lack of information on spoilage and the shelf-life of pasteurized low-acid RTE foods (by different novel pasteurization methods including HPP) in cold storage. This article provides an overview of the microbial concerns and related regulatory guidelines for the pasteurization of low-acid RTE foods and summarizes the effects of HPP in terms of microbiology (both pathogens and spoilage microorganisms), quality, and shelf-life on low-acid RTE foods. This review also includes the most recent research articles regarding a comparison between HPP pasteurization and thermal pasteurization treatments and the limitations of HPP for low-acid chilled RTE foods.

Hybrid mixture theory-based modeling of transport of fluids, species, and heat in food biopolymers subjected to freeze-thaw cycles

A hybrid mixture theory (HMT)-based unsaturated transport (pores not saturated with liquid) model was applied to a food matrix subjected to freezing and freeze-thaw cycles. The model can explain the fluid, species, and heat transport, ice formation, thermomechanical changes, and the freezing point depression occurring inside food biopolymers during freezing. Volume changes during freezing were calculated using the stresses due to pore pressure and the phase-change based mechanical strain. The Eulerian-Lagrangian transformation was performed for solving the equations using a finite element mesh in Lagrangian coordinates. The predicted temperature profiles for constant and fluctuating freezing temperature conditions showed agreement with experimental data with reasonable accuracy (RMSE = 2.86°C and 2.23°C, respectively). The multiscale transport model coupled with a physical chemistry-based relation was able to predict solute concentration and the freezing point depression in potatoes with greater accuracy than an empirical equation published in the literature. Sudden temperature fluctuations representing the opening and closing of a freezer door were investigated using this solution scheme, and conditions causing less damage to the food were identified. PRACTICAL APPLICATION: Food materials are subjected to freeze-thaw cycles during storage, shipping, and distribution to the consumers. The study uses numerical modeling and experimental validation to elucidate the principles affecting ice formation, solute migration, and temperature changes. Outcomes will allow processors to improve the quality of frozen foods with improved design of freezing operation, and storage and distribution strategies.

Evaluation of electrostatic powder coating method to prolong the shelf life of cheese slices

Electrostatic coating is being developed as an attractive alternative to overcome the problems encountered during conventional coating which includes non-uniform coating, dust generation, high energy and time consuming, equipment cleaning, and operating expenses. In this method, powder particles are charged by passing through an ion-rich region, which repel each other to produce an evenly distributed coating. This results in a uniform distribution of powder on target surface. In this study, the electrostatic coating of black pepper powder was applied by varying the applied voltage (0-20 kV), at a conveyor belt speed of 10 m/s and compared with manually coated cheese slices. The values of transfer efficiency (52.7%-87.0%), dust reduction (76.2%-85.8%), and adhesion (20.8%-85.3%) were higher for electrostatic coatings. The weight losses were lower (0.19%) at 15 kV as compared to 20 kV (0.67%). The total plate count of cheese slice coated at 20 kV was significantly higher (p < 0.05), whereas at 15 kV it was lower than all other treatments. The shelf life of coated cheese slices at 15 kV lasted up to 1 month due to better coating compared to other treatments. From the results, it can be concluded that electrostatic coating of cheese slice with black pepper is best at 15 kV along with higher transfer efficiency and dust reduction. PRACTICAL APPLICATION: Electrostatic powder coating of cheese resulted in higher transfer efficiency and reduction in dust production. later one has reduce the coating material requirement, thereby, reducing the processing cost. Moreover, dust reduction will reduce the burden of cleaning cost of environment and enhance worker health.

Machine learning-based modeling in food processing applications: State of the art

Food processing is a complex, multifaceted problem that requires substantial human interaction to optimize the various process parameters to minimize energy consumption and ensure better-quality products. The development of a machine learning (ML)-based approach to food processing applications is an exciting and innovative idea for optimizing process parameters and process kinetics to reduce energy consumption, processing time, and ensure better-quality products; however, developing such a novel approach requires significant scientific effort. This paper presents and evaluates ML-based approaches to various food processing operations such as drying, frying, baking, canning, extrusion, encapsulation, and fermentation to predict process kinetics. A step-by-step procedure to develop an ML-based model and its practical implementation is presented. The key challenges of neural network training and testing algorithms and their limitations are discussed to assist readers in selecting algorithms for solving problems specific to food processing. In addition, this paper presents the potential and challenges of applying ML-based techniques to hybrid food processing operations. The potential of physics-informed ML modeling techniques for food processing applications and their strategies is also discussed. It is expected that the potential information of this paper will be valuable in advancing the ML-based technology for food processing applications.

Quality changes in chicken livers during cooking

Raw chicken livers are often contaminated with Campylobacter and Salmonella. Cooking is considered the last defense of pathogen control for meals containing chicken livers. However, consumers' preference for pink color and a creamy texture as desired attributes in preparing liver pâté may lead to inadequate cooking, thereby increasing the risk of foodborne illness. This study aimed to investigate the effects of different cooking conditions (60-90°C, 0-65 min) on quality changes in frozen and fresh chicken livers and develop cooking recommendations to produce safe liver products with desired qualities. Frozen storage reduced the water holding capacity of raw chicken livers and led to more cooking loss (reduction in the weight of liver pieces during cooking) and area shrinkage after heating. The cooking loss and area shrinkage increased with increasing heating time and temperature, following the first-order fractional model. Compared with fresh livers, the shear resistance for cutting through the cooked livers increased after heating at 73.9°C to 90°C and decreased at 60°C, whereas the livers heated at 70°C had shear resistance (~4.5 N/g) similar to the fresh liver, regardless of the heating times used in this study. Heating resulted in color changes in livers, shifting from red hue (0°) toward yellow hue (90°), as characterized by the increased hue angles after heating. Cooking livers to an internal temperature of 70°C to 73.9°C and hold for 101 to 26 s is recommended for food processing plants or restaurants to prepare ready-to-eat meals containing chicken livers to achieve microbial safety with respect to Salmonella and provide cooked livers with desired texture and pink color.