The effects of different dry roast parameters on peanut quality using an industrial belt-type roaster simulator.

Peanuts roasted to equivalent surface colors at different temperature/time combinations can vary substantially in chemical and physical properties related to product quality. This study used a pilot plant scale roaster that simulates the configurations of one of the most common industrial roaster, a multi-zone belt roaster. Jumbo-size runner-type peanuts were systematically roasted at 5 temperatures (149-204°C) to three Hunter l-values of 53, 48.5, and 43, corresponding to light, medium, and dark roasts. Moisture and tocopherol contents were more closely correlated with roast color rather than temperature, with exceptions at 149°C. Moisture decreased with darker roast color, while the total tocopherols were greatest in peanut oils with darker colors. Yield stress of peanut pastes increased as the color darkened, indicating spreadability correspondingly decreased with darker roast colors. The overall flavor of roasted peanuts was found to be optimized at 177°C/15min with the medium roast color.

Mitochondrial DNA Fragmentation to Monitor Processing Parameters in High Acid, Plant-Derived Foods.

Mitochondrial DNA (mtDNA) fragmentation was assessed in acidified foods. Using quantitative polymerase chain reaction, Ct values measured from fresh, fermented, pasteurized, and stored cucumber mtDNA were determined to be significantly different (P > 0.05) based on processing and shelf-life. This indicated that the combination of lower temperature thermal processes (hot-fill at 75 °C for 15 min) and acidified conditions (pH = 3.8) was sufficient to cause mtDNA fragmentation. In studies modeling high acid juices, pasteurization (96 °C, 0 to 24 min) of tomato serum produced Ct values which had high correlation to time-temperature treatment. Primers producing longer amplicons (approximately 1 kb) targeting the same mitochondrial gene gave greater sensitivity in correlating time-temperature treatments to Ct values. Lab-scale pasteurization studies using Ct values derived from the longer amplicon differentiated between heat treatments of tomato serum (95 °C for <2 min). MtDNA fragmentation was shown to be a potential new tool to characterize low temperature (<100 °C) high acid processes (pH < 4.6), nonthermal processes such as vegetable fermentation and holding times of acidified, plant-derived products.

Mitochondrial DNA Fragmentation as a Molecular Tool to Monitor Thermal Processing of Plant-Derived, Low-Acid Foods, and Biomaterials.

Cycle threshold (Ct) increase, quantifying plant-derived DNA fragmentation, was evaluated for its utility as a time-temperature integrator. This novel approach to monitoring thermal processing of fresh, plant-based foods represents a paradigm shift. Instead of using quantitative polymerase chain reaction (qPCR) to detect pathogens, identify adulterants, or authenticate ingredients, this rapid technique was used to quantify the fragmentation of an intrinsic plant mitochondrial DNA (mtDNA) gene over time-temperature treatments. Universal primers were developed which amplified a mitochondrial gene common to plants (atp1). These consensus primers produced a robust qPCR signal in 10 vegetables, 6 fruits, 3 types of nuts, and a biofuel precursor. Using sweet potato (Ipomoea batatas) puree as a model low-acid product and simple linear regression, Ct value was highly correlated to time-temperature treatment (R(2) = 0.87); the logarithmic reduction (log CFU/mL) of the spore-forming Clostridium botulinum surrogate, Geobacillus stearothermophilus (R(2) = 0.87); and cumulative F-value (min) in a canned retort process (R(2) = 0.88), all comparisons conducted at 121 °C. D121 and z-values were determined for G. stearothermophilus ATCC 7953 and were 2.71 min and 11.0 °C, respectively. D121 and z-values for a 174-bp universal plant amplicon were 11.3 min and 9.17 °C, respectively, for mtDNA from sweet potato puree. We present these data as proof-of-concept for a molecular tool that can be used as a rapid, presumptive method for monitoring thermal processing in low-acid plant products.

Recent advances in biopolymers and biopolymer-based nanocomposites for food packaging materials.

Plastic packaging for food and non-food applications is non-biodegradable, and also uses up valuable and scarce non-renewable resources like petroleum. With the current focus on exploring alternatives to petroleum and emphasis on reduced environmental impact, research is increasingly being directed at development of biodegradable food packaging from biopolymer-based materials. The proposed paper will present a review of recent developments in biopolymer-based food packaging materials including natural biopolymers (such as starches and proteins), synthetic biopolymers (such as poly lactic acid), biopolymer blends, and nanocomposites based on natural and synthetic biopolymers. The paper will discuss the various techniques that have been used for developing cost-effective biodegradable packaging materials with optimum mechanical strength and oxygen and moisture barrier properties. This is a timely review as there has been a recent renewed interest in research studies, both in the industry and academia, towards development of a new generation of biopolymer-based food packaging materials with possible applications in other areas.

A review of experimental and modeling techniques to determine properties of biopolymer-based nanocomposites.

The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). One of the reasons for unique properties of bio-nanocomposites is the difference in physics at nanoscale as compared to that at macroscale. Therefore, the effect of nanoscale on the properties of bio-nanocomposites is discussed. Properties of bio-nanocomposites are governed by the extent of dispersion of nanoparticles in the biopolymer matrix and interaction between nanoparticles and the biopolymer. Selection of proper technique to determine properties of these bio-nanocomposites is very critical in assessing their performance. Experimental techniques (tensile testing, barrier property measurement, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological measurement) to determine the mechanical, barrier, thermal, and rheological properties of bio-nanocomposites are discussed in terms of methodology, interpretation of results, and application in studying the properties of bio-nanocomposites. Mathematical modeling plays an important role in predicting the properties of bio-nanocomposites and comparing them to the measured properties. This comparison helps in better understanding the mechanism for much improved properties of bio-nanocomposites. Mathematical modeling is also helpful in understanding the effects of different parameters on the properties of bio-nanocomposites. Therefore, the article describes mathematical modeling of mechanical and barrier properties of bio-nanocomposites using analytical micromechanics.

Effect of type and content of modified montmorillonite on the structure and properties of bio-nanocomposite films based on soy protein isolate and montmorillonite.

The nonbiodegradable and nonrenewable nature of plastic packaging has led to a renewed interest in packaging materials based on bio-nanocomposites (biopolymer matrix reinforced with nanoparticles such as layered silicates). Bio-nanocomposite films based on soy protein isolate (SPI) and modified montmorillonite (MMT) were prepared using melt extrusion. The effect of different type (Cloisite 20A and Cloisite 30B) and content (0% to 15%) of modified MMT on the structure (degree of intercalation and exfoliation) and properties (color, mechanical, dynamic mechanical, thermal stability, and water vapor permeability) of SPI-MMT bio-nanocomposite films were investigated. Extrusion of SPI and modified MMTs resulted in bio-nanocomposites with exfoliated structures at lower MMT content (5%). At higher MMT content (15%), the structure of bio-nanocomposites ranged from intercalated for Cloisite 20A to disordered intercalated for Cloisite 30B. At an MMT content of 5%, bio-nanocomposite films based on modified MMTs (Cloisite 20A and Cloisite 30B) had better mechanical (tensile strength and percent elongation at break), dynamic mechanical (glass transition temperature and storage modulus), and water barrier properties as compared to those based on natural MMT (Cloisite Na(+)). Bio-nanocomposite films based on 10% Cloisite 30B had mechanical properties comparable to those of some of the plastics that are currently used in food packaging applications. However, much higher WVP values of these films as compared to those of existing plastics might limit the application of these films to packaging of high moisture foods such as fresh fruits and vegetables.

Overview of RFID technology and its applications in the food industry.

Radio frequency identification (RFID) is an alternative technology with a potential to replace traditional universal product code (UPC) barcodes. RFID enables identification of an object from a distance without requiring a line of sight. RFID tags can also incorporate additional data such as details of product and manufacturer and can transmit measured environmental factors such as temperature and relative humidity. This article presents key concepts and terminology related to RFID technology and its applications in the food industry. Components and working principles of an RFID system are described. Numerous applications of RFID technology in the food industry (supply chain management, temperature monitoring of foods, and ensuring food safety) are discussed. Challenges in implementation of RFID technology are also discussed in terms of read range, read accuracy, nonuniform standards, cost, recycling issues, privacy, and security concerns.

Continuous flow microwave-assisted processing and aseptic packaging of purple-fleshed sweetpotato purees.

Pumpable purees from purple-flesh sweetpotatoes (PFSP) were subjected to microwave heating using a 60 kW, 915 MHz continuous flow system, followed by aseptic packaging in flexible containers to obtain a shelf-stable product. Initial test runs were conducted using a 5 kW 915 MHz microwave system to measure dielectric in-line properties and examine the puree temperature profiles. The results demonstrated uniformity in heating of the puree at sterilization temperatures (>121 degrees C), and the dielectric constants and loss factors were within the range of published values for orange-fleshed sweetpotato purees. The pilot-scale test runs in a 60 kW microwave unit produced shelf-stable puree packages stable at room temperature. Polyphenolic content of the PFSP purees were evaluated and the results showed that while total phenolics increased (5.9%) and total monomeric anthocyanins slightly decreased (14.5%) with microwave application, antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and oxygen radical absorbance capacity (ORAC) assays did not significantly change as a result of microwave processing. Color values showed that microwave-processed samples differed from fresh puree in saturation and hue angle, but not in overall color change. PFSP purees increased in gel strength when microwave processed, packaged, and stored, but the gel could be easily disrupted into flowable purees. Overall, high-quality retention can be obtained by microwave processing and aseptic packaging of PFSP purees so that they can be used as functional food ingredients.

Design of conservative simulated particles for validation of a multiphase aseptic process.

Simulated food particles with conservative (fast moving and slow heating) properties are required for validation of multiphase aseptic processing for production of shelf-stable low-acid foods. The validation process requires simulated particles to contain residence time tags, thermosensitive implants, and/or bioloads for temperature detection, time-temperature integration, and bactericidal efficacy confirmation. Conservative particle design (CPD) software was used to determine the wall thickness required for conservative behavior of such particles made with polypropylene (PP) and polymethylpentene (PMP) of wall thickness 1 mm (0.0393 inches) and 2 mm (0.0787 inches) containing tube inserts. Thermocouples were inserted in the simulated and real food particles and the particles were heated up to 127 degrees C under pressurized (24 psi) conditions. Based on the heating rates of the real and simulated particles, an appropriate simulated particle was identified for each type of real food particle. This would allow a food processor to use these designed particles with an appropriate tube insert (diameter) to validate an aseptic process for a multiphase food containing any or all the above tested food materials.

Feasibility of utilizing bioindicators for testing microbial inactivation in sweetpotato purees processed with a continuous-flow microwave system.

Continuous-flow microwave heating has potential in aseptic processing of various food products, including purees from sweetpotatoes and other vegetables. Establishing the feasibility of a new processing technology for achieving commercial sterility requires evaluating microbial inactivation. This study aimed to assess the feasibility of using commercially available plastic pouches of bioindicators containing spores of Geobacillius stearothermophilus ATCC 7953 and Bacillus subtilis ATCC 35021 for evaluating the degree of microbial inactivation achieved in vegetable purees processed in a continuous-flow microwave heating unit. Sweetpotato puree seeded with the bioindicators was subjected to 3 levels of processing based on the fastest particles: undertarget process (F(0) approximately 0.65), target process (F(0) approximately 2.8), and overtarget process (F(0) approximately 10.10). After initial experiments, we found it was necessary to engineer a setup with 2 removable tubes connected to the continuous-flow microwave system to facilitate the injection of indicators into the unit without interrupting the puree flow. Using this approach, 60% of the indicators injected into the system could be recovered postprocess. Spore survival after processing, as evaluated by use of growth indicator dyes and standard plating methods, verified inactivation of the spores in sweetpotato puree. The log reduction results for B. subtilis were equivalent to the predesigned degrees of sterilization (F(0)). This study presents the first report suggesting that bioindicators such as the flexible, food-grade plastic pouches can be used for microbial validation of commercial sterilization in aseptic processing of foods using a continuous-flow microwave system.

Measurement of dielectric properties of pumpable food materials under static and continuous flow conditions.

Continuous flow microwave sterilization is an emerging technology that has the potential to replace the conventional heating processes for viscous and pumpable food products. Dielectric properties of pumpable food products were measured by a new approach (under continuous flow conditions) at a temperature range of 20 to 130 degrees C and compared with those measured by the conventional approach (under static conditions). The food products chosen for this study were skim milk, green pea puree, carrot puree, and salsa con queso. Second-order polynomial correlations for the dependence of dielectric properties at 915 MHz of the food products on temperature were developed. Dielectric properties measured under static and continuous flow conditions were similar for homogeneous food products such as skim milk and vegetable puree, but they were significantly different for salsa con queso, which is a multiphase food product. The results from this study suggest that, for a multiphase product, dielectric properties measured under continuous flow conditions should be used for designing a continuous flow microwave heating system.

Feasibility of aseptic processing of a low-acid multiphase food product (salsa con queso) using a continuous flow microwave system.

Aseptic processing of a low-acid multiphase food product using a continuous flow microwave heating system can combine the advantages of an aseptic process along with those of microwave heating. Dielectric properties of 2 different brands of 1 such product (salsa con queso) were measured under continuous flow conditions at a temperature range of 20 to 130 degrees C. At 915 MHz, the dielectric constant ranged from 58.7 at 20 degrees C to 41.3 at 130 degrees C with dielectric loss factor ranging from 41.0 at 20 degrees C to 145.5 at 130 degrees C. The loss tangent at 915 MHz ranged from 0.61 at 20 degrees C to 3.52 at 130 degrees C. The temperature profiles at the outlet during processing of salsa con queso in a 5-kW microwave unit showed a narrow temperature distribution between the center and the wall of the tube. The study showed the feasibility of aseptic processing of salsa con queso using a continuous flow microwave system.

Quantifying the significance of phage attack on starter cultures: a mechanistic model for population dynamics of phage and their hosts isolated from fermenting sauerkraut.

We investigated the possibility of using starter cultures in sauerkraut fermentation and thereby reducing the quantity of salt used in the process. This, in turn, would reduce the amount of waste salt that would enter in our water resources. Phage, naturally present in sauerkraut fermentation, could potentially affect the starter cultures introduced. Thus, a mechanistic mathematical model was developed to quantify the growth kinetics of the phage and starter cultures. The model was validated by independent experiments with two Leuconostoc mesenteroides strains isolated from sauerkraut and their corresponding phage. Model simulations and experimental evidence showed the presence of phage-resistant cell populations in starter cultures which replaced phage-sensitive cells, even when the initial phage density (P(0)) and multiplicity of infection (MOI) were low (P(0) < 1 x 10(3) PFU/ml; MOI < 10(-4)) in the MRS media. Based on the results of model simulation and parameter optimization, it was suggested that the kinetic parameters of phage-host interaction, especially the adsorption rate, vary with the initial phage and host densities and with time. The model was validated in MRS broth. Therefore, the effects of heterogeneity and other environmental factors, such as temperature and pH, should be considered to make the model applicable to commercial fermentations.