Kit L. Yam

A SIMPLE DIGITAL IMAGING METHOD FOR MEASURING AND ANALYZING COLOR OF FOOD SURFACES

Abstract This paper presents a simple method that uses a combination of digital camera, computer, and graphics software to measure and analyze the surface color of food products. The method has also the advantages of being versatile and affordable. The images of the food products can be displayed on computer screen or printed on paper for qualitative analysis of color and structure. Quantitative information such as color distribution and averages (in terms of L ∗ , a ∗ and b ∗ values) can also be determined readily.

Food Packaging Science and Technology

Overview of Food Packaging Systems Introduction Science and Technology of Food Packaging Socioeconomic Needs Packaging Functions Packaging Environments Food Packaging Systems Tables for Analyzing Food Packaging Systems Food Package Development Chemical Structures and Properties of Packaging Materials Chemical Constituents Chemical Bonding Intermolecular Forces Spatial Arrangements Chemical Reactivity and Susceptibility of Packaging Physical Properties of Packaging Materials Introduction Thermal Properties Electromagnetic Properties Mechanical Properties Permeation of Gas and Vapor Introduction Basic Concepts of Permeation Theoretical Analysis Terminology and Units for Permeation Permeability Coefficients of Food Packaging Polymers Factors Governing Permeation Measurements for Permeation Properties Migration and Flavor Scalping Introduction Phenomenal Description of Migration Process Migration Issues in Food Packaging Flavor Scalping and Sorption Migration Testing Predictive Migration Models Regulatory Considerations Food Packaging Polymers Basic Concepts of Polymers Polymerization Reactions Plastics versus Polymers Composition/Processing/Morphology/Properties Relationships Characteristics of Packaging Polymers Food Packaging Polymers Polymer Processing Glass Packaging Introduction Chemical Structure Glass Properties Glass Containers Manufacturing Glass Container Strengthening Treatments Use of Glass Containers in Food Packaging Other Ceramic Containers Metal Packaging Introduction Aluminum Coated Steels Stainless Steel Metal Corrosion Metal Container Manufacturing Protective Lacquers Cellulosic Packaging Introduction Cellulose Fiber-Morphology Cellulose Fiber-Chemistry Paper and Paperboard Production Paper Bags & Wrappings Corrugated Board and Boxes Folding Cartons and Set-up Boxes Composite Cans and Fiber Drums Cartons for Liquids Molded Cellulose Cellophane Other Quasi Cellulosic Materials End-of-Line Operations Introduction Printing Label and Labeling Coding Sealing of Plastic Surfaces Case Study: Finding Sealing Conditions for a LLDPE Film Food Packaging Operations and Technology Food Packaging Line Filling of Liquid and Wet Food Products Filling of Dry Solid Foods Closure and Closing Operation Methods of Wrapping and Bagging Form/Fill/Seal Various Forms of Contact and Contour Packaging Case Studies Thermally Preserved Food Packaging: Retortable and Aseptic Introduction Thermal Destruction of Microorganisms and Food Quality Basics of Thermal Processing Design Hot Filling In-container Pasteurization and Sterilization Aseptic Packaging Case Study: Design of a Thermal-Processed Tray-Set Containing High- and Low-Acid Foods Vacuum/Modified Atmosphere Packaging Basic Principles Non-respiring Products Respiring Products Case study: Design of Modified Atmosphere Package for Blueberries Microwavable Packaging Microwaves and Microwave Oven Microwave/Food/Packaging Interactions Challenges in Microwave Heating of Foods Microwavable Packaging Materials Interactive Microwave Food Packages Case Study: Effect of Metal Shielding on Microwave Heating Uniformity Active and Intelligent Packaging Introduction Active Packaging - Absorbing System Active Packaging - Releasing System Active Packaging - Other System Intelligent Packaging Framework Smart Packaging Devices Legislative and Human Behavior Issues Case Study: Intelligent Microwave Oven with Barcode Reader Shelf Life of Packaged Food Products Introduction Food Distribution Channel Criteria Determining Shelf Life Kinetics Measurements and Prediction Case Study: Shelf Life of a Potato Chip Product with Two Interacting Quality Deterioration Mechanisms Elements of Packaging, Distribution and Shelf Life of Each Category Foods Introduction Cereals and Bakery Products Meat and Fish Products Dairy Products Confectionery Products Fats and Oils Drinks Fresh Fruits and Vegetables Frozen Foods Sustainable Food Packaging Sustainable Packaging Packaging Related Environmental Issues Management of Packaging Wastes Recycling of Packaging Materials Biodegradable Materials Degradable Packaging Life Cycle Assessment Sociological and Legislative Considerations Introduction Tamper Evident Packaging Product Liability Labeling Information

EFFECTIVE CONTROL OF LISTERIA MONOCYTOGENES BY COMBINATION OF NISIN FORMULATED AND SLOWLY RELEASED INTO A BROTH SYSTEM

In order to identify conditions for efficient food preservation by nisin, the sensitivity of Listeria monocytogenes to this preservative was studied under the following three model conditions: (1) the instantaneous addition of nisin into broth medium to simulate the formation of nisin in foods, (2) the slow delivery of nisin solution into broth medium using a pump to simulate the slow release of nisin from packaging materials to foods, (3) a combination of the two delivery methods. Based on the following results, we conclude that the antimicrobial effectiveness of nisin strongly depends on its mode of delivery. The instantaneous and slow methods for adding nisin inhibited L. monocytogenes, but over time of exposure, L. monocytogenes developed tolerance to nisin. Our data indicate that cells treated with instantaneously added nisin developed resistance to higher concentrations of nisin (200 IU/ml), compared to cells treated with slowly added nisin at the same total amount of the antimicrobial. Further studies indicated that nisin-tolerant cells recovered from treatments in which 200 IU/ml nisin was added instantaneously were likely to be mutants, which became resistant to the bacteriocin. In contrast, when 200 IU/ml of the antimicrobial was added slowly to the cells, only a temporary tolerance was developed; these cells became nisin-sensitive after passage through nisin-free medium. Due to the development of nisin-resistant cells, excessive amounts of nisin in the model system did not further inhibit L. monocytogenes. These results signify that excess nisin in foods does not necessarily improve the efficiency of controlling L. monocytogenes. Our data suggest that the combination of packaging material containing nisin used in conjunction with nisin-containing foods will provide the most effective means of preventing L. monocytogenes growth.

Design of modified atmosphere packaging for fresh produce

Controlled atmosphere (CA) storage and modified atmosphere packaging (MAP) are two useful technologies to extend the shelf-life of fresh agricultural and horticultural produce. Simply stated, these technologies involve storing a fruit or vegetable in a modified atmosphere usually consisting of reduced O2 and elevated CO2 concentrations compared to air. The modified atmosphere reduces the rates of respiration and ethylene production, which are often associated with the benefits of retardation of physiological, pathological, and physical deteriorative processes occurring in the product. Aerobic respiration is a complicated process that involves a series of enzymatic reactions taking place through the metabolic pathways of glycolysis, the tricarboxylic acid (TCA) cycle, and the associated electron transport system (Kader, 1987).

Modeling respiration–transpiration in a modified atmosphere packaging system containing blueberry

Abstract A respiration–transpiration model was developed by applying simultaneous heat and mass transfer principles along with known physiological behavior for the design of MAP systems containing fresh produce. The model equations were solved numerically using Adams–Moulton method to predict gas compositions, RH, and temperature in model packages. The applicability of the model to packages containing blueberry at 15 and 25 °C was successfully verified using different types of packaging films. The difference between the experimental and predicted headspace gas composition was less than 1%. The predicted and experimental values were in agreement for RH (within 2%) and temperature (within 0.5 °C).

DECOUPLING APPROACH TO MODELING PERFORATED TUBE MUFFLER COMPONENTS.

A transformation is derived to decouple the two differential equations describing one‐dimensional acoustic wave propagation in the presence of mean flow, in mufflers with partitioned, perforated tubes. The following analysis leads to compact and exact expressions for the matrix parameters of crossflow elements without any concern for convergence of infinite series or segmental analysis employed in earlier studies. The present analysis is, however, based on assumptions of a uniform perforate impedance on the tube, and of equal mean flow in the two ducts. The predicted transmission loss curves agree very well with published data. The decoupled equations make transparent the connection between high‐frequency resonances of perforated elements and the axial propagation of radial velocity fluctuations through the holes, without mean flow. The resonance frequencies of a plug muffler are seen to coincide with resonance frequencies of crossflow elements, which in turn may be correlated very simply and accurately w...

Release kinetics of tocopherol and quercetin from binary antioxidant controlled-release packaging films.

This paper investigated the feasibility of manipulating packaging polymers with various degrees of hydrophobicity to release two antioxidants, tocopherol and quercetin, at rates suitable for long-term inhibition of lipid oxidation in food. For example, one antioxidant can be released at a fast rate to provide short-term/intermediate protection, whereas the other antioxidant can be released at a slower rate to provide intermediate/long-term protection of lipid oxidation. Controlled-release packaging films containing tocopherol and quercetin were produced using ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVA), low-density polyethylene (LDPE), and polypropylene (PP) polymers; the release of these antioxidants to 95% ethanol (a fatty food simulant) was measured using UV-vis spectrophotometry, and Fickian diffusion models with appropriate initial and boundary conditions were used to fit the data. For films containing only quercetin, the results show that the release of quercetin was much faster but lasted for a much shorter time for hydrophilic polymers (EVOH and EVA) than for hydrophobic polymers (LDPE and PP). For binary antioxidant films containing tocopherol and quercetin, the results show that tocopherol released more rapidly but for a shorter period of time than quercetin in LDPE and EVOH films, and the difference is more pronounced for LDPE films than EVOH films. The results also show the presence of tocopherol can accelerate the release of quercetin. Although none of the films produced is acceptable for long-term lipid oxidation inhibition, the study provides encouraging results suggesting that acceptable films may be produced in the future using polymer blend films.

Relationships between residence time and process variables in a corotating twin-screw extruder

Abstract Degerminated yellow corn meal was extruded with a Werner and Pfleiderer ZSK-30 corotating twin-screw extruder under a wide range of processing conditions. The effects of process variables on mean residence time were examined by changing one variable at a time, as well as by applying statistical models to analyze situations when two or more process variables were changing. The most significant process variables affecting mean residence time were screw speed followed by throughput. Moisture content had only borderline effect, while die pressure and die temperature had no significant effect.

Inhibition of Saccharomyces cerevisiae by Slow Release of Propyl Paraben from a Polymer Coating

The inhibition of Saccharomyces cerevisiae by slow release of propyl paraben from a styrene-acrylate copolymer coating was examined and compared with the inhibition by direct addition of propyl paraben. Under slow release condition, a slow but continuous microbial inhibition was observed, whereas a cell outgrowth was observed under direct addition condition after a sufficient incubation time. S. cerevisiae cells isolated from the culture under direct addition condition were more tolerant of propyl paraben than cells isolated from the culture under slow release condition. The equilibrium propyl paraben concentrations under both conditions were 150 ppm. The release kinetics of propyl paraben from the coating at 30 degrees C was found to be controlled by Fickian diffusion within the coating. The estimated partition and diffusion coefficients were 4.65 x 10(-3) and 2.01 x 10(-10) cm2/s, respectively.

Simple models for assessing migration from food-packaging films

Owing to their simplicity, two migration models based on Ficks Second Law have been frequently used for the assessment of migration of additives and contaminants from food-packaging films. While the two models are known to provide accurate estimates of diffusion coefficients for complete migration, they could generate considerable estimation errors for significantly partitioned migration. In this paper, the applicability of the two models to partitioned migration is defined by examining the assumptions and derivations of the two models as well as their errors in estimating diffusion coefficients. Furthermore, a simple migration model, based on more realistic assumptions than the two models, is proposed. The proposed model can provide far better estimates of diffusion coefficients for partitioned migration than the two models.