EFFECT OF OXYGEN-ENRICHED ATMOSPHERES ON STORAGE QUALITY OF PACKAGED FRESH MEAT

SUMMARY —The extension of fresh meat shelf-life is important from both practical and theoretical points of view. Color is usually used as a measure of fresh meat quality during storage. Beef top-round slices were prepared using sanitary precautions. Meat slices were enclosed in a thermally sealed semi-rigid polyvinyl chloride tray system of special design. Face-to-face meat samples were used to compare the effects of high oxygen with normal air atmospheres. One package from each pair was evacuated and the atmosphere readjusted to approximately 90% oxygen through a septum. Packages were kept at 4 ± 0.5°C and gas chromatographic readings for CO₂, O₂ and N₂ were conducted daily. Spectrophotometric and bacteriological evaluations were made on selected pack ages during storage to determine pigment oxidation and microbial growth. Three experiments each containing six to eight pairs of samples were conducted. The generation of CO₂ was observed in two periods–the first immediately after packaging and lasting for 1–2 days, after which the CO₂ level remained approximately stable up to 8—9 days, when it again started to increase in correspondence with increased bacterial growth. There was more CO₂ produced than O₂ utilized in the stored samples. In the first stage, samples stored in oxygen-enriched atmospheres had higher O₂ uptake than samples stored in air. Microbial growth was similar in both atmospheres. Under conditions of this study, head space enrichment to about 90% oxygen prolonged acceptable meat color when compared with samples stored in an air atmosphere.     

A WEB-BASED MULTI-AGENT SYSTEM FOR TRANSPORTATION MANAGEMENT TO PROTECT OUR NATURAL ENVIRONMENT

To improve the situation of wasting natural resources, the existing transportation systems have to be optimized. This means that we should not only think about new technologies for saving energy but also about better use of the existing trafficways. The most efficient way to achieve these objectives is to automate the existing means of communication and to improve transportation management. Since most of the communication channels and technologies for automation in transportation management are Web-based, we want to describe how to improve Web-based transportation management. Talking about Web-based environments means talking about the Internet and services it offers. These Web-based environments build up a good basis for an agent-based approach, because all aspects for communication and information processing are also used in agent systems. In this approach, Web servers build the agents by themselves and an agent-based interaction works with the support of Web services. Thus, we can build an agent-based structure for transportation control that is similar to the structure of the Internet. Agent-based transportation management is a possible contribution to make transportation management more effective in regard to saving energy (fuel) and protecting our environment by stopping the increase of existing trafficways.     

IMPROVEMENT OF SHELF LIFE STABILITY OF CAKES

ABSTRACT

The effects of new ingredient strategies to slow down starch retrogradation rate in cakes were investigated. In this study, devil's fudge cakes were formulated using gum, modified starch and enzyme technology. Cake samples that were prepared with combinations of gums, bacterial amylases and pregelatinized starch were found to have slower starch retrogradation rates. An accelerated shelf life protocol was followed to observe the effect of predescribed ingredients on slowing the starch retrogradation rate. The samples were evaluated for moisture content, water activity, texture and thermal properties, as well as morphological characteristics. The staling rate was found to be accelerated by the fluctuations in temperature from high to low temperatures. Modified starches, enzymes and gums were found to decrease the rate of staling and improve product quality. The formulated cakes were found to have 25% lower toughness and hardness values as compared with the control product. It was found that for all the cake formulations, there was a significant decrease in both hardness and toughness values, whereas springiness values did not change much. The basic differences within formulations were created by incorporation of gums, enzymes, soluble fibers, emulsifiers and modified flours in the cake.

PRACTICAL APPLICATIONS

Nutritional balance is quite important for each individual. For certain groups of people, based on their activity levels, high energy supplies are required to help them to achieve their optimal performance. Cakes, waffles and pancakes are in the group of breakfast bakery items that provide high energy for these groups of people. In bakery food products, staling reactions start before microbial deteriorations; as a result, they are the major factor in determining shelf life. Cakes that are acceptable to the consumers should be moist and soft in texture. Starch retrogradation is the primary mechanism determining the shelf life of the product. Although the product is microbiologically safe, the adverse affects of starch crystals on textural properties is the main cause of product rejection by the consumer, which leads to huge economical losses. The current methods of controlling starch retrogradation lean on technologies of the 1980s. Despite several studies on bread staling, there is hardly any study on the staling mechanism of cakes and other bakery food items. This study provides information on how to retard staling in cakes by the use of an in‐house developed accelerated shelf life protocol.     

QUANTITATIVE DETERMINATION OF METMYOGLOBIN AND TOTAL PIGMENT IN AN INTACT MEAT SAMPLE USING REFLECTANCE SPECTROPHOTOMETRY

SUMMARY— A technique for determining the relative quantities of oxymyoglobin, metmyoglobin and total pigment concentration at the surface of on intact meat sample was developed. A Beck-man DK-2 spectrophotometer with reflectance attachment was used and spectra were recorded on the R_A scale. The sample port of the spectrophotometer was modified so that a uniform and high intensity light beam measuring 0.5 × 0.6 cm reached the surface being evaluated. A sample holder was constructed so that known proportions of oxygenated and oxidized meat could be exposed to the light beam. A family of curves representing varying known amounts of metmyoglobin and oxymyoglobin were obtained. The height of the peak at 632 nm (ΔR_A632) was directly related to the amount of metmyoglobin at the surface of the meat sample. For 100% oxymyoglobin, ΔR_A632 was at a minimum and equal to R_A750. For 100% metmyoglobin, ΔR_A632 was at a maximum and the height of the response depended upon the amount of total pigment present. A linear relation was obtained when ΔR_A362 was plotted against percent metmyoglobin or against total pigment determined by the Hornsey (1956) method. The method requires making two readings of the meat samples at a single wave length. One reading of the sample followed by one reading of the same sample after oxidation with K₃ Fe(CN)₆ provides a quantitative evaluation of the metmyoglobin concentration and the total heme pigment concentration. The accuracy of the method may be improved by making multiple readings.     

Properties of the nonparametric autoregressive bootstrap

For nonparametric autoregression, we investigate a model based bootstrap procedure (`autoregressive bootstrap') that mimics the complete dependence structure of the original time series. We give consistency results for uniform bootstrap confidence bands of the autoregression function based on kernel estimates of the autoregression function. This result is achieved by global strong approximations of the kernel estimates for the resample and for the original sample. Furthermore, it is obtained that the autoregressive bootstrap also yields asymptotically correct approximations for distributions of parametric statistics, for which regression-type bootstrap-techniques like the wild bootstrap do not work. For this purpose, we prove geometric ergodicity and absolute regularity of the nonparametric autoregressive bootstrap process. We propose some particular estimators of the autoregression function and of the density of the innovations such that the mixing coefficients of the autoregressive bootstrap process can be bounded uniformly by some exponentially decaying sequence. This is achieved by using well-established coupling techniques. Moreover, by using some `decoupling' argument, we show that the stationary density of the bootstrap process converges to that of the original process. The paper may serve as a template for proving similar consistency results for other bootstrap techniques such as the Markov bootstrap.     

PHOTO SENSITIVITY OF FRESH MEAT COLOR IN THE VISIBLE SPECTRUM

SUMMARY –The effect of specific wavelengths of visible light on fresh meat color was investigated. 2-in. diam cores of meat were aseptically prepared from top rounds (adductor muscle and semimembranosus muscle). Freshly oxygenated face-to-face cuts were used as the sample and control. The sample and control were packaged in mylar polyethylene pouches and cooled moist filtered air was circulated through the pouch for the duration of the experiment. Samples were exposed to the following wavelengths at an energy level of 0.5 mw/cm²: 420.0, 510.0, 550.0, 570.0, 590.0 and 632.8 nm. Experiments were conducted at 34°± 1°F and 41°± 1°F for 2 and 5 days of exposure. The controls were next to the sample but kept in darkness during the exposure period. There was no temperature differential between the sample and control. Oxidized heme pigment content was determined by reflectance spectrophotometry. No wavelength enhanced the formation of oxidized heme pigment more than any other, however illuminated samples contained an average of 5.5% more oxidized heme pigment than did the controls. Oxidized heme pigment content increased with lengthened storage time and increased temperature. The increase in oxidized heme pigment content as a result of illumination may be due to a photochemical activation of a compound such as riboflavin which then may react with oxygenated heme pigments to form oxidized heme pigments.