CONSISTENCY CHECKING ALONG TIME

Most model-based approaches to diagnosis require a consistency-checking procedure to perform their task. When dealing with a dynamically changing system, such a procedure must take into account time-varying data. This requires suitable techniques for reasoning over time. Additional difficulties arise when delays are involved in interactions between variables. The worst case occurs when some of the delays are completely unspecified. This report presents an approach to consistency checking that handles qualitative models of dynamic systems exhibiting time lags. A component-centered ontology is adopted to model the structure of the physical system, and an episode-based approach is adopted for representing its behavior over time. An example consisting of a physical process exhibiting transportation lags is used to illustrate the power of the approach. We present algorithms and an implementation in PROLOG called C-CAT (consistency checking along time). Some meaningful outputs from the program are used as examples. The solution proposed represents an extension to B. C. Williams' temporal constraint propagation methodology. It also extends the applicability range of existing approaches to model-based diagnosis, permitting its use in tasks such as online diagnosis of dynamic systems.     

MICROBIOLOGICAL QUALITY OF ARTISAN-MADE MEXICAN BOTANERO CHEESE IN THE CENTRAL HIGHLANDS

Artisan-made Mexican Botanero cheese in the northwest of the state of Mexico in the central highlands is a soft-paste, fresh product made from raw cow milk. The microbiological quality was determined in cheese from 10 cheese producers. Milk and cheese samples were taken, and the hygienic process was recorded. Milk was analyzed for aerobic mesophil bacteria (AMB) and total coliform bacteria (TC), and in cheese TC and fecal coliforms (FCs) were determined. Results were compared with the Mexican COFOCALEC (milk) and NMX-462 (cheese). All bacterial counts were above those allowed for AMB (100,000 cfu/mL) and TC (1,000 cfu/mL). The norm allows up to 100 cfu/g of TC, but all cheese samples were above the norm. FC should always be negative, but all cheese samples were also positive. Raw milk is bought in with microbiological problems, and the artisan-manufacturing process further contaminates the final product, which constitutes a risk for human health. Even more rigorous legislation could not be met by artisan cheese makers in the highlands of central Mexico under the current conditions.

PRACTICAL APLICATIONS

In Mexico, there is an ample variety of artisan-made cheeses with a potential to be positioned in regional, national and even export markets by obtaining quality certification either as appellation controleé or as collective trademarks. However, in order to obtain this certification, it is necessary to analyze the situation of all the characteristics of the cheeses such as bacteriological quality. Before carrying out this study, the bacteriological quality of the Botanero cheese was unknown. Taking into account the obtained results, it is intended to carry out joint collaboration with cheese producers, so that their products can achieve the required standards and can reach a better position in the market, without being a risk for human health.     

PHYTIC ACID HYDROLYSIS AND BEAN SUSCEPTIBILITY TO STORAGE INDUCED HARDENING1

Two bean cultivars were stored over a 33-day period (75% RH and 41°C). After this period, cooked hardness, levels of phytate, phytase activity and integrity of protein bodies were monitored. The Michigan cultivar, which was the most susceptible to hardening, showed higher initial content of phytate which decreased by 20.7% after 30 days of storage. In contrast, Ojo de cabra, the cultivar less susceptible to hardening, presented lower initial content of phytate and a marked drop of 66.1% in its level during the same period of time. The phytase activity and the autolytic protein body destruction were higher in the last one than those in the former one. These results suggest that the contents of phytate or its rate of hydrolysis are not the major contributor to the seed susceptibility to storage induced hardening of different bean varieties.     

TEMPERATURE DISTRUBITIONS AND LIQUID-SIDE HEAT TRANSFER COEFFICIENTS IN MODEL LIQUID FOODS IN CANS UNDERGOING FLAME STERILIZATION HEATING

Heat transfer studies were performed with clay suspensions and sugar solutions in 303 × 406 cans heated singly in a flame process simulator. Experimental results show that the can wall temperature does not reach excessive temperatures and that the temperature distribution throughout the can is uniform. The slowest heating point was on the axis near the end of the can but this temperature lagged the center temperature by less than 3°C even with adverse heating conditions (i.e., no head space). The liquid-side heat transfer coefficient in 60% sucrose solution at 30 rpm was measured to be 466 ± 34 W/m²K based on the cylindrical area of the can. Rotational speed had only a small effect on heating rate in the range of 10 to 120 rpm.     

Correction Factor of Deviant Thermal Processes Applied to Packaged Heat Conduction Food

A procedure was developed to estimate the values of correction factor, Cf, for deviant thermal processes applied to canned or other packaged heat conduction food. Sterilizing values at the thermal center of the food were used as a criterion for this estimation. In this procedure empirical heat transfer parameters, f and j values, were used to estimate Cf values. The devleoped procedure is based on the use of a regression equation, which was obtained through the dimensional and statistical analyses of theoretically determined Cf values. According to a series of experiments which were performed by using 307 × 409 and 211 × 300 cans of 8% bentonite suspension, there was reasonably good agreement in Cf values estimated theoretically and determined experimentally.     

INHIBITION OF ASPERGILLUS PARASITICUS GROWTH AND TOXIN PRODUCTION BY GARLIC

Mycelial growth and toxin production by Asperigillus parasiticus were inhibited by garlic concentrations of 0.3–0.4%. When the fungus was grown in broth, aflatoxin B₁ production was inhibited at a garlic concentration of 0.3% while aflatoxin G₁ production was inhibited by 0.25% garlic. When growth on rice, aflatoxin B₁ was detected at garlic concentrations of up to 2.5%. Aflatoxin G₁ was detected at 1.25% garlic concentration but not above this level.     

PREDICTIVE MODELING APPLIED TO GROWTH OF SPOILAGE VIRGIBACILLUS PANTOTHENTICUS ON INDUSTRIAL CRÈME CARAMEL

The aim of this work was to identify the spoilage microorganisms in commercially produced crème caramel and to study their growth kinetic in different conservation conditions. Fifty‐four randomly selected strains were isolated from altered crème caramel samples with typical “medicine smell.” In order to detect the strains that cause the smell alterations, an experimental medium (PM) was prepared with crème caramel. Nineteen out of 28 isolated strains of gram‐positive spore‐former bacteria developed “medicine smell” in PM medium. Of the 19 isolated strains, five were identified as Virgibacillus pantothenticus. One was studied in a fermenter in aerobiosis at 4, 12 and 30C and in anaerobiosis at 30C. The modified Gompertz model was applied. In aerobic conditions, the maximum growth rate decreased with the temperature: μ = 1.68 at 30C and μ = 0.28 at 12C; at 4C, there was neither growth nor alteration. In anaerobic conditions, at 30C the maximum growth rate was lower than in aerobiosis (μ = 0.90), and there was no smell alteration. The appearance of these alterations was independent of the maximum growth rate. “Medicine smell” was a result of piperonal alterations. Microbiological spoilage risk could be reduced with tight control of the temperature in the production chain.     

Quality of Fresh-Market Melting- and Nonmelting-Flesh Peach Genotypes as Affected by Postharvest Chilling

After storage for 3 wk at 4°C and ripening 3 days at 20°C, nonmelting-flesh peaches(‘Oro A’, FL 90–35C, FL 90–47C) did not develop visual symptoms of mealiness, while melting-flesh (MF) fruit (FL 90-20, FL 90-21, FL 91-16) did. Sensory evaluation showed that only MF fruit were more “mealy” and less “sweet” and “peachy” as a result of chilling. Volatile analysis revealed that chilling caused increases in(E)-2-hexenal and decreases in γ and δ decalactones in both MF and NMF types. However, the decline was considerably less in NMF than in MF fruit. Results indicate that chilling affects the quality of MF more than NMF genotypes.     

Improvement of transfection with reprogramming factors in urinederived cells

Human-induced pluripotent stem cells (iPSCs) are an accessible source of adult-derived, patient-specific pluripotent stem cells for use in basic research, drug discovery, disease modeling, and stem cell therapy. Improving the accessibility of methods to obtain iPSCs regardless of the cell source can enhance their clinical application. Therefore, our purpose is to report a simple protocol to obtain iPS-like cells from urine-derived renal epithelial cells (RECs) using different extracellular matrices and transfection reagents. In this study, we began by culturing urine-derived cells from healthy donors to establish a primary culture of renal epithelial cells, followed by their characterization. Subsequently, we generated iPS-like cells by transfecting renal epithelial cells (RECs) with vectors expressing Oct4, Sox2, L-Myc, Lin-28, and Klf4, and we compared the efficacy of different extracellular matrices and transfection reagents. The resultant iPS-like cells showed a human embryonic stem cell-like morphology and expressed the specific pluripotency markers Oct3/4, Nanog, Lin28, and Klf4. We concluded that Lipofectamine Stem Cell transfection reagent is more effective than FuGENE in obtaining iPS-like cells under the conditions tested. Moreover, the three matrices are similar in their efficiency of obtaining iPS-like cells. This report provides an experimental protocol for obtaining and generating iPS-like cells from urine samples for further cell therapy research on different human diseases.