No description available.

No description available.

Apples growing in New Zealand, Argentina, Mexico, Michigan and Washington were used to provide the compositional data and to develop the analytical procedures for the use in verification of authenticity of apple juices. High Performance Liquid Chromatography (HPLC) techniques were applied for glucose, fructose, sucrose, sorbitol, malic, citric, quinic, shikimic, fumaric, chlorogenic acid, and hydroxymethylfurfural (HMF). L-malic acid was determined by an enzymic method. Sep-Pak C18 cartridge, anion exchange resin and millipore filter were used for sample preparation of HPLC. Influence of postharvest storage on sucrose and sorbitol content was observed but it had no effect on the glucose/fructose ratios. Quinic was the next most abundant acid in all the apple varieties examined. Paired t-test showed good agreement (p<0.01) between HPLC and enzymic determination for malic acid. Significantly high variability in chlorogenic acid content limits its utility. The influence of processing procedures on the phenolic compound was observed by comparison with commercial, self-pressed and gelatin treated apple juices. All apple juices showed two characteristic UV absorption maxima at around 280nm and 320nm, the ratio of the two maxima being relatively constant. First, second derivative spectra and fluorescence excitation and emission maxima were measured. As the order of derivative increased, the spectra became more complex and the resolution was enhanced. For the stable carbon isotope ratio analysis, juice, pulp, seeds and sugars, acids, and phenolics were fractionated using ion exchange resins and polyclar AT. Mass spectrometric measurements of ¹³C/ ¹²C ratio from whole juices showed low variability as compared to other fractions. Organic acids showed more negative values than the sugars. Phenolic fraction was most enriched in ¹²C when compared to the juice by as much as 4.6 ppt. The evidence suggests that postharvest storage and processing conditions played an important role in the variability of apple juice components. There are no marked differences in del ¹³C values with regard to apple variety or geographic origins. / Graduation date: 1985

The feasibility of using hollow fiber ultrafi1tration for clarification, stabilization and preservation of white grape juice was evaluated. Flux and process parameters of a hollow fiber membrane ultrafi1tration unit (Romicon pilot scale, model FXS-MXII), were studied using white Riesling grape juice. Optimum processing conditions were determined for different nominal membrane molecular weight cut-off values. The effect of cut-off value changes on viscosity, pectin retention, pH, sugar content, titratable acidity, haze reduction and color were evaluated. Optimum conditions for processing were nominal membrane molecular weight cut-off = 50,000, temperature = 50°C, inlet pressure = 1.75 Kg/cm², outlet pressure = 1.40 Kg/cm², permeate flux = 72.57 L/M²-H. Concentration polarization and fouling of the membrane increased with feed juice viscosity and were limiting factors in permeation rate. A 93% retention of pectins was achieved and haze reduction was in the range of 91-93%. Sugar content, pH, titratable acidity, and color were not affected for any of the nominal membrane molecular weight cut-off values. / Graduation date: 1984

Fruit juice concentrates- hard pear, soft pear, fig, prune, raisin, white grape, and pineapple, and sweeteners-invert beet, invert cane, and high fructose corn syrup (HFCS) were characterized by sugar profiles, nonvolatile acid profiles, UV spectral profiles, and mineral content. These fruit juices and sweeteners were also used to adulterate commercial apple juice at levels of 40%, 20%, and 10%. Sugar and nonvolatile acid analyses were performed by HPLC and isotopic carbon analyses were applied to selected samples. Data analysis included the application of Pattern Recognition methods and Chi-square test. Analysis by Pattern Recognition was restricted to sugar profiles because of the availability of an extensive data base on sugar composition of authentic apple juice, the compositional data base for the other components being limited. The "potential adulterants" were clearly distinguished from the cluster of authentic apple juice. Apple juice samples adulterated at 40% were at the perimeter and also distinguishable from the cluster, while the samples adulterated at 20% and 10% were intermingled within the cluster. Pattern Recognition methods were also used for classification of the authentic apple juice data base obtained from Mattick and Moyer (1983). Apple samples were classified by variety and geographical origin. Sucrose, glucose/fructose ratio, and sorbitol were important variables in the separability of the samples. Pattern Recognition methods are effective in classification of authentic juices and show potential as a powerful technique in discriminating between adulterated and authentic apple juice. / Graduation date: 1987

No description available.

The present study investigated the possibility of using an electrolytic cell to prevent nonenzymatic browning in lemon juice products. A single-strength, a double strength and a triple-strength lemon juice were subjected to four different current densities (0.116, 0.231, 0.463 and 0.926 A/m$ sp2)$ for 30 minutes using an electrolytic cell. Dissolved oxygen level, conductivity, redox potential, pH in juices and the voltage applied to the electrodes required to maintain constant current density through the cell were monitored. Juice samples were taken at 0, 5, 15 and 30 minutes and then stored for one month at 30$ sp circ$C. / After one month of storage, juice samples were assessed for browning and quality alteration. The chemical indices used were the browning index and concentrations in furfural and 5-hydroxymethylfurfural (HMF). Although redox potentials and concentrations in dissolved oxygen were significantly reduced by the electrolytic cell treatment, none of the electrochemical treatments significantly retarded detrimental reactions in juices over the storage period. Initial levels in dissolved oxygen and redox potential do not seem to have any significant effect on browning or chemical quality deterioration in lemon juices. Thus, the present study suggests that nonenzymatic browning in lemon juice products may be due to factors other than oxidative reactions.

Salmonella species are among the major foodborne intestinal pathogens that are of public concern with respect to food safety. The ability of intestinal pathogens to resist gastric acidity corresponds to their oral infective dose (ID). The survival and lipopolysaccharide (LPS) profiles of Salmonella typhimurium grown at different pH values and to different phases of growth were examined in simulated gastric fluid (pH 1.5), ileal fluid (pH 7.0), colon fluid (pH 8.0). The survival and growth of S. typhimurium were also examined during sequential passage through all three fluids. Viable cells were rapidly reduced from 106 CFU.ml-1 to <10 CFU.ml-1 within 4 min in gastric fluid. Cells inoculated directly into ilea] and colon fluids survived and multiplied extensively. When low numbers of viable cells of Salmonella in contact with gastric fluid (0.5 min of contact) were transferred sequentially to ileal and colon fluids, only the early and late stationary phase cells were capable of recovery and growth to high numbers. The harsh environment of the gastric fluid did not change the LPS profiles of the inoculated Salmonella cells. Entrapment of S. typhimurium in calcium alginate beads and chocolate increased its survival in gastric fluid. This implies that Salmonella cells are protected from killing when ingested with food. These results may explain why Salmonella species have a very low ID when consumed as part of some contaminated food sources.

Graduation date: 1953

Graduation date: 1992