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

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

In order to prevent enzymatic oxidation of phenols during the centrifugal extraction of juice from apple purée, a sulfite or ascorbic acid treatment followed by blanching has been proposed. However, juice from blanched puree is more turbid and difficult to clarify than juice processed without blanching. In order to better understand the effect of blanching on juice turbidity as well as to provide more information concerning the effect of cultivar, post-harvest storage and enzyme treatment on juice quality, the chemical and physical properties of apple juice and apple juice particulate from fresh and stored McIntosh, Red Delicious and Spartan apples processed with and without enzyme digestion and with and without blanching were examined. Analysis of juice included measurement of: soluble solids, total sugars (by HPLC), sucrose, glucose, fructose, sorbitol, pH, titratable acidity, total acidity (by HPLC), citric acid, galacturonic acid, malic acid, quinic acid, succinic acid, pectin (as anhydrogalacturonic acid by HPLC) and turbidity (as absorbance at 600 nm). Analysis of particulate included measurement of dry matter weight, pectin, protein and zeta potential as well as thin sectioning, negative staining and shadow casting transmission electron microscopy. Chemical analysis of apple juice showed that the levels of organic acids, sugars and soluble pectin differed between cultivars. However, no varietal differences were observed in the chemical or microscopic analysis of cloud material. Blanching of apple puree, on the other hand, increased apple juice turbidity by increasing the amount of particulate suspended in the juice. Furthermore, blanching stabilized suspended particulate by what appeared to be the formation of a protective colloid which prevented particle aggregation through electrostatic repulsion. Post-harvest apple storage also resulted in changes to juice particulate, which were observed as gel formation during juice storage at 0°C and as a web-like aspect in the microscopic appearance of juice particulate. Treatment of apple purée with Ir-gazyme 100 decreased juice turbidity, resulting in the concomitant decrease in both the level of soluble juice pectin and the amount of suspended cloud material. Use of enzyme treatment and blanching in the processing of apple juice was demonstrated by stepwise discriminant analysis to allow production of four unique apple juice products. / Land and Food Systems, Faculty of / Graduate

No description available.

High pressure (HP) processing, a novel technology, has excellent potential for non-thermal preservation of apple juice, the largest consumed fruit juice in North America. The objective of this research was to evaluate the application of HP treatment for inactivation of enzymes and destruction of microorganisms in apple juice. HP inactivation kinetics of selected enzymes (amylase, pectin methyl esterase and polyphenol oxidase) and microorganisms [Leuconostoc mesenteroides, Pichia membranaefaciens and Zygosaccharomyces badii, Escherichia coli (29055) and Escherichia coli (O157:H7)] in apple juice were evaluated under various test conditions (100--400 MPa, 0--60 min and 6--40°C) using a central composite design of experiments. The enzymes selected were of importance in apple juice preparation and/or storage stability of the processed juice. Microorganisms included those that are responsible for spoilage and/or public health concern as well as those that are indicative of unsanitary handling conditions. / Enzyme inactivation and microbial destruction due to pressure followed a dual-effect model consisting of a pressure pulse effect (PE) and a subsequent semi-logarithmic (first order) inactivation during the pressure hold-time. In general, results showed that inactivation of enzymes and destruction of microorganisms was more prominent at higher-pressure levels, higher temperature and longer treatment times, and at lower pH levels of juice. Pressure pulse effect was dependent on pressure level, with higher PE achieved at higher pressures. During the pressure-hold, as expected, the associated decimal reduction times (D values) decreased with an increase in pressure. Pressure dependency of D values was well described by the conventional death time model. The pressure resistance of enzymes and microorganisms varied, but complete inactivation of enzymes and destruction of microorganisms was possible with the combination of lower pH, higher pressure and higher temperatures. / Commercial PME from a citrus source was more pressure sensitive than PME from microbial source. Spoilage bacteria (L. mesenteroides) were more pressure resistant than the yeasts. E. coli enumerated on an enrichment media (supporting both injured and healthy cells) showed larger survivors and a greater resistance than on a more selective media. An increasing number of cells got injured than killed with the application of pressure treatment until they were all finally injured or killed. High-pressure treatment (pulse at 400 MPa or by holding about 10 min at 350 MPa and 30°C) resulted in complete destruction of the pathogenic microorganism E. coli (O157:H7) ensuring the public health safety of the process.

No description available.

No description available.

Graduation date: 1939

Graduation date: 1939