No description available.

No description available.

The specific activities of citrate synthase and malate dehydrogenase extracted from mature green fruit of Lycopersicon esculentum, fell 60% during the first two weeks of a twelve week experiment in which the fruit were stored in an atmosphere designed to inhibit ethylene synthesis. Throughout the remainder of the experiment, the specific activities were relatively constant. In the initial two week period, the specific activity of NADP-linked malic enzyme rose by 400%, malic acid concentration fell by 50%, while the concentration of citric acid rose by 20%. Those features of ripening such as the de novo synthesis of lycopene and polygalacturonase, which were thought to depend on ethylene for initiation of response, could not be detected until the fruit were removed to a normal atmosphere. Additionally, citrate synthase and malate dehydrogenase from mature green tomato fruit stored in the presence or absence of ethylene, showed similar trends in specific activity, and the presence of the olefin made no significant difference to the rate of loss of enzyme specific activity. The purification and partial characterisation of citrate synthase from Lycopersicon esculentum is described. The enzyme is a dimer with sub-units of similar size and a total Mr of approximately. 100,000. The characterisation revealed no obvious regulatory features that would easily account for the fall in specific activity. Sub-cellular fractionation studies demonstrated unequivocally that the site of organic acid metabolism was the mitochondrion. Citrate synthase, NAD-dependent isocitrate dehydrogenase and NAD-dependent malic enzyme were shown to be located exclusively in the mitochondrion, while malate dehydrogenase was located both in the cytosol and the mitochondrion. All these enzymes including cytosolic malate dehydrogenase exhibited the co-ordinated fall in specific activity described above. A hypothesis is proposed which includes a novel coarse control of the citric acid cycle and related enzymes, as an early indicator of senescence.

No description available.

No description available.

Over the past decades, there has been increase in the consumption of the fresh tomato in the United States; this has been attributed to the nutritional benefits of fresh tomato, its widespread use in cooking and its availability throughout the year. In a Food and Agricultural Organization report, the United States was ranked as one of the largest producers of the fresh tomato in the world. In spite of its large production capacity, large quantities of the tomatoes are still being imported to the United States annually from Mexico. Series of multistate outbreaks of Salmonella infection have been associated with consumption of the fresh tomatoes; traceback of the tomatoes implicated in salmonellosis has been traced to tomatoes grown domestically. However, a survey conducted by U.S. Department of Agriculture on both domestic and imported tomatoes determined that imported fresh tomato was Salmonella positive. The purpose of this study was to determine the microbiological quality of fresh tomatoes imported from Mexico to the United States. The study consisted of sampling surfaces of cleaned tomatoes in Mexico prior to packing and shipping to the United States, and sampling of the tomato wash water at the end of the work shift at a Mexican tomato packinghouse. Four tomatoes were randomly sampled prior to packing, and they were rinsed with Universal Preenrichment Broth (UPB), this was repeated 10 times per working shift, with 2 shifts per day. 102 l of tomato wash water were collected and sampled with the aid of Modified Moore’s Swab (MMS) and membrane filter. The tomato wash water was collected at the end of shift twice daily. Both fruit and wash water samplings were repeated 3 times during the tomato harvesting season. Both the tomato UPB rinsates and the membrane filter were assayed for the E. coli and enterococci populations. Additionally, the tomato UPB rinsates and MMS were assayed for the presence of Salmonella. The results of the microbiological analysis on the UPB rinsates showed that no Salmonella was present, E. coli was not detectable (< 1.0), and the mean populations of enterococci were log 3.8, 2.6, and 1.0 CFU/g in sampling trials 1, 2, and 3 respectively. In the tomato wash water, no Salmonella was present, and no E. coli and enterococci were detected. Therefore, it was concluded that the microbiological quality of the tomatoes that were sampled and tested were high, this was due to the fact that all the samples collected tested negative to Salmonella analysis, and no E. coli was detected in any of the samples.

No description available.

The purpose of this investigation was to study the role of pectin in protecting casein from coagulation by heat and acid during the preparation of tomato soup. Three varieties of tomatoes were used for the study, Ace, Improved Garden State and Campbell 146, and each variety was processed two ways, by heating the tomatoes rapidly to 100°C before juicing (hot break) and by holding the mascerated tomatoes for 30 minutes before heating (cold break). Juice of the Ace variety had the highest pH and Campbell 146 the lowest by both processing methods. In all cases, cold break juice had lower pH values than did the hot break juice. Proportion of serum to solids resulting from centrifugation of a sample of each juice was used as one index to the amount of degradation of the pectin. The amount of solids in the cold break juice was less than the amount of solids in the hot break juice. Serums from juices prepared by the hot break method were more viscous than those by the cold break method. Of the hot break juices, Improved Garden State was the most viscous and Campbell 146 the least. The concentration of pectin in the serums of juices prepared by the cold break method was from one-third to one-half that in serums of juices by the hot break method. Juices of the three varieties of tomatoes by both methods of processing were combined with reconstituted non-fat milk and heated as for tomato soup. Curdling was assessed by measuring the nitrogen in the filtrate by the micro-Kjeldahl method. Juices of Ace, the low acid variety, caused the least amount of curdling. Of the four juices from the two more acid varieties, Campbell 146 by the cold break method had the lowest concentration of pectin in the serum and the soup curdled most, while Improved Garden State by the hot break method was highest in pectin and resulted in the least curdling of the soup. Juice from Campbell 146 by the cold break method was the most acid of the four and that of Improved Garden State by the hot break method was the least acid. When an amount of high-methoxy pectin equal to the difference between the concentration of pectin in the cold break and that in the hot break juices of the Improved Garden State variety was added to a sample of the juice before making soup, curdling was less than when untreated juice was used, and the pH was slightly higher. Thus any protective effect that pectin might have had. on the casein was clouded by differences in the pH values of the juices. Pectin possibly has a role in protecting the casein, but the acidity certainly is the determining factor in the coagulation of casein in the preparation of tomato soup. / Graduation date: 1963

Graduation date: 1953

Thesis (Ph. D. in Plant Pathology)--University of California, Davis, Jan. 1954. / Includes bibliographical references (leaves 68-72). Also available via the World Wide Web. (Restricted to UC campuses).