Pectin in tomatoes as a protective colloid for casein Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/zp38wg578

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  • 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.
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  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2012-02-01T21:49:04Z (GMT) No. of bitstreams: 1 PAASCHEBETTE1963.pdf: 833670 bytes, checksum: 7267e0087f26ead829813ff54cc70545 (MD5)
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