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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27388 |
| Date | 14 May 1963 |
| Creators | Paasche, Bette Marie |
| Contributors | Charley, Helen G. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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