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                        Issued January 9, 1909.

                   U. S. DEPARTMENT OF AGRICULTURE,
                BUREAU OF CHEMISTRY--BULLETIN No. 119.
                     H. W. WILEY, Chief of Bureau.

                      EXPERIMENTS ON THE SPOILAGE
                          OF TOMATO KETCHUP.

                                  BY
                            A. W. BITTING,
                    INSPECTOR, BUREAU OF CHEMISTRY.

 [Illustration: Shield of the United States Department of Agriculture]

                              WASHINGTON:
                      GOVERNMENT PRINTING OFFICE.
                                 1909.




LETTER OF TRANSMITTAL.


                   U. S. Department of Agriculture,
                         Bureau of Chemistry,
                  _Washington, D. C., July 15, 1908_.

Sir: I have the honor to submit for your approval a report made by
Inspector Bitting of experimental work on the spoilage of tomato
ketchup, the conditions contributing thereto, methods of prevention,
the action of preservatives, and the length of time that the product
will keep under varying conditions of manufacture and temperature, both
before and after opening. Every effort has been made to conduct the
work in a practical way, and the results obtained can not fail to be of
interest and profit both to the manufacturer and consumer. I recommend
that this report be published as Bulletin No. 119 of the Bureau of
Chemistry.

  Respectfully,                H. W. Wiley,
                                   _Chief_.

Hon. James Wilson,
    _Secretary of Agriculture_.




CONTENTS.


                                                              Page.

Introduction                                                      7

Process of manufacture                                            8
    Selection and preparation of stock                            9
    Pulping                                                       9
    Cooking and seasoning                                        10
    Evaporation and finishing                                    11
    Bottling                                                     11
    Processing                                                   11

Character of products                                            12
    First-class products                                         12
    Inferior products from “trimming stock”                      13

Labels                                                           14

Manufacturing experiments without the use of preservatives       15
    Outline of experiments                                       15
    Discussion of results                                        17
        Spoilage of ketchup after opening                        17
        Spoilage of unopened ketchup                             20
        Spoilage of market brands                                20
        Sterility of ketchup                                     21

Experiments with preservatives                                   22
    Sodium benzoate                                              22
    Salt                                                         23
    Sugar                                                        23
    Spices                                                       24
        Water infusions                                          24
        Acetic acid extracts                                     25
        Oil extracts                                             25
    Vinegar and acetic acid                                      26
    Oil                                                          27

Study of Penicillium in ketchup                                  28
    Development                                                  29
    Reproduction                                                 29
    Growth in ketchup                                            30
    Temperature tests                                            31

Histological structure of ketchup                                33

Microscopical examination of some commercial brands              34

Summary                                                          35




ILLUSTRATIONS.


PLATES.

                                                              Page.
PLATE I. Penicillium. Fig. 1.--Conidia, normal growth
     and in various stages of germination, some with branching
     hyphæ. Fig. 2.--Conidiophore, showing unusually large
     development of conidia; from culture in moist chamber       28

     II. Cultures from ketchup preserved with sodium
     benzoate. Fig. 1.--Conidia and hyphæ from culture in
     experimental ketchup containing one-sixteenth of 1 per cent
     of sodium benzoate. Fig. 2.--Conidia and hyphæ from culture
     in experimental ketchup containing one-tenth of 1 per cent
     of sodium benzoate                                          28


TEXT FIGURES.

Fig. 1. A model receiving platform                                8

2. Large receiving room showing the sorting belt                  9

3. A section of a kitchen showing the copper cookers             10

4. An example of factory practice                                12

5. Another factory interior                                      14




EXPERIMENTS ON THE SPOILAGE OF TOMATO KETCHUP.




INTRODUCTION.


The tomato, _Lycopersicum esculentum_, is supposed to be native to
South or Central America. The large fruits commonly used grow only
under cultivation, but the variety with small, spherical fruits,
known as _L. cerasiforme_, has been found on the shore of Peru and is
considered by De Candolle[A] as belonging to