Masters Theses

Date of Award

5-1999

Degree Type

Thesis

Degree Name

Master of Science

Major

Food Science and Technology

Major Professor

John Mount

Committee Members

David Golden, Riette Van Laack, Carl Sams

Abstract

Broccoli florets were cut into 3 to 10 g and, washed in a 200 ppm chlorine solution or left unwashed. The florets were packaged and stored at 7 and 13°C for a 16- d period. The initial washing reduced the microbial counts by 2 log CFU/g on the florets. After 16-d storage at 7 and 13°C, there were significant differences in microbial counts between washed and unwashed broccoli (P>0.05). There was a greater increase in microbial counts on broccoli stored at 13° C, 3.5 log CFU/g, than on broccoli stored at 7°C, 2.5 log CFU/g. Temperature had more effect on controlling microbial growth over the 16-d period than washing the broccoli. Endogenous polygalacturonase (PG) activity in the broccoli did not increase during16-d storage at 7, or 12-d storage at 13° C. However, PG increased for the broccoli stored 16-d at 13° C (P<0.05).

Endogenous PG activity of broccoli florets stored at 13°C did not increase during an 8-d storage period. Internal broccoli tissue did not soften for the 8-d period (P>0.05). A method for measuring enzyme activity due to PG produced by spoilage microorganisms was developed. Total PG activity levels increased during 8-d storage indicating increased microbial activity.

Broccoli cores softened after 4-d storage at 13°C in broccoli medium that was inoculated with indigenous broccoli aerobic spoilage microorganisms. At that time, aerobic microbial counts in the medium were 7.5 log CFU/g. Broccoli cores stored in sterile broccoli medium did not soften after 4-d. This would indicate that PG produced by the high level of microorganisms has a softening effect on the broccoli texture.

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