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United States Department of Agriculture

Agricultural Research Service

Title: Inhibitory Effect of Freeze-Dried Spinach Powder on the Growth of Listeria Species and Strains in Tryptic Soy Broth

item Babic, Isabelle
item Watada, Alley

Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 8, 1998
Publication Date: N/A

Interpretive Summary: The atmosphere within film-wrapped containers of fresh-cut fruits, also known as minimally processed, becomes altered due to oxygen consumption and carbon dioxide production by respiration of the product. The beneficial or deleterious effects of the modified atmosphere is not known. This study showed that oxygen lowered to 1.0 percent and carbon dioxide elevated to 5 or 10 percent was beneficial for strawberries and peach slices and 2 percent oxygen and 10 percent carbon dioxide was beneficial for honeydew cubers. These atmospheres also restricted the growth of natural microorganisms. These results will benefit the packaging industry in providing the proper films for packaging of fresh-cut fruits.

Technical Abstract: A study was undertaken to determine the inhibitory effect of freeze- dried spinach powder and its native mesophilic aerobic microorganisms (MAM) on the growth of Listeria monocytogenes strains and other Listeria species in tryptic soy broth (TSB). Six strains representing three species of Listeria were cultivated in pure TSB, TSB containing freeze- dried spinach powder or TSB containing MAM isolated from spinach powder. The cultures were incubated at 10 degrees C for 6 days and growth was measured daily. Both spinach and MAM treatments significantly inhibited the growth of Listeria species/strains as noted by the maximum population at 6 days, which was 8.8 Log10 CFU per ml in control, 6.4 in spinach powder cultures and 7.4 in mixed cultures. However, all Listeria species/strains were similarly affected. Thus, the spinach powder had a bacteriostatic effect on all Listeria species/strains studied and the native microorganisms played a major role as competitors.

Last Modified: 4/21/2015
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