Purpose: This study evaluated the effectiveness of buffered vinegar (V) in controlling growth of LM and extending shelf life of frozen vegetable products.
Methods: A cold-adapted, five-strain cocktail of LM was used to inoculate (2 log CFU/g) frozen corn, edamame, and broccoli. After cell attachment for 2 h at 40°F, vegetables were sprayed with three treatments V (0.4%), DI water, and control (no spray) using a prototype sprayer. Six sub-treatments in this test included: inoculated DI, V, and control; un-inoculated DI, V, and control. Bacterial counts (25 g, n = 2) were determined (LM on MOX, shelf life on TSA, MRS and YM) after overnight freezing (day 1) and then during storage (45°F, 10 days) on days 3, 5, 8, and 10.
Results: LM counts did not increase (showed slight decrease 0.3 - 0.8 log CFU/g) throughout the 10 day abuse storage; control samples (DI and no treatment) showed an increase of 1.3 - 1.5 log CFU/g. Treatment with V also allowed shelf life extension to 10 days at 45°F. Total aerobic counts increased by 2.2 - 2.3 as compared to significant increase of 3.3 - 4.3 log CFU/g in controls. V treatment allowed yeast and mold counts to stay below 4 log CFU/g throughout the 10 day storage, while in controls, the counts were reported too numerous at day 8.
Significance: If there is a potential for temperature abuse, V can be used as a control measure to inhibit growth of LM in frozen vegetables post-thawing and extend shelf life.