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- Title
- COMPARISON OF THE EFFICACY OF THREE SANITIZERS WITH 20,000 PPM CALCIUM HYPOCHLORITE FOR INACTIVATION OF SALMONELLA ON ARTIFICIALLY CONTAMINATED ALFALFA SEEDS
- Creator
- Li, Qing
- Date
- 2015, 2015-12
- Description
-
This study evaluated the efficacy of three alternative sanitizers, acidified sodium chlorite (ASC, also known as Sanova), stabilized oxychloro...
Show moreThis study evaluated the efficacy of three alternative sanitizers, acidified sodium chlorite (ASC, also known as Sanova), stabilized oxychloro-based sanitizer (SOC, also known as Germin-8-or), and Tsunami 100 in comparison with 20,000 ppm Ca(OCl)2 for treatment of alfalfa seeds artificially inoculated with Salmonella. Small-scale experiments were conducted to determine the best treatment conditions for each sanitizer and how the initial Salmonella contamination level on seeds or Salmonella type may have on the efficacy of the sanitizers. Large-scale studies were performed to evaluate the commercial applicability of these sanitizers. As a comparison, seeds were also treated with 20,000 ppm Ca(OCl)2 for 15 min. To determine the optimal treatment condition, ten g of seeds containing 103 CFU/g (seed lot 1) or 105 CFU/g (seed lot 2) of S. Typhimurium expressing green fluorescent protein was treated with different concentrations of ASC, SOC, and Tsunami 100 for different period of treatment time. Results showed that the efficacy of ASC and SOC increased with increasing concentrations (up to 1500 ppm) and treatment time (up to 3 h); however, the germination rates for seeds treated with > 1200 ppm of either sanitizer was < 80%. When seeds from lot 1 were treated with 800 ppm of ASC or SOC for 3 h, the level of Salmonella reduced, respectively, by 2.6 log units or >2.5 log units to an undetectable level, compared with the 1.1 log unit decrease observed in seeds treated with Ca(OCl)2. When seeds from seed lot 2 (5 log units) were treated with 800 ppm of ASC or SOC for 3 h, the level of Salmonella were reduced by 3.8 log units or >4.3 log units to an undetectable level, respectively, compared with the 2 log units decrease observed in seeds treated with Ca(OCl)2. Treatment with 80 ppm of Tsunami 100 from 10 min to 24 h kept the germination rate higher than 85% but only reduced the Salmonella count by 0 to 1.8 log units. Between two seed lots, results of ASC showed that sanitizer could reduce more pathogen when the seeds contained higher initial Salmonella level. Ten g of seeds containing 105 CFU/g of four-strain cocktail of Salmonella was treated with ASC and SOC by optimal treatment condition. SOC and ASC eliminated Salmonella number by 2.8 and 1.6 log units respectively, less effective compare with the treatment of seed lot 1. For large-scale runs, 1 kg of seeds spiked with 1 % (w/w) of inoculated seeds containing 105 CFU/g of S. Typhimurium was treated with SOC and ASC under optimal treatment conditions. Salmonella level in seeds treated with 800 ppm SOC or ASC for 3 h decreased by 3.9 or 3.6 log units, compared with a 3.3 log reduction in seeds treated with 20,000 ppm Ca(OCl)2. The stabilized oxychloro-based sanitizer may provide an alternative seed treatment method for sprout growers.
M.S. in Food Safety and Technology, December 2015
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- Title
- Evaluation of Salmonella Proliferation on Alfalfa Sprouts during Storage at Different Temperatures
- Creator
- Lin, Chih Tso
- Date
- 2020
- Description
-
Sprouts, a low-calorie vegetable rich in nutrition, have been a popular ingredient in many meals in the USA. They are grown either at...
Show moreSprouts, a low-calorie vegetable rich in nutrition, have been a popular ingredient in many meals in the USA. They are grown either at commercial sprout farms or at home and served raw or lightly cooked. However, sprouts are also known as a source of foodborne illness outbreaks. FDA Food Code identifies raw sprouts as a time/temperature control for safety food. However, little information is known about the growth profile of foodborne pathogens in sprouts stored at different temperatures. This study aimed at evaluating the proliferation of Salmonella in alfalfa sprouts during storage at 4, 10, and 25℃ under two different contamination routes: 1) sprouts that were inoculated with Salmonella after harvest and 2) sprouts that were grown from contaminated seeds. Alfalfa sprouts grown from uninoculated seeds and harvested after 5 days of sprouting were divided into 25-g portions. Each portion was inoculated with a cocktail of five Salmonella serovars at levels of 10^1, 10^3 or 10^5 CFU/g prior to storage at 4, 10, or 25℃. Alternatively, sprouts grown for five days from seeds spiked with 1% of seeds previously inoculated with the Salmonella cocktail were divided into 25-g portions and stored at 4, 10, or 25℃. At defined time points (Days 0, 2, 4, 7, 14, and 21), levels of Salmonella and background microflora in stored sprouts were determined by plate count. Alfalfa sprouts appeared fresh during the 21 days of storage at 4 or 10℃ but started to show signs of spoilage after 4 days of storage at 25℃. The total plate counts maintained at a level above 9 log CFU/g throughout 21 d of storage at 4 and 10℃ or during the first 7 d of storage at 25℃. Storing sprouts at 4 or 10℃ could inhibit the proliferation of Salmonella. After 21 d of storage, the Salmonella counts in inoculated sprouts decreased slightly, by 0.88 or 0.93 log units, respectively. For sprouts stored at 25℃, the Salmonella growth profile differed depending on the route of contamination and the level of Salmonella at the start of storage. In sprouts inoculated at levels of 1.41, 2.83, and 4.75 log CFU/g, the Salmonella counts increased to 6.62, 6.86, and 6.68 log units, respectively, during the first 4-7 days of storage. For alfalfa sprouts grown from contaminated seeds, the Salmonella counts remained at a level similar to that in the harvested sprouts (8.16 log CFU/g) during the first 7 d. Results from this study further the understanding of pathogen growth in sprouts and will aid in the development of guidelines for proper storage of sprouts.
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