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United States Department of Agriculture

Agricultural Research Service

Research Project: INTERVENTION TECHNOLOGIES FOR ENHANCING THE SAFETY AND SECURITY OF FRESH AND MINIMALLY PROCESSED PRODUCE AND SOLID PLANT-DERIVED FOODS

Location: Food Safety and Intervention Technologies

Title: Percent Moisture and Seed Coat Characteristics of Alfalfa Seeds After Artificial Inoculation

Author
item Rajkowski, Kathleen

Submitted to: Journal of Food Safety
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 5, 2008
Publication Date: April 20, 2009
Citation: Rajkowski, K.T. 2009. Percent Moisture and Seed Coat Characteristics of Alfalfa Seeds After Artificial Inoculation. Journal of Food Safety. 224-235.

Interpretive Summary: Vegetable sprout seeds may be contaminated with very low levels of human bacterial pathogens, therefore researchers use artificially contaminated seeds to study the efficacy of decontamination methods. At this time there is no standardized procedure to inoculate the seeds with the bacteria, nor information on the seed coat characteristics during inoculation. This study was conducted to compare the different published procedures as they impact the percent moisture of alfalfa seeds and to observe the seed coat characteristics. The percent moisture after drying was similar for the various procedures, verifying that the inoculation method was not a factor. Using UV light at 360 nm, the exposed inner seed fluoresced making it easier to view wrinkled, broken or cracked seed coats. Under UV light, the cracked or broken seed coat was easily seen to curl upward when wet. This left a space between the cotyledon and the coat where the liquid containing the bacteria can lodge. During drying, the bacteria can be trapped under the seed coat, and the seed coat did not return to the original observed position. It was concluded that the condition of the seeds used for artificial inoculation would impact the results of a decontamination study. Examination of seeds lots using UV light can be used to determine the quality of the seeds.

Technical Abstract: Vegetable sprouts can be a vehicle for food borne illness and the seeds used for sprouts are considered the probable source of the pathogen contamination. Since naturally contaminated seeds have a very low pathogen level, most reports on the efficacy of sanitizing decontamination methods use artificially inoculated seeds. At this time no standardized procedure exists for artificially inoculating seeds with the bacteria pathogen. This study was conducted to compare 15 different published inoculation procedures as they impact the percent moisture of alfalfa seeds. The percent moisture after drying was similar for the various procedures, verifying that the inoculation method had no effect. Further investigations were conducted using white and UV light at 360 nm to examine the physical characteristics of different alfalfa varieties seed coats. Exposed cotyledon fluoresced under the UV light making for easier viewing of the wrinkled, broken and cracked alfalfa seed coats, which were observed for all varieties studied. The effects of wetting and drying on broken or cracked seed coats were photographed. During inoculation, the cracks or breaks in the seed coats became more pronounced and curled upwards away from the cotyledon, thus bacteria cells in the inocula could become trapped in the cracks or under the seed coat. Upon drying the seed coat did not return to the original observed condition. The condition of the seeds used for artificial inoculation would therefore be expected to impact the result of a decontamination procedure. Examination of seed lots using the UV light could potentially be used to remove the cracked and wrinkled seeds.

Last Modified: 4/19/2014
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