Assignment:
INTRODUCTION
Blueberries (Vaccinium corymbosum) have become a leading berry crop in the United States(U.S.); however, blueberries are very perishable postharvest (Sun et al). The U.S. is the world's largest producer of blueberries (FAOSTAT, 2016). In 2019, the National Agricultural Statistics Service (NASS) reported a 21% increase in production of blueberries in the United States (NASS, 2019). With blueberries being small in size, blueberries are manually harvested and directly picked into baskets before being transported from fields to a packing house. Many small production operations use reusable plastic containers (RPC), for instance, polypropylene material. Polypropylene is a material that has low density, heat retardation properties, and chemical resistance (Calhoun, 2016).
On the contrary, the RPC does not completely protect the fruit from injury during harvesting due to their thin skin and juicy pulp. As a result, fresh and frozen berries microbial safety are becoming more of a concern, with any probable recall or outbreak having a detrimental impact on the entire industry (Krasniewsk et al).
Blueberries are susceptible to contamination by various foodborne pathogens, such as Salmonella, Escherichia coli O157:H7, human norovirus, and hepatitis A virus, and have been implicated in several outbreaks (Oliveira et al). There are many sources of contamination for fresh fruit, for example, irrigation, injury, animal feces, cross-contamination, and equipment. In many cases, the source has been unknown. For instance, it has been stated Salmonella is prevalent in horticulture fruit production as it was detected Salmonella was positive on 4.9% of fruit and 7.1% of equipment used in packhouses. However, no Salmonella was present during pre-harvest operations (Gomba et al). In addition, six people were infected with Salmonella Newport in Minnesota, which was traced back to fresh blueberries (Miller et al). Approximately 15% of all Salmonella enterica-related salmonellosis infections are thought to be linked to the eating of fruits, seeds, and sprouts. (Deblais et al).
Cross-contamination, the transfer of pathogens from one surface to another, has been identified as a major risk factor in a number of food processing and handling environment. The transfer of pathogens between food and surfaces is dependent on the type of bacteria, surface, moisture level, and incubation dose (Brar et al). The primary causes of fruit spoilage and reduced stability are respiration and transpiration, as well as growth of fungal and bacterial species (Krasniewsk et al). Not only are there issues with pathogenic organisms, fresh fruit and vegetables are the most frequently wasted foods (Kelly et al). At a retail level, improper display conditions, limited shelf-life, and aesthetic standards have been linked to waste. Consumers typically store fruits and vegetables improperly which leads to food waste. (FAO; Porat et al). Hence, the utilization of chitosan as an edible coating and proper storage methods, food waste and spoilage could be decreased at a retail and consumer level.
Chitosan is a polysaccharide deacetylated form of chitin. Chitosan, which has attracted attention as a potential food preservative of natural origin, has been approved by the United States Food and Drug Administration (USFDA) as a Generally Recognized as Safe (GRAS) food additive (USFDA). Edible coatings can help preserve perishable food products by decreasing dehydration, respiration, microbial growth while providing a selective barrier to moisture. This also aids in retaining volatile flavor compounds and improving texture quality (Hussain et al).
With the implementation of essential oils, the antimicrobial activity may increase and assist in preserving and extending shelf-life of produce. EOs are excellent sources of biologically active compounds, like terpenoids and phenolic acids; among them, carvacrol and thymol are present in oregano EO (Jahani et al). Carvacrol has proven its antimicrobial activity against several pathogens, including Salmonella (Dhumal et al). Therefore, for this study, the objectives were:
1) Evaluate the efficacy of chitosan-based coatings to extend shelf of blueberries in standard grocery store packing materials up to 5 days of storage
2) Evaluate the effectiveness of the chitosan-based coatings to inhibit growth or survival of Salmonellaspp on reusable plastic containers (RPCs)