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Safety and Sensory Evaluations of Baby Spinach Leaves Packed in Bio-nanocomposites

Tahergorabi, Reza
North Carolina A&T State University
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The long-range goal of this project is to develop bio-nanocomposite films that can successfully be used in packaging of fresh produce. The overall objective of this researchis to develop biodegradable nanocomposite-based food packaging films which incorporate thyme EO and biodegradable MMT nanofillers with SPS to address issues of food safety, environmental impact, and agricultural sustainability. The specific objectives of the proposed research are to: Objective 1: Develop biodegradable MMT nanocomposite films with SPS by incorporating thyme EO; Objective 2: Evaluate the physico-mechanical characteristics of the films; Objective 3: Investigate the antibacterial activity of the films on inoculated baby spinach leaves; Objective 4: Sensory evaluation of baby spinach leaves during storage at refrigerated temperature.

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NON-TECHNICAL SUMMARY: Baby spinach leaves as a ready-to-eat fresh produce is responsible for one third of foodborne illnesses. Commercially processed baby spinach leaves are currently packaged with perforated films. This practice raises a food safety concern that human pathogenic bacteria may transfer through the perforations and result in contamination of the produce. Thereby, it is essential that a packaging system be developed to improve the safety, as well as to maintain the sensory properties of fresh-cut baby spinach. The proposed research will address objectives 6 and 8 of the USDA-NIFA NCSU and NCA&T combined research initiatives which highlight "processing for food safety and fresh produce safety" and "human health, nutrition and well-being" respectively by developing a novel biodegradable, low-cost, and broadly effective nanocomposite packaging film that maintains the sensory properties and provide long lasting protection against pathogens throughout the distribution of baby spinach leaves. The biodegradable nanocomposite (bio-nanocomposite) film will be obtained by incorporating various concentrations of thyme essential oil into the film formulations prepared from sweet potato starch and montmorillonite nanoclays. The study will be conducted in two main parts. The first part will be developing the best possible bio-nanocomposite film and characterize its mechanical properties. In the second part, sensory properties of baby spinach leaves packed in the film and antibacterial effect of the film on inoculated baby spinach leaves against Salmonella spp. Listeria innocua and E. coli during refrigerated storage will be periodically evaluated.

APPROACH: The study will be conducted in two main parts. The first phase will be developing the bio-nanocomposite films and characterize their mechanical properties (film thickness, water vapor permeability, tensile strength, color, transmission electron microscopy, and oxygen permeability). In the second phase, antibacterial effect of the developed novel film on the growth and survival of E. coil K-12 (a surrogate of E. coli O157:H7), Listeria innocua (a surrogate of Listeria monocytogenes), Salmonella Enteriditis and Salmonella Typhimurium inoculated on baby spinach leaves during refrigerated storage will be investigated. In addition, sensorial attributes (vegetable aroma, off-odor, color, browning, texture, and overall acceptability) of baby spinach leaves packed in the films will be studied as well. Sample preparation: Fresh packaged baby spinach leaves will be purchased from a local grocery market 1 day before the experiment. Aseptic conditions will be maintained over the whole process (use of a disinfected stainless steel knife, use of sterile gloves, and covering of the work benches with sterile sheets and use of biosafety cabinet). Samples will be stored under refrigeration at the edge of acceptable (4 - 5 C) for 12 days to be analyzed at day 0, 2, 4, 6, 8, 10, and 12 for sensory and microbiological tests.

Funding Source
Nat'l. Inst. of Food and Agriculture
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Escherichia coli
Bacterial Pathogens