Quality and nutritional aspects of conventional and novel food proteins
Date
2020
Authors
Thompson, Tyler Warren, author
Nair, Mahesh Narayanan, advisor
Belk, Keith E., advisor
Geornaras, Ifigenia, committee member
Weir, Tiffany, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Cattle weights have increased during the last couple of decades and have not always been accompanied by improvements in facility capabilities and management. Alongside quality issues of color, tenderness, and water holding capacity, issues such as sour muscles and bone taints are now appearing with high frequency in the meat industry. Development of off-flavor/sourness in deep muscles such as knuckles (vastus femoris, vastus lateralis, vastus medialis, and rectus femoris) has been a long-standing issue in the beef industry, however, has not been well characterized. Therefore, the objective of this study was to investigate the potential cause and to characterize the sour odor associated with beef knuckles using microbial, odor panel, and gas chromatography-mass spectrometric (GC-MS) analyses. Knuckles (n = 10) identified as having no sour odor (control), slight sour odor (SLI-SO), or severe sour odor (SVR-SO) were collected from the fabrication line of a commercial beef processing plant. Upon collection of knuckles, synovial fluid and the femur surface were swabbed to determine psychrotrophic anaerobic sporeformer presence. The collected knuckles were transported on ice to the laboratory where they were aseptically separated into two halves, with one half destined for microbial, odor, and GC-MS analyses on the day of collection (day 0) and the other half for the same analyses (excluding GC-MS) after 35 days of vacuum packaged storage at 0 - 2°C (day 35). For microbial analysis, 15 g of tissue was excised from the muscle surface and was analyzed for aerobic plate counts (Petrifilm Aerobic Count plates) and lactic acid bacteria counts (Lactobacilli MRS agar). Samples (5 g) for GC-MS were held at -80°C until analysis. The remainder of the sample was diced and used for trained odor panels. Odor panelists identified differences (P < 0.05) for all tested attributes (off odor, oxidation, putrid, and sour notes) between control and sour knuckles (SLI-SO and SVR-SO) on day 0. Similarly, on day 35, differences (P < 0.05) were observed between control, SLI-SO, and SVR-SO knuckles for all attributes, with SVR-SO samples receiving the highest score for all categories. However, the microbiological analysis found no differences between aerobic plate counts and lactic acid bacteria counts of control, SLI-SO, and SVR-SO knuckles on day 0 or day 35. In addition, GC-MS analysis did not indicate a difference (P > 0.05) in the abundance of volatiles between the treatments (probably due to high variations within treatment groups). Overall, compounds such as acetic, acetoin, propionic, butyric, and isobutyric acid were trending towards having greater abundance in sour samples. Although animal proteins have been the primary source of protein in the human diet, plant-based proteins have gained popularity in recent years. While some studies have indicated lesser environmental impacts, the nutritional composition of plant-proteins has not been readily investigated. Therefore, the objectives were to evaluate the nutritional composition of Morning Star Farms spicy black bean burger (VB), Beyond Meat's Beyond Burger (BB), Impossible Food's Impossible Burger (IB), a boneless top loin pork chop (PC), and 80% lean 20% fat ground pork (GP). Six different cities were selected for product collection to give a representative view of the products (Seattle, WA; Peyton, CO; Memphis, TN; Newburgh, IN; Houston, TX; and Brooklyn, NY). Following collection, products were brought back to Colorado State University. Half of the products sampled from each city were cooked, and the remaining half were left in their raw state. All ground products were cooked to an internal temperature of 71°C while the PC was cooked to 63°C. Samples (both raw and cooked) were then homogenized individually and stored under vacuum-packaged conditions at -80°C until further analysis. Methodologies for proximate analysis, amino acids, fatty acids, minerals, vitamins, organic acids, and allergens were conducted following the Association of Official Analytical Chemist (AOAC) guidelines. Overall, the product state (raw or cooked) had little effect on the nutritional composition. Analysis indicated that the PC contained the highest (P < 0.05) amounts of protein, essential amino acids, and B-vitamins. Cholesterol was found highest (P < 0.05) in the pork products (PC and GP) with no cholesterol being identified in the plant-based products (VB, BB, and IB). However, when evaluating mineral make-up, the plant-based products contained the highest (P < 0.05) amounts, especially in sodium and iron levels. Sodium levels were about ten times higher, along with iron levels being 3 to 4 times higher in plant-based products. Overall, the pork products were found to contain the greatest amounts of amino acids, and B-vitamins needed in a diet. While the plant-based products were generally lower in nutrients, the IB was found at nutritional levels close to the GP and PC.