We hypothesized that beef patties formulated with the addition of a beef fat, plant oil and rosemary extract (antioxidant) blend would increase unsaturated fatty acid content and maintain desirable sensory attributes as compared to 10 and 20% fat control beef patties. Treatment patties were formulated by combining beef trimmings (6% fat) with a lipid blend mixture (4% or 14% addition, respectively) containing 57% beef tallow, 0.3% rosemary extract and 43% of either high oleic safflower oil (SO), olive oil (OO), or corn oil (CO) to achieve a total fat content of 10 or 20%. Treatment patties were similar to control patties for lipid oxidation at 0 and 3 d of refrigerated (2oC) storage and up to 56 d of frozen (-10oC) storage. Cooked lipid blend patties at 10 or 20% fat content were similar to or higher, respectively, than control patties for juiciness and were no different for other sensory attributes evaluated. At 10 and 20% fat levels, oleic acid (18:1) in cooked SO patties (46.1 and 50.3%, respectively) and OO patties (43.8 and 48.1%, respectively) was higher than the control (37.3 and 37.6%, respectively). Unsaturated to saturated fatty acid ratios at the 10 and 20% fat levels were higher in SO (1.37 and 1.60, respectively) and CO (1.40 and 1.48, respectively) patties than the control (0.97 and 0.94, respectively). The incorporation of nutritionally enhanced lipid blends increased unsaturated fatty acid content and maintained desirable sensory attributes of beef patties while suppressing lipid oxidation.

Kudzu (Pueraria lobata) plant is an edible leguminous vine. This study focused on the utilization of kudzu starch and kudzu root extract in beef patties. We hypothesized that a) physicochemical and sensory properties of beef patties formulated with kudzu starch, is comparable to those of potato starch; b) the kudzu root extract is rich in isoflavones, and isoflavones quantity is not affected during cooking. In Study I, beef patties were formulated using modified commercially available kudzu and potato starch each at 2.0, 4.0 and 6.0% (wt/wt). Starch treated beef patties were compared with respect to change in physical, chemical, color, textural and consumer responses as affected by starch type (kudzu, potato) and starch level (2, 4, 6 %). Additionally starch treated patties were compared to all-beef patties. Kudzu starch treated patties were significantly lower in moisture % (62.7 vs. 64.4), higher in fat % (9.1 vs. 8.3), protein % (26.3 vs. 24.7), hardness (9.3, vs. 6.9 N) and gumminess (3.7 vs. 1.9 N) compared to potato starch treated patties. Starch treated samples were significantly lighter in color and had lower (P <0.05) expressible moisture compared to all-beef patties. Patties with 6% kudzu or potato starch were significantly higher in cooking yield than all-beef patties. No significant difference existed in consumer overall liking scores of kudzu or potato starch treatments and control beef patties with no added starch. The overall liking scores ranged between 5 ‘neither like nor dislike’ and 6 ‘like slightly’ for all samples. In study II, kudzu root extract was prepared, and using HPLC, ten isoflavones were detected with puerarin and daidzein accounting for 95% of the total isoflavones. Beef patties were formulated with kudzu root extract at 0, 1, and 3% (wt/wt), and four isoflavones were detected in uncooked and cooked patties, considering other isoflavones diluted to undetectable levels in patties. Results indicated that cooking did not change the amount of isoflavones in beef patties. This study illustrates the characteristics of kudzu starch compared to conventionally used potato starch in meat model system and verifies the thermal stability of isoflavones in beef patties.

Bacterial responses to environmental stresses may be easily observed and predicted under controlled laboratory conditions. However, realistic conditions encountered during manufacturing, in retail or in households may cause unpredicted responses of spoilage or pathogenic bacteria. Therefore it is essential to identify and understand the microbial dynamics under such conditions. The overall aim of the present study was to simulate the most common environmental conditions and consumer-style practices during storage or preparation of Ready-to-Eat (RTE) and Ready-to-Cook (RTC) products in the domestic environment, and predict the microbial dynamics which may deteriorate the quality or compromise the safety of these foods. Aiming to develop a unified mathematical model for the prediction of the growth of the specific spoilage microorganisms (SSOs), the spoilage pattern of three RTE acidic spreads of low pH was described in relation to microbial, physicochemical and molecular changes during storage. Results showed that the spoilage profile of the products was primarily affected by the initial pH and the storage temperature, despite the differences in their formulation. These findings enabled the assessment of two unified models (polynomial and Ratkowsky) for the prediction of the growth of lactic acid bacteria (LAB; SSOs) in such acidic spreads, using only the initial pH, the concentration of undissociated acetic acid and the storage temperature. The models were validated under realistic conditions in household refrigerators. Despite the abrupt fluctuations of the temperature during validation procedure, they both were able to adequately predict the growth of LAB in the spreads. However, the initial contamination level was proved to be necessary and crucial for the accurate prediction of microbial dynamics. The time-temperature profiles of the validation procedure revealed that the suggested storage conditions were not followed promptly and, therefore, concerns were raised on the effect of such consumer mishandlings on the safety of foods. Therefore, the responses of Salmonella spp. and Escherichia coli O157:H7 to the stresses encountered during frozen storage, thawing and cooking of ground beef, simulating typical scenarios followed by the consumers, were evaluated. The results revealed that the guidelines issued by the food safety authorities lack of some specific points that may affect the safety of the final product, such as the duration of frozen storage and the method of cooking. In particular, it was found that the heat resistance of E. coli O157:H7 was likely increased after long term frozen storage, while cooking in pan-grill did not ensure the safety of the final product, even when cooked at the suggested temperature. As shown in the first study, the initial contamination level played a significant role on the predictions of the models and further on the shelf-life of the products. Therefore, the dynamics of realistically low initial populations of Listeria monocytogenes and Salmonella Typhimurium versus higher levels of the pathogens (such those used during in vitro trials) in RTE fresh-cut salads were compared. In addition, any potential uncertainty sources for the growth potential of the pathogens in broth-based simulations were investigated. Results showed that the growth variability of low inocula is highly affected by the marginal storage temperatures, the indigenous microflora and the availability of nutrients. Because of this, growth from low populations showed the likelihood to exceed the growth derived from unrealistically high inocula, suggesting that ―fail-dangerous‖ implications may derive from such challenge tests. Data derived from this part were compared with broth-based simulations and the results showed that high uncertainty should be expected when extrapolating such predictions from low initial populations in fresh-cut salads, due to the various factors affecting the microbial growth on a real food, which are (inevitably) ignored by broth-based models. Overall, the present Thesis highlights the significant impact of consumer mishandlings on the food safety and quality of foods and contributes to the identification of unpredicted potential risk origins in the domestic environment.

Extra lean (3.3% fat) and lean (20.0% fat) hamburgers in three pH groups (≤ 6.0; 6.01-6.49; 6.50-6.92) were evaluated for cooking-temperature profile, total process lethality, and physical properties after cooking to 71°C by double-side frying on an electric grill. Neither cooking-temperature profile nor cooking time was affected by hamburger fat content or pH. Double-side frying to 71.1°C internal temperature was adequate for more than 6-log destruction of viable E. coli O157:H7 and Salmonella at the geometrical center of extra lean and lean hamburgers. The coldest spot was on the circumferential surface, as indicated by the presence of a red ring of undenatured myoglobin, and confirmed by the finite-element temperature distribution model. The effect of pH (5.80, 6.29, 6.73) on myoglobin denaturation in extra lean (3.3% fat) and lean (20.0% fat) hamburgers was studied. Compared to normal meat (pH= 5.8), raw extra lean ground beef of pH = 6.73 had significantly lower oxidation-reduction potential (ORP) value, lower concentration of metmyoglobin after 48 hr of refrigerated storage, and more distinct cherry-red color. Percent of myoglobin denaturation during cooking was affected mainly by pH and was not affected by total pigment or fat content of hamburgers. A pH ≥ 6.5 and ORP ≤ -200 mV were characteristic of dark-cutting beef In a third experiment, extra lean (3.5%) and lean (20.0%) beef patties were made from normal beef (pH= 5.70) and dark-cutting beef (pH = 6.60). Controls were made with no additives or with 1% salt and 10% added water. Various browning agents (1% glucose, 0.2% caramel colorant, 0.3% calcium peroxide, or 2.5% encapsulated lactic acid) were added with 10% water and 1% salt. Salt had a pronounced prooxidant effect on myoglobin. Distinctive absorption peaks at 541-548 nm and 577-582 nm indicated that the undenatured pigment in cooked patties was oxymyoglobin. Dark-cutting patties had more rubbery texture and slightly perceptible off-flavor. Patties with lactic acid were less juicy and had lower intensity of beef flavor than other patties, and moderate intensity of sour off-flavor. Addition of salt and encapsulated lactic acid to beef patty formulation could solve the problem of hard-to-cook patties.