Available at: https://digitalcommons.calpoly.edu/theses/3297
Date of Award
6-2026
Degree Name
MS in Agriculture - Animal Science
Department/Program
Animal Science
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Iksoon Kang
Advisor Department
Animal Science
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Broiler meat became the most widely consumed meat within the United States and across the world in 2019. The trend of increasing broiler consumption is expected to continue due to affordability, health benefits, and production efficiency. To meet the growing demand of broilers, a substantial number of birds need to be produced and processed while minimizing bacteria contamination, water consumption and wastewater generation.
In this study, the microbial safety (mesophilic aerobic bacteria, coliforms, and Escherichia coli) of broiler carcasses and post-chill water (red water) was assessed, using innovative processing techniques and red water recycling. A total of 144 broilers were processed with two replications (72 birds per replication) at the Cal Poly Meat Processing Center (San Luis Obispo, CA). Chilling water from each treatment was recycled after an initial chill over the following two days to determine the viability of water recycling in the poultry industry. In this experiment, two pre-chill water dips, explicitly tap water dip (TWD-15 °C/1min) and hot water dip (HWD-68 °C/1min) were applied after evisceration. After the water dip, carcasses were chilled using water immersion chilling (WIC-0% NaCl/0.5 °C) and sub-zero saline chilling (SSC-4% NaCl/-2.4 °C). Subsequently, this research evaluated the effects of four treatments on the microbial safety of carcasses and recycled red water: WIC with TWD (WICT- 15 °C/1min, 0% NaCl/0.5 °C), WIC with HWD (WICH- 68 °C/1min, 0% NaCl/0.5 °C), SSC with TWD (SSCT- 15 °C/1min, 4% NaCl/-2.4 °C), and SSC with HWD (SSCH- 68 °C/1min, 4% NaCl.-2.4 °C). Microbial swabs of broiler skin were collected at three stages per bird: 1) after evisceration, 2) after water dip, and 3) after chilling. Images of breast skin were taken to assess the relationship between microbial contamination and skin morphology after evisceration, water dipping, and chilling.
Data were analyzed using mixed models in SAS. The data of both replications were not combined due to significant differences. In pre-chill dips, HWD significantly reduced microbial counts on the skin compared to the control (P < 0.05) and exhibited intermediate reductions compared to TWD. After chilling, SSCH recorded the best reduction on carcass skin regardless of bacteria species except for E. coli on Day 1 and 2 in replication II (P > 0.05). In skin morphology results, both SSCH and SSCT broilers exhibited tauter skin surfaces and smaller follicular pores in comparison to swollen and wrinkled surfaces in WICH and WICT broilers. In recycled red water, significant treatment differences were more evident in replication II than in replication I. SSCT and SSCH-treated water generally showed lower microbial counts than WICT and WICH, with significant differences observed in coliform and E. coli (P < 0.05). These findings indicate that the combination of HWD and SSC not only improves the microbial safety of broiler carcasses but also suggests the potential for red water recycling.