Hong Chul Lee

Effect of hot water spray on broiler carcasses for reduction of loosely attached, intermediately attached, and tightly attached pathogenic (Salmonella and Campylobacter) and mesophilic aerobic bacteria

Chickens are known to harbor many bacteria, including pathogenic microorganisms such as Salmonella and Campylobacter. The objective of this study was to evaluate the efficacy of hot water spray (HWS, 71°C for 1 min) in reducing bacterial contamination of prechilled broiler carcasses. For each of 4 replications, skin samples from 5 broilers were collected at 3 processing stages: after bleeding (feathers removed manually), after evisceration (with/without HWS), and after water chilling. Broiler skin was quantitatively assessed for loosely attached (by rinsing the skin), intermediately attached (by stomaching the rinsed skin), and tightly attached (by grinding the rinsed/stomached skin) mesophilic aerobic bacteria (MAB) and Campylobacter as well as for the prevalence of Salmonella and Campylobacter. Broiler skins possessed 6.4 to 6.6 log cfu/g, 3.8 to 4.1 log cfu/g, and 2.8 to 3.5 log cfu/g of MAB populations after bleeding, evisceration, and chilling, respectively. The HWS resulted in more than 1 log unit of reduction in MAB immediately after evisceration and immediately after chilling regardless of microbial sampling method. Compared with MAB, the contamination of Campylobacter was low (1.7 to 2.6 log cfu/g) after bleeding, but the level was not reduced throughout the processing steps regardless of HWS. The application of HWS reduced the prevalence of Salmonella after chilling, but not for Campylobacter except for loosely attached cells. After hot water exposure, a partially cooked appearance was seen on both broiler skin and skinless breast surface. More research is required to effectively eliminate pathogenic organisms during processing and suppress any recovery of bacteria regardless of attachment type after chilling.

Antilisterial effects of hop alpha and beta acids in turkey slurry at 7 and 37°C

ABSTRACT Chemical components of hop resins effectively inhibit the growth of L. monocytogenes in microbiological culture media. This study was conducted to investigate antilisterial activities of hop &agr;‐ and &bgr;‐acid in turkey slurry. Turkey slurries were inoculated with L. monocytogenes, formulated with hop &agr;‐ or &bgr;‐acid from 0 to 1,000 ppm, and incubated at 37°C for 24 h or at 7°C for 12 days. During storage at 37°C for 24 h, L. monocytogenes populations were reduced from 2.40 log CFU/g to non‐detectable (<1 log CFU/g) in &agr;‐acid at ≥750 ppm and &bgr;‐acid at 1,000 ppm, whereas the control (0 ppm) allowed the pathogen to grow to 8.0 log CFU/g. During storage at 7°C for 12 d, the slurry treated with &agr;‐acid at ≥100 ppm and &bgr;‐acid at ≥500 ppm showed listeristatic effects, while listericidal effects were observed in the slurries at 1,000 ppm, regardless of hop acid type. Hop &agr;‐acid ≤ 50 ppm and &bgr;‐acid ≤ 100 ppm failed to inhibit L. monocytogenes, and the pattern of bacterial growth was similar to that of control with no significant difference (P > 0.05). Based on these results, the concentration of &agr;‐acid > 100 ppm or &bgr;‐acid > 500 ppm is minimally required to inhibit L. monocytogenes when turkey batters are formulated with hop acids as a single antilisterial agent prior to cooking and storage at 7°C.

Improvement of turkey breast meat quality and cooked gel functionality using hot-boning, quarter sectioning, crust-freeze-air-chilling and cold-batter-mincing technologies

The effect of rapid carcass chilling on breast meat quality was evaluated using commercial (COMM) and random-bred (RB) turkeys. Immediately after slaughter, 48 turkeys from COMM or RB line were randomly subjected to one of four chilling methods: 1) water-immersion chilling (WIC) of the carcasses at 0°C ice slurry, 2) WIC after temperature abuse (TA) of the carcasses at 40°C for 30 min (TA-WIC), 3) hot-boning, quarter sectioning, and crust-freeze-air-chilling (HB-(1)/4CFAC) of breast fillets at -12°C, and 4) HB-(1)/4CFAC of fillets after TA of carcasses (TA-HB-(1)/4CFAC). The TA increased carcass and fillet temperatures by ∼1.3 and ∼4.1°C, respectively, regardless of turkey line, whereas HB-(1)/4CFAC of fillets required 28 and 33% of carcass chilling time for COMM and RB, respectively. During chilling, COMM breast pH rapidly reduced from 6.04 to 5.82, resulting in a significantly lower pH than RB after chilling (P < 0.05), whereas COMM R-value sharply increased from 1.17 to 1.43, causing no difference from RB (P > 0.05). Significantly higher L* value and cooking yield (P < 0.05) were seen in the samples of TA and WIC than those of no TA and HB-(1)/4CFAC, respectively, with no difference observed between COMM and RB fillets (P > 0.05). Higher values of hardness, gumminess, and chewiness were found for RB, no TA, and HB-(1)/4CFAC gels than COMM, TA, and WIC, respectively. These results generally indicated that protein quality and textural properties of turkey fillets were improved, regardless of strains or temperature abuse, using HB-(1)/4CFAC technology.

Evaluation of Mixed Probiotic Starter Cultures Isolated from Kimchi on Physicochemical and Functional Properties, and Volatile Compounds of Fermented Hams

The objective of this study was to investigate the effects of mixed starter cultures isolated from kimchi on physicochemical properties, functionality and flavors of fermented ham. Physicochemical properties, microbial counts, shear force, cholesterol contents and volatile compounds of fermented ham were investigated during processing (curing and ripening time). Curing process for 7 d increased saltiness, however, decreased hunter color values (L, a, and b values). Ripening process for 21 d increased most parameters, such as saltiness, color values, weight loss, shear force and cholesterol content due to the drying process. The mixed starter culture had higher lactic acid bacteria than the commercial one. While eight volatile compounds were identified from fermented hams during curing process, total fiftyeight volatile compounds were identified from fermented hams during ripening process. The main volatile compounds were alcohols, esters and furans. However, no differences in volatile compounds were observed between two batches. Fermented hams (batch B) manufactured with probiotic starter culture (LPP) had higher sensory score in texture, color and overall acceptability than counterparts (batch A), while the opposite trend was observed in flavor. Therefore, mixed probiotic starter culture isolated from kimchi might be used as a starter culture to be able to replace with commercial starter culture (LK-30 plus) for the manufacture of fermented ham.

Inhibition of Listeria monocytogenes in deli-style Turkey using hop acids, organic acids, and their combinations

ABSTRACT This study was conducted to evaluate antilisterial activity in deli‐style turkey using one of the inhibitors: hop &agr;‐ or &bgr;‐acids at 5 ppm, potassium acetate/potassium diacetate (PAPD) at 0.5%, their combinations, potassium lactate/sodium diacetate (PLSD) at 2.5% for positive control, and ethanol at 5 ppm for negative control. Deli‐style turkey was formulated and manufactured traditionally. To simulate Listeria contamination in processing plants, the deli turkey was sliced in <24 h of production, inoculated with Listeria monocytogenes (2 to 3 log CFU/g), and vacuum‐stored at 4 or 7°C for 60 d. To simulate Listeria contamination in grocery stores, the deli turkey was vacuum‐stored for 30 and 60 d prior to slicing, inoculation, and aerobic storage at 4 or 7°C for 10 d. Physicochemical properties of the deli turkey were not significantly different among treatments (P > 0.05). Addition of hop acids at 5 ppm did not inhibit Listeria in deli meat during 60 d of vacuum‐storage at 4 or 7°C, whereas organic acids and hop acids/PAPD significantly inhibited Listeria (P < 0.05), with the best inhibition observed for hop &bgr;‐acids/PAPD at 7°C/60 d. During 10 d of aerobic storage at 4°C, hop acid/PAPD, PLSD, or PAPD showed listeristatic effects, whereas hop acids alone allowed Listeria to grow by 0.9 CFU/g. During 10 d of aerobic storage at 7°C, hop acid/PAPD, PLSD, and PAPD significantly reduced Listeria populations than hop &agr;‐acids, &bgr;‐acids, and no‐inhibitor control (P < 0.05). These results indicated the combination of hop &bgr;‐acids/PAPD provides more effective inhibition than any single addition of hop acids and PLSD (P < 0.05) at 7°C/60 d in vacuum storage, with intermediate inhibition observed for PAPD and &agr;‐acids/PAPD.

Effects of Red Bean (Vigna angularis) Protein Isolates on Rheological Properties of Microbial Transglutaminase Mediated Pork Myofibrillar Protein Gels as Affected by Fractioning and Preheat Treatment

Fractioning and/or preheating treatment on the rheological properties of myofibrillar protein (MP) gels induced by microbial transglutaminase (MTG) has been reported that they may improve the functional properties. However, the optimum condition was varied depending on the experimental factors. This study was to evaluate the effect of red bean protein isolate (RBPI) on the rheological properties of MP gels mediated by MTG as affected by modifications (fractioning: 7S-globulin of RBPI and/or preheat treatment (pre-heating; 95℃/30 min): pre-heating RBPI or pre-heating/7S-globulin). Cooking yields (CY, %) of MP gels was increased with RBPI (p<0.05), while 7S-globulin decreased the effect of RBPI (p<0.05); however, preheating treatments did not affect the CY (p>0.05). Gel strength of MP was decreased when RBPI or 7S-globulin added, while preheat treatments compensated for the negative effects of those in MP. This effect was entirely reversed by MTG treatment. Although the major band of RBPI disappeared, the preheated 7S globulin band was remained. In scanning electron microscopic (SEM) technique, the appearance of more cross-linked structures were observed when RBPI was prepared with preheating at 95℃ to improve the protein-protein interaction during gel setting of MP mixtures. Thus, the effects of RBPI and 7S-globulin as a substrate, and water and meat binder for MTG-mediated MP gels were confirmed to improve the rheological properties. However, preheat treatment of RBPI should be optimized.

Evaluation of Porcine Myofibrillar Protein Gel Functionality as Affected by Microbial Transglutaminase and Red Bean [Vignia angularis] Protein Isolate at Various pH Values

This study was investigated to determine the effect of microbial transglutaminase (MTG) with or without red bean protein isolate (RBPI) on the porcine myofibrillar protein (MP) gel functionality at different pH values (pH 5.75-6.5). Cooking yield (CY, %), gel strength (GS, gf), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) were determined to measure gel characteristics. Since no differences were observed the interaction between 1% RBPI and pH, data were pooled. CY increased with the addition of 1% RBPI, while it was not affected by pH values. GS increased with increased pH and increased when 1% RBPI was added, regardless of pH. There were distinctive endothermic protein peaks, at 56.55 and 75.02℃ at pH 5.75, and 56.47 and 72.43℃ at pH 6.5 in DSC results, which revealed decreased temperature of the first peak with the addition of 1% RBPI and increased pH. In SEM, a more compact structure with fewer voids was shown with the addition of 1% RBPI and increased pH from 5.75 to 6.5. In addition, the three-dimensional structure was highly dense and hard at pH 6.5 when RBPI was added. These results indicated that the addition of 1% RBPI at pH 6.5 in MTG-mediated MP represent the optimum condition to attain maximum gel-formation and protein gel functionality.