Jeong-Weon Kim

Cetylpyridinium Chloride (CPC) Treatment on Poultry Skin To Reduce Attached Salmonella

Cetylpyridinium chloride (1-hexadecylpyridinium chloride, CPC) was evaluated for its effectiveness in removing or killing salmonellae attached to poultry skin. Two different treatment methods were used: (i) spraying 0.1% CPC solution at 15 degrees C or 50 degrees C against inoculated skin surface for I min at 138 kPa, and (ii) immersing inoculated skin surface in 0.1% CPC solution at room temperature for either 1 min, 1 min plus 2 min holding without CPC, or 3 min. After rinsing, cells on the skins were enumerated by conventional plating as well as direct counting from scanning electron microscopy (SEM). Compared with controls, CPC spraying reduced the numbers of salmonellae by 0.9 to 1.7 log units (87 to 98%) assayed by the plating method (P < 0.05). SEM gave results similar to plating. Generally 50 degrees C CPC spraying showed greater reduction than 15 degrees C CPC spraying; however, the differences were not always significant. Water spraying at either temperature did not show any reduction compared to nonsprayed skins. In the immersion test, significant differences also were noticed among the control and the three other CPC-immersed groups (P < 0.05) as assayed by plating, ranging from 1.0 to 1.6 log units, which were similar to the CPC spraying results. However, no difference was noticed among the three CPC-immersed groups. Direct counting from SEM was not a suitable method for recovering cells in CPC immersion tests because dead cells were still attached to the skin while retaining their intact morphology. On the basis of the amount of CPC used, immersion appears to be more cost-effective than spraying CPC on poultry skin.

Effect of trisodium phosphate on Campylobacter attached to post-chill chicken carcasses

Trisodium phosphate (TSP) was evaluated as a means to reduce Campylobacter on chicken carcasses. Post-chill chicken carcasses were dipped into a 10% TSP solution at 50°C for 15 s. After storing the TSP-treated carcasses for 0, 1 or 6 days at 4°C, the carcasses were subjected to the recovery of Campylobacter . The incidence and reduction of Campylobacter attached to the carcasses were measured using a nitrocellulose (NC) membrane lift, conventional culture method, and a most probable number (MPN) technique. In trials 1 and 2, the incidence of Campylobacter was measured. For 1 day-stored groups, Campylobacter was present on 96 and 100% of control carcasses and present on 24 and 28% of TSP-treated carcasses as measured by NC membrane lift method. The reduction was less (4 to 36%) when measured by culture method. For carcasses immediately subjected for the recovery of cells after treatment, there was no difference between TSP-treated and control carcasses by either NC membrane or culture method. In trial 3, the reduction levels of Campylobacter were quantified by using a MPN method. The levels of Campylobacter on carcasses were decreased by 1.5 and 1.2 logs in 1- and 6-day stored, TSP-treated carcasses, respectively (p < 0.05). However, TSP treatment at 10°C reduced the level of Campylobacter only by 0.16 log (p > 0.10).

Reduction of Salmonella and Campylobacter on Chicken Carcasses by Changing Scalding Temperature

Chickens were processed at three scalding temperatures, 52, 56, or 60°C, and the numbers of Salmonella and Campylobacter attached to the fully processed carcasses in each group were compared. For Salmonella , carcasses scalded at 52 or 56°C showed ~ 0.3 to 0.5 lower log numbers than carcasses at 60°C (P < 0.05). There were no significant differences between the carcasses at 52 and 56°C. For Campylobacter , carcasses scalded at 56°C showed ~ 0.7 lower log counts than the carcasses at 60°C (P < 0.05) in the first two trials; however, no difference was observed in a third trial. Although the reduction of bacteria attached to the chicken carcasses was not as great as shown in previous attachment studies using skin samples (1.0 to 1.4 log cycles), these results show that reductions in bacterial numbers on chicken carcasses can be achieved by simply changing the scalding temperature.

Changes in Eggshell Surface Microstructure after Washing with Cetylpyridinium Chloride or Trisodium Phosphate

The effects of egg-washing chemicals on microstructural changes of the eggshell were examined. Fresh-laid eggs were washed with solutions of cetylpyridinium chloride (CPC) at 10, 50, or 100 ppm, or trisodium phosphate (TSP) at 0.5, 1.0, or 5.0% and changes in the shell surface were examined using scanning electron microscopy (SEM). As the concentration of CPC increased, the eggshell surface became pitted and the cuticle layer became thinner. TSP caused the cuticle layer to fissure and flake and even cuticle-free areas were observed at 5.0%. When the porosity of eggs was measured by using the blue lake staining method, there were significant differences between control and TSP- or CPC-washed eggs as observed by SEM. These results suggest that depending on the types of chemicals used in the wash water, different microstructural changes occur in eggshell surfaces, and the more damaged eggshell surfaces allow more bacterial penetration.

Attachment of Salmonella typhimurium to skins of chicken scalded at various temperatures

Microtopography of chicken skin was studied by varying scalding temperature to determine the least favorable skin surface for salmonellae attachment. Birds were scalded at 52, 56, and 60°C, and the changes of skin morphology were examined by light and transmission electron microscopy throughout the whole processing. Breast skins obtained immediately after picking were inoculated with Salmonella typhimurium, and the attachment was quantified by using scanning electron microscopy and microbiological plating techniques. Skins scalded at 52 and 56°C retained most of the epidermis, although the latter temperature caused the loss of twice as much stratum corneum layers and produced a smoother surface than the former. Skins at 60°C began to lose most of epidermal layers during scalding and exposed dermal surface after picking, which was sometimes covered with thin fragmental epidermis or basal tissue. The number of salmonellae attached to 60°C-processed skins was 1.1~1.3 logs higher than those attached to the skins processed at 52 and 56°C, as measured by scanning electron microscopy. Microbiological plating, however, showed no significant difference in attachment among three skins processed at different temperatures. This was probably due to the insensitivity of the plating method to differentiate attachment strengths of salmonellae to the skin. The above results suggest that removal of whole epidermis should be avoided in processing to reduce salmonellae attachment to the skin.

Morphological Changes of Salmonella typhimuriumCaused by Electrical Stimulation in Various Salt Solutions

To better understand what physical changes occur in bacteria subjected to low-voltage, low-current electrical stimulation (ES), morphological changes in Salmonella typhimurium killed by ES were examined using electron microscopy. Cells (107 CFU/ml) were suspended in 0.015 M NaCl, 0.015 M Na2CO3, or 0.005 M Na3PO4·12H2O solutions and pulsed electric signals at 10 mA/cm2 current, 1 kHz frequency and 50% duty cycle were applied until more than 90% of the cells were dead. In NaCl solutions, cells were swollen before collapsing into amorphous bodies. In Na2CO3 solutions, cells showed irregular surfaces and the cytoplasm became less dense at the centers of the cells. In Na3PO4 solutions, the cytoplasm was scattered into small aggregates within the cell and many fibrils were formed outside. The results of this research suggest that the mechanisms of destruction of S. typhimurium by ES depend on the salt used an electrolyte.

Variation in saltiness perception of soup with respect to soup serving temperature and consumer dietary habits

Little is known about the effect of serving temperature on saltiness perception in food products such as soups that are typically consumed at high temperature. This study focused on determining whether serving temperature modulates saltiness perception in soup-base products. Eight trained panelists and 62 untrained consumers were asked to rate saltiness intensities in salt water, chicken broth, and miso soup, with serving temperatures of 40, 50, 60, 70, and 80 °C. Neither trained nor untrained panelists were able to find significant difference in the saltiness intensity among salt water samples served at these five different temperatures. However, untrained consumers (but not trained panelists) rated chicken broth and miso soup to be significantly less salty when served at 70 and/or 80 °C compared to when served at 40 to 60 °C. There was an interaction between temperature-related perceived saltiness and preference; for example, consumers who preferred soups served at lower temperatures found soups served at higher temperatures to be less salty. Consumers who frequently consumed hot dishes rated soup samples served at 60 °C as saltier than consumers who consumed hot dishes less frequently. This study demonstrates that soup serving temperature and consumer dietary habits are influential factors affecting saltiness perception of soup.

Perception Gaps on Food Additives among Various Groups in Korea: Food Experts, Teachers, Nutrition Teachers, Nongovernmental Organization Members, and General Consumers

The purpose of this study was to determine the perceptions and information needs of food experts, teachers, nutrition teachers, members of nongovernmental organizations, and general consumers concerning food additives. Questions in a survey format included perceptions, information needs, and preferred communication channels. The survey was conducted both off-line and on-line via e-mail and Google Drive in March 2015. The results indicated that most Korean consumers are concerned about the safety of using food additives in processed foods and do not recognize these additives as safe and useful materials as part of a modern diet. We also identified perception gaps among different groups regarding food additives. Nutrition teachers and members of nongovernmental organizations in Korea appeared to have a biased perception of food additives, which may cause general consumers to have a negative perception of food additives. The group of food experts did not have this bias. Governmental institutions must overcome the low confidence levels of various groups as an information provider about food additives. Based on the findings in this study, it will be possible to develop a strategy for risk communication about food additives for each group.