Won-Il Cho

Sporicidal Activities of Various Surfactant Components against Bacillus subtilis Spores.

The sporicidal activities against Bacillus subtilis spores of surfactant components with hydrophilic and hydrophobic properties that can lead to the denaturation of various proteins comprising the spore structure were investigated. The reduction in spore numbers by each of the surfactant components bornyl acetate, geranyl acetate, pinene, p-cymene, camphene, citral, 2,3-dihydrobenzofuran, polylysine, and thiamine dilaurylsulfate at 1% was estimated at 1 to 2 log CFU/ml. The average hydrophilelipophile balance value of surfactants with sporicidal activity causing a reduction of 1 to 2 log CFU/ml was 9.3, with a range from 6.7 to 15.8, which is similar to the values of various chemical surfactants of 9.6 to 16.7. The results also showed that the surfactants that were hydrophobic were more effective than those that were hydrophilic in killing B. subtilis spores. Furthermore, the sporicidal effect of surfactants like geranyl acetate and γ-terpinene was significantly enhanced in the presence of a germinant, because L-alanine and synergistic cofactors (e.g., K(+) ions) trigger cortex hydrolysis in spores.

A study on increasing the water holding capacity of retorted beef for texture softening by pre-treatment

This study was conducted to soften the tough texture of retorted beef in storage by increasing the water holding capacity (WHC) after pretreatment involving soaking and blanching in a phosphate solution. The yield of pretreated beef, based on weight as an indirect indicator of WHC, soaked in 0.35% (w/w) complex phosphates for 1 h, increased by 5-10%, in contrast to the untreated control in which the rib and shank was heated at 100℃ for 5-40 min. Additionally, strength of mechanical toughness in the fore rump and rib after phosphate curing at 115oC for 30 min and blanching at 100℃ for 2 min were significantly decreased to 1.3 and 1.4 kgf (p<0.05) as compared to 2.0 and 1.8 kgf in the control, respectively. During storage of retorted beef for 30 days at 10oC, rib and shank pretreated with 0.35% complex phosphates exhibited a highly soft texture as compared to that of untreated beef. The softening of pretreated beef was based on the increased WHC due to complex phosphates.

Study on Pretreatment Methods to Prevent Tissue Softening of Heated Onion

Various pretreatment methods were evaluated to prevent tissue softening of heated onion. Changes in onion tissue firmness during heating were explained by 3-mechanism model consisting of texture hardening at low temperature (60-80C) and substrate softening at high temperature. Preheating of onion in a Ca-containing solution significantly improved its texture after high-temperature heating. The improvement of firmness by preheating at low temperature was related to the formation of strong cross-linking between carboxyl groups and Ca by the action of pectin methylesterase in onion. The highest firmness was obtained by pre-heating at 70C for 120 min in 0.5% calcium solution. This result was supported by chemical analysis showing that the amount of bound calcium was the highest at 70C. Further investigation should be carried out to establish the optimal conditions to prevent the softening of various vegetables. Keywards: heated onion, preheating, 3-mechanism, pectin methylesterase, calcium adsorption

Optimization of sterilization conditions for retorted meatballs based on prediction of heat penetration

Optimum sterilization conditions for production of meatballs in retort trays using computer simulation for prediction of temperature profiles, F0 values, and lethality of the heat treatment were determined. A finite element method (FEM) was developed for prediction of temperature history and F0 values during thermal processing of retorted meatballs. The cold point, which is the geometric center of the meatball product where the temperature increase and decrease are slowest, was located at the innermost part of the retort tray. Lethality was strongly correlated with microbial inactivation, and the temperature profile predicted using the FEM developed based on computer simulation was accurate, based on experimental data. Optimization of sterilization conditions for retorted meatballs based on prediction of temperature and F0 values using a mathematical model is possible.

Quality improvement of retorted frozen seafood by adding sorbitol

This study was conducted to prevent hardened texture in retorted frozen seafoods such as small octopus, squid, and top shell by adding sorbitol; the strength of mechanical hardness and other qualities were measured. The hardness of the 3 kinds of seafood pretreated with 2-4% (w/w) sorbitol solution decreased by 9-36% compared to the control. The hardness of retorted frozen octopus, squid, and top shell treated with sorbitol solution upon freezing significantly decreased to 1670, 1015, and 521 gf/cm² compared to levels in untreated food of 1841, 1291, and 815 gf/cm2 (p<0.05), respectively. Yields based on weight in retorted seafood treated with sorbitol were increased by 2-5% compared to untreated samples. Additionally, the overall preference of texture was 0.4 points higher than that of control samples in descriptive sensory evaluation (p<0.05). The tissue softening of pretreated seafood was based on decreased dewatering due to the formation of small ice crystals during freezing as a result of sorbitol treatment.

Textural Characteristics and Bacterial Reduction in Glutinous Rice and Brown Rice Pretreated with Ultra-High Pressure

Ultra-high pressure (UHP) was applied to glutinous rice (Dongjin) and brown rice (Shindongjin) to determine its effects on the textural characteristics of cooked rice and bacterial reduction in uncooked rice. Hardness and stickiness of the cooked glutinous and brown rice pretreated with 500 MPa for 5 min were significantly attenuated compared to that of the control rice (p<0.05). After the UHP treatment, particles of the glutinous and brown rice were observed to be finer when cross sections of the rice were analyzed using field emission scanning electron microscope. The total bacterial count in the brown rice treated with 600 MPa for 5 min was reduced from 10 CFU/g to 10 CFU/g, while the number of thermoduric bacteria in the brown rice was not significantly different after the UHP treatment. These results suggest that UHP may be an effective method for improving texture of dried rice and to reduce bacterial count in raw rice.

Sterilization of Gochujang Sauce with Continuous Ohmic Hea

In this study, five different Gochujang (a traditional Korean sauce prepared using fermented red pepper paste) sauces were heated at 100oC for 5 min using a continuous ohmic heating system. Ohmic heating yielded greater reduction in microbial counts (90-95% reduction) than did conventional heating (65-75% reduction). The sterilization effect of the continuous ohmic heater increased with increasing sample flow rate and decreasing Reynolds number inside the pipe. Lowviscosity samples had higher electrical conductivity and were better suited for ohmic heating than were high-viscosity samples. The color and texture were also satisfactorily maintained after ohmic heating. Compared with conventional heating, ohmic heating provided rapid and uniform heating, which is more suitable for aseptic thermal processing of viscous foods.