The effects of pulsed electric field (PEF) treatments on tenderization of beef were investigated. The beef was prepared by using the eye of round. PEF treatment of beef was performed using a newly manufactured movable batch chamber. The PEF treatment was conducted with electric field strength of 0.5~2.0 kV/cm using a fixed pulse width of 30 μs and frequency of 20 Hz. There was no significant change in appearance of PEF treated beef. The cutting force [N] of the sample was greatly reduced as the field strength of the PEF was stronger. The cutting force of beef treated with PEF at 2.0 kV / cm was 41.18 ± 3.28 N and the control was 57.25 ± 4.16 N. In the texture profile analysis, hardness and chewiness weakened as the field strength increased (p <0.05). There was no difference in springiness, cohesiveness, resilience before and after PEF treatment (p <0.05).

Mushroom is cultivated as one of the major economical crops in many areas in Korea. The total production has steadily increased from approximately 186,400 M/T in 2007 to 198,563 M/T in 2009. Several bacteria are known as the causal agents of diseases of the cultivated button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus). Pseudomonas tolaasii is the causal agent of brown blotch disease of commercial mushrooms. Colonization of mushroom caps by the bacterium results in development of brown or cream lesions on pileus and stipe. These lesions are slightly concave spots and can be round or spreading. Antagonists against P. tolaasii, HC1 were selected and their control efficacy of brown blotch disease was investigated in this study. The HC1 isolate was selected as an inhibitor of tolaasin activity by bioassay on potato and it was identified as Pseudomonas sp. by the cultural, physiological and biochemical properties and analysis of the 16S rRNA. Control efficacy of brown blotch disease by HC1 treatment was 69% on Agaricus bisporus, 68% on Flammulina velutipes and 55% on pleurotus ostreatus respectively.

The total production has steadily increased from approximately 186,400 M/T in 2007 to 198,563 M/T in 2009. Winter mushroom, Flammulina velutipes, with 61,057913 M/T in 2009, showed the highest production. Several bacteria are known as the causal agents of diseases of the cultivated button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus). Pseudomonas tolaasii is the causal agent of brown blotch disease of commercial mushrooms. Antagonists against P. tolaasii, HC5 were selected and their control efficacy of brown blotch disease was investigated in this study. After proceeding antagonistic test, HC5 was selected as a strong antagonist against P. tolaasii and the HC5 strain was identified as P. azotoformans with the cultural, physiological and biochemical properties and analysis of the 16S rRNA. Control efficacy of brown blotch disease by HC5 treatment was 73% on Agaricus bisporus, 78% on Flammulina velutipes and 71% on pleurotus ostreatus respectively.

Several bacteria have been known as the causal agents of certain diseases of the cultivated button mushroom (Agaricus bisporus) and oyster mushroom (Pleurotus ostreatus). It is well known as bacterial diseases of the cultivated mushroom such as brown blotch, mummy disease, bacterial pit, bacterial rot and weeping disease, ginger blotch, and drippy gill. Brown blotch is the most critical cause of crop loss in the commercial mushroom industry. The classical bacterial blotch disease of mushrooms is caused by a fluorescent pseudomonad, Pseudomonas tolaasii. Affected mushrooms show lesions which become dark chocolate-brown, are wet, and deeply pit the caps and stalks. Although Pseudomonas tolaasii has been known as the casual agent of bacterial blotch, much controversy exists regarding the identification of this bacterium and whether blotch may be caused by more than one organism. This study was carried out to investigate characterization and biological control of Pseudomonas tolaasi and other possible browning pathogens isolated from cultivated mushrooms. One hundred seventy four bacteria were isolated from the cultivated mushroom and collected from main producing districts throughout the country. The isolates were classified into Pseudomonas tolaasii(20 strains), Pseudomonas gingeri(1 strains), Pseudomonas agarici(4 strains), Pseudomonas putida(11 strains), Pseudomonas sp.(46 strains), Ewingella americana(14 strains), Stenotrophomonas sp.(4 strains), and others(74 strains) on the basis of 16 rDNA analysis. The most dominants of these species were Pseudomonas tolaasii and Ewingella americana. Pseudomonad isolates were mainly divided into two groups in white line test and a sharply defined white line of precipitate forms in Pseudomonas agar F(Difco) between the opaque white colonies of P. tolaasii and translucent colonies of certain unidentified pseudomonads. The white line test was positive when 20 isolates of P. tolaasi from different countries were examined, whereas 62 isolates of pseudomonads did not give the white line reaction with a reacting translucent colony Pseudomonas. All the isolates tested for white line forming bacteria including P. tolaasi were highly pathogenic to mushroom tissue. Although browning of mushrooms in host tests does not perfectly help in the identification of P. tolaasi, a conspicuous pitting produced at the cut surface of mushroom tissue is as specific as the white line test in detecting P. tolaasii in suspension in distilled water. URP2F primers of 20-mer were used to assess the genetic diversity of white line forming bacteria. The phylogenetic tree was constructed by using the neighbor-joining method. In the analysis of RAPD pattern, all isolates of white line precipitate have some of the different genetic traits as collected districts. Phylogenetic analysis of 16S rDNA revealed that twenty isolates including white line forming bacteria were closely related to P. tolaasii and showed high similarity. To biological control on bacterial browning disease of cultivated mushrooms, six hundreds plant extracts (332 EtOH extracts, 268 water extracts) was used for control of mushroom disease. Thirty plant extracts in bacterial disease(Pseudomonas tolaasii, P. agarici, B. gladioli, E. americana) and thirty three in fungus disease(T. harzianum, C. mycophilum, V. fungicola) showed strong anti-microbes activity. They showed stronger anti-microbes activity at ethanol extracts than water extracts. MIC of extract BCW128 on Pseudomonas tolaasii was 700ppm and HDE17 was 330ppm. MIC of extract YCE107 on P. agarici was 330ppm, JGE96 was 330ppm and BCW128 was 700ppm. The bacteria inhibit tolaasin secreted by Pseudomonas tolaasii was selected three genus(Bacillus sp. etc). Now we are carrying out more research on these bacteria.