Abstract:
Effects of chitosan on mycelial growth of fruit rot pathogens; Greeneria sp., Gliocephalotrichum
sp., Lasiodiplodia theobromae and Pestalotiopsis sp. of rambutan fruit were evaluated on potato
dextrose agar (PDA) incorporated with chitosan at concentrations of 200, 600, 1,000, 1,400 and
1,800 ppm. The results revealed that mycelial growth of chitosan treated fungi was reduced
compared to untreated sample. Chitosan treatment at concentrations of 600 to 1,800 ppm completely
inhibited mycelial growth of Greeneria sp. while 1,800 ppm chitosan delayed the growth of
Gliocephalotrichum sp., L. theobromae and Pestalotiopsis sp. at 83.29, 69.44 and 57.52%,
respectively. Effects of chitosan on spore germination of Greeneria sp., Gliocephalotrichum sp., L.
theobromae and Pestalotiopsis sp. were studied on PDA incorporated with chitosan at
concentrations of 100, 200, 300 and 400 ppm. Chitosan treatment at 400 ppm resulted in the
inhibition of spore germination of Greeneria sp., Gliocephalotrichum sp., L. theobromae, and
Pestalotiopsis sp. at 41.89, 39.96, 34.94 and 39.96%, respectively. However, PDA medium
containing fungicidal benomyl at 1,000 ppm was able to inhibit mycelial growth and spore
germination of all tested fungi completely. Effects of 1,800 ppm chitosan coating on natural infected
rambutan fruit were conducted at 13?C with 95% relative humidity. Dipping fruit in chitosan
showed the decease of rot disease as well as benomyl treatment with 20% of disease incidence but
there were no significantly difference in disease incidence compared to untreated fruit (27.5%).
L. theobromae inoculated rambutan fruit before coating with chitosan presented 25% of disease
incidence similar to benomyl treatment, while control fruit were 50%. Chitosan treatment of
inoculated fruit also appeared the significantly reduction of disease severity with 12.5%, while
untreated fruit were 30%. However, decrease of disease incidence and severity did not associate
with the activity of peroxidase and chitinase but the increase of these enzymatic activities related to
the wound and pathogenic infection. Effects of chitosan on changes in quality and biochemistry of
rambutan fruit were found that chitosan coating at 1,800 ppm delayed colour (L value) and
anthocyanin content in peel but did not show any effects to decrease on weight loss, respiration rate
and ethylene production. Moreover, the sensory quality of peel colour, pulp colour, soaking of fresh
and off-flavour of chitosan treated fruit was not significantly difference with untreated fruit. The
quality of treated fruit was acceptable until days 12 of storage.
CO2 removal from biogas by novel micro bubble dissolving technology มหาวิทยาลัยเทคโนโลยีพระจอมเกล้าธนบุรี
Thesis Committee : Prof. Dr. Navadol Laosiripojana Asst. Prof. Dr. Nutthachai Pongprasert Prof. Dr. Suttichai Assabumrungrat Assoc. Prof. Dr. Varit Srilaong Prof. Dr. Ratana Jiraratananon