Sri Raharjo - Universitas Gadjah Mada (Yogyakarta) (original) (raw)
Related Authors
Uploads
Papers by Sri Raharjo
Journal of Agricultural and Food Chemistry, 1992
The objectives of this study were to improve the speed, specificity, and limit of determination o... more The objectives of this study were to improve the speed, specificity, and limit of determination of the aqueous acid extraction thiobarbituric acid (TBA) method for measuring malonaldehyde (MA) as a marker of lipid peroxidation in ground beef. The TBA reaction time was reduced from 30 to 5 min at 94 & 1 OC by increasing the concentration of TBA from 20 to 80 mM. The TBA-reactive substances (TBARS) in ground beef extracts and MA standard solution were stable for up to 2 and 12 days, respectively, in 5% (w/v) trichloroacetic acid (TCA) at 4 OC. Neither the MA standard nor the TBARS were stable at 35 O C in 5% (w/v) TCA. Substances from meat samples interfering with the MA-TBA reaction were removed by the use of a Sep-Pak c 1 8 cartridge. The limit of determination of this modified TBA-& method was 25 times lower compared to that of the unmodified aqueous acid extraction TBA method.
Journal of The American Oil Chemists Society, 2010
The effect of chlorophyll in photo-oxidation of virgin coconut oil (VCO) during production and st... more The effect of chlorophyll in photo-oxidation of virgin coconut oil (VCO) during production and storage was studied. Photo-oxidation during VCO production was performed under accelerated conditions using fluorescent lights (4,000 lux) for 8 h. Peroxide values (PVs) and chlorophyll contents of the samples were measured at 1 h intervals. To compare the photo-oxidation during storage, VCO samples were separately stored under ambient and normal room light intensity (380–400 lux) for up to 4 months and PVs were measured weekly. The results indicated that relatively low light intensity during the settling stage of VCO production had no significant effect on photo-oxidation. Photo-oxidation of VCO, however, was observed during storage when exposed to high intensity fluorescent light. The degradation of chlorophyll content in VCO was evident during exposure to a high fluorescent light intensity which was accompanied by high lipid peroxide accumulation. A significant negative correlation between PV and chlorophyll content was found in VCO without light protection. The storage of VCO significantly increased the PV after 10 weeks. This study confirmed that chlorophyll which is naturally present in VCO even at a very low level (less than 0.1 ppm) could initiate a photo-oxidation reaction leading to quality deterioration during prolonged storage or display at retailers.
Journal of Agricultural and Food Chemistry, 1992
The objectives of this study were to improve the speed, specificity, and limit of determination o... more The objectives of this study were to improve the speed, specificity, and limit of determination of the aqueous acid extraction thiobarbituric acid (TBA) method for measuring malonaldehyde (MA) as a marker of lipid peroxidation in ground beef. The TBA reaction time was reduced from 30 to 5 min at 94 & 1 OC by increasing the concentration of TBA from 20 to 80 mM. The TBA-reactive substances (TBARS) in ground beef extracts and MA standard solution were stable for up to 2 and 12 days, respectively, in 5% (w/v) trichloroacetic acid (TCA) at 4 OC. Neither the MA standard nor the TBARS were stable at 35 O C in 5% (w/v) TCA. Substances from meat samples interfering with the MA-TBA reaction were removed by the use of a Sep-Pak c 1 8 cartridge. The limit of determination of this modified TBA-& method was 25 times lower compared to that of the unmodified aqueous acid extraction TBA method.
Journal of The American Oil Chemists Society, 2010
The effect of chlorophyll in photo-oxidation of virgin coconut oil (VCO) during production and st... more The effect of chlorophyll in photo-oxidation of virgin coconut oil (VCO) during production and storage was studied. Photo-oxidation during VCO production was performed under accelerated conditions using fluorescent lights (4,000 lux) for 8 h. Peroxide values (PVs) and chlorophyll contents of the samples were measured at 1 h intervals. To compare the photo-oxidation during storage, VCO samples were separately stored under ambient and normal room light intensity (380–400 lux) for up to 4 months and PVs were measured weekly. The results indicated that relatively low light intensity during the settling stage of VCO production had no significant effect on photo-oxidation. Photo-oxidation of VCO, however, was observed during storage when exposed to high intensity fluorescent light. The degradation of chlorophyll content in VCO was evident during exposure to a high fluorescent light intensity which was accompanied by high lipid peroxide accumulation. A significant negative correlation between PV and chlorophyll content was found in VCO without light protection. The storage of VCO significantly increased the PV after 10 weeks. This study confirmed that chlorophyll which is naturally present in VCO even at a very low level (less than 0.1 ppm) could initiate a photo-oxidation reaction leading to quality deterioration during prolonged storage or display at retailers.