Determination of melamine in pet food by enzyme immunoassay, high-performance liquid chromatography with diode array detection, and ultra-performance liquid chromatography with tandem mass spectrometry.

Melamine in pet food (fortified or originally contaminated) was determined by enzyme immunoassay (EIA), high-performance liquid chromatography with diode array detection (HPLC-DAD), and ultra-performance liquid chromatography with tandem mass spectrometry (UPLC-MS/MS). The limits of detection (LOD) for EIA and HPLC-DAD were 0.02 and 0.1 microg/mL, respectively. The linear ranges of the calibration curves for EIA and HPLC-DAD were 0.02-0.5 and 0.1-500 microg/mL, respectively. The coefficient of determinations (r2) of the standard curves for EIA and HPLC were 0.9991 and 0.9999, respectively. Coefficient of variations from both inter- and intra-assay were <9.31%, and recovery range for all concentrations was between 71 and 105%. The r2 values between the EIA and HPLC-DAD methods for melamine analysis of the fortified and originally contaminated samples were 0.9973 and 0.9885. The r2 values for UPLC-MS/MS with HPLC-DAD and with EIA were 0.9566 and 0.9489, respectively.

A comparison of single oxidants versus advanced oxidation processes as chlorine-alternatives for wild blueberry processing (Vaccinium angustifolium).

Advanced oxidation processes and single chemical oxidants were evaluated for their antimicrobial efficacy against common spoilage bacteria isolated from lowbush blueberries. Predominant bacterial flora were identified using biochemical testing with the assessment of relative abundance using non-selective and differential media. Single chemical oxidants evaluated for postharvest processing of lowbush blueberries included 1% hydrogen peroxide, 100 ppm chlorine, and 1 ppm aqueous ozone while advanced oxidation processes (AOPs) included combinations of 1% hydrogen peroxide/UV, 100 ppm chlorine/UV, and 1 ppm ozone/1% hydrogen peroxide/UV. Enterobacter agglomerans and Pseudomonas fluorescens were found to comprise 90-95% of the bacterial flora on lowbush blueberries. Results of inoculation studies reveal significant log reductions (p< or 5) in populations of E. agglomerans and P. fluorescens on all samples receiving treatment with 1% hydrogen peroxide, 1% hydrogen peroxide/UV, 1 ppm ozone, or a combined ozone/hydrogen peroxide/UV treatment as compared to chlorine treatments and unwashed control berries. Although population reductions approached 2.5 log CFU/g, microbial reductions among these treatments were not found to be significantly different (p< or 5) from each other despite the synergistic potential that should result from AOPs; furthermore, as a single oxidant, UV inactivation of inoculated bacteria was minimal and did not prove effective as a non-aqueous bactericidal process for fresh pack blueberries. Overall, results indicate that hydrogen peroxide and ozone, as single chemical oxidants, are as effective as AOPs and could be considered as chlorine-alternatives in improving the microbiological quality of lowbush blueberries.

Evaluation of chemical and photochemical oxidation processes for degradation of phosmet on lowbush blueberries (Vaccinium angustifolium).

Chemical and photochemical oxidation processes were evaluated for their ability to degrade residual phosmet on lowbush blueberries and for their role in the conversion of phosmet to phosmet oxon--a toxic metabolite of phosmet. Chemical processes included 1 ppm of aqueous ozone, 1% hydrogen peroxide, 100 ppm of chlorine, and UV, whereas photochemical processes included hydrogen peroxide/UV, chlorine/UV, and ozone/hydrogen peroxide/UV. Phosmet applied as Imidan 2.5EC under laboratory conditions resulted in a mean residual concentration of 44.4 ppm, which was significantly degraded (p < 0.05) by ozone and chlorine, yielding reductions of 57.7 and 46%, respectively. Interaction between phosmet (Imidan 2.5EC) and any chemical or photochemical treatment did not result in conversion to phosmet oxon. Residual analysis of commercially grown blueberries revealed mean phosmet (Imidan 70W) levels of 10.65 ppm and phosmet oxon levels of 12.49 ppm. Treatment of commercial blueberries resulted in significant reductions in phosmet regardless of treatment type; however, only UV, hydrogen peroxide/UV, and ozone treatments degraded phosmet (Imidan 70W) to less toxic metabolites and reduced phosmet oxon levels. Treatment-induced conversion of phosmet to phosmet oxon was noticeably influenced by variations between phosmet formulations. Acceleration of photochemical degradation by UV was not observed. Selective oxidation by ozone represents a significant postharvest process for degrading residual phosmet on lowbush blueberries.

Effect of Growth-Location and Length of Storage on Glycoalkaloid Content of Roadside-Stand Potatoes as Stored by Consumers.

Potato tubers were purchased from roadside stands at 25 locations in the State of Maine and were stored from 1 to 3 months under home storage conditions at 12.2°C. Initially and after 1 and 3 months of storage, tubers were analyzed for their α-chaconine, α-solanine and total glycoalkaloid (TGA) contents. Mean α-chaconine, α-solanine and total glycoalkaloid contents of the tubers ranged from 0.41 to 3.45, 0.35 to 1.51 and 0.75 to 6.16 mg/100 g of tuber (wet weight), respectively. Statistical analysis of the results indicated that the interaction of location and storage time had a significant (P<0.05) effect on concentration of the individual and total glycoalkaloids in the tubers. The results also demonstrated that storage under these suboptimum conditions did not cause an increase of glycoalkaloids to a toxic level.