Determination of total glycoalkaloids in potato tubers using a modified titration method

A new method for determining total glycoalkaloid content of potatoes (TGA) was developed by extensively modifying the comprehensive titration procedure of Fitzpatrick and Osman (1). This modified titration method eliminates the need to hydrolyze the glycoalkaloids and to purify the resulting aglycones by partitioning them into an organic solvent such as benzene or methylene chloride. Instead the glycoalkaloids are precipitated using ammonium hydroxide with the precipitate being dissolved in a tetrahydrofuran-water-acetonitrile (50:30:20) mixture. An aliquot is evaporated and quantitated using the nonaqueous titration procedure developed by Fitzpatrick and Osman (1). A comparison between this modified method and a high-performance liquid Chromatographic (HPLC) procedure was made using three commercial potato varieties and five experimental selections. Results from the two methods compared favorably.     

The proximate composition and glycoalkaloid content of three potato meals

The proximate composition and glycoalkaloid content of a dried potato by-product meal (tater meal) and two dried potato pulp meals (potato meal and potato meal plus 10% molasses) were determined. All three feeds demonstrated variable compositions: the tater meal averaged 8.7% moisture, 9.1% crude protein, 5.4% ether extract, 5.0% crude fiber, 4.1% ash and 56.8% nitrogen-free extract; the potato meal averaged 14.5% moisture, 6.0% crude protein, 0.5% ether extract, 9.5% crude fiber, 2.2% ash and 57.1% nitrogen-free extract; the potato meal plus 10% molasses averaged 15.3% moisture, 6.4% crude protein, 0.3% ether extract, 8.0% crude fiber, 2.6% ash and 57.8% nitrogen-free extract. The phosphorus concentration was determined to be approximately 0.2% for the three samples. Other minerals were found in lesser concentrations. The riboflavin and thiamine concentrations of the three potato meals were less than 10% of the values reported for raw potato pulp and peel. The niacin concentration was approximately 40% of the values reported for raw potato pulp and peel. Tater meal contained 11.5 mg a-chaconine and 6.5 mg α-solanine per 100g meal. Analysis of potato meal gave 15.8 mg α-chaconine and 7.8 mg α-solanine per 100g meal while the potato meal plus 10% molasses was found to contain 13.2 mg α-chaconine and 7.3 mg α-solanine per l00g meal.     

The extraction and partial purification of a rhamnosidase from Colorado potato beetle larvae (Leptinotarsa decemlineata (Say))

An enzyme which hydrolyzed a terminal rhamnose moiety from α-chaconine was extracted and partially purified from Colorado potato beetle (CPB) (Leptinotarsa decemlineata) larvae. This ammonium sulfate precipitated enzyme fraction resulted in nearly 97% metabolism of α-chaconine after a 144 hour incubation period at 42 C as determined by high performance liquid Chromatographic (HPLC) analysis. Approximately 81% of the metabolized α-chaconine was detected asβ ₂-chaconine. The isolated enzyme fraction from CPB larvae exhibited no metabolism of α-solanine. Metabolism was also followed over time by thin layer chromatography (tlc).     

Inhibition of acetyl cholinesterase by solanaceous glycoalkaloids and alkaloids

Seven solanaceous glycoalkaloids (α-chaconine, β₂-chaconine, α-solanine, dehydrocommersonine, commersonine, demissine and tomatine) and three alkaloids (solanidine, tomatidine and demissidine) were tested for their ability to inhibit acetyl cholinesterase in anin vitro system. Glycoalkaloids at concentrations of 33–41 parts per million (ppm) gave cholinesterase inhibition ranging from 4.2 to 26.8%. All three alkaloids had lower anticholinesterase (4.2 to 15.4%) than the seven glycoalkaloids, except for tomatine. Two well-known cholinesterase inhibitors, carbaryl, a carbamate insecticide and Guthion, an organophosphate insecticide, were also tested for comparison. It required only 1 to 2 ppm of the insecticides to give the same average percent inhibition as was observed with the glycoalkaloids at concentrations of 33–35 ppm.     

Surgical removal of a fish hook from the oesophagus of a turtle

An adult male Macquarie turtle was presented for examination after swallowing a fish hook. Radiographs taken to determine the position of this foreign body within the gastrointestinal tract revealed the fish hook lodged in the turtle's oesophagus. Surgical removal of the fish hook involved an approach through the soft tissues of the lateral neck. The turtle recovered well and was returned to the wild.     

Microbiological evaluation of dressing procedures for crocodile carcases in Queensland

SUMMARY Microbiological testing of crocodiles during the dressing procedure has shown that sanitising the skin before skinning reduces the bacterial count on the skin and that dipping crocodile meat in 1.3% acetic acid solution effectively reduces bacterial levels. The total bacterial count on the processed meat sample was comparable with that obtained in the beef, pork and lamb industries. Salmonellae were isolated from 14 of the 72 carcases. Most (65%) of these isolates were in Salmonella subspecies III, formerly classified as Arizona.     

Sulfur compounds reduce potato toxins during extrusion cooking.

Free sulfhydryl groups in sulfur compounds have been reported to act directly on natural toxins to reduce toxicity. The objective of this study was to reduce protease inhibitors and glycoalkaloids in simulated snack foods by the addition of sulfur-containing compounds prior to extrusion. Thiamine, methionine, and benzyl disulfide were added to potato flakes at levels of 0.5% or 1.0% prior to twin-screw extrusion. Total and free thiols and protease inhibitors were monitored before and after extrusion by colorimetric assays. Potato glycoalkaloids were analyzed by HPLC and by immunoassay. Extrusion reduced potato flake disulfide bonds; disulfide bonds were higher in samples containing added sulfur compounds. Trypsin inhibitor activity was reduced by as much as 79% by extrusion plus methionine. Extrusion significantly reduced carboxypeptidase inhibitor, but only when benzyl disulfide and 0.5% methionine were not added. One percent methionine and thiamine resulted in 60% reductions in glycoalkaloids.     

Programs for surveillance and monitoring of antibacterial residues in Australia, 1989 to 1993

SUMMARY The development of a State-based confirmatory testing capability for antibiotic residues in meat in Australia has allowed the rapid feedback to producers failing to comply with antibiotic maximum residue limits. The identification of problem areas in various categories of livestock, and subsequent focused surveillance programs, has reduced the prevalence of antibacterial residues in both domestic and export meat products. Failure to observe withholding periods of antibacterial drugs after treatment is the most significant cause of non-compliance. In the period July 1991 to June 1993 the compliance rate for antibacterial residues for all species was 99.9%.