Fred Hillig

Bio: Fred Hillig is an academic researcher from Food and Drug Administration. The author has contributed to research in topics: Butyric acid & Tuna. The author has an hindex of 7, co-authored 42 publications receiving 176 citations.

Chemical quality index of canned tuna as determined by high-pressure liquid chromatography

Abstract: A chemical quality index of canned tuna was established for estimating the extent of decomposition in fresh tuna prior to canning. Histamine has frequently been used as such an indicator but by itself it has not always proved useful. The relationship of 5 amines (histamine, putrestine, cadaverine, spermine and spermidine) was studied to generate a chemical index of tuna decomposition. The amines were extracted from authentic pack and commercially prepared canned tuna samples. The dansyl derivatives were formed and determined by reverse phase, linear gradient elution, high pressure liquid chromatography. An index was developed from the individual amines and the resulting chemical indices scores compared favorably to organoleptic and authentic pack value scores.

Histamine (?) Toxicity from Fish Products

Abstract: Publisher Summary This chapter discusses about histamine toxicity from fish products, often called scombroid poisoning, generally involves the ingestion of scombroid fish from the families Scomberesocidae and Scombridae. Scombroid fish include saury, tuna, bonito, seerfish, butterfly kingfish, and mackerel. The free histidine can, under certain conditions, be decarboxylated by some bacteria to produce high levels of histamine. Scombroid fish poisoning clinically resembles that of histamine poisoning intoxication, although controversy still exists as to whether histamine ingested orally is actually toxic, whether histamine is the sole toxic factor or not. It is generally found at high concentrations in foods causing scombroid poisoning. “Samma sakuraboshi” was incriminated in many of the Japanese histamine and histamine–like fish poisonings. The incriminated fish generally contains histamine levels in excess of 100 mg%. No fish could be obtained for chemical analysis, but the outbreak was presumed to be caused by bacterial degradation of histidine to histamine. It is most likely that the histamine produced by autolysis was because of previous bacterial contamination or unsterile conditions during experimentation, thus enabling histamine production by the contaminating microorganisms. However, the use of ammonia levels as a freshness indicator becomes unreliable when fish are kept at a room temperatures of 20°C. Several studies of bacterial histidine decarboxylase have indicated that the addition of vitamins and coenzymes did not enhance histamine formation. Histamine formation in aerated cultures, achieved by the addition of bubbled gas, was much less than that from anaerobic and aerobic cultures.

Molar growth yields and fermentation balances of Lactobacillus casei L3 in batch cultures and in continuous cultures.

Abstract: SUMMARY: Fermentation balances determined for different substrates in batch and continuous cultures of Lactobacillus casei revealed two pathways of pyruvate conversion by this organism, a reduction to lactate and the phosphoroclastic cleavage. Pyruvate formed anaerobically from mannitol and citrate was split by the phosphoroclastic enzyme. Lactate was the main fermentation product formed during aerobic growth on mannitol and anaerobic and aerobic growth on glucose. In glucose-limited continuous cultures pyruvate conversion was dependent on the dilution rate. At low dilution rates glucose was fermented exclusively to acetate, ethanol and formate. At high rates only small amounts of acetate, ethanol and formate were formed and lactate production was maximal. Lactate dehydrogenase of L. casei had an absolute requirement for fructose-1,6-diphosphate and manganous ions. The specific activity of lactate dehydrogenase did not differ significantly at different dilution rates. It was concluded that the intracellular level of fructose-1,6-diphosphate controlled the pathway of pyruvate conversion. In batch cultures Y ATP values were between 18.2 and 20.9. No evidence for oxidative phosphorylation was found. In continuous cultures YATP values varied from 18.7 at low dilution rates to 23.5 at high dilution rates. From the dependence of YATP on the dilution rate, a maintenance coefficient of 1.52 x 10-3 was calculated. The Y ATP value corrected for energy of maintenance was 24.3. The possibility that the molar growth yields were erroneously high because of assimilation of growth substrate into intracellular polysaccharides, or because of energy yield from components of the medium other than the added energy source, was excluded.

Histamine-producing bacteria in decomposing skipjack tuna (Katsuwonus pelamis)

Abstract: Spoilage in skipjack tuna (Katsuwonus pelamis) was studied under controlled conditions by incubating whole, fresh fish in seawater at 38 degrees C, the optimum temperature for histamine formation. Bacterial isolates were obtained from the loin tissue of a decomposing tuna containing 134 mg of histamine per 100 g and a total anaerobic count of 3.5 x 10(5)/g after incubation for 24 h. Over 92% of the 134 isolates obtained were facultatively or obligately anaerobic bacteria. Eighteen isolates produced histamine in culture media containing histidine, and these were identified as Clostridium perfringens, Enterobacter aerogenes, Klebsiella pneumoniae, Proteus mirabilis, and Vibrio alginolyticus. Histidine decarboxylase activity of several isolates was measured in a tuna broth medium and with resting cells suspended in a buffered histidine solution.