Showing papers in "Journal of Agricultural and Food Chemistry in 1991"

Pyrolysis-GC-MS characterization of forage materials

Abstract: Pyrolysis-GC-MS pyrograms from a series of alfalfa preparations, a ggrass, an angiosperm wood, a cellulose and an arabinoxylan were obtained under pyrolytic conditions optimal for aromatic components of plant cell walls. Approximately 130 pyrolytic fragments have been identified

Isolation and characterization of nutrients and value-added products from snow crab (Chinoecetes opilio) and shrimp (Pandalus borealis) processing discards

Abstract: Byproducts from shrimp and different parts of crab contained, on a dry basis, from 17.0 to 32.2% of chitin and from 3.4 to 14.7 mg/100g of carotenoid pigments, mostly astaxanthin and its esters. Chitin was produced at a yield of about 86%, and carotenoids were extracted in cod liver oil at a yield of up to 74%. Optimal deproteinization involved treatment with 1% KOH solution for shrimp and 2% KOH for crab shells, at 90 degrees C for 2 h, with a shells to alkali solution ratio of 1:20 (w/v). Optimal conditions of demineralization were 2.5% HCl at 20 degrees C for 1 h with a solid to solvent ratio of 1:10 (w/v). The chitin preparations isolated from shell waste without or with the initial extraction of carotenoids were not different. They contained 6.29% nitrogen in shrimp and 6.42% nitrogen in crab chitins. The residual protein contents in chitin from shrimp and crab shells were 2.3 and 0.4%, respectively. The ash content in both cases did not exceed 0.11%.

Fumonisin Contamination of Commercial Corn-Based Human Foodstuffs

Abstract: Corn-based human foodstuffs from retail outlets in five countries were analyzed for fumonisin B1 (FBI) and fumonisin B2 (FB2) The highest mean concentrations occurred in two Egyptian samples (2380 ng/g FBI and 595 ng/g FB2) Only one of four Peruvian samples contained 660 ng/g FBI and 68 ng/g FB2, while only one of two Canadian samples contained a detectable level of FBI The 16 cornmeal (CM) and 10 corn grits (CG) products from the United States contained mean concentrations of 1048 ng/g FBI and 298 ng/g FB2 and 601 ng/g FBI and 375 ng/g FB2, respectively, while the mean concentrations in 52 CM and 18 CG samples from South Africa were 138 ng/g FBI and 83 ng/g FB2 and 125 ng/g FBI and 85 ng/g FB2, respectively Only 1 of 10 cornflakes/lime-treated samplescontained a low level of FBI Of several samples obtained from a high esophageal cancer (EC) risk area in the United States 7/7 contained FBI (105-1915 ng/g) and 6/7 FB2 (70-460 ng/g)

Oxygen free radical scavenger capacity in aqueous models of different procyanidins from grape seeds

Abstract: Etude de l'effet des degres de polymerisation, de l'esterification de l'acide gallique et des liaisons entre unites monomeres sur la capacite des procyanidines a pieger les radicaux superoxydes et hydroxyles

HPLC method for quantitating ergovaline in endophyte-infested tall fescue: seasonal variation of ergovaline levels in stems with leaf sheaths, leaf blades, and seed heads

Abstract: (.)The detection limit of ergovaline in fescue seed and vegetative tissue was 50 μg/kg. Replicate samples, collected each week during two growing seasons from experimental plots of KY-31 tall fescue (85-100% endophyte-infested), were separated into stems with leaf sheaths, leaf blades and developing seed heads. Ergovaline levels in all plant tissues were 300-500 μg/kg from March through mid-June. In late June, ergovaline increased in seed heads to 1000-5000 μg/kg, while stems with leaf sheaths and leaf blade values remained at 300-500 μg/kg

Antibacterial agents from the cashew Anacardium occidentale (Anacardiaceae) nut shell oil

Abstract: Sixteen phenolic compounds have been isolated from the cashew Anacardium occidentale (Anacardiaceae) nut shell oil. Their antimicrobial activity has been tested against four typical microorganisms, Bacillus subtilis, a Gram-positive bacterium; Escherichia coli, a Gram-negative bacterium; Saccharomyces cerevisiae, a yeast; and Penicillium chrysogenum, a mold. Most of them exhibited potent antibacterial activity against only Gram-positive bacteria, among which Streptococcus mutans, one of several bacteria responsible for tooth decay, and Propionibacterium acnes, one of the bacteria responsible for acne, were the most sensitive bacteria. Anacardic acids also showed weak activity against molds. Their structure-activity relationships are also described.

Starch determination by perchloric acid vs enzymes: evaluating the accuracy and precision of six colorimetric methods.

Abstract: Different methods of polymer extraction can markedly affect the accuracy of starch determination in plant tissues. This study compared starch values in pine root tissue extracted with either perchloric acid or starch-digesting enzymes. Three variations of the two extraction methods were tested. The accuracy of starch determination was assessed for five methods by comparing results to a standard method that employed perchloric acid and KI precipitation. Methods that employed commercial enzymes without additional purification yielded starch values slightly higher than the standard method. Commercial enzymes subjected to additional purification yielded starch values slightly lower than the standard method. Perchloric acid methods without KI precipitation yielded starch values 20-40 5% higher than the standard method. Also, enzyme methods had the highest precision for extraction and colorimetric steps and were more convenient than perchloric acid methods if additional enzyme purification was not performed. Detailed protocols for the laboratory procedures are provided.

Primary odorants in popcorn

Abstract: Application of an aroma extract dilution analysis to freshly prepared popcorn revealed 23 odorants among which 2-acetyl-1-pyrroline (roasty, popcorn-like), (E,E)-2,4-decadienal (fatty), 2-furfurylthiol (coffee-like), and 4-vinyl-2-methoxyphenol (spicy) predominated with the highest FD factors (odor activities). Further potent flavor compounds showing roasty odors were 2-acetyltetrahydropyridine and 2-propionyl-1-pyrroline. The latter compound showed a very low odor threshold of 0.02 ng/L (air), which was in the same magnitude as that reported for the 2-acetyl-1-pyrroline homologue. Sensory analysis of homologues 2-butanoyl- and 2-hexanoyl-1-pyrroline revealed that a longer alkyl side chain canceled the roasty flavor note and increased the odor thresholds by a factor of 10(5).

Lipid peroxidation of muscle food as affected by sodium chloride

Abstract: The prooxydant effect of NaCl on minced turkey muscle lipid peroxidation was demonstrated by using 2 methods that determine accumulation of TBA-Rs and conjugated dienes. The prooxydant effect of NaCl was inhibited by EDTA and ceruleoplasmin

Oxidation of methyl linoleate encapsulated in amorphous lactose-based food model

Abstract: A food model was used to study the effect of physical changes in the amorphous matrtix on the rate of lipid oxidation. The glass transition temperature (T g ) and crystallisation behaviour of the material were determined by using differential scanning calorimetry. The rate of oxidation was measured spectrophotometrically in samples incubated at various temperatures above T g .

Relationship between the levels of soluble nonstarch polysaccharides and the apparent metabolizable energy of wheats assayed in broiler chickens

Abstract: The total arabinoxylan contents of 13 wheats grown in different regions of New South Wales, Ausralia, were determined. The nonstarch polysaccharide content of each of the extracted fractions was determined.

New antimicrobial characteristics of lysozyme-dextran conjugate

Abstract: Lysozyme-dextran conjugate may act on the outer membrane of Gram-negative bacteria, and the conjugate is expected to show a lytic action spectrum different from that of native lysozyme. The paper describes the characteristics of the conjugate and the possibility of application as a new food preservative.

Influence of lipids on the thermal and mechanical properties of concentrated starch gels.

Abstract: The study was undertaken to determine the effect of lipids (endogenous granular and added lipids) on the viscoelastic properties of thermoset starch gel using small-strain oscillatory rheological testing. The ability of lipids to interact with the starch as well as their antistalting action was proned by DSC and small deformation rheological measurements.

Thermal gelation of globular proteins: influence of protein conformation on gel strength

Abstract: Circular dichroic analysis of protein fluid expressed from globular protein gels at high centrifugal force has been used to elucidate the structural state of globular proteins in gels. In the case of bovine serum albumin gels, gelation involved transconformation of α-helix and aperiodic structures into β-sheet conformation. In the case of soy proteins, only a reduction in th eβ-sheet content and a increase in aperiodic structure content were observed in the gel state.

Proposed nomenclature for the alcohol-soluble proteins (kafirins) of Sorghum bicolor (L. Moench) based on molecular weight, solubility, and structure

Abstract: SDS-PAGE and differential solubility were used to demonstrate similarities between maize zein and sorghum kafirins. Polypeptides with similar apparent molecular weights were found in the zein and sorghum karafin fractions. To identify structural similarities among the karafin polypeptides and the zein polypeptides, Western blot was carried out by using α-, β-, and γ-zein antisera. A nomenclature for sorghum karafins is proposed based on similarities in molecular weight, solubility, and structure to zeins.

Characterization of the products of nonenzymic autoxidative phenolic reactions in a caffeic acid model system

Abstract: Products of nonenzymic autoxidation of caffeic acid were analyzed and isolated by analytical and preparative HPLC with diode array detection By 1H and 13C nuclear magnetic resonance spectrometry, UV-visible spectrophotometry, and fast atom bombardment mass spectrometry, these oxidation products are shown to be specific (structures given) dimers and trimers of caffeic acid formed by reactions involving the side chain of at least one of the caffeic acid units Compounds analogous to natural lignans and neolignans result, with dioxane, furan, or cyclohexene bridges between the caffeic units The large effect of pH on the production rate indicates the involvement of phenolate anions in the formation of these products

Thermal decomposition of some phenolic antioxidants

Abstract: The loss of antioxidants at elevated temperature occurs as a result of both evaporation and decomposition. The stability of 4 phenolic antioxidants (BHA, BHT, TBHQ, PG) at 185°C was examinated by TLC and gas chromatography. Several products arising from thermal oxidation of the antioxidants were separated and identified by GC-MS and mechanisms of their formation suggested

Changes in the content of lipid autoxidation and sulfur-containing compounds in cooked beef during storage

Abstract: Changes in the content of carbonyl- and sulfur-containing compounds were determined for ground beef patties at 4°C for 0-4 days. Volatiles compounds were analysed by GC/MS. Free-radical reactions, the proposed mechanism for lipid autoxidation, may catalyse the degradation of sulfur-containing compounds and contribute to the increase in the content of the aliphatic and cyclic sulfur compounds.

Levels of fumonisins B1 and B2 in feeds associated with confirmed cases of equine leukoencephalomalacia

Abstract: Leukoencephalomalacia (LEM) is a neurotoxic disease of Equidae caused by the ingestion of feed contaminated with the fungus Fusarium moniliforme. Feed samples from the United States that were fed to horses prior to the development of LEM were analyzed for fumonisin B1 (FBI) and fumonisin Bz (FBz), toxic secondary metabolites of F. moniliforme. In addition, FBI, FBz, and moniliformin were determined in corn cultures of 10 isolates of F. moniliforme from these samples. None of the cultures produced moniliformin but all contained both FBI (160-3800 pg g-') and FBz (20-950 pg g-l). All 14 feed samples contained both FBI (1.3-27.0 pg g-l) and FBz (0.1-12.6 pg 6'). FBI was the major fumonisin in the cultures (80-96%) as well as in the feed samples (53-9396). These results support the finding that the fumonisins are causative factors in the development of LEM in horses.

Type V collagen in trout (Salmo gairdneri) muscle and its solubility change during chilled storage of muscle

Abstract: Post-mortem changes of types I and V collagens in rainbow trout muscle were examined in relation to the softening of fish muscle during chilled storage. Degradation of helical regions of collagens was not detected. On the other hand, the solubility of type V collagen increased significantly, while that of type I collagen did not change. These facts suggest that degradation of nonhelical regions or intermolecular cross-links occur preferentially in type V collagen.

Electrophoretic, solubility and functional properties of commercial soy protein isolates

Abstract: The aim was to determine the degree of protein denaturation and the relative amounts of the different protein species and to determine the incidence of the structural features of the proteins on the solubility, water-imbibing capacity, viscosity, and gelation capacity of commercial soy protein isolates

Cysteine as an inhibitor of enzymatic browning. I, Isolation and characterization of addition compounds formed during oxidation of phenolics by apple polyphenol oxidase

Abstract: The purpose was to develop a rapid method of preparation and purification of cysteine adduct compounds using different phenols, namely, 4-methylcatechol, chlorogenic acid,catechin and epicatechin, with a purified PPO from apple to improve their structure and to investigate their role as effectors in the enzymatic reaction.

Volatile components of dry-cured ham

Abstract: The volatile components of dry-cured ham were isolated by vacuum distillation and analyzed by gas chromatography-mass spectrometry. The structures of 76 molecules were identified by mass spectrometry, cochromatography, or measured Kovats indices. The compounds identified may come from the catabolism of the main constituent parts of the meat (glucids, lipids and protids) during the curing of the hams, from the pig feed, or from technological processes. The volatile compounds extracted from 50 g of ham according to the technique described correspond to a chromatographical surface equivalent to 0.12 mg of the dodecane internal standard, or approximately 2.4 ppm of the weight of the sample. Flavor tests showed the existence of several aromatic molecules of which some, still unidentified, had the characteristic odor of salted products.