Showing papers in "Journal of Agricultural and Food Chemistry in 1992"

Antioxidative properties of xanthan on the autoxidation of soybean oil in cyclodextrin emulsion

Abstract: The autoxidation of soybean oil in a cyclodextrin emulsion system was studied in the presence of an emulsion stabilizer consisting of polysaccharides such as xanthan, tragacanth gum, and methylcellulose. Xanthan strongly inhibited the peroxidation of soybean oil containing tocopherols but showed no antioxidant activity on soybean oil without tocopherols in the emulsion. Xanthan did not have hydrogen donating ability but expressed Fe2+-binding activity. The Fe2+-binding activity corresponded to the pyruvate content of xanthan. Depyruvated xanthan did not inhibit effectively the autoxidation of soybean oil. The Fe2+-chelating structure of xanthan is discussed

Content of potentially anticarcinogenic flavonoids of 28 vegetables and 9 fruits commonly consumed in the Netherlands

Abstract: The content of the potentially anticarcinogenic flavonoids quercetin, kaempferol, myricetin, apigenin, and luteolin of 28 vegetables and 9 fruits was determined by RP-HPLC with UVdetection. Fresh foods were purchased in a supermarket, a grocery, and a street market and combined to composites. Processed foods were purchased additionally. Sampling was carried out in spring, summer, winter, and spring of the following year

Simple and hydrolyzable phenolic compounds in virgin olive oil. 1. Their extraction, separation, and quantitative and semiquantitative evaluation by HPLC

Abstract: Phenolic compounds have a fundamental importance in the nutritional and sensory characteristics of virgin olive oil. Problems regarding their qualitative and quantitative evaluation have not been completely solved; hence, in this paper the extractive and HPLC methods of analysis are examined and some modifications are presented. By means of these techniques, elenolic acid and four unknown compounds having phenolic behavior were separated from virgin olive oil. Four of them were correlated with total phenols evaluated by means of the Folin-Ciocalteu reagent, and two of them were correlated with olive oil autoxidation stability

Optimization of a quantitative HPLC determination of potentially anticarcinogenic flavonoids in vegetables and fruits

Abstract: A rapid method based on RP-HPLC with UV detection is presented for the quantitative determination of five major flavonoid aglycons, viz. quercetin, kaempferol, myricetin, luteolin, and apigenin, in freeze-dried vegetables and fruits, after acid hydrolysis of the parent glycosides. Completeness of hydrolysis and extraction have been optimized by testing systematically different conditions such as acid concentration, reaction period, and methanol concentration in the extraction solution using samples containing various types of flavonoid glycosides. Optimum hydrolysis conditions are presented for flavonol glucuronides, flavonol glucosides, and flavone glycosides. Identity of the flavonoids was confirmed with diode array. Repeatability of the method was good, with coefficients of variation of 2.5-3.1% for quercetin, 4.6-5.6% for kaempferol, 4.6% for myricetin, 3.3% for luteolin, and 2.8% for apigenin. CV of the within-laboratory reproducibility was less than 2 times the CV of repeatability. Recoveries of the flavonols quercetin, kaempferol, and myricetin ranged from 77 to 110%, and recoveries of the flavones apigenin and luteolin ranged from 99 to 106%. The method presented allows a fast, quantitative, and reproducible determination of five flavonoids in freeze-dried foods

Dynamic Viscoelastic Study on the Gelation of 7S Globulin from Soybeans.

Abstract: 7S globulin was isolated according to a new method from soybeans. Its physicochemical properties were studied by differential scanning calorimetry (DSC) and by dynamic viscoelastic measurements. Heating DSC curves for 7S globulin showed only one endothermic peak. Extrapolation of the incipient temperature (T i ) and the endothermic peak temperature (T p ) observed at slow heating rates in DSC curves to 0 o C/min led to the result T i0 =64 o C and T p0 =70 o C

Modified thiobarbituric acid assay for measuring lipid oxidation in sugar-rich plant tissue extracts

Abstract: Use of the thiobarbituric acid (TBA) assay for thiobarbituric acid-reactive substances (TBARS) of lipid oxidation in extracts of plant materials was examined. Sucrose, fructose, glucose, lactose, citrus pectin, and bovine serum albumin (BSA) interfered with the TBA assay reaction. To correct for the interference caused by sugars (the major interference), a modified procedure was developed using standard curves for both malondialdehyde (MDA) and sucrose. Molar absorbance (MA) of adducts from TBA-MDA and TBA-sucrose reactions increased when the acidity in the reaction mixture increased and the time of heating and the temperature of heating for the reaction increased

Phenolics of apple, pear, and white grape juices and their changes with processing and storage. A review

Abstract: The phenolic composition of apple, pear, and white grape juices is reviewed. Attention is given to the importance of phenolics in fruit juices, the factors that affect the phenolic composition of fruit juices, and the improvements in the techniques that have been employed in the analysis of phenolics

Effect of food preparation on qualitative and quantitative distribution of major carotenoid constituents of tomatoes and several green vegetables

Abstract: The major carotenoid constituents of extracts from several raw and cooked green vegetables (broccoli, green beans, spinach), red ripe tomatoes, and tomato paste have been identified and quantified by high-performance liquid chromatography on a C18 reversed-phase column. The predominant carotenoids in raw green vegetables were neoxanthin, violaxanthin, lutein epoxide, lutein, alpha-carotene, and beta-carotene. The carotenoids in tomatoes and tomato paste were lutein, 5,6-dihydroxy-5,6-dihydrolycopene, lycopene 1,2-epoxide, lycopene 5,6-epoxide, lycopene, neurosporene, gamma-carotene, zeta-carotene, beta-carotene, phytofluene, and phytoene. The effect of various means of cooking on the levels of carotenoids in raw and cooked (microwaved, boiled, steamed, stewed) green vegetables and tomatoes has been extensively studied. It was shown that while the epoxycarotenoids were somewhat sensitive to heat treatment, lutein and hydrocarbon carotenoids such as neurosporene, alpha- and beta-carotene, lycopene, zeta-carotene, phytofluene, and phytoene survived the heat treatments.

Chemical treatment of pesticide wastes. Evaluation of Fe(III) chelates for catalytic hydrogen peroxide oxidation of 2,4-D at circumneutral pH

Abstract: A number of structurally diverse organic and inorganic polydentate chelators were tested for their ability to solubilize Fe(III) at pH 6 and catalyze the oxidation of 0.1 mM (22 ppm) 2,4-dichlorophenoxyacetic acid (2,4-D) by 10 mM (340 ppm) hydrogen peroxide in aerated aqueous solution. Of 50 compounds tested, 20 organic compounds gave soluble complexes capable of oxidizing 2,4-D in periods ranging from minutes to less than 5 h. The reaction rate was proportional to the concentration of H 2 O 2 and inversely proportional to the concentration of chelator (...)

Effect of glass transition on rates of nonenzymatic browning in food systems

Abstract: The effect on browning of dehydrated vegetables and of model systems (composed of amino acids and sugars reacting in matrices with different physical characteristics) was studied. Glass transition temperature (T g ) was determined by differential scanning calorimetry. The rates of nonenzymatic browning were then from the literature for vegetables and were determined for model systems by measuring absorbance at 280 and 420 nm. Rate constants were analyzed as a function of temperature (T) and of (T-T g )

Stabilization of the Prussian blue color in the determination of polyphenols

Abstract: A stabilized reagent for the determination of total polyphenols by the Prussian blue method was developed. H3PO4 complexed with excess Fe3+ in the mixture, stopping the reaction. Gum acacia, a protective colloid, prevented precipitation by impeding the coalescence of the colloidal particles formed. Efficiency of chelating agents tried was H3PO4 (A) Na4EDTA (B) sodium hexametaphosphate (C). Effectiveness of protective colloids was gum acacia (D) = Reten (an anionic polyacrylamide) (E) Methocel 60 HG (F) phosphomannan 2448 (G) starch (H) polysaccharide B 1828 (I). Both the chelating agent and the protective colloid must be added to effect stabilization. Effectiveness of combinations was (A + D or E) (B + D) (A + F) (A + G) all other combinations. (A + D) prevented change in color density and prevented precipitation for up to 60 h with catechin as the polyphenol

Antioxidant activity of durum wheat bran

Abstract: Freeze-dried extract from durum wheat bran exhibited stronger antioxidant activity than extracts from other milling fractions. At 9 h under active oxygen method (AOM) conditions, peroxide value (PV) determinations showed that oil with the bran extract had a PV of 38.0 Mequiv/kg while the control oil had a PV of 129.0 Mequiv/kg. Extracts from the bran fractions of six durumwheat varieties had similar antioxidant activities in soy oil (PV 37.6-42.0 Mequiv/kg)

Allium chemistry: HPLC analysis of thiosulfinates from onion, garlic, wild garlic (ramsoms), leek, scallion, shallot, elephant (great-headed) garlic, chive, and Chinese chive. Uniquely high allyl to methyl ratios in some garlic samples

Abstract: Room temperature vacuum distillates and extracts of onion (Allium cepa), garlic (Allium sativum), wild garlic (Allium ursinum), leek (Allium porrum L.), scallion (Allium fistulosum L.), shallot (Allium ascalonicum auct.), elephant (or great-headed) garlic (Allium ampeloprasum L. var. ampeloprasum auct.), chive (Allium schoenoprasum L.), and Chinese chive (Allium tuberosum L.) were analyzed by HPLC and 1H NMR using authentic samples of suspected thiosulfinate components to evaluate the methods. Of the eight different thiosulfinates separated and identified in each plant extract, several are reported here for the first time. It is concluded that gas chromatography, as typically performed with high injector and column temperatures, presents an erroneous picture of the competition of room temperature extracts from Allium species and that HPLC provides a reliable qualitative and semiquantitative measure of what is actually present. A simple vacuum distillation procedure facilitating qualitative analysis of Allium volatiles is described. A number of significant trends are noted regarding the varying proportions of different thiosulfinates in each Allium species. In particular, some garlic varieties grown in cooler climates show a higher allyl to methyl ratio than garlic grown in warmer climates.

Carotenoid composition in raw and cooked Spanish vegetables

Abstract: An HPLC study of 18 of the fresh vegetables (raw and coolied) most frequently consumed in Spain was done to determine their carotenoid composition. The results are grouped according to the color of the edible potion of each: green, red-orange, or yellowish-white vegetables. β-Carotene and lutein were found to be present in all of the vegetables analyzed except the sweet red pepper, which contains zeaxanthin but not lutein. Lutein and zeaxanthin are present in five of the vegetables analyzed, with the highest concentration of both of these components being found in spinach

Simple and hydrolyzable phenolic compounds in virgin olive oil. 2. Initial characterization of the hydrolyzable fraction.

Abstract: This paper reports the preliminary characterization of unknown phenolic compounds in virgin olive oil, separated by HPLC using hydrolytic, chromatographic, and spectrophotometric techniques. It was possible to characterize oleuropeine aglycon and three hydrolyzable phenols containing (3,4-dihydroxyphenyl)ethanol or (p-hydroxyphenyl)ethanol

Improved speed, specificity, and limit of determination of an aqueous acid extraction thiobarbituric acid-C18 method for measuring lipid peroxidation in beef

Abstract: 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 o C 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 o C

Chitosan-lipid films: microstructure and surface energy

Abstract: Composite films of chitosan-laurate were shown to have low water permeability, while films containing other fatty acids or esters were not effective in this respect. Electron microscopy revealed the microstructure of these films to be very different, in terms of density, pore formation, channeling, surface contour, and packing pattern. The surface energy of the films was estimated, and the dispersion force component (γ s d ) and the polar component (γ s d ) were calculated

Maillard browning kinetics in a liquid model system

Abstract: Liquid model systems containing varying concentrations of glucose and glycine in a 0.1 M phosphate buffer at pH 1.0 were stored at 31 o C. Formation of brown pigments and fluorescent compounds as well as the loss of glucose and glycine was monitored over time. Glucose and glycine loss individually followed first-order Kinetics and second order overall, as predicted mechanistically. Amino acid loss went into a no-loss period, as expected mechanistically from Bodenstein steady-state kinetics

Antioxidant activity of tropical ginger extracts and analysis of the contained curcuminoids.

Abstract: Antioxidant activities of the rhizomes of nine tropical gingers (Curcuma aeruginosa, Curcuma domestica, Curcuma heyneana, Curcuma mangga, Curcuma xanthorrhiza, Zingiber cassumunar, Phaeomeria speciosa, Alpinia galanga, and Amomum kepulaga) have been measured by thiocyanate and TBA methods in a water/alcohol system after extraction and fractionation with organic solvents. The quantity of three known curcuminoids, one of the potent antioxidant family of ginger species, in the extracts has been analyzed by HPLC

Importance of phenolic compounds for the characterization of fruit juices

Abstract: Several commercial juices of orange, apple, pineapple, peach, apricot, pear, and grape have been analyzed by HPLC and TLC to establish their phenolic composition Benzoic acids and aldehydes, 3-flavanols, flavonols, chalcones, cinnamic acids, and their derivatives in the form of esters and glycosides have been studied Hydroxycinnamic acid esters with tartaric acid are typical of grape,phloridzin is typical of apple, and isorhamnetin glycosides are typical of pear Myricetin is only found in peach, and luteolin and apigenin glucosides are found only in orange

Persistent organochlorine residues in foodstuffs from India and their implications on human dietary exposure

Abstract: Foodstuffs collected from different regions in India were analyzed for the presence of HCH (BHC), DDT, HCB, aldrin, dieldrin, heptachlor, and PCBs. Significantly high levels of food contamination with HCH, DDT, aldrin, and dieldrin were evident throughout India. Dairy products and livestock meat are the prime sources of human dietary exposure to these chemicals. Concentrations of these organochlorine compounds in a few dairy products were above the maximum residue limits (MRLs) set forth by the FAO/WHO as well as the Ministry of Health of the Indian government. The average daily intakes of HCH and DDT by Indians were estimated to be 115 and 48 pg/person, respectively, which were higher than those observed in most of the developed nations. The dietary intakes of aldrin and dieldrin exceeded the acceptable daily intake (ADI) recommended by the FAO/ WHO. Food pollution and dietary intakes of PCBs, HCB, and heptachlor were relatively low in India.

Preformed and induced antifungal materials of citrus fruits in relation to the enhancement of decay resistance by heat and ultraviolet treatments.

Abstract: Two mechanisms of the resistance of citrus fruits against pathogens-preformed and induced antifungal materials-were investigated. Flavedo tissue of lemon contains the following preformed antifungal materials: citral, limettin, 5-geranoxy-7-methoxycoumarin, and isopimpinellin, which act as the first line of defense against pathogens. Exogenous application of citral to Penicillium-inoculated lemon fruit prevented development of decay. Being subjected to fungal challenge and/or abiotic stress, citrus fruits are elicited to produce the phytoalexin scoparone, considered as another line of fruit defense. According to median effective dose (ED50) of the inhibition of germ-tube elongation or percent germination, scoparone had higher fungitoxicity against Penicillium digitatum Sacc. than the preformed antifungal materials. Different citrus species (lemon, orange, grapefruit, lime, kumquat) varied in their capacities to produce scoparone responding to the combined Penicillium inoculation and heat treatment or to UV illumination. UV illumination of lemon fruit reduced its susceptibility to P. digitatum. Expression of this effect was directly related to the level of scoparone in illuminated fruit. UV light and citral application were visibly injurious to the flavedo tissues in high dose.

Cysteine as an inhibitor of enzymic browning. 2. Kinetic studies

Abstract: The effect of cysteine and cysteine-quinone addition compound (CQAC) on apple polyphenol oxidase (PPO) activity was investigated by HPLC and polarography, using 4-methylcatechol(4MC), chlorogenic acid (CG), and (-)-epicatechin (EC) as substrate. With 2.2 mM 4MC, in the presence of cysteine at thiolto phenol ratios above 1, there was no effect in the degradation rates of 4MC, while CQAC formation was proportional to the 4MC loss but without color formation. For cysteine to phenol ratios below 1, the degradation rate of 4MC was slowed down; the lower the cysteine content, the earlier the decrease in 4MC degradation was observed. In the latter case, the CQAC content increased and then decreased but developed a strong color. Similar results were obtained with CG or EC as substrate. In the presence of CQAC, polarography experiments showed that they were not substrate but competitive inhibitors of apple PPO with a slightly higher affinity than their phenol precursors. HPLC analysis showed that Cys-5-MC (the CQAC derived from 4MC) was rapidly degraded, whereas 4MC degradation was slowed with a strong violet color formation. Nonenzymatic cooxidation reactions between CQAC and o-quinone leading to the regeneration of phenol and the formation of pigments were observed. Cysteine at a higher concentration prevented color development by trapping o-quinones as colorless CQAC, while at low amounts the o-quinones formed in excess can cooxidize CQAC, leading to a phenol regeneration with a deep color formation.

Aroma components and free amino acids in strawberry variety Chandler during ripening

Abstract: Aroma components and free amino acids of strawberry Fragaria ananassa×Duchesne var. Chandler were studied at different ripening stages. Ethyl esters were the major volatile compounds in all ripening stages studied, ethyl butanoate and ethyl hexanoate being the two main esters identified in fully ripe berries. Asparagine, glutamine, and alanine were found to be the most prominent free amino acids in the HPLC profile

Studies on the control of lipid oxidation in ground fish by some polyphenolic natural products

Abstract: Oxidative rancidity leads to the qualitative deterioration of muscle foods, resulting in the production of un palatable flavor and odor,there by shortening shelflife. Lipid oxidation, measured by the production of thiobarbituric acid reactive substances (TBARS), proceeded to a greater extent in raw and cooked fish stored at 4 degrees C than in that stored at -20 degrees C over 3 weeks. Several antioxidants were used to study their effects on lipid oxidation in ground fish. On storage (4 degrees C) day 14, all of the antioxidants, except rutin (200 and 30 ppm) and alpha-tocopherol (30 ppm), were effective in inhibiting lipid oxidation in raw fish. L-Ascorbic acid acted as a prooxidant in steam- and microwave-cooked fish, as well as in the 1-week-stored (at either 4 or -20 degrees C) steam-cooked fish. The polyphenols quercetin (200 ppm), myricetin (200 ppm), tannic acid (30 and 200 ppm), and ellagic acid (30 and 200 ppm) were potent antioxidants under the same conditions.

Flavor compounds of dry-cured ham

Abstract: Volatile compounds of dry-cured Parma hem, the most representative among those of Italian style, were extracted by means of the dynamic headspace technique followed by adsorption onto Tenax traps. GC-FID end GC-FPD were used to obtain the aromatic profiles of the samples; gas chromatography-mass spectrometry was also used to identify the structure of the volatile components. One hundred twenty-two compounds were identified in this study, several of which have not been previously reported

Changes in sugars, acids, and amino acids during ripening and storage of apples (cv. Glockenapfel)

Abstract: Changes in sugars, the principal acids, and amino acids were monitored in the ethanol-soluble matter of apples during a 6-month period between the beginning of July, while the apples were still on the tree, and January, after storage at 4 o C. Fructose was the principal sugar. Fructose, sucrose, and glucose increased at different rates till harvest, and then the levels remained constant after an initial drop. Malic acid was the principal acid. The amino acid content declined steadily during development

Chlorogenic acid content of fresh and processed potatoes determined by ultraviolet spectrophotometry

Abstract: Chlorogenic acid is reported to be involved in preharvest defenses of the potato plant against fungi and insects, in postharvest browning, and in after-cooking blackening, all of which affect quality and safety. As part of a program of potato improvement, HPLC and ultraviolet spectroscopy were evaluated to measure the chlorogenic content of commercial and experimental potatoes, of parts of the potato plant, and of processed potato products. HPLC analysis appears to be less satisfactory because chlorogenic acid undergoes a time- and light-dependent change in the methanolic and ethanolic extracts of potatoes used

Facile large-scale synthesis of coniferyl, sinapyl, and p-coumaryl alcohol

Abstract: Coniferyl, sinapyl, and p-coumaryl alcohols are rapidly and cleanly prepared by selective 1,2-reduction of the corresponding cinnamate esters using diisobutylaluminum hydride (DIBAL-H) in toluene as reducing agent.