Identification of bitterness-masking compounds from cheese

Bitterness-masking compounds were identified in a natural white mold cheese. The oily fraction of the cheese was extracted and further fractionated by using silica gel column chromatography. The four fractions obtained were characterized by thin-layer chromatography and nuclear magnetic resonance spectroscopy. The fatty acid-containing fraction was found to have the highest bitterness-masking activity against quinine hydrochloride. Bitterness-masking activity was quantitated using a method based on subjective equivalents. At 0.5 mM, the fatty acid mixture, which had a composition similar to that of cheese, suppressed the bitterness of 0.008% quinine hydrochloride to be equivalent to that of 0.0049-0.0060% and 0.5 mM oleic acid to that of 0.0032-0.0038% solution. The binding potential between oleic acid and the bitter compounds was estimated by isothermal titration calorimetry. These results suggest that oleic acid masked bitterness by forming a complex with the bitter compounds.     

Identification of six phenylpropanoids from garlic skin as major antioxidants

The extract of garlic skins (peels) showed strong antioxidant activity, and some responsible constituents were isolated and identified. Garlic (Allium sativum L.) has been used as an herbal medicine, but there is no report on the health benefits of the skin or peel. In this study, the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of garlic skin extract was evaluated. Using chromatographic techniques, the active constituents were isolated and subsequently identified. Analyses by high-performance liquid chromatography coupled with a photodiode array detector (HPLC-PDA) suggested that these compounds were phenylpropanoids, which had a characteristic absorbance at 300-320 nm. Liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance analyses allowed the chemical structures of the isolated constituents to be postulated. The proposed compounds were subsequently synthesized and compared with the constituents in the extract using HPLC-PDA and LC-MS. N-trans-Coumaroyloctopamine, N-trans-feruloyloctopamine, guaiacylglycerol-beta-ferulic acid ether, and guaiacylglycerol-beta-caffeic acid ether were identified as were trans-coumaric acid and trans-ferulic acid. Also, the antioxidant activities of these compounds were determined.     

Identification and quantification of zeaxanthin esters in plants using liquid chromatography-mass spectrometry

It has been suggested that lutein and zeaxanthin may decrease the risk for age-related macular degeneration. Surprisingly, oleoresins rich in zeaxanthin are not yet available on the market. Several authors have reported enhanced stability of esterified xanthophylls, so plants containing zeaxanthin esters were investigated to establish valuable sources for the production of durable oleoresins. Liquid chromatography-atmospheric pressure chemical ionization mass spectrometry [LC-(APCI)MS] was used to unequivocally identify zeaxanthin esters of a standard mixture and in several plant extracts. Zeaxanthin esters were quantified on the basis of their respective molecular masses using zeaxanthin for calibration; total zeaxanthin was determined after saponification of aliquots of the extracts. Thus, dried wolfberries (Lycium barbarum), Chinese lanterns (Physalis alkekengi), orange pepper (Capsicum annuum), and sea buckthorn (Hippophae rhamnoides) proved to be valuable zeaxanthin ester sources. The present LC-MS method allows for an even more detailed analysis of zeaxanthin esters than reported previously.     

Identification of a peptide in enzymatic hydrolyzate of cheese that inhibits ovalbumin permeation in Caco-2 cells

Because the first step in the triggering of food allergy is the permeation of the allergen through the intestine, enhancement of the intestinal barrier function is thought to be effective for preventing food allergy. In this study, a peptide that inhibits ovalbumin (OVA) permeation in an in vitro Caco-2 cell model was isolated from enzymatic hydrolyzate of cheese (EHC). Amino acid sequence analysis identified the active peptide as GPIVLNPWDQ, a sequence identical to amino acids 102-111 of alphas2-casein. The decapeptide significantly inhibited OVA permeation at a concentration of 10(-6) M. In addition, it was found that a pentapeptide half, NPWDQ, is essential for the inhibitory activity because NPWDQ but not GPIVL had nearly the same inhibitory activity as GPIVLNPWDQ. The possibility exists that EHC and/or peptides possessing the NPWDQ sequence can be practically applied to the prevention of food allergy.     

Spectrometric and liquid chromatographic determination of natamycin in cheese and cheese rind

Methods for determining natamycin content of cheese rind and cheese are presented. Cheese and rind samples are extracted with methanol and the fat precipitated by cooling the sample solution in methanol-water at -15 to -20 degrees C for ca 1 h. Natamycin levels are measured by UV spectrometric detection at absorbance minimum 311 nm, maximum 317 nm, and at exactly 329 nm, or by LC separation over Lichrosorb RP-8 column with detection at 303 nm. For measuring low levels, a concentration step is provided. The method is applicable to natamycin in cheese rind and in the interior of the cheese. Detection limit is 0.5 mg/kg. The method is suitable for controlling a maximum tolerance of natamycin on the cheese rind, at a level of 1 mg/dm2, and for detecting migration of natamycin into the cheese.     

Determination of natamycin in cheese and cheese rind: interlaboratory collaborative study

A collaborative test on the determination of natamycin in cheese and cheese rind was conducted. Participants were from 37 laboratories in 13 countries. Eight samples, consisting of 4 duplicates, were investigated by a spectrometric method and a liquid chromatographic (LC) method. The spectrometric method gave good results (coefficient of variation [CV] = 12%) and the LC method with ultraviolet detection gave reasonable results (CV = 25%) for levels down to 15 mg/kg (0.9 mg/dm2). For very low levels, a preconcentration step is necessary, but even then quantitation is poor (CV = 35-37%) for both methods at 1.7 mg/kg, although the presence of natamycin can be detected qualitatively. For a level of 0.3 mg/kg, quantitation is poor (CV = 39%) for the LC method and impossible (CV = 60%) for the spectrometric method.     

Identification of synthetic regioisomeric lutein esters and their quantification in a commercial lutein supplement

Synthetic mixtures of 24 mono- and diesters of the asymmetric hydroxylated carotenoid lutein with lauric, myristic, palmitic, and stearic acids were analyzed by liquid chromatography-ultraviolet/visible spectroscopy (LC-UV-vis) and characterized by LC-mass spectrometry (MS) and nuclear magnetic resonance spectroscopy (NMR). These compounds were then used for identifying the composition of a commercial lutein supplement. This is the first report of chromatographic separation of mixed fatty acid lutein diesters. Preferential MS loss of fatty acids or water occurred initially at the 3'-hydroxy position in the epsilon-ionone ring and subsequently at the 3-hydroxy position in the beta-ionone ring. This selective fragmentation leads to facile assignment of the specific fatty acids to the appropriate regioisomeric ionone ring. A commercial lutein supplement contained low levels of two pairs of regioisomeric monoesters and nearly equal levels of three homogeneous diesters and five pairs of mixed diesters. Palmitic acid was the predominant fatty acid, with lower amounts of myristic, stearic, and lauric acids.     

Identification of two novel pigment precursors and a reddish-purple pigment involved in the blue-green discoloration of onion and garlic

By using a model reaction system representing blue-green discoloration that occurs when purees of onion (Allium cepa L.) and garlic (Allium sativum L.) are mixed, we isolated two pigment precursors (PPs) and a reddish-purple pigment (PUR-1) and determined their chemical structures. PPs were isolated from a heat-treated solution containing color developer (CD) and either l-valine or l-alanine, and their structures were determined as 2-(3,4-dimethylpyrrolyl)-3-methylbutanoic acid (PP-Val), and 2-(3,4-dimethyl-1H-pyrrolyl) propanoic acid (PP-Ala), respectively. Next, PUR-1 was isolated from a heat-treated solution containing PP-Val and allicin, and its structure was determined as (1E)-1-(1-((1S)-1-carboxy-2-methylpropyl)-3,4-dimethyl-1H-pyrrol-2-yl)-prop-1-enylene-3-(1-((1S)-1-carboxy-2-methylpropyl)-3,4-dimethyl-1H-pyrrol-2-ylidenium). The structure of PUR-1 suggested that PP molecules containing a 3,4-dimethyl pyrrole ring had been cross-linked by an allyl group of allicin to form conjugated pigments. While PUR-1 is a dipyrrole compound exhibiting a reddish-purple color, a color shift toward blue to green can be expected as the cross-linking reaction continues to form, for example, tri- or tetrapyrrole compounds.     

Identification of the production chain of Asiago d'Allevo cheese by nuclear magnetic resonance spectroscopy and principal component analysis

In the present work, a rapid and simple NMR method to discriminate Asiago d'Allevo cheese samples from different production chains is described. A fast and reproducible extraction of the organic fraction was employed. By applying chemometric analysis to NMR data, it is possible to differentiate PDO Asiago cheese produced in alpine farms from that produced in lowland and mountain industrialized factories. PCA of both (1)H and (13)C NMR spectra showed a good separation of alpine farm products from the other ones, whereas the lowland and mountain industrialized cheeses are undistinguishable. The samples were differentiated on the basis of a higher content of unsaturated fatty acids, principally oleic, linoleic, linolenic, and conjugated linoleic acids for the alpine farm cheeses and a higher content of saturated fatty acids for the industrialized products. Conjugated linoleic acid and 1-pentene are also discriminating components.     

Silicon alleviates mercury toxicity in garlic plants

Abstract

Silicon (Si) can increase plant stress tolerance. Mercury (Hg) is one of the major elements of heavy metal pollution. However, little attention has been paid to the possible effect of Si on Hg toxicity in plants. Here, the effects of Si on growth, photosynthesis, Hg accumulation and antioxidant defense were investigated in garlic grown in pots under Hg stress. Before sowing, Hg and Si were added at 3?mg Kg^?1 and 500?mg Kg^?1, respectively. The treatments included CT (control), Si, Hg and Hg?+?Si. The results showed that in non-stress conditions, added Si did not affect the garlic growth, photosynthetic gas exchange, malonaldehyde concentration or activities of antioxidant enzymes in leaves, except that it increased the superoxide dismutase activity. Under Hg stress, the garlic growth, leaf net photosynthetic rate, stomatal conductance, transpirational rate and superoxide dismutase activity in leaves were all inhibited, while the malondialdehyde concentration was increased; whereas these changes were all reversed in the presence of added Si. Added Si significantly decreased Hg concentrations in the root, bulb and shoot, and it also decreased exchangeable Hg level in the soil. These results suggest that Si could alleviate Hg toxicity in garlic through improving antioxidant defense ability, and decreasing Hg availability in soil and thus Hg uptake.     

Thin layer chromatographic determination of sterigmatocystin in cheese

A one-dimensional thin layer chromatographic method has been developed for determining sterigmatocystin in cheese. Cheese is extracted with acetonitrile-4% KCl (85 + 15). A simplified liquid-liquid partition cleanup is used, and the sample extract is passed through a cupric carbonate column for final purification. Sterigmatocystin is visualized by spraying the plate with aluminum chloride. The fluorescence of the spot is enhanced 10-fold by additional plate spraying with a silicone-ether mixture, enabling sterigmatocystin detection and quantitation at 2 and 5 micrograms/kg, respectively. Average recoveries were 88.3 and 86.4% at the 10 and 25 micrograms/kg levels, respectively.     

Changes in organosulfur compounds in garlic cloves during storage

We determined the changes in the contents of three gamma-glutamyl peptides and four sulfoxides in garlic cloves during storage at -3, 4, and 23 degrees C for 150 days using a validated high-performance liquid chromatography method that we reported recently. When garlic was stored at 4 degrees C for 150 days, marked conversion of the gamma-glutamyl peptides, gamma-L-glutamyl-S-allyl-L-cysteine and gamma-L-glutamyl-S-(trans-1-propenyl)-L-cysteine (GSPC), to sulfoxides, alliin and isoalliin, was observed. Interestingly, however, when garlic was stored at 23 degrees C, a decrease in GSPC and a marked increase in cycloalliin, rather than isoalliin, occurred. To elucidate in detail the mechanism involved, the conversion of isoalliin to cycloalliin in both buffer solutions (pH 4.6, 5.5, and 6.5) and garlic cloves at 25 and 35 degrees C was examined. Decreases in the concentration of isoalliin in both the solutions and the garlic cloves during storage followed first-order kinetics and coincided with the conversion of cycloalliin. Our data indicated that isoalliin produced enzymatically from GSPC is chemically converted to cycloalliin and that the cycloalliin content of garlic cloves increases during storage at higher temperature. These data may be useful for controlling the quality and biological activities of garlic and its preparations.     

Identification of fatty acid esters of pectenotoxin-2 seco acid in blue mussels (Mytilus edulis) from Ireland

Pectenotoxins from marine dinoflagellates of the genus Dinophysis are rapidly hydrolyzed by many shellfish to give pectenotoxin-2 seco acid, which isomerizes to 7-epi-pectenotoxin-2 seco acid. Three series of fatty acid esters of pectenotoxin-2 seco acid (PTX-2 seco acid) and 7-epi-PTX-2 seco acid were detected by LC-MS analysis of extracts from blue mussels (Mytilus edulis) from Ireland. The locations of the fatty acid ester linkages were identified by a combination of LC-MSn in positive- and negative-ion modes, LC-MS analysis of the products from reaction of the esters with sodium periodate, and NMR analysis of purified samples of the two most abundant ester derivatives. The 37-O-acyl esters of PTX-2 seco acid were the most abundant, followed by the corresponding 11-O-acyl esters, accompanied by low levels of the 33-O-acyl esters. The most abundant fatty acid esters in the fractionated sample were, in order, the 16:0, 22:6, 14:0, 16:1, 18:4, and 20:5 fatty acids, although a wide array of other PTX-2 seco acid fatty acid esters were also present at low levels.     

Chemometric analysis of Ragusano cheese flavor

Ragusano cheeses were produced in duplicate from milk collected from pasture-fed and total mixed ration (TMR)-fed cattle at four time intervals. The cheeses were subjected to chemical analysis, conventional sensory testing, and gas chromatography-olfactometry (GCO). Data from each type of analysis were examined by principal component and factor analysis and by pattern recognition (SIMCA) to see if sufficient information for classification into pasture-fed and TMR-fed groups was contained therein. The results clearly indicate that there are significant differences in sensory panel and chemical analysis results between the two cheeses. The data were also examined to see if models of sensory responses as a function of analytical or GCO results or both could be constructed with the modeling technique partial least-squares regression (PLS). Strong PLS models of some sensory responses (green and toasted odor; salt, pungent, bitter, and butyric sensations; and smooth consistency) were obtained.     

磷石膏对大蒜的增产效果和效益分析

磷石膏是制造磷酸的下脚料,主要成分是石膏(CaSO4·2H2O),含量约为65%,还含有少量的磷,P2O5含量约为2%。大蒜素含量越高,大蒜的品质越好。为了验证对大蒜产量的增产效果,分析投入产出情况,于2002～2003年设计了底施价格低廉的磷石膏对大蒜的试验,通过连续两年的产量分析,证实了     

Factors affecting the retention of rennet in cheese curd

The coagulant retained in cheese curd is a major contributor to proteolysis during ripening. The objective of this study was to quantify the effects of several milk-related factors and parameters during cheese manufacture on the retention of coagulant in cheese curd. The amount of coagulant retained in curd was determined by its activity on a synthetic heptapeptide (Pro-Thr-Glu-Phe-[NO2-Phe]-Arg-Leu) using reversed-phase HPLC. The retention of chymosin in cheese curd increased significantly when the pH of milk was reduced at rennet addition below pH 6.1, the pH at whey drainage below pH 5.7, or the average casein micelle size in milk and when the ionic strength of milk was increased. The casein content of milk and the quantity of chymosin added to milk had no significant effect on the retention of chymosin in curd; the quantity of coagulant bound per gram of casein remained unchanged.     

Study of light-induced volatile compounds in goat's milk cheese

Light-induced volatile compounds in goat cheese were studied by a combination of solid phase microextraction (SPME)-gas chromatography (GC)-mass spectrometry (MS), headspace oxygen depletion, and sensory evaluation. Samples stored under fluorescent light for 2 days at 30 degrees C had 90% more volatile compounds and 4 times more headspace oxygen depletion than samples stored in the dark at 30 degrees C. The volatiles 1-heptanol, heptanal, nonanal, and 2-decenal were formed and increased only in the light-stored samples, which may be formed from singlet oxygen oxidation of unsaturated fatty acids. Sensory evaluation showed that samples stored under light had significantly more off-flavor than samples stored in the dark at 30 degrees C (P < 0.05), and 1-heptanol, heptanal, nonanal, and 2-decenal increased the goat cheese off-flavor significantly (P < 0.05).     

Time course and specificity of lipolysis in Swiss cheese

Controlling lipolysis in cheese is necessary to ensure the formation of desirable flavor. To get a better understanding of the mechanism of lipolysis in Swiss cheese, cheeses were manufactured with and without (control) the addition of Propionibacterium freudenreichii. Products of lipolysis were quantified throughout ripening. Half of the free fatty acids (FFA) released in milk (3.66 mg/g fat), in particular the short-chain FFA, were lost in the whey during curd drainage, whereas diglycerides and monoglycerides were retained within the curd. P. freudenreichii was responsible for the release of most FFA during ripening (10.84 and 0.39 mg/g fat in propionibacteria-containing and control cheeses, respectively). Indices of lipolysis displayed low specificity. All types of FFA were released, but butyric and palmitic acids more significantly, which could be due to a low sn-1,3 regioselectivity. All glycerides were hydrolyzed in the following order: monoglycerides>diglycerides>triglycerides. The results of this study show the quantitative and qualitative contributions of the different lipolytic agents to Swiss cheese lipolysis.     

豫东潮土地区大蒜喷施微量元素肥料效果试验

试验表明在豫东潮土地区大蒜喷施钼酸铵、硫酸锌、硼砂、硫酸锰、硫酸铜有明显增产效果，比对照增产幅度为1890．0～3844．5kg／hm^2，增产9．6％～19．4％；同时提高大蒜的品级，改善大蒜品质，经济效益高，比对照增收3712．17～6566．54元／hm^2，增值达16．4％～27．3％。     

Induction of detoxication enzymes in mice by naturally occurring allyl nitrile

Little is known about whether glucosinolate-derived nitriles have the ability to increase phase 2 detoxication enzymes and glutathione (GSH) in vivo. In this study, the ability of allyl nitrile, a hydrolysis product of the glucosinolate sinigrin, to increase tissue levels of the phase 2 detoxication enzymes glutathione S-transferase and quinone reductase and GSH in a variety of mouse tissues was examined. At the lowest dose level (11.8 mg/kg/day), allyl nitrile showed inductive ability in the stomach and lungs. At 23.6 mg/kg/day, the inductive effect was observed in the stomach, rectum, urinary bladder, and lungs, whereas at 47.2 mg/kg/day, it was recorded in the stomach, rectum, urinary bladder, kidneys, and lungs. These results show that allyl nitrile displays its maximum potency in the stomach and lungs, which is of interest in light of epidemiological studies demonstrating an inverse association between crucifer intake and the incidence of stomach and lung cancers.