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).     

Changes in the volatile profile of oats induced by processing

Samples of an Australian oat cultivar, Echidna, were pilot-scale processed. At each stage of the processing (raw oats, groats, kiln dried dehulled oats (KDHO), and rolled (flaked)) samples were removed for later sensory and GC-MS analysis of the flavor components. Mean taste panel scores from a trained taste panel were calculated according to attributes (cereal, burnt, toasted, floury, and yeasty). Attributes were generally similar for both KDHO and flaked oats except in the yeasty attributes. Panelists were able to differentiate between groats, KDHO, and flaked oats (raw oats were not included). The largest effects of heat processing were found for the attributes toasted and yeasty aroma; toasted, cereal, and yeasty flavor; and toasted and yeasty aftertaste. A multi-organoleptic sensor analyzer was able to differentiate all samples when the output was subjected to discriminant function analysis. A reintroduced sample was recognized with a confidence level better than 96%. Solid-phase microextraction (SPME) of headspace followed by GC--MS was used to identify volatiles after either dry or slurry heating. Several SPME fiber types were evaluated as to their ability to sorb oat volatiles. A 100-microm poly(dimethylsiloxane) SPME fiber was found to provide the best adsorption profile as measured by number of compounds sorbed and peak area response. A range of alcohols, aldehydes, alkyl benzenes, dienes, and ketones was identified in the processed samples.     

Changes in volatile flavor components of guava juice with high-pressure treatment and heat processing and during storage.

The changes in volatile flavor components of guava juice during pressure processing (25 degrees C, 600 MPa, 15 min), heat processing (95 degrees C, 5 min), and storage at 4 and 25 degrees C were evaluated by purge and trap/gas chromatography/mass spectrometry. Esters were the major volatile fraction in guava juice, and alcohols were the second. Pressure processing could maintain the original flavor distribution of the juice. Heat processing (95 degrees C, 5 min) caused decreases in the majority of flavor components in the juice when compared with freshly extracted juice. High-pressure treatment at 600 MPa for 15 min can effectively sterilize microbes but partially inactivate enzymes of guava juice; therefore, volatile components in pressure-treated juice gradually changed during storage periods. Pressure-treated guava juice showed increases in methanol, ethanol, and 2-ethylfuran with decreases in the other components during storage period. Nevertheless, the volatile distribution of 600 MPa treated guava juice was similar to that of freshly extracted juice when stored at 4 degrees C for 30 days.     

不等量翻压紫云英处理下黄泥田土壤磷组分的变化

黄泥田是我国南方主要的中低产水稻土类型之一,采用定位试验的方法,研究了单施化肥(NPK)、化肥+紫云英(12 000、24 000、36 000、48 000 kg·hm-2)5个处理下土壤磷组分的变化。结果表明,与单施化肥相比,紫云英翻压与化肥配施的土壤有效磷增幅达10.23%～22.69%,全磷含量增加3.09%～13.31%,以化肥配施24 000 kg·hm-2紫云英(NPK+MV2)增幅最为明显;其中,有机磷占总磷含量的36.52%～43.14%,无机磷占56.86%～63.48%;无机磷组分主要以Fe-P和O-P为主,不等量紫云英翻压与化肥配施土壤无机磷组分含量与NPK相比都有所增加,当翻压量小于NPK+MV2处理时,增加幅度均表现为显著水平,大于NPK+MV2处理时,则差异不显著;紫云英翻压与化肥配施处理水稻产量较NPK增产达12.51%～23.01%,以NPK+MV2处理增产最为明显,增产1 345.7 kg·hm-2。表明在黄泥田中紫云英翻压配施化肥比单施化肥能提高土壤磷组分及其含量,水稻产量与土壤磷含量密切相关,以翻压紫云英24 000 kg·hm-2与化肥配施为较适宜的施肥模式。     

Changes in red wine soluble polysaccharide composition induced by malolactic fermentation

The polysaccharide content of wine is generally assumed to originate from grapes and yeasts, independent of bacterial metabolism, except for the action of certain spoilage species. This study shows that malolactic fermentation (MLF) significantly modifies the soluble polysaccharide (SP) concentration of various red Bordeaux wines. Wines with the highest initial SP concentration go on to present decreased SP concentration, whereas those with the lowest initial SP concentration rather go on to have a higher SP concentration after MLF. These tendencies were observed whatever the Oenococcus oeni strain (indigenous or starter) used for MLF. Neutral and charged SPs were affected, but to a degree that depended on the microorganisms driving the MLF. The SP modifications were directly linked to bacterial development, because non MLF controls did not present any significant change of SP concentration.     

Use of recombinant cyprosin in the manufacture of ewe's milk cheese

A recombinant cyprosin from the cardoon (Cynara cardunculus L.) was assayed and compared with calf rennet in batches of ewes' milk cheese by determining different chemical, biochemical, and microbiological parameters over 4 months of ripening. There were no differences between the two types of coagulants in most chemical parameters, a(w), and pH. Proteolysis was more marked and rapid in cheese containing recombinant cyprosin as coagulant, the soluble nitrogen content of which was significantly higher (p < 0.01) than that of the cheese obtained with animal rennet; at the end of ripening the nonprotein nitrogen of cheese produced with recombinant cyprosin was slightly higher (p > 0.05) as compared with that in cheeses obtained with animal rennet. Microbial counts in the milk used for making cheese were high in most of the groups analyzed. Despite slight differences in counts, the main microbial groups analyzed were similar in cheese produced with both types of coagulants throughout ripening.     

Hydrocarbon and fatty acid composition of cheese as affected by the pasture vegetation type

The determination of the geographical origin of dairy products is an ongoing issue. In this paper the effects of botanical diversity of two pastures on the hydrocarbon and fatty acid composition of cheese fat were studied, over 2 years of experimentation. Two areas in the Italian southwestern Alpine region, dominated by Trifolium alpinum (T) and Festuca nigrescens (F) vegetation, respectively, were chosen, and milk obtained from cows grazing on these pastures was used to produce a semihard traditional cheese. Cheese samples showed a significantly different composition of most linear hydrocarbons, odd-chain (C15, C17, and C17:1) and unsaturated (trans-11,cis-15-C18:2, C18:3, C20:4n-6, C20:4n-3, and 20:5n-3) fatty acids, according to pasture type. The ratio between C(29) and C(27) linear hydrocarbons, unlike the absolute content of the single molecules, showed a good discriminating ability between the two pastures and was little affected by the natural variability due to the climatic and environmental factors.     

Effect of high-pressure treatment on the carotenoid composition and the radical scavenging activity of persimmon fruit purees

The carotenoid composition of persimmon fruit purees of two cultivars, cvs. Rojo Brillante and Sharon, grown in Spain was determined by HPLC to assess the effects of high-pressure processing on some sensory (carotenoids), nutritional (provitamin A value), and health-related (radical-scavenging capacity) parameters. Total carotenoid content was higher in untreated Rojo Brillante puree (22. 11 microg g(-)(1)) than in untreated Sharon puree (15.22 microg g(-)(1)). Purees of both untreated cultivars showed similar carotenoid patterns after saponification with beta-cryptoxanthin, beta-carotene, and zeaxanthin as the main pigments. A high content of lycopene was quantified in Rojo Brillante (5.34 microg g(-)(1)), whereas only traces were detected in Sharon. The provitamin A value, reported as retinol equivalents (RE), was in untreated Rojo Brillante puree (77 RE/100 g) similar to that of Sharon (75 RE/100 g). Scavenging free radical capacity, measured as antiradical efficiency (AE), showed in untreated Rojo Brillante puree a value (12.14 x 10(-)(3)) 8.5 times higher than that in untreated Sharon (1. 42 x 10(-)(3)). Nonuniform behavior of high-pressure treatment was detected. Pressure treatments at 50 and 300 MPa/15 min/25 degrees C for Rojo Brillante and at 50 and 400 MPa/15 min/25 degrees C for Sharon increased the amount of extractable carotenoids (9-27%), which are related with the increase of vitamin A value (75-87 RE/100 g). No correlation with the increase of AE (from 1.42 x 10(-)(3) to 16.73 x 10(-)(3) and 19.58 x 10(-)(3)) after some pressure treatments (150 and 300 MPa/15 min/25 degrees C) was found.     

Changes in the enantiomeric distribution of selected volatile constituents of Mentha pulegium L. powders caused by hot water treatment

The variation, in general, of the composition of the aromatic fraction and, in particular, of the enantiomeric composition of certain chiral volatile compounds of commercial Mentha pulegium L. powders caused by boiling water was evaluated. A comparison between the volatile profile of the studied herbs demonstrated that most M. pulegium L. samples contained high proportions of Mentha piperita L., even when this information was not specified on the label. Likewise, substantial changes in the volatile fraction of the infusions with respect to the composition of the original plant used in their preparation were found. The enantiomeric composition of some chiral compounds of the dried plant material, particularly limonene, was modified by adding hot water, whereas others were kept invariable. The results shown in this work reflect the need for the control of the composition of commercial powders and brews of M. pulegium L. to ensure their correct application.     

Changes in a wetland plant association induced by impoundment and draining

In 1977 a newly constructed gravel access road blocked water flow across a shrub swamp in Tewksbury, Massachusetts, draining one section and impounding another. Within one year, the vegetation in the drained area shifted substantially toward a denser and more species-rich association. After three years the changes slowed, but they had not stopped after six. Many of these changes would not be expected to reverse themselves once a more normal flooding pattern was established. In the newly flooded area there was little changes for the first three years, but after that time many species began to decline in numbers, with the most pronounced effect occurring after five years. Even short-term alterations in the flooding cycle can be expected to have substantial and long-lasting effects on wetland vegetation.     

Proteomic profiling of the coagulation of milk proteins induced by chymosin

Chymosin-induced coagulation of individual milk proteins during incubation at 30 °C was investigated using a proteomic approach. The addition of chymosin (0.006 units/mL) caused the milk proteins to coagulate after a 3 h incubation period. Approximately 88% of the milk proteins were coagulated into the milk pellet fraction, and the protein concentration of the milk supernatant fraction (MSF) decreased from 29.88 ± 0.12 to 3.74 ± 0.13 mg/mL. SDS-PAGE analysis showed that α(S)-, β- and κ-caseins in the MSF were almost depleted and that the total intensity of the protein bands corresponding to α(S)-caseins (α(S1) and α(S2)), β-casein, and κ-casein decreased from 1088.0, 901.5, and 617.0 area units to 6.9, 6.1, and 5.2 area units, respectively. Two-dimensional electrophoresis analysis indicated that α(S1)-, α(S2)-, β-, and κ-casein and a fraction of the β-lactoglobulin and serum albumin were found in the MSF following incubation with chymosin.     

Differential characteristics of fatty acids in cheese from milk of various animal species by capillary gas chromatography

The kind of milk used in the manufacture of cheese has been identified by analysis of the fatty acids. The milk fat is extracted from the cheese and saponified. The methyl esters of the fatty acids are prepared and determined by capillary column gas chromatography. Seven major fatty acids are separated and quantitated, namely, C8:0, C10:0, C12:0, C14:0, C16:0, C18:0, and C18:1. Many of the 21 simple ratios that can be formed from these 7 quantities are characteristic of the type of milk from which the fatty acids were obtained. The method allows the identification of cheese prepared with the milk of cows, buffalo, sheep, or goats. Substitution or adulteration of milk can also be detected.     

Changes in the chemical composition of basil caused by different drying procedures

Basil (Ocimum basilicum L.) leaves were dried using a microwave oven at atmospheric pressure or two traditional methods: air-drying at 50 degrees C and freeze-drying. The microwave-drying was carried out at different powers and times on raw basil leaves, while for air and freeze-drying techniques, both raw and blanched leaves were used. The raw and dried basil was analyzed for selected aroma compounds by gas chromatography/mass spectrometry-selected-ion-monitoring, the chlorophyll a and b by HPLC and the color by a reflected-light colorimeter. For dried samples microwaved for 1 min at 270, 2 min at 440, 1 min at 650, and 1 min at 1100 W, the percentage retentions of the characteristic volatile compounds (eucalyptol, linalool, eugenol, and methyl eugenol) were higher than in the samples dried by traditional methods, with the exception of freeze-dried unblenched basil. Microwave drying allowed a larger retention of chlorophyll pigments than air-drying and freeze-drying (with or without blanching) and preserved the color of the raw basil. Microwave drying requires a much shorter treatment and implied the simultaneous blanching of the material.     

Prediction of the ripening times of ewe's milk cheese by multivariate regression analysis of capillary electrophoresis casein fractions

The effect of the ripening time on the proteolytic process in cheeses made from ewe's milk during a 139-day ripening period was monitored by the use of capillary electrophoresis of pH 4.6 insoluble fraction. Totals of 18 and 21 peaks were recognized and matched in the electropherograms obtained with a fused-silica capillary and a neutral capillary (hydrophilically coated), respectively. These peaks correspond to intact ovine caseins and their hydrolysis products (alpha(s1)-casein I, alpha(s1)-casein II, alpha(s1)-casein III, alpha(s2)-casein, beta(1)-casein, beta(2)-casein, p-kappa-casein, alpha(s1)-I-casein, gamma(1)-casein, gamma(2)-casein, and gamma(3)-casein). The alpha(s)-caseins (alpha(s1)- and alpha(s2)-casein) displayed similar degradation pattern to one another, but different from those of beta-caseins (beta(1)- and beta(2)-casein). beta-Caseins were very much undergoing lesser degradation during the ripening time than alpha(s)-casein. Finally, partial least-squares regression and principal components regression were used to predict the ripening time in cheeses. The models obtained yielded good results since the root-mean-square error in prediction by cross validation was <8.6 days in all cases.     

Chemical and olfactometric characterization of volatile flavor compounds in a fish oil enriched milk emulsion

Development of objectionable fishy off-flavors is an obstacle in the development of fish oil enriched foods. Only little is known about the sensory impact of specific volatile fish oil oxidation products in food emulsions. This study examined the volatiles profiles of fish oil enriched milk during cold storage (2 degrees C) for 14 days by dynamic headspace sampling followed by gas chromatography-mass spectrometry analyses. Different volatiles (n = 60) comprising alkenals, alkadienals, alkatrienals, and vinyl ketones were identified in the fish oil enriched milk. The potent odorants identified by gas chromatography-olfactometry were 1-penten-3-one, (Z)-4-heptenal, 1-octen-3-one, (Z)-1,5-octadien-3-one, (E,E)-2,4-heptadienal, and (E,Z)-2,6-nonadienal, but despite their potency, none of the separated volatiles imparted a fishy or metallic odor. Two isomers, (E,Z,Z) and (E,E,Z) of 2,4,7-decatrienal were identified in fish oil enriched milk emulsions with peroxide values 0.8 and 3.4 meq/kg, respectively. To our knowledge, this is the first report on appearance of these decatrienals in food emulsions having a relatively low peroxide value.     

Determination of the heat treatment undergone by milk by following the denaturation of alpha-lactalbumin with a biosensor

Dairy industries are interested in knowing the heat treatment undergone by milk so as to control the quality of drinking milks or to control their heating systems. Among the different techniques available to characterize the heat treatment of milk, estimation of the denaturation of proteins has been widely used. However, because the concentration of the proteins in raw milk can fluctuate significantly, determining only the concentration of a native protein without knowing its concentration in the raw milk before undergoing heat treatment can lead to significant imprecision. The objective of this study was to develop, on Biacore 3000, a biosensor assay for determining the denaturation index of alpha-lactalbumin by quantifying separately the native and "heat-denatured" forms of alpha-lactalbumin with specific monoclonal antibodies. alpha-Lactalbumin denaturation index is independent of the concentration of alpha-lactalbumin in the original raw milk. The technique developed is discriminating, fast, repeatable, fully automated, and requires no pretreatment of the milk sample.     

Changes in headspace volatile concentrations of coffee brews caused by the roasting process and the brewing procedure

Headspace-solid-phase microextraction technique (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O) were used to characterize the aroma compounds of coffee brews from commercial conventional and torrefacto roasted coffee prepared by filter coffeemaker and espresso machine. A total of 47 volatile compounds were identified and quantified. Principal component analysis (PCA) was applied to differentiate coffee brew samples by volatile compounds. Conventional and torrefacto roasted coffee brews were separated successfully by principal component 1 (68.5% of variance), and filter and espresso ones were separated by principal component 2 (19.5% of variance). By GC olfactometry, a total of 34 aroma compounds have been perceived at least in half of the coffee extracts and among them 28 were identified, among which octanal was identified for the first time as a contributor to coffee brew aroma.     

Comparison of the volatile composition in thyme honeys from several origins in Greece

Thyme honey is the most appreciated unifloral Greek honey in Greece as well as around the world. In an effort to investigate the headspace composition of this type of honey, 28 samples were analyzed by means of solid-phase microextraction coupled to a gas chromatography-mass spectrometry system. The botanical origin of the samples was ascertained by pollen analysis, and samples displayed relative frequencies of thyme pollen between 18 and 41%. A total of 62 compounds were isolated, and phenylacetaldehyde was the most abundant (32.9% of the total peak area). Possible botanical markers are 1-phenyl-2,3-butanedione (13.4%), 3-hydroxy-4-phenyl-2-butanone, 3-hydroxy-1-phenyl-2-butanone (14.7%), phenylacetonitrile (4.8%), and carvacrol (0.9%), since these compounds are found only in thyme honey. Additionally, high proportions of phenylacetaldehyde are also characteristic ( F = 12.282, p < 0.001). The average concentrations of seven compounds were significantly different ( p < 0.05), namely phenylacetaldehyde, acetophenone, octanoic acid, carvacrol, phenylethyl alcohol, nonanal, and hexadecane. Applying principal component analysis to the data, six components were extracted, explaining 85.4% of the total variance. The first component explained 46.2% of the total variance and was positively correlated to phenylacetaldehyde, nonanoic acid, acetophenone, decanoic acid, benzaldehyde, phenylacetonitrile, isophorone, and nonanal. The extracted components were used as variables to the discriminant analysis, which showed good discrimination, especially for samples from Crete. A leave-one-out classification showed 85.7% of cross-validated grouped cases correctly classified. These results are promising to establish a discrimination model for these geographical regions. This is crucial for local beekeeper corporations on their effort to produce honey with geographical origin label.     

Comparison of the volatile constituents in cold-pressed bergamot oil and a volatile oil isolated by vacuum distillation

The vacuum distillation of bergamot peels furnishes a high-quality essential oil that is totally bergapten-free. This oil was compared with that produced by distillation of cold-pressed oils and those commercially available. The oil obtained by vacuum distillation of the bergamot vegetable matrix shows a composition quite similar to that of the cold-pressed oil. It also displays qualitative characteristics that are superior with respect to those normally observed for essential oils isolated by distillation of cold-pressed oils. Oils isolated by the method presented here can constitute ideal candidates in producing foods, for example, Earl Grey tea, and cosmetic preparations.