共查询到20条相似文献,搜索用时 15 毫秒
1.
Thermoxidation of substrate models and their behavior during hydrolysis by porcine pancreatic lipase
Ruth Arroyo Francisco J. Sánchez-Muniz Carmen Cuesta José V. Sinisterra José M. Sánchez-Montero 《Journal of the American Oil Chemists' Society》1997,74(12):1509-1516
The behavior of thermoxidized triacylglycerols during hydrolysis catalyzed by porcine pancreatic lipase was evaluated using
nonpolar triacylglycerols isolated from palm olein (NPTPO), triolein, and sn-1,3 diolein substrates. Substrates were thermoxidized at 180°C for 1 to 4 h. Owing to formation of polymers and dimers of
triacylglycerols, the molecular weight of the thermoxidized substrates increased. After 1 h heating, the concentration of
polymers and dimers was similar for the sn-1-3 diolein and triolein samples but higher in NPTPO samples. Conjugated double bonds were formed in all samples, and α,β-unsaturated
carbonyl compounds developed through allylic oxidations. These caused increased ultraviolet absorbance at 232 nm. The hydrolysis
of heated and unheated samples by the lipase can be described by a Michaelian equation. The enzyme showed a higher apparent
V
max and K
M
with heated sn-1,3 diolein and triolein than with their unheated counterparts. This was due to the generation of polar compounds which acted
as emulsifiers and which favored the formation of an oil/water microemulsion. This behavior was not observed in NPTPO, where
heating decreased the apparent V
max and K
M
over the first 2 h. Later, a tendency to increase these values was observed. The results could be explained by a balance between
concentration of surfactants and of natural emulsifiers in the thermoxidized samples. 相似文献
2.
Sergio Cruz Khaled Yousfi Jesús Oliva José M. García 《Journal of the American Oil Chemists' Society》2007,84(11):1063-1068
To determine the effect of hot water pre-treatment on olive oil extraction, six cultivars of olive fruit (Olea europaea L. cvs. “Arbequina”, “Hojiblanca”, “Lechín”, “Manzanilla”, “Picual”, and “Verdial”) were heated at 50, 55, and 60 °C prior
to laboratory scale oil extraction. Heat treatment resulted in higher oil extraction than unheated control samples. Quality
parameters of the oils were not significantly (P < 0.05) affected by these treatments; however, oil stability and bitterness intensity were reduced and pigment content was
increased through pre-heat treatment. This process may be incorporated economically into olive oil processing. 相似文献
3.
Frying Quality Characteristics of French Fries Prepared in Refined Olive Oil and Palm Olein 总被引:2,自引:0,他引:2
Elham Tabee Margaretha Jägerstad Paresh C. Dutta 《Journal of the American Oil Chemists' Society》2009,86(9):885-893
The objective of this study was to compare two oils with different polyunsaturated/saturated (P/S) fatty acid ratios, refined
olive oil (P/S 0.75) and palm olein (P/S 0.25), in frying French fries. The chemical qualities of the oil residues extracted
from the French fries were assayed for five consecutive batches fried at 1-h intervals. The levels of total polar compounds,
free fatty acids, p-anisidine value and phytosterol oxidation products (POPs) were elevated in French fries fried in both oils. The level of total
polar compounds increased from 4.6 in fresh refined olive oil to 7.3% in final batches of French fries. The corresponding
figures for palm olein were 9.8–13.8%. The level of free fatty acid in fresh refined olive oil increased from 0.06 to 0.11%
in final products. These figures for palm olein were 0.04–0.13%. The p-anisidine value increased from 3.7 to 32.8 and 2.5 to 53.4 in fresh oils and in final batches of French fries in refined
olive oil and palm olein, respectively. The total amount of POPs in fresh refined olive oil increased from 5.1 to 9.6 μg/g
oil in final products. These figures were 1.9 to 5.3 μg/g oil for palm olein. 相似文献
4.
Effect of natural antioxidants in virgin olive oil on oxidative stability of refined,bleached, and deodorized olive oil 总被引:1,自引:0,他引:1
M. Teresa Satue Shu-Wen Huang Edwin N. Frankel 《Journal of the American Oil Chemists' Society》1995,72(10):1131-1137
The factors influencing the oxidative stability of different commercial olive oils were evaluated. Comparisons were made of
(i) the oxidative stability of commercial olive oils with that of a refined, bleached, and deodorized (RBD) olive oil, and
(ii) the antioxidant activity of a mixture of phenolic compounds extracted from virgin olive oil with that of pure compounds
andα-tocopherol added to RBD olive oil. The progress of oxidation at 60°C was followed by measuring both the formation (peroxide
value, PV) and the decomposition (hexanal and volatiles) of hydroperoxides. The trends in antioxidant activity were different
according to whether PV or hexanal were measured. Although the virgin olive oils contained higher levels of phenolic compounds
than did the refined and RBD oils, their oxidative stability was significantly decreased by their high initial PV. Phenolic
compounds extracted from virgin olive oils increased the oxidative stability of RBD olive oil. On the basis of PV, the phenol
extract had the best antioxidant activity at 50 ppm, as gallic acid equivalents, but on the basis of hexanal formation, better
antioxidant activity was observed at 100 and 200 ppm.α-Tocopherol behaved as a prooxidant at high concentrations (>250 ppm) on the basis of PV, but was more effective than the
other antioxidants in inhibiting hexanal formation in RBD olive oil.o-Diphenols (caffeic acid) and, to a lesser extent, substitutedo-diphenols (ferulic and vanillic acids), showed better antioxidant activity than monophenols (p- ando-coumaric), based on both PV and hexanal formation. This study emphasizes the need to measure at least two oxidation parameters
to better evaluate antioxidants and the oxidative stability of olive oils. The antioxidant effectiveness of phenolic compounds
in virgin olive oils can be significantly diminished in oils if their initial PV are too high. 相似文献
5.
G. Márquez-Ruiz M. C. Pérez-Camino M. C. Dobarganes 《Journal of the American Oil Chemists' Society》1992,69(9):930-934
This study was designed to determine digestibilities of fatty acid monomers, dimers and polymers as components of diets containing
thermally oxidized oils. Male Wistar rats were fed semipurified diets supplemented with unheated, heated and a 1:1 mixture
of unheated/heated olive oils at 6, 12 and 20% w/w of diet. In a 14-d experimental period, fecal lipids were extracted and
analyzed by a combination of adsorption and high-performance size-exclusion chromatographies. Thus, it was possible to separate
and quantitate five groups of fatty acids—nonpolar monomers, oxidized monomers, nonpolar dimers, oxidized dimers and polymers.
Nonpolar fatty acid monomers showed high digestibilities, although significantly influenced by the alteration level of the
dietary oil. The apparent absorption of oxidized fatty acid monomers averaged 76.6%. Among polymeric fatty acids, the lowest
digestibilities were found for nonpolar dimers (10.9% on average), whereas oxidized dimers and polymers possessed higher apparent
absorbability than expected, ranging from 22.7% to 49.6%. Chemical modifications prior to absorption, leading to less complex
products, may have contributed to enhanced digestibility of polymers. 相似文献
6.
Rosario Zamora Gemma Gómez M. Carmen Dobarganes Francisco J. Hidalgo 《Journal of the American Oil Chemists' Society》2002,79(3):261-266
One hundred nine oil samples were separated chromatographically to obtain oil fractions with a decreased TAG content but with
enhanced levels of the minor components that define oil genuineness and quality. The oils, which included virgin olive oils
from different cultivars and regions of Europe and north Africa and refined olive, “lampante” olive, refined olive pomace,
hazelnut, rapeseed, high-oleic sunflower, corn, grapeseed, soybean, and sunflower oils, were fractionated on a silica gel
column with hexane/diethyl ether as the mobile phase eluent. The method was highly reproducible, and the fraction obtained
contained about 15% unmodified TAG and 85% polar compounds, which included polymeric TAG, oxidized TAG, DAG, MAG, and FFA,
in addition to other minor polar components of the oils. The presence of these compounds, in an enriched fraction, should
provide information about the thermal, oxidative, and hydrolytic alterations of the oils, as well as many compounds of interest
in determining oil genuineness. The results indicate that these fractions can provide more information than the original oils
for NMR or other spectroscopic studies used in the determination of oil quality. 相似文献
7.
Fitó M Covas MI Lamuela-Raventós RM Vila J Torrents L de la Torre C Marrugat J 《Lipids》2000,35(6):633-638
The protective effect of phenolic compounds from an olive oil extract, and of olive oils with (extra-virgin) and without (refined)
phenolic components, on low density lipoprotein (LDL) oxidation was investigated. When added to isolated LDL, phenolics [0.025–0.3
mg/L caffeic acid equivalents (CAE)] increased the lag time of conjugated diene formation after copper-mediated LDL oxidation
in a concentration-dependent manner. Concentrations of phenolics greater than 20 mg/L inhibited formation of thiobarbituric-acid
reactive substances after AAPH-initiated LDL oxidation. LDL isolated from plasma after preincubation with phenolics (25–160
mg/L CAE) showed a concentration-dependent increase in the lag time of conjugated diene formation after copper-mediated LDL
oxidation. Refined olive oil (0 mg/L CAE) and extra-virgin olive oil (0.1 and 0.3 mg/L CAE) added to isolated LDL caused an
increase in the lag time of conjugated diene formation after copper-mediated LDL oxidation that was related to olive oil phenolic
content. Multiple regression analysis showed that phenolics were significantly associated with the increase in lag time after
adjustment for effects of other antioxidants; α-tocopherol also achieved a statistically significant effect. These results
indicate that olive oil phenolic compounds protect LDL against peroxyl radical-dependent and metal-induced oxidation in vitro and could associate with LDL after their incubation with plasma. Both types of olive oil protect LDL from oxidation. Olive
oil containing phenolics, however, shows more antioxidant effect on LDL oxidation than refined olive oil. 相似文献
8.
The relationships between FA and the volatile profiles of olive and walnut oils from Argentina were studied using GC and solid-phase
microextraction coupled with GC-MS. The major volatiles were aldehydes and hydrocarbons, produced mainly through the oxidative
pathways. n-Pentane, nonanal, and 2,4-decadienal were predominant in walnut oils, whereas nonanal, 2-decenal, and 2-undecenal were the
most abundant components in olive oils. A multivariate analysis applied to the chemical data emphasized the differences between
the oils and allowed us to see a pattern of covariation among the FA and the volatile compounds. The main differences between
walnut and olive oils were the presence of larger amounts of short-chain (C5–C6) saturated hydrocarbons and aldehydes in the former and the greater quantities of medium-chain (C7–C11) compounds in olive oil. This can be explained by their different origins, mainly from the linoleic acid in walnut oil or
almost exclusively from the oleic acid in olive oil. 相似文献
9.
Reports on the methylsterol fractions of hazelnut oils are scarce. The objectives of this study were to characterize methylsterols
in hazelnut and virgin olive oils and to study the possibility of detection of adulteration of virgin olive oils. In hazelnut
oils, 4-desmethylsterols were present in higher proportions (86 to 91%) than in virgin olive oils where this fraction was
ca. 50% of the total sterol. In the 4-monomethylsterol fraction, citrostadienol was the major component in both kinds of oils
followed by cycloeucalenol and obtusifoliol in virgin olive oils, and obtusifoliol in hazelnut oils. 24-Methylenecycloartanol
was predominant in both kinds of oils in the 4,4′-dimethylsterols. For the first time, δ-amyrin was tentatively identified
by comparing published mass spectral data in the analyzed samples of both kinds of oils. An unknown compound X (containing
a lupane skeleton) and lupeol were detected only in the 4,4′-dimethylsterols fraction of hazelnut oils at a level of 2–8 and
6–10%, respectively. GC-MS analysis showed that adulteration of virgin olive oil by hazelnut oil could be detected at a level
less than 4% by using these two compounds as possible potential markers. 相似文献
10.
In this study, the effect of deep fat frying on oil degradation, total phenols (TP) and total antioxidant activity (TAA) of
hazelnut, corn, soybean and olive oils were investigated. Oil degradation and oxidation were monitored by measuring the total
polar compounds (TPC) and the peroxide value (PV). The amount of TPC in corn, soybean and olive oils increased significantly
with the time increment (p < 0.05). The PV of the oils did not exceed the maximum acceptable limit of 10 mequiv O2/kg after 125 min frying except for hazelnut oil (10.64 mequiv O2/kg). Deep-fat frying did not cause any significant change in the TP of corn oil, soybean oil and olive oil (p < 0.05). A significant decrease in the antioxidant activity was observed after 50 min frying using hazelnut oil and corn
oil (p < 0.05). However, the antioxidant activity of soybean oil and olive oil significantly decreased after 75 and 25 min frying,
respectively. 相似文献
11.
Dietary oils—tuna, salmon, cod liver, soybean, olive, and corn oils—were treated with accelerated storage conditions (60°C
for 3 and 7 d) and a cooking condition (200°C for 1 h). Genotoxic malonaldehyde (MA), glyoxal, and methylglyoxal formed in
the oils were analyzed by GC. Salmon oil produced the greatest amount of MA (1070±77.0 ppm of oil) when it was heated at 60°C
for 7 d. The highest formation of glyoxal was obtained from salmon oil heated at 60°C for 3 d. More glyoxal was found from
salmon and cod liver oils when they were heated for 3 d (12.8±1.10 and 7.07±0.19 ppm, respectively) than for 7d (6.70±0.08
and 5.94±0.38 ppm, respectively), suggesting that glyoxal underwent secondary reactions during a prolonged time. The amount
of methyglyoxal formed ranged from 2.03±0.13 (cod liver oil) to 2.89±0.11 ppm (tuna oil) in the fish oils heated at 60°C for
7 d. Among vegetable oils, only olive oil yielded methylglyoxal (0.61±0.03 ppm) under accelerated storage conditions. When
oils were treated under cooking conditions, the aldehydes formed were comparable to those formed under accelerated storage
conditions. Fish oils produced more MA, glyoxal, and methylglyoxal than did vegetable oils because the fish oils contained
higher levels of long-chain PUFA, such as EPA and DHA, than did the vegetable oils. A statistically significant correlation
(P<0.05) between the α-tocopherol content and the oxidation parameters was obtained from only MA and fish oils heated at 60°C
for 3 d. 相似文献
12.
Chlorophyll and β-carotene concentrations were determined by high-performance liquid chromatography (HPLC) in virgin olive
oils, which were press-extracted from green and semi-black olives. Pheophytin A was found to be the major chlorophyll isomer
in all oil samples. The occurrence of this pigment at higher concentrations in oil extracted from green olives is a possible
indication of its time-related destruction during olive ripening. Some evidence for thein vivo existence of pheophytin A is also presented. Beta-carotene concentration in oils was found to decrease during olive ripening. 相似文献
13.
Oxidative Evolution of Virgin and Flavored Olive Oils Under Thermo-oxidation Processes 总被引:1,自引:0,他引:1
Manel Issaoui Guido Flamini Myriem Ellouze Hajaij Pier Luigi Cioni Mohamed Hammami 《Journal of the American Oil Chemists' Society》2011,88(9):1339-1350
Changes in the oxidative status of Chétoui olive oil were monitored to attest the efficiency of some bioactive compounds from
aromatic plants to improve the stability of olive oils after a maceration process at different concentrations. Aromatized
olive oils were prepared by addition of lemon and thyme extracts at four different concentrations (20–80 g kg−1 of oils) to virgin olive oils. The following parameters were monitored: free fatty acids, peroxide value, ultra violet absorption
characteristics at 232 and 270 nm, fatty acid composition and aromatic profiles. After thermo-oxidation processes, the oleic/linoleic
acid ratio remained stable (4.5). Oxidative stability slightly decreased during thermo-oxidation processes. The heating of
the oils changed their volatile profile and led to the formation of new volatile compounds, such as the two isomers of 2,4-heptadienal
after heating at 100 °C or (E,Z)-2,4-decadienal and (E,E)-2,4-decadienal after thermo-oxidation at 200 °C. The use of lemon and thyme extracts modified the aromatic and the nutritional
value of the olive oil by the transfer of some bioactive compounds, such as limonene and carvacrol. In contrast, the oxidative
stability of the product did not change. Furthermore, the aromatized oils may be employed in seasoning and cooking of some
foods. 相似文献
14.
M. Tasioula-Margari G. Márquez-Ruíz M. C. Dobarganes 《Journal of the American Oil Chemists' Society》1996,73(11):1579-1584
Precipitates enriched in oligomeric triacylglycerides were separated from thermally oxidized olive residue oil, conventional
and high-oleic sunflower oils, and soybean oil by solvent fractionation in methanol/acetone at 4–5°C for 16 h. Different fractionation
conditions were evaluated in an effort to isolate the oligomeric triacylglycerides (OTG). OTG, formed in frying oils upon
heating at low concentations, were not detectable with conventional methods to determine polymeric compounds. The best conditions
found from the different assays were the following: (i) weight of oil sample-to-solvent volume ratio of 1∶20; and (ii) solvent
system methanol/acetone 10∶90 (vol/vol) for monounsaturated oils and 15∶85 (vol/vol) for polyunsaturated oils. Precipitates,
enriched in oligomers, were formed when heated oils and used frying oils contained more than 27% polar compounds, a value
which is widely accepted as the upper limit for use of frying oils. 相似文献
15.
The purpose of this investigation was to study differences in the chlorophyll, carotenoid, and phenolic fractions of virgin
olive oils from the Arbequina variety cultivated in different olive growing areas of Spain. Virgin olive oil from Lleida was
less heavily pigmented, and these oils showed more negative values for the ordinate a* (of the CIELAB colorimetric system). Pheophytin a was the major chlorophyll pigment, and lutein was the major component of the carotenoid fraction in all oils analyzed. The
chlorophyll a concentration in virgin olive oils from Lleida was 700 μg kg−1, but was 175 μg kg−1 in oils from Jaén, and 200 μg kg−1 in oils from Tarragona. Finally, the chlorophyll a/chlorophyll b ratio was 9 in oils from Lleida and around 0.6 in the other two Arbequina olive oils. In relation to the phenolic fraction,
the hydroxytyrosol and tyrosol contents were significantly higher in olive oils from Jaén (grown at higher altitude and precipitation
rates). The secoiridoid derivatives showed a significantly higher concentration in olive oils from Tarragona, probably due
to the low altitude where they grow, and finally the ratio of (dialdehydic form of elenolic acid linked to tyrosol)/lignans
had a value of 1.4 in olive oils from Lleida, whereas this value was around 0.7 in the other Arbequina olive oils. 相似文献
16.
Ana G. Pérez Carmen Romero Khaled Yousfi José M. García 《Journal of the American Oil Chemists' Society》2008,85(7):685-691
The use of four concentrations of common salt (NaCl) used as coadjuvant for the extraction of virgin olive oil has been tested
on a laboratory scale and the quality attributes of the oils obtained were compared to those obtained with talc as coadjuvant.
The oils extracted from Picual fruits after NaCl addition were not significantly affected in terms of the physicochemical
requirements established for extra virgin olive oil, the best level of quality of this produce. Addition of NaCl during the
extraction process was positively correlated with the presence of o-diphenol compounds and the stability of the oils obtained. Moreover the use of NaCl resulted in a significant increase in
contents of pigments (β-carotene, lutein and chlorophylls a and b) and volatile compounds in the oils. 相似文献
17.
Georgios Kalantzakis Georgios Blekas 《European Journal of Lipid Science and Technology》2006,108(10):842-847
The effect of ethanol and acetone extracts obtained from Greek sage (Salvia fruticosa) and summer savory (Satureja hortensis L.) on the thermal stability of vegetable oils heated at frying temperature (180 °C) was studied. Virgin olive oil (VOO), refined olive oil (ROO), sunflower oil (SO), and a commercial oil blend suitable for frying (BL), enriched with each extract obtained from the two plant materials at a concentration of 3 g/kg oil, were heated at 180 °C for 10 h. Changes during heating were assessed by quantification of total polar materials and determination of p‐anisidine values. The acetone extract obtained from Greek sage showed a better inhibitory effect against thermal oxidation of heated refined oils (BL, ROO, SO) than the respective ethanol extract, although the latter was found to have a relatively higher total phenol content. Both summer savory extracts effectively retarded the thermal oxidation reactions during oil heating, showing a more pronounced effect than the Greek sage acetone extract. The activity of the acetone extract obtained from summer savory was stronger (SO, BL) or similar (ROO, VOO) to that of the summer savory ethanol extract, although the latter was found to have a higher total phenol content. 相似文献
18.
Derya Alkan Figen Tokatli Banu Ozen 《Journal of the American Oil Chemists' Society》2012,89(2):261-268
The aim of this research was to characterize the extra virgin olive oil samples from different locations in the Aegean coastal
area of Turkey in terms of their phenolic compositions for two consecutive years to show the classification of oil samples
with respect to harvest year and geography. Forty seven commercial olive oil samples were analyzed with HPLC–DAD, and 17 phenolic
compounds were quantified. Hydroxytyrosol, tyrosol, vanillic acid, p-coumaric acid, ferulic acid, cinnamic acid, luteolin and apigenin were the characteristic phenols observed in all oil samples
for two harvest years. Syringic acid, vanillin and m-coumaric acid were the phenolic compounds appeared in the olive oil depending on the harvest year. Partial least square-discriminant
analysis (PLS-DA) of data revealed that oils from the north Aegean and south Aegean areas had different phenolic profiles.
The phenolic compounds, which played significant roles in the discrimination of the olive oils, were tyrosol, oleuropein aglycon,
cinnamic acid, apigenin and hydroxytyrosol to tyrosol ratio. The Aegean coastal region is the largest olive oil producer and
exporter of Turkey. This study shows that the olive oils from different parts of the region have their own defining characteristics
that can be used in the authentication studies and geographical labeling of Turkish olive oils. 相似文献
19.
Evaluation of Authenticity of Iranian Olive Oil by Fatty Acid and Triacylglycerol Profiles 总被引:4,自引:0,他引:4
Z. Piravi-Vanak M. Ghavami H. Ezzatpanah J. Arab H. Safafar Jahan B. Ghasemi 《Journal of the American Oil Chemists' Society》2009,86(9):827-833
For evaluation of the authenticity of Iranian olive oil, samples from many Iranian olive oil producers especially north of
Iran in the production year 2007 were collected. The fatty acid and triacylglycerol compositions were measured. The most recent
calculation methods including ∆ECN the difference between the actual and theoretical ECN42 (equivalent carbon number), triglyceride
content and R of olive oils according to IOOC methods were applied. On the basis of our results, we were able to classify
the olive oils into the extra virgin, virgin olive and olive oil categories. The important fatty acids are oleic, palmitic
and linoleic acids and their main triacylglycerols are OOO, POO, OOL, PLO, SOS plus POP, and OLL, respectively. On the basis
of the triacylglycerol results, experimental ECN48, ECN46, ECN50, ECN44 and ECN42 were obtained. By using the fatty acids
results and a computer program, the theoretical ECN42 and ECN44 were calculated. Then R values, being the ratio of r ECN42/r ECN44 for authenticity of all olive oils and ∆ECN for determining categories of olive oils, were defined. The results of
olive oil samples were in the accepted limits of Codex and IOOC. Finally we suggest that the R and ∆ECN can be used in identification of adulteration of olive oils and also they are useful from the point of view of authenticity
and classification. 相似文献
20.
M. Andjelkovic S. Acun V. Van Hoed R. Verhé J. Van Camp 《Journal of the American Oil Chemists' Society》2009,86(2):135-140
Although large amounts of olive oil are produced in Turkey, not much information on its chemical composition is available
in the literature to date. The aim of this study was to evaluate the chemical composition of commercial olive oils produced
from the Ayvalik olive cultivar in Canakkale, Turkey. Five different samples corresponding to the olive oil categories of
extra virgin (conventional, extra virgin olive oil (EVOO), and organic extra virgin olive oil (OGOO) production), virgin olive
oil (OO-1), ordinary virgin olive oil (OO-2) and refined olive oil (RFOO) were evaluated. Olive oils were collected from two
consecutive production years. According to the free fatty acids, the absorbance values (K232 and K270), and peroxide values of all the samples conformed to the European standards for olive oil. The level of oleic acid was in
the range of 68–73%; while the linoleic acid content was significantly lower in the refined olive oils. The tocopherol and
polyphenol content was in the lower range of some European olive oils. However, pinoresinol was a major phenolic compound
(5–77 mg/kg depending on the oil category). Its content was markedly higher than in many other oils, which would be a useful
finding for olive oil authentication purposes. 相似文献