共查询到20条相似文献,搜索用时 19 毫秒
1.
The induction times for the crystallization, under isothermal conditions, of refined, bleached, and deodorized palm oil from
the melt were studied by viscometry. At temperatures below 295 K, the crystallization of palm oil was observed to occur in
a two-stage process. This two-stage process was caused by the fractionation of palm oil, most probably into the stearin and
olein fractions. At temperatures higher than 295 K, only a single-stage crystallization process was observed. As seen under
polarized light microscopy, spherical crystals were initially formed from the first fraction at temperatures from 287 to 293
K. The diameters of these spherical crystals decreased as the temperature increased. After that, needle-shaped crystals were
formed from the second fraction and continued to grow from the surface of these spherical crystals until the spherical crystals
were fully enclosed, i.e., the cocrystallization of two polymorphs was observed. At temperatures higher than 293 K, the needle-shaped
crystals formed from a mixture of the two fractions were found to be the only polymorphs developed with the onset of crystallization.
X-ray diffraction results showed that for temperatures below 295 K, the spherical crystals formed from the first fraction
were in α form, whereas the needle-like crystals that nucleated later from the second fraction were in β′ form. β′ crystals
were the only polymorphs formed for temperatures above 295 K. The results obtained were in good agreement with the discontinuity
observed in the induction time vs. temperature curve. Activation free energies for nucleation were calculated according to
the Fisher-Turnbull equation for the various polymorphic forms. Viscometry was observed to be a sensitive method for characterizing
the overall crystallization process. This technique is suitable for induction time studies of palm oil crystallization, especially
at lower temperatures and with viscous oil. 相似文献
2.
The addition of antioxidants butylated hydroxytoluene (BHT), propyl gallate (PG), tertiary butylhydroquinone (TBHQ), dilaurylthiodipropionate
(DLTDP), and trihydroxybutyrophenone (THBP) at a level of 200 ppm to refined, bleached and deodorized (RBD) palm olein resulted
in the retardation of the oxidative deterioration of the oil when stored at 60 C for a period of 10 weeks. The extent of oxidative
deterioration was determined by measuring the peroxide and anisidine values and E
1 cm
1%
at 232 nm and 268 nm of the oil. Butylated hydroxyanisole (BHA) proved to be a relatively ineffective antioxidant, whereas
TBHQ afforded the most protection for the RBD olein. 相似文献
3.
The addition of antioxidants propyl gallate (PG), α-tocopherol and ethoxyquin at a level of 250 ppm to refined, bleached avocado
oil resulted in the retardation of the oxidative deterioration of the oil when it was stored in the dark at room temperature,
exposed to daylight at room temperature (on the shelf) and at 60 C.
The extent of oxidation was followed by measuring the peroxide and anisidine values and oil color. Ethoxyquin and α-tocopherol
were relatively ineffective antioxidants, whereas PG greatly improved the stability of avocado oil stored in the dark at 60
C, but not in oil exposed to daylight. 相似文献
4.
N. N. Nkpa T. A. Arowolo F. C. Osanu 《Journal of the American Oil Chemists' Society》1992,69(9):854-857
Refined, bleached, deodorized palm oil (RBD palm oil) was packaged in lacquered metal cans (LMC), green glass bottles (GGB),
amber glass bottles (AGB), clear glass bottles (CGB), clear plastic bottles (CPB) and sealed polyethylene film (POLET), and
stored in direct sunlight (40 ± 1°C) or in darkness (27 ± 1°C). Measurements of free fatty acid (FFA), peroxide value and
anisidine value, at 14-day intervals for a period of 98 days, were used to assess the stability of the oil towards hydrolytic
and oxidative deterioration. Total oxidation values for packaged oils stored in direct sunlight showed that LMC gave the greatest
protection against oxidative deterioration, followed by GGB and AGB. POLET offered the least protection to the oil against
oxidative deterioration, while CPB and CGB proved superior to POLET but inferior to GGB and AGB. For storage in the dark,
LMC, AGB and GGB gave the greatest protection to RBD palm oil against oxidative deterioration, with no significant statistical
differences between them, while CPB, CGB and POLET followed in that order, with significant differences between their respective
abilities to protect the oil against oxidative deterioration. Oils packaged in CPB gave the highest FFA levels (statistically
significant). The investigations clearly indicated that LMC is superior to all other tested packaging materials in offering
maximum protection to RBD palm oil against hydrolytic and oxidative deterioration. Amber and green glass bottles could serve
as viable alternatives to LMC, while CGB and CPB could be tolerated as suitable packaging systems for RBD palm oil. However,
the study also clearly showed that POLET is unsatisfactory for use as packaging material for RBD palm oil. 相似文献
5.
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
6.
Y. A. Tan S. H. Ong K. G. Berger H. H. Oon B. L. Poh 《Journal of the American Oil Chemists' Society》1985,62(6):999-1006
One of the most obvious changes when oils are heated is color darkening. Palm oil darkens very rapidly compared to other oils. The cause of this rapid color development was investigated. Various methods used to pretreat Lotox crude palm oil (CPO) to retard darkening during heating were by agitation with activated carbon S511, by water and water/isopropyl alcohol (95:5) washing of neutralized and unneutralized oil, and by liquid/liquid extraction of oil using water and water/isopropyl (95:5). Pretreatment of CPO did succeed in retarding color development. Retardation was especially evident in oils previously neutralized with sodium hydroxide before washing with water and water/isopropyl alcohol. The UV spectra of the liquid/liquid extracts showed strong absorption maxima at 256 nm. The addition of a base resulted in darkening of the extracts accompanied by shifts to longer wavelengths (288 nm). Reaction with freshly diluted 1–2% ferric chloride solution gave a brown color. The development of paper chromatography in butanol: acetic acid:water (6:1:2) revealed a blue fluorescence near the solvent front, with the same relative retention time as that of tannic acid. This evidence indicates that phenolic compounds were responsible for color darkening in palm oil. 相似文献
7.
Peck Hong Yap J. M. de Man L. de Man 《Journal of the American Oil Chemists' Society》1989,66(5):693-697
Palm oil, palm stearin, hydrogenated palm oil (IV 27.5) and hydrogenated palm olein (IV 28) were crystallized at 5°C, temperature
cycled between 5 and 20°C, and kept isothermally at 5°C for 36 days. The polymorphic state of the fats was monitored by X-ray
diffraction analysis. Soft laser scanning of X-ray films was used to establish the increase inβ crystal content. Palm stearin was least stable in theβ′ form, followed by palm oil. The hydrogenated oils were very stable in theβ′ form. Differential scanning calorimeter (DSC) analysis was used to complement the X-ray data. 相似文献
8.
T. Haryati Y. B. Che Man P. Z. Swe 《Journal of the American Oil Chemists' Society》1997,74(4):393-396
Thermal behavior of crude palm oil (CPO) is important to determine the optimal fractionation process and product yield. In
this study, the effects of repeated heating on thermal behavior of CPO were examined by differential scanning calorimetry.
CPO was heated at 80°C for 5 min, and heating was repeated five times to simulate the common conditions experienced by an
oil before reaching the refinery. The result revealed that the thermal behavior of CPO changed after heating. The change,
however, occurred only in the behavior of the high-melting stearin peak but not in the low-melting olein peak. Overheating
split the stearin peak at 17.30°C to two peaks at 18.88 and 17.30°C and formed a new peak at 11.28°C. Apparently, a new substance
has been synthesized. 相似文献
9.
Nnadozie N. Nkpa F. C. Osanu T. A. Arowolo 《Journal of the American Oil Chemists' Society》1990,67(4):259-263
Lacquered metal cans, green glass bottles, amber glass bottles, clear glass bottles and clear plastic bottles filled with
freshly produced Nigerian crude palm oil were stored in direct sunlight (40±1°C) and in the dark (27±1°C). Assessment of the
stability of the oils towards hydrolytic and oxidative deterioration was made periodically by measuring the free fatty acid,
peroxide and anisidine values over a period of 98 days. The study showed that crude palm oil packaged in plastic bottles and
clear glass bottles recorded higher total oxidation values than oils packaged in either lacquered metal cans or amber and
green glass bottles. Lacquered metal cans gave the greatest protection against oxidation. Oxidation proceeded faster in cases
where the packaging materials were stored in direct sunlight. 相似文献
10.
The aim of this study was to find out how the refining process affects the susceptibility of rice bran oil to oxygen of air at high temperature. Samples of crude and refined rice bran oil were heated at 180 °C for 8 h with and without stirring in laboratory‐scale experiments. After every 30 min, samples were taken for analysis. The influence of stirring on rice bran oil heat stability was related to the loss of tocopherols and sterols, and to the thermooxidative state of the samples, which was evaluated according to polymer formation and changes occurring in fatty acid composition and triacylglycerol (TAG) structure. The results demonstrated a significant loss of natural antioxidants during the heating process with stirring, accompanied by a decrease in the levels of linoleic acid (18:2) and TAG (LLO, LLP and OLO) which resulted in a substantial increase of polymer TAG. The unsaturated fatty acids in the sn‐2 and sn‐1,3 positions were differently affected during the heating process. 相似文献
11.
12.
Effects of natural and synthetic antioxidants on changes in refined, bleached, and deodorized palm olein during deep-fat frying of potato chips 总被引:2,自引:0,他引:2
The effects of antioxidants on the changes in quality characteristics of refined, bleached, and deodorized (RBD) palm olein
during deep-fat frying (at 180°C) of potato chips for 3.5 h/d for seven consecutive days in five systems were compared in
this study. The systems were RBD palm olein without antioxidant (control), with 200 ppm butylated hydroxytoluene (BHT), 200
ppm butylated hydroxyanisole (BHA), 200 ppm oleoresin rosemary, and 200 ppm sage extract. Fried oil samples were analyzed
for peroxide value (PV), thiobarbituric acid (TBA) value, iodine value (IV), free fatty acid (FFA) content, polymer content,
viscosity, E1%
1 cm at 232 and 268 nm, color, fatty acid composition, and C18:2/C16:0 ratio. Sensory quality of the potato chips fried in these systems prior to storage was also evaluated. The storage stability
of fried potato chips for 14 wk at ambient temperature was also determined by means of the TBA values and sensory evaluation
for rancid odor. Generally, in the oil, oleoresin rosemary gave the lowest rate of increase of TBA value, polymer content,
viscosity, E1%
1 cm at 232 and 268 nm compared to control and three other antioxidants. The order of effectiveness (P<0.05) in inhibiting oil oxidation in RBD palm olein was oleoresin rosemary > BHA > sage extract > BHT > control. Prior to
storage, the sensory evaluation of fried potato chips for each system showed that there was no significant (P>0.05) difference in terms of flavor, odor, texture, and overall acceptability. The same order of effectiveness (P<0.05) of antioxidants was observed for storage stability study of fried potato chips by TBA values. However, there was no
significant (P > 0.05) difference in sensory evaluation for rancid odor during storage periods. 相似文献
13.
A. K. Kiritsakis C. M. Stine L. R. Dugan 《Journal of the American Oil Chemists' Society》1983,60(7):1286-1290
Virgin unrefined olive oil was protected from oxidation with the antioxidants butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and tertiary butylhydroquinone (TBHQ) and in one case propyl gallate (PG). All the antioxidants improved the stability of olive oil under accelerated conditions (oven test) and storage conditions at 50 C. In the oven test, where the type of oil used was the same as that used in long-term storage studies (room temperature and 50 C) the relative inhibition effect of the antioxidants was in the following order: TBHQ = BHA > BHT. The combinations of BHA and BHT with TBHQ displayed better stabilizing qualities. Antioxidants did not prevent peroxide formation in olive oil stored at room temperature in daylight; these samples oxidized to a high degree, probably due to the catalytic action of chlorophyll. Citric acid (CA) used alone did not affect the oxidative stability of the oil in the oven test and at room temperature in the dark, but exhibited a negative effect at 50 C. The reduction in peroxide content with teritary butylhydroquinone (TBHQ) in the dark at 50 C was greater than anticipated from the oven studies. Potency of the antioxidants under these conditions (50 C) was in the following order: TBHQ> BHT > BHA. The combinations of BHA 0.01% or BHT 0.01% with TBHQ 0.005% used in the dark at 50 C were less effective than TBHQ 0.01%. 相似文献
14.
15.
The effects of enzymatic transesterification on the melting behavior of palm stearin and palm olein, each blended separately
with flaxseed oil in the ratio of 90∶10 and catalyzed by various types of lipases, were studied. The commercial lipases used
were Lipozyme IM, Novozyme 435, and myceliumbound lipases of Aspergillus flavus and A. oryzae. The slip melting point (SMP) of the palm stearin/flaxseed oil (PS/FS) mixture transesterified with lipases decreased, with
the highest drop noted for the mixture transesterified with Lipozyme IM. However, when palm stearin was replaced with palm
olein, the SMP of the palm olein/flaxseed oil (PO/FS) mixture increased, with the commercial lipases causing an increase of
41 to 48% compared to the nontransesterified material. As expected, the solid fat content (SFC) of the transesterified PS/FS
was lower at all temperatures than that of the nontransesterified PS/FS sample. In contrast, all transesterified PO/FS increased
in SFC, particularly at 10°C. Results from DSc and HPLC analyses showed that the high-melting glycerides, especially the tripalmitin
of palm stearin, were hydrolyzed. Consequently, 1,3-dipalmitoylglycerol was found to accumulate in the mixture. There was
no difference in the FA compositions between the transesterified and nontransesterified mixtures. 相似文献
16.
E. Deffense 《Journal of the American Oil Chemists' Society》1985,62(2):376-385
Because of its fatty acid composition, which includes 50% saturated and 50% unsaturated fatty acids, palm oil can readily
be fractionated, i.e. partially crystallized and separated into a high melting fraction or stearin and a low melting fraction
or olein.
Three main commercial processes for fractionating palm oil are in use: the fast dry process, the slow dry process and the
detergent process. All these processes lead to specific products of different quality with different yield and operating costs.
The physical and chemical characteristics as well as the triglyceride compositions by high performance liquid chromatography
(HPLC) of palm oil fractions from these industrial fractionation processes are given.
Other varieties of products produced by specific fractionation are presented with analytical data: the superoleins, palm-mid-fractions
and cocoa butter substitutes. 相似文献
17.
Susumu Miura Akihiro Yamamoto Kaoru Sato 《European Journal of Lipid Science and Technology》2002,104(12):819-824
In this study, the stability of a model cream was investigated using palm oil as sole fat source. It was found that the addition of monomyristoylglycerol (MM), monopalmitoylglycerol (MP), and monostearoylglycerol (MS) to palm oil promoted the solidification of the model cream while the addition of monolauroylglycerol (ML) and monobehenoylglycerol (MB) had no such effect. The solid fat content (SFC) values of pure palm oil cream and palm oil with the above‐mentioned additives were measured after cooling the cream from 60 °C to 5 °C. The SFC values in the cream with added MM, MP and MS were found to be lower than those of pure palm oil and palm oil with ML and MB. Fractionation of palm oil with the help of acetone resulted in a palm oil fraction containing a decreased amount of tripalmitin and 1, 3‐dipalmitoyl‐2‐oleoyl‐glycerol (POP). It was found that the model cream prepared with this fraction and the above‐mentioned monoacylglycerols remained stable even in the presence of MM, MP, and MS. From the above results, it was suggested that the agglomeration of tripalmitin and POP around MM, MP, and MS, which were preferentially adsorbed at the oil‐water interface of oil droplets in the model cream, led to a destabilization of the oil‐in‐water emulsion and to the solidification of the model cream. At the same time, it was suggested that the combination of the fatty acid moiety of monoacylglycerols with tripalmitin and POP played an important role in the destabilization of the model cream. 相似文献
18.
19.
Effect of refining of crude rice bran oil on the retention of oryzanol in the refined oil 总被引:3,自引:0,他引:3
A. G. Gopala Krishna Sakina Khatoon P. M. Shiela C. V. Sarmandal T. N. Indira Arvind Mishra 《Journal of the American Oil Chemists' Society》2001,78(2):127-131
The effect of different processing steps of refining on retention or the availability of oryzanol in refined oil and the oryzanol
composition of Indian paddy cultivars and commercial products of the rice bran oil (RBO) industry were investigated. Degumming
and dewaxing of crude RBO removed only 1.1 and 5.9% of oryzanol while the alkali treatment removed 93.0 to 94.6% of oryzanol
from the original crude oil. Irrespective of the strength of alkali (12 to 20° Be studied), retention of oryzanol in the refined
RBO was only 5.4–17.2% for crude oil, 5.9–15.0% for degummed oil, and 7.0 to 9.7% for degummed and dewaxed oil. The oryzanol
content of oil extracted from the bran of 18 Indian paddy cultivars ranged from 1.63 to 2.72%, which is the first report of
its kind in the literature on oryzanol content. The oryzanol content ranged from 1.1 to 1.74% for physically refined RBO while
for alkali-refined oil it was 0.19–0.20%. The oil subjected to physical refining (commercial sample) retained the original
amount of oryzanol after refining (1.60 and 1.74%), whereas the chemically refined oil showed a considerably lower amount
(0.19%). Thus, the oryzanol, which is lost during the chemical refining process, has been carried into the soapstock. The
content of oryzanol of the commercial RBO, soapstock, acid oil, and deodorizer distillate were in the range: 1.7–2.1, 6.3–6.9,
3.3–7.4, and 0.79%, respectively. These results showed that the processing steps—viz., degumming (1.1%), dewaxing (5.9%),
physical refining (0%), bleaching and deodorization of the oil—did not affect the content of oryzanol appreciably, while 83–95%
of it was lost during alkali refining. The oryzanol composition of crude oil and soapstock as determined by high-performance
liquid chromatography indicated 24-methylene cycloartanyl ferulate (30–38%) and campesteryl ferulate (24.4–26.9%) as the major
ferulates. The results presented here are probably the first systematic report on oryzanol availability in differently processed
RBO, soapstocks, acid oils, and for oils of Indian paddy cultivars. 相似文献
20.
Nesaretnam K Radhakrishnan A Selvaduray KR Reimann K Pailoor J Razak G Mahmood MM Dahliwal JS 《Lipids》2002,37(6):557-560
Biological therapies are new additions to breast cancer treatment. Among biological compounds, β-carotene has been reported
to have immune modulatory effects, in particular, enhancement of natural killer cell activity and tumor necrosis factor-alpha
production by macrophages. The objective of this study was to investigate the effect of palm carotene supplementation on the
tumorigenicity of MCF-7 human breast cancer cells injected into athymic nude mice and to explore the mechanism by which palm
carotenes suppress tumorigenesis. Forty-eight 4-wk-old mice were injected with 1×106 MCF-7 cells into their mammary fat pad. The experimental group was supplemented with palm carotene whereas the control group
was not. Significant differences were observed in tumor incidence (P<0.001) and tumor surface area and metastasis to lung (P<0.005) between the two groups. Natural killer (NK) cells and B-lymphocytes in the peripheral blood of carotene-supplemented
mice were significantly increased (P<0.05 and P<0.001, respectively) compared with controls. These results suggest that palm oil carotene is able to modulate the immune
system by increasing peripheral blood NK cells and B-lymphocytes and suppress the growth of MCF-7 human breast cancer cells. 相似文献