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1.
Prachuab Kwanyuen Vincent R. Pantalone Joseph W. Burton Richard F. Wilson 《Journal of the American Oil Chemists' Society》1997,74(8):983-987
Although soybeans produce high-quality meal, modern animal and fish production systems often require synthetic essential amino
acid supplements to fortify feed rations. However, biotechnology may enable development of soybeans with naturally adequate
levels of certain essential amino acids for advanced feed formulations. One approach involves genetic manipulation of glycinin
(11S) and β-conglycinin (7S) contents, the principal components of soybean storage proteins. Because 11S contains more cysteine
and methionine than 7S protein, a higher 11S:7S ratio could lead to beneficial changes in the nutritional quality of soybean
meal. Although genotypic variation for 11S:7S may be low among soybean [Glycine max (L.) Merr.] germplasm, ratios ranging from 1.7–4.9 were observed among accessions of the wild ancestor of cultivated soybean
(Glycine soja Sieb, and Zucc.). Thus, wild soybean germplasm was evaluated as a potential source of genes that govern protein synthesis
that may have been lost during the domestication of G. max. Change in the amount of 11S protein accounts for a significant portion of the genotypic variation in protein concentration
and composition among wild soybeans. Strong positive correlation exists between the 11S:7S ratio and methionine or cysteine
concentration of total protein. Moderate positive associations were found for threonine or tyrosine. A moderate negative correlation
was found between lysine and 11S:7S. No association was found for leucine and phenylalanine or for total essential amino acid
concentration. Based on these data, G. soja may contain a different complement of genes that influence expression of 11S and 7S proteins than G. max germplasm. Thus, through interspecific hybridization, wild soybeans may be a useful genetic resource for the further improvement
of protein quality in cultivated soybeans. 相似文献
2.
James B. Sinclair 《Journal of the American Oil Chemists' Society》1995,72(12):1415-1419
The proportion of off-colored seed is a primary quality-rating factor that influences the market grade of soybean,Glycine max L. Merrill. Off-colors, attributed to biological agents such as fungi and viruses, are visual characteristics that arbitrarily
result in lower grade ratings when soybeans show more than ten percent discoloration. These damaged seeds may be further classified
under current United States Department of Agriculture, Federal Grain Inspection Service standards as: moldy, weathered, bicolored,
mottled, or other colors. Presently, all types of fungal damage and virus symptoms are evaluated equally in the application
of discount schedules at grain-elevators. However, recent information shows that superficial discoloration caused by some
biological agents does not lower grain quality. Indeed, methods are available to distinguish those symptoms that actually
reduce seed quality from those that are more cosmetic in nature. This communication provides guidance on fungi that are involved
most often in seed damage or discoloration. The following organisms are listed in descending order of importance:Phomopsis longicolla, Alternaria, Nematospora coryli, Fusarium graminearum, Colletotrichum, andCercospora kikuchii. Discoloration caused byPeronospora manchurica (downy mildew) and the soybean mosaic virus have limited effect on seed quality. Discoloration caused by each of these agents
may be identified by recognizable characteristics. Therefore, knowledge of the relative impact of these organisms on seed
quality should be practiced in the application of soybean grading standards and discount schedules. 相似文献
3.
Hiromi Yoshida Sachiko Takagi Sayaka Mitsuhashi 《Journal of the American Oil Chemists' Society》1999,76(8):915-920
Whole soybeans (Glycin max L.) were roasted by exposure to microwaves at a frequency of 2,450 MHz, and their hypocotyls were separated from other tissues
(seed coat and cotyledons). The quality characteristics and composition in the hypocotyl oils were studied in relation to
their tocopherol distributions and were evaluated as compared to an unroasted oil sample. Only minor increases (P<0.05) in chemical and physical changes of the oils, such as carbonyl value, anisidine value and color development, occurred
with increased roasting time. Significant decreases (P<0.05) were observed in the amounts of phospholipids in the oils after microwave roasting. Nevertheless, compared to the original
level, more than 80% tocopherols still remained after 20 min of roasting. These results suggest that the exposure of soybeans
to microwaves for 6 to 8 min caused no significant loss or changes in the content of tocopherols and polyunsaturated fatty
acids in the hypocotyls. Therefore, a domestic microwave oven would be useful as a simple and quick means for preparing hypocotyl
oil of good quality. 相似文献
4.
J. A. Robertson R. G. Roberts W. H. Morrison III 《Journal of the American Oil Chemists' Society》1987,64(2):224-228
Thirty-four samples of commercial oil-type sunflower-seed graded No. 1, 10 samples graded No. 2 and 33 samples graded Sample
grade (SG) were used to study the relationship between percent heat damage, an important grading character, and percent FFA,
percent color and UV absorption of extracted oil, percent germination and number and identities of fungi present. Seventy-two
fungal species belonging to 28 genera were isolated. Thirty-seven fungal species in 17 genera were isolated from grade No.
1 seed; 68 species in 13 genera were isolated from grade No. 2 seed, and 68 species in 26 genera were isolated from SG seed.
The genera most frequently isolated from grade No. 1 seed wereAlternaria (85.3%),Phoma (4.7%) andCladosporium (4.5%).Alternaria alternata was recovered from all No. 1 samples and comprised 75.6% of all isolates. The genera most frequently isolated from grade
No. 2 seed wereAlternaria (74.5%),Eurotium (8.4%) andPhoma (7.7%). Fewer fungal species were isolated from grade No. 2 than from No. 1 seed, but a greater recovery of storage fungi
was found for No. 2 seed (13.3%) than for No. 1 seed (2.5%).Alternaria (33.8%),Eurotium (33.1%) andMicroascus (8.3%) were the genera most frequently isolated from SG seed. Species of common storage fungi (Eurotium, Microascus, Penicillium andAspergillus) were recovered more frequently from SG than from Grades No. 1 and No. 2. In general, as the quality of the seed decreased
from grade No. 1 to grade No. 2 to SG, there was an increase in percent heat damage, percent FFA, Lovibond color and UV absorption
of extracted oil, and a decrease in percent germination. Analysis of variance of the quality characteristics data showed no
significant differences between grade No. 1 and No. 2 seed except for UV 228 nm absorption. However, the quality characteristics
of SG seed all differed significantly from those of grades No. 1 and No. 2 seed with the exception of percent seed yielding
fungi. Correlation coefficients of the quality characteristics of SG showed a slight relationship between heat damage and
percent FFA (r=0.63) and UV 228 nm absorbance (r=0.68). Although many of the SG seed were badly heat damaged, no statistical
relationship was found between percent heat damage and percent seed yielding fungi or total isolates of storage fungi. The
data in this study show that errors exist in grading decisions when seed are judged visually to be heat damaged. 相似文献
5.
Perilla frutescens, an edible oilseed of Northeast India, was evaluated for its nutrient composition and protein quality. It was found to be
a rich source of protein (17.0%) and fat (51.7%). The fatty acid profile indicated that perilla oil is rich in polyunsaturated
fatty acids, such as linolenic (56.8%) and linoleic (17.6%). The amino acid composition showed that valine was the limiting
amino acid of perilla protein. The protein efficiency ratio of the seed protein (2.07) was lower than that of casein (2.99),
but comparable to common oilseeds. True digestibility of the seed protein (82.6%) was also lower than that of casein (89.3%). 相似文献
6.
Potential involvement of seed storage proteins in susceptibility to aflatoxin contamination was assessed with in vitro tests. Initially, two oilseed storage proteins [cottonseed storage protein (CSP) and zein] were compared with bovine serum
albumin (BSA) and collagen. Supplementation of a complete defined medium with either oilseed storage protein resulted in significantly
more aflatoxin production by Aspergillus flavus than supplementation with either BSA or collagen. Little or no aflatoxin was produced when either BSA, CSP, or zein was employed
(at 0.5%) as both the sole carbon and the sole nitrogen source. Media with collagen (0.5%) as the sole nitrogen and carbon
source supported aflatoxin production similar to the complete defined medium. Although lower than levels observed with defined
medium, aflatoxin production increased with both increasing CSP concentration (0 to 2.0%) and increasing zein concentration
(0 to 6.0%) when these proteins served as both the sole carbon and sole nitrogen source. Denaturing polyacrylamide gel electrophoresis
and protease activity assays indicated that fungal acquisition of protein carbon was probably via hydrolysis mediated by the 35 kD metalloprotease of A. flavus. Media lacking nitrogen but containing sucrose (5.0%) and supplemented with either zein (1.7%) or CSP (2.0%) supported three-
to eightfold more aflatoxin production than the complete defined medium. The results suggest seed storage proteins, when present
with an accessible carbon source, may predispose oilseed crops to support production of high levels of aflatoxins by A. flavus during seed infection. 相似文献
7.
Potential involvement of seed storage proteins in susceptibility to aflatoxin contamination was assessed with in vitro tests. Initially, two oilseed storage proteins [cottonseed storage protein (CSP) and zein] were compared with bovine serum
albumin (BSA) and collagen. Supplementation of a complete defined medium with either oilseed storage protein resulted in significantly
more aflatoxin production by Aspergillus flavus than supplementation with either BSA or collagen. Little or no aflatoxin was produced when either BSA, CSP, or zein was employed
(at 0.5%) as both the sole carbon and the sole nitrogen source. Media with collagen (0.5%) as the sole nitrogen and carbon
source supported aflatoxin production similar to the complete defined medium. Although lower than levels observed with defined
medium, aflatoxin production increased with both increasing CSP concentration (0 to 2.0%) and increasing zein concentration
(0 to 6.0%) when these proteins served as both the sole carbon and sole nitrogen source. Denaturing polyacrylamide gel electrophoresis
and protease activity assays indicated that fungal acquisition of protein carbon was probably via hydrolysis mediated by the 35 kD metalloprotease of A. flavus. Media lacking nitrogen but containing sucrose (5.0%) and supplemented with either zein (1.7%) or CSP (2.0%) supported three-
to eightfold more aflatoxin production than the complete defined medium. The results suggest seed storage proteins, when present
with an accessible carbon source, may predispose oilseed crops to support production of high levels of aflatoxins by A. flavus during seed infection. 相似文献
8.
Increasing the level of protein in soybean seeds has been a major target for soybean [Glycine max (L.) Merr.] breeders. The objective of this study was to examine the potential of predicting soybean seed protein based on
oil values as determined by NMR. Seed protein and oil concentrations were determined in an F2 population generated from the cross between a G. max (NK, S08-80), and a G. soja (PI 458536) cultivar. The protein concentration in the population ranged from 40.4 to 52.6%. Protein-oil regression analysis
was used to generate an equation for predicting seed protein concentration based on oil readings. The regression equation
Protein=62.3–1.3 [Oil] (R
2=0.46) was developed, with a corresponding correlation of −0.69 between the traits. With this equation, the mean protein concentration
of the selected 25% of the population (a simulated breeding pressure) was greater than the mean of the unselected population
(46.1%, SE=0.13) by about 1.9%. Individual F2 plants that exceeded the mean protein value of the population constituted 86.4% of the selected samples. Selection based
on oil concentration, however, failed to include 27.1% of the plants that were among the top 25% for protein concentration.
Selection of high-protein plants based on NMR oil measurement was reasonably effective in the test population and might offer
a new and rapid method of selecting high-protein individuals in soybean populations derived from the wild soybean progenitor,
G. soja. If further tested on other populations and samples, it might be used as an analytical alternative for an indirect measurement
of protein concentration based on NMR measurements of the oil. 相似文献
9.
Lipid-Derived flavors of legume protein products 总被引:5,自引:4,他引:5
Legumes contain unsaturated lipids that are susceptible to oxidative deterioration. Enzymic and non-enzymic deterioration
of these lipids results in the development of off-flavors. The primary objective of this review is to summarize what is currently
known about lipid-derived flavors of soybeans and underblanched pea seeds(Pisum sativum). Identifying the numerous volatile compounds arising from breakdown of lipid hydroperoxides coupled with organoleptic evaluation
defines the flavor problem. Major contributors to the green-beaniness of soybeans were found to be 3-cis-hexenal, 2-pentyl furan, and ethyl vinyl ketone. Oxidized phosphatidylchohnes cause some of the bitter taste. The interaction
of lipid breakdown products with proteins, carbohydrates, and other constituents can affect flavor characteristics and also
increase the problems of their removal from soy protein products. To prepare bland products, it will be necessary to develop
processes that effectively remove bound flavor components and prevent formation of derived flavors. Solvent systems based
on alcohol have been used to extract flavor principles from soybeans; aqueous alcohol treatment of the intact seed or blanching
with hot water or steam inhibits formation of off-flavors in peas and soybeans. A new approach involving infusion of antioxidants
into the intact seed to control lipid deterioration during processing and storage is proposed to minimize flavor formation
without subsequent undesirable changes in protein which occur with alcohol treatments.
Presented at the AOCS Meeting, New Orleans, April 1976. 相似文献
10.
V. R. Pantalone G. J. Rebetzke R. F. Wilson J. W. Burton 《Journal of the American Oil Chemists' Society》1997,74(5):563-568
Soybean [Glycine max (L.) Merr.] oil from current commercial cultivars typically contains ca. 8% linolenic acid (18:3). Applications of plant biotechnology have enabled plant breeders to develop germplasm having as
low as 2.0% 18:3. Oils that are naturally low in 18:3 exhibited improved flavor characteristics and greater oxidative stability
in high-temperature frying applications compared to hydrogenated soybean oil. As an extension of that research, efforts are
underway to characterize genes in soybean that govern expression of higher than normal 18:3 concentration. Such oils may be
of interest to the oleochemicals industry for various nonfood applications. Relatively high 18:3 in seed oil is a characteristic
trait of the ancestor of modern soybean cultivars, Glycine soja (Sieb. and Zucc.). Accessions of this species have rarely been utilized in soybean improvement, and thus represent a virtually
untapped genetic resource for genes governing 18:3 synthesis. We have hybridized cultivated soybean with wild soybean plant
introductions. F3:4 seed from the resultant G. max × G. soja populations exhibited a wide segregation pattern for 18:3 and seed mass. A strong negative association was found between
18:3 concentration and seed mass. Oil concentration was positively correlated with seed mass. Evaluation of glycerolipid composition
revealed that high 18:3 was not associated with an altered proportion of phospholipid and triacylglycerol among lines segregating
for seed mass. Thus, smaller seed mass may be a convenient trait to distinguish future soybean cultivars with highly polyunsaturated
oils from other cultivars in production. 相似文献
11.
Temperature and precipitation during the growing season have been shown to influence the protein and oil composition of the
soybean [Glycine max L. Merr.] seed. A method based on these parameters was developed to estimate protein and oil concentrations of the seed before
harvest. This method was developed with protein and oil data and temperature and precipitation data from the Uniform Soybean
Tests, Southern Region, for the years 1975 to 1983. Classification and regression “tree-based” analyses were used to determine
the month and numeric value (“splitting point”) of the environmental variable that correctly classified the variation from
median protein and oil composition for the 126 location-years. Temperature in September was most influential in determining
the splitting point for three of the four variables. Oil concentrations from the location-years were separated into low vs.
high median-based boundary categories most readily by the September sum of minimum temperatures. Total protein and oil concentrations
from the location-years were classified best by September growing degree days. Protein-to-oil ratios were best separated by
the September mean minimum temperature. The August mean maximum temperature best separated protein concentration. These data
demonstrate that temperature during specific months of the crop year were useful in estimating the final concentration of
protein and oil in the seed and could be used by seed processors to estimate seed composition before harvest. 相似文献
12.
Ernest L. Piper Kenneth I. Boote 《Journal of the American Oil Chemists' Society》1999,76(10):1233-1241
The soybean [Glycine max (L.) Merr.] industry is interested in cultivar and climate effects on seed composition. These factors may underlie the known
geographic variation in seed protein and oil concentrations. Regression analyses were used to test hypotheses of the effect
of temperature and cultivar on oil and protein concentrations of soybean seed using a large data set from the U.S.A. Soybean
Uniform Tests. The data set included 20 cultivars representing 10 maturity groups across 60 locations (latitude 29.4 to 47.5°
N) for a total of 1863 cultivar by location by year observations. Temperature was determined for each observation as the average
daily mean temperature from predicted first pod (first pod at least 5 mm long), using the SOYGRO phenology model, to observed
maturity. The mean temperature ranged from 14.6 to 28.7°C among the observations. Linear, quadratic, and linear plateau regression
models of oil and protein concentrations vs. temperature were evaluated. The quadratic model gave the best-adjusted R
2 values for oil and protein with temperature, of 0.239 and 0.003, respectively. The analyses showed that the oil concentration
increased with increasing temperature and approached a maximum at a mean temperature of 28°C. Unaccounted variation in the
protein concentration may be from other factors such as photoperiod, water stress, or high temperatures during seed fill.
Protein plus oil had a linear relationship with temperature (adjusted partial R
2=0.183). These data document the contribution of climate and cultivar to geographic variability of oil and protein concentrations
in the United States. 相似文献
13.
The unavailability of protein foods, particularly in the context of population growth, has been an important factor in the
protein malnutrition encountered in developing countries. The fractionation, gel filtration and polyacrylamide gel electrophoresis
(PAGE) of Ailanthus excelsa seed (a nontraditional source containing 15.81% protein) proteins were carried out in the present study, and their solubility
profiles, surface topographies and amino acid compositions were evaluated. The globulin fraction dominated the seed protein
composition, accounting for 51.31% (w/w) of the total soluble proteins in the seeds. Protein isolate and protein fractions
of A. excelsa seeds showed similar topographical structures to those of other plant seed proteins. Analysis of the isolated proteins identified
17 amino acids, of which nine were essential. Gel filtration on Sephadex G-200 revealed the presence of seven components.
PAGE detected different polypeptide bands in the range of 28.8−154.9 kDa in the protein isolate as well as in protein fractions
for A. excelsa. The amino acid compositions, the solubility patterns and the high abundances of low molecular weight proteins indicate that
the isolated seed protein of A. excelsa may be a potential food protein. 相似文献
14.
Temperature and precipitation variables during linear seed fill are known to be environmental determinants of protein and
oil composition of the soybean [Glycine max (L.) Merr.] seed. However, the contribution of other precipitation and temperature events during the growing season and a
method that would determine the precipitation and temperature variables most related to protein and oil concentration values
of the seed has not been fully explored. The former was evaluated by comparing monthly temperature and precipitation variables
of the growing seasons to protein and oil data for the years 1959 to 1996 from three locations listed in the Uniform Soybean
Tests, Northern Region. The data set comprised locations from Maturity Groups II and III and consisted of 186 location-years.
Classification and regression “tree-based” analysis were conducted to determine the month, environmental variable, and “splitting”
points that correctly classified most of the 186 location-years for below-vs.-above-median protein or oil composition. The
protein concentrations from the location-years were separated into these two median-boundary categories most readily by temperature
variables from the months of April and August. The oil concentrations from the location-years were classified best by August
and September temperature variables and precipitation in May and September. The sum of protein and oil concentrations from
the location-years were best separated by August and July temperature variables and precipitation in May and July. The protein-to-oil
ratios from the location-years were best separated by September precipitation and July and June temperature variables. These
data demonstrate that tree-based models can use monthly temperature and precipitation variables during linear seed fill and
other specific months of the crop year and relate them to the final protein and oil concentration in the seed. These results
could be used by the processing industry to estimate seed composition before harvest. 相似文献
15.
Loblolly and shortleaf pine growing on a single site in the North Carolina piedmont were examined to determine similarities and differences in their defensive mechanisms against the southern pine beetle,Dendroctonus frontalis Zimmermann, and its fungal associate,Ceratocystis minor (Hedgecock) Hunt. Both species responded to wounding and fungal inoculation by forming a hypersensitive lesion around the wound site. There were significantly less soluble sugars and more monoterpenes in the lesion tissue than in unwounded inner bark. The two species were similar in resin flow rate and inner bark soluble sugar content, but the loblolly pines had thicker bark, longer hypersensitive lesions, and a higher concentration of inner bark monoterpenes. Inner bark monoterpene composition was also significantly different between the two pine species. It is hypothesized that two different defensive strategies against southern pine beetle attack may be utilized. 相似文献
16.
Malakiba Sen Dipak Kumar Bhattacharyya 《European Journal of Lipid Science and Technology》2000,102(12):727-733
The effect of removing anti‐nutritional factors from n‐hexane‐extracted mustard meal using 80% isopropanol (to reduce thioglucosides, phenolics, etc.) on growth, food efficiency ratio, serum and liver lipid profiles and protein content of young rats was examined. For this n‐hexane‐extracted mustard meal was extracted with 80% isopropanol giving a fraction with 68% protein and low residual thioglucoside (0.5%) as well as phenolic (0.3%) content. This isopropanol‐extracted mustard seed protein fraction reduced the growth of young rats slightly when compared with casein. The food efficiency ratio between rats fed isopropanol‐extracted mustard seed protein or casein did not differ, nor did the protein composition affect serum total cholesterol, triglyceride, HDL‐cholesterol, LDL‐cholesterol, VLDL‐cholesterol and LDL‐C/HDL‐C ratio. However, rats fed isopropanol‐extracted mustard seed protein showed a significantly lower (p<0.05) liver cholesterol concentration than rats fed casein. Liver triglyceride and phospholipid concentrations did not differ between rats fed the two proteins, nor was serum protein affected. This study indicates that extraction of hexane‐extracted mustard meal with 80% isopropanol reduced a number of anti‐nutritional factors like thioglucoside and phenolics. Furthermore the nutritional quality of mustard seed protein fraction is comparable to casein in respect to growth, food efficiency ratio, serum lipid and protein concentrations and organ weights. 相似文献
17.
Roque L. Evangelista Steven C. Cermak 《Journal of the American Oil Chemists' Society》2007,84(12):1169-1175
Cuphea PSR23, a semi-domesticated, high-capric-acid hybrid from Cuphea viscosissima × Cuphea lanceolata, is being developed as a potential commercial alternative source of medium-chain fatty acids. The present study evaluated
the effects of initial seed moisture and final moisture contents of cooked flaked seed on Cuphea’s pressing characteristics
and the quality of the extracted oil. Seeds with 9 and 12% initial moisture contents (MC) were flaked and cooked at different
residence times to produce cooked seeds with MC of 3.0–5.5%. Cooked seeds were pressed using a laboratory screw press. Eighty
and 84% oil were extracted from cooked seeds with 5.5 and 3.0% MC, respectively. The seeds with 9% initial MC exhibited lower
pressing load increase (9.1 per 1% decrease in MC) than the seeds with 12% initial MC (16.4 per 1% decrease in MC). The pressing
rate decreased by 3% as the cooked flaked seed MC decreased. The amount of foots in the oil increased from 3 to 6.6% and chlorophyll
content increased from 200 to 260 ppm as cooked flaked seed MC decreased from 5.5 to 3.0%. FFA contents were 2.5% for all
treatments MC studied. The phosphatide content increased as the cooked flaked seed MC decreased but the amounts were still
within the levels of water-degummed oil.
This paper may contain brand names that are necessary to report factually on available data; however, the USDA neither guarantees
nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion
of others that may also be suitable. 相似文献
18.
Characterization of yam bean (Pachyrhizus spp.) Seeds as potential sources of high palmitic acid oil
W. J. Grüneberg F. D. Goffman L. Velasco 《Journal of the American Oil Chemists' Society》1999,76(11):1309-1312
Seeds from 22 accessions of the yam bean species Pachyrhizus ahipa (14 accessions), P. erosus (5), and P. tuberosus (3) were investigated for oil and protein contents, fatty acid composition of the seed oil, and the total tocopherol content
and composition. Plants from the accessions were grown under greenhouse conditions during one (P. erosus and P. tuberosus) or two years (P. ahipa). The pattern of the investigated seed quality traits was very similar in the three species. Yam bean seeds were characterized
by high oil (from about 20 to 28% in one environment) and protein contents (from about 23 to 34%). Seed oil contained high
concentrations of palmitic (from about 25 to 30% of the total fatty acids), oleic (21 to 29%), and linoleic acids (35 to 40%).
Levels of linolenic acid were very low, from about 1.0 to 2.5%. Total tocopherol content was relatively low in P. erosus (from 249 to 585 mg kg−1 oil) and P. tuberosus (from 260 to 312 mg kg−1 oil) compared with the levels found in P. ahipa grown under identical conditions (508 to 858 mg kg−1 oil). In all the samples, γ-tocopherol was predominant, accounting for more than 90% of the total tocopherol content. The
combination of high oil and protein contents, together with high palmitic acid, low linolenic acid, and high γ-tocopherol
concentration, makes these crops an interesting alternative as sources of high palmitic acid oil for the food industry. 相似文献
19.
Relation between diacylglycerol acyltransferase activity and oil concentration in soybean 总被引:2,自引:0,他引:2
Sharon B. Settlage Prachuab Kwanyuen Richard F. Wilson 《Journal of the American Oil Chemists' Society》1998,75(7):775-781
Diacylglycerol acyltransferase (EC 2.3.1.20; DGAT) catalyzes synthesis of triacylglycerol from acyl-CoA and diacylglycerol.
Activity of this enzyme and developmental changes in oil accumulation were estimated at various stages of seed growth in soybean
germplasm with phenotypic differences in oil content. Oil deposition in seed of these genotypes followed a sigmoid pattern
that was modeled to predict incremental rates of oil accumulation during seed development. A strong positive correlation was
found between the estimated peak rate of oil deposition (near the mid-term of seed development) and oil concentration in mature
seed. At saturating substrate levels, DGAT activity measured near the peak rate of oil deposition also was correlated positively
with oil phenotype. In the latter stages of seed development, a positive correlation between estimates of enzyme activity
at or below the apparent K
m for diolein and comparable oil accumulation rates was attributed to reduced synthesis of substrates and/or potential change
in affinity for substrate as suggested by an increase in apparent K
m for diolein in older seed. These data indicated that DGAT activity may be a rate-limiting step in triacylglycerol synthesis.
However, it is difficult to accept the idea of a single rate-limiting step at the end of a complex metabolic pathway. Because
oil is a quantitatively inherited trait, several genes determine genotypic differences in oil content among soybeans. Hence,
DGAT activity may be an indicator of coordinated genetic expression of gene-products in the entire glycerolipid synthetic
pathway for a given genotype. In any case, results of this investigation demonstrated that genotypic differences in DGAT activity
contributed to expression of genetic variation in oil content among soybean gemplasm. 相似文献
20.
Nicolas A. Deak Lawrence A. Johnson 《Journal of the American Oil Chemists' Society》2007,84(4):369-376
Phytic acid (myo-inositol hexaphosphate) is present in soybeans and soy protein products at 1–2% dry matter. Phytate causes
poor absorption of essential electrolytes and minerals, and binds to proteins and co-precipitates with isoelectric soy protein
isolates. We determined how phytic acid partitioned during different procedures to prepare soy protein ingredients. Procedure
and soybean variety significantly affected phytic acid content and recovery. High-sucrose/low-stachyose (HS/LS) soybeans contained
significantly (P < 0.05) less phytate than did a typical variety of commodity soybeans (IA2020). In addition, phytate was more readily extracted
from the commodity soybeans than from HS/LS soybeans. Among all procedures studied, ethanol-washed soy protein concentrate
had the highest phytate contents and yields in the protein products for both soybean varieties (~80 mg/g and 99%, respectively).
When protein extraction was carried out at room temperature the protein products had significantly lower phytate yields (60–78%)
than when extraction was at 60 °C (80–99%). The protein products obtained from normal soybeans had significantly higher phytate
contents than the same products made from HS/LS soybeans. When fractionating soy proteins, the glycinin-rich fraction contained
significantly less phytate than the β-conglycinin fraction except for the fractionation procedure performed at room temperature
instead of 4 °C. 相似文献