Surface Lipid Content Research Articles

Quality Characteristics of Long‐Grain Rice Milled in Two Commercial Systems

ABSTRACTLong‐grain rice variety Kaybonnet was milled to three degree of milling (DOM) levels in two commercial milling systems (a single‐break, friction milling system and a multibreak, abrasion and friction milling system) and separated into five thickness fractions. For both milling systems, the surface lipid content (SLC) and protein content of the milled rice varied significantly across kernel thickness fractions. SLC was influenced by DOM level more than by thickness, while the protein content was influenced by thickness more than by DOM level. Particularly at the low DOM levels, the thinnest kernel fraction (<1.49 mm) had higher SLC than the other kernel fractions. Protein content decreased with increasing kernel thickness to 1.69 mm, after which it remained constant. In both milling systems, thinner kernels were milled at a greater bran removal rate as indicated by SLC differences between the low and high DOM levels. For rice milled to a given DOM level, the multibreak system produced fewer brokens than did the single‐break system.

Quantifying Surface Lipid Content of Milled Rice via Visible/Near‐Infrared Spectroscopy

ABSTRACTVisible/near‐infrared calibrations were developed and tested for surface lipid content (SLC) of milled long‐grain rice. Three rice varieties were divided into two sample sets, with one containing two variables (degree of milling and variety) and another containing three variables (degree of milling, variety, and kernel thickness). The reflectance calibration equation from the set with three variables was much more accurate in predicting SLC than was the calibration from the two‐variable set. Optimal calibration and prediction were obtained by combining both visible and near‐infrared wavelength ranges and using the modified partial least squares technique on spectra pretreated by standard normal variate and first derivative methods. The best calibration yielded a coefficient of determination (R2) of 0.99 and a standard error of prediction of 0.04% SLC, which was approximately 1.5 times the standard error of calibration and also 1.5 times the SLC measurement error.

Starch Lipids of Barley and Malt

ABSTRACTBarley and malt starches were compared with respect to their lipid content and composition. The starch lipids were first fractionated into internal and surface lipid fractions followed by lipid class and fatty acid analyses of each fraction. Barley starch contained 13 mg/g lipids, of which 9.3 mg were internal lipids and 3.7 mg were surface lipids. The total lipid content of malt starches varied between 11 and 13 mg/g of starch. However, malt starch contained only 1 mg of surface lipids; therefore, the internal lipid contents were as high as or even higher than those in the corresponding fraction of barley starch. Lipid class analyses suggested that the ability for hydrolysis of starch surface lipids was increased in malt. The hydrolysis occurred during the malting or the isolation process, resulting in reduced surface lipid content in malt starch. However, no reduction in the portion of polyunsaturated fatty acids was seen; therefore, lipid oxidation could not have been responsible for the lower content of malt starch surface lipids. Also, not only was the content of starch internal lipids higher in malt, but the composition of these lipids was different when compared to barley starch. The increase in starch internal lipids during malting may be due to transportation and reacylation of free fatty acids that had been liberated by hydrolysis from surface lipids.

Size-Dependent Bioconcentration Kinetics of Hydrophobic Organic Chemicals in Fish Based on Diffusive Mass Transfer and Allometric Relationships

Download Hi-Res ImageDownload to MS-PowerPointCite This:Environ. Sci. Technol. 1995, 29, 11, 2769-2777

Skin Surface Lipid and Skin Friction: Relation to Age, Sex and Anatomical Region

Differences in the skin surface lipid content (SSL) and the dynamic friction coefficient (mu) were investigated with respect to age, sex, and anatomical region in 29 volunteers. The group consisted of (a) 7 young adult females (24.9 +/- 1.1 years old, mean +/- SD), (b) 7 old females (75.3 +/- 2.4 years old), (c) 7 young adult males (28.7 +/- 0.5 years old), and (d) 8 old males (73.8 +/- 1.9 years old). Measurements were obtained on 11 anatomical regions, namely, the forehead, upper arm, volar and dorsal forearm, postauricular, palm, abdomen, upper and lower back, thigh, and ankle. Skin surface lipid content data were compared with mu measurements to determine the relative contribution of the former to frictional properties of skin. mu and SSL were not statistically different between age groups on all regions except for the ankle, where lipid content was lower in the elderly. Similarly, mu did not vary between sex groups. Skin surface lipid content was statistically lower on the forehead, dorsal forearm and postauricular area in females. Both parameters, however, showed considerable regional variability. A significant linear correlation was established between mu and SSL combining all regions from all volunteers. When mu was plotted against SSL among individual anatomic sites, only the forehead and postauricular area showed significant linear correlations between the two parameters. These data suggest that surface lipid content plays a limited role in frictional properties of skin.

Structural properties of high density lipoprotein subclasses homogeneous in protein composition and size.

We isolated native high density lipoprotein (HDL) subclasses homogeneous in size and in their protein content with the objective of investigating the differences and similarities in their apolipoprotein AI (apoA-I) structures. Defined particles were isolated from ultracentrifugally prepared HDL by immunoaffinity and gel-filtration chromatography. The isolated 88-A LpAI, 106-A LpAI, 96-A LpAI/AII particles (LpAI, particles contain only apoA-I; LpAI/AII, particles contain apoA-I and apoA-II), together with a 93-A reconstituted HDL were analyzed for purity, composition, and content of apolipoprotein molecules per particle, and were examined by far and near circular dichroism and intrinsic fluorescence spectroscopic methods, as well as by reaction kinetics with lecithin:cholesterol acyltransferase. The spectroscopic analyses indicated that the secondary structures and three-dimensional arrangements of apoA-I in all these particles are remarkably similar: their tryptophan residues are located in similar nonpolar environments and become exposed to increasing concentrations of guanidine hydrochloride in comparable denaturation steps; the 60-65% alpha-helical structures in apoA-I are denatured in similar patterns with 0-5 M denaturant concentrations. However, increasing surface lipid contents and the presence of apoA-II stabilize apoA-I on the HDL particles. The reaction kinetics with lecithin:cholesterol acyltransferase are similar and slow for the isolated HDL particles, reflecting product inhibition, and/or an apoA-I conformation that is unfavorable for the activation of the lecithin:cholesterol acyltransferase reaction.

The effect of aging on percutaneous absorption in man

Despite much research into the mechanisms of cutaneous aging and the identification of significant age-associated biological and biophysical changes within the skin, the question "How does aging affect percutaneous absorption (PA) in vivo?" remains unanswered. We have made in vivo measurements of PA in young (18-40 years) and old (greater than 65 years) subjects. Standard radiotracer methodology was employed and PA was quantified from the urinary excretion profiles of 14C radiolabel (corrected for incomplete renal elimination). Testosterone (TST), estradiol (EST), hydrocortisone (HC), benzoic acid (BA), acetylsalicylic acid (ASA), and caffeine (CAFF) have been studied. Permeation of HC, BA, ASA, and CAFF was significantly (p less than 0.01, 0.01, 0.01, and 0.05, respectively) lower in aged subjects, whereas the absorption of TST and EST was similar in the two groups. Thus it appears that aging can affect PA in vivo and that relatively hydrophilic compounds are particularly sensitive. The diminished surface lipid content of "old" skin implies a diminished dissolution medium for compounds administered topically. It is reasonable to speculate that this physiologic change will impact most severely upon those permeants whose lipid solubility is lowest (that is, HC, BA, ASA, CAFF). Furthermore, the typically reduced hydration of aged stratum corneum will compound this effect for these chemicals. Conversely, highly lipid-soluble chemicals (TST and EST) may still be able to dissolve readily into the stratum corneum even when the available lipid medium is reduced.

The neutral lipid composition and size of recombinant high density lipoproteins regulates lecithin:cholesterol acyltransferase activity

Recombinant high density lipoprotein (rHDL) particles were prepared from purified lipids and human apoproteins, and the ability of these complexes to act as substrates for purified lecithin:cholesterol acyltransferase (LCAT) was determined. Increasing the triacylglycerol content relative to cholesteryl ester in rHDL markedly decreased the maximum catalytic potential of LCAT. Kinetic analysis showed that the Vmax of the LCAT reaction was significantly and negatively correlated to the triacylglycerol content. The apparent Km was not directly affected by relative neutral lipid content, but was significantly related to protein and surface lipid content as well as to particle size. These results suggest that while particulate size may regulate the interaction between LCAT and HDL, the relative neutral lipid content of the particle may play a major role in regulating the catalytic potential of the enzyme, particularly with HDL from hypertriglyceridemic patients.

Studies on leaf surface lipid of tobacco. I. Changes in leaf surface lipid and duvatrienediol during growth, senescence and curing of tobacco leaves.

Duvatrienediol is a diterpene specifically occurred in tobacco plants and thought to be a precursor of tobacco aroma. Green tobacco leaves contained 0.2_??_1% of duvatrienediol per dry weight and it was corresponded to 30_??_60% of leaf surface lipid. Leaves on upper stalk position contained more of leaf surface lipid and duvatrienediol. In leaves on each stalk position, leaf surface lipid and duvatrienediol contents increased with leaf growth and decreased by over-maturation. Production of leaf surface lipid and duvatrienediol was affected by soil conditions or applied amount of nitrogen fertilizer. Both leaf surface lipid and duvatrienediol were decreased during curing of tobacco leaves, but the change in the latter was more drastic. Comparing to leaf surface lipid, changes in cytoplasmic lipid were less during growth and senescence of tobacco leaves.

Infrared Spectra of Milled Rice

ABSTRACT COMPUTERIZED spectroscopy was used to study the infrared spectra of milled rice. The reflectance at three principal oil absorption bands 0.928, 1.215, and 1.725 jLttn was found to be highly correlated with surface and total lipid contents and to a lesser degree with weight loss due to milling.