A. Proctor

Determination of pectin degree of esterification by diffuse reflectance Fourier transform infrared spectroscopy

Abstract A diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) method was developed to measure the degree of esterification (DE) of commercial pectin samples. The relationship between infrared spectroscopy data and titrimetrically determined DE values was investigated. The ester carbonyl band area (CO) occurring at a mean frequency of 1756 cm −1 had the highest correlation ( R 2 =0.822) with the mean DE of the bands observed. The DE values of pectin samples calculated from the line fit equation were comparable to those obtained from the titrimetric method. Mean DE values obtained were within 3.23% for DE 71.6, 2.9% for DE 62, and less than 1% for DE 55.3 of values obtained by titrimetric method. Spectral variations due to sample source have to be considered in developing prediction equations using FTIR. DRIFTS can be a rapid, alternative method to titrimetric analysis of pectin DE.

Effect of acid extraction and alcohol precipitation conditions on the yield and purity of soy hull pectin

Abstract Soy hull pectin was prepared by hydrochloride acid extraction, followed by alcohol precipitation, and the effect of extracting acid concentration and the pH of precipitating solvent on the yield and purity of pectin were investigated. Strength of acid used for extracting pectin from soy hull and the pH of precipitation had significant effects on the pectin yield. Highest yields of 26 and 28% were obtained when the acid strength was 0.05 and 0.1 N, respectively, and the pH of the precipitating solution was 3.5. Extraction of pectin with 0.2 and 0.3 N acid, or precipitation of pectin at pH 2.0, reduced pectin yield. Strength of acid used for extraction or pH of the solution during precipitation did not significantly affect the purity or degree of esterification of the product. Galacturonic acid content and degree of esterification of the products varied from 68–72% and 56–60%, respectively.

Preparation of soy hull pectin

Abstract Soy hull, a co-product of soybean processing, was investigated as a source of pectin. Pectin content of soy hull extracts expressed as percent galacturonic acid content, varied from 76.7% to 88.3%. Enzymatic pretreatment of soy hulls increased content of alkali soluble pectins. X-ray diffraction patterns of soy hull pectins were similar to those of commercial citrus pectin; however, enzymatic pretreatment increased X-ray diffraction intensities corresponding to interatomic distances of 17.5, 7.5, 4.3, 3.0, 2.9, and 2.7 A. Fourier transform infrared spectroscopy of soy hull pectins revealed differences in the region between 1800 and 1600 cm−1. Size exclusion high performance liquid chromatography was useful in identifying soy hull pectins. ©

Ambient-temperature extraction of rice bran oil with hexane and isopropanol

Hexane and isopropanol were compared as solvents for use in ambient-temperature equilibrium extraction of rice bran oil (RBO). Isopropanol was as effective as hexane in extracting RBO when 20 mL of solvent was used to extract 2 g of bran. Free fatty acid levels were 2–3% in both solvents and similar to that previously reported for hexane extraction of RBO hexane extraction by this method. Larger-scale extractions with 30 g of bran and 150 mL of solvent produced oil with a similar free fatty acid content and a phosphorus level of approximately 500 ppm. The oil extracted with isopropanol was significantly more stable to heat-induced oxidation than hexane-extracted oil. Antioxidants that are more easily extracted by isopropanol than hexane may be responsible for the increased stability.

Determination of polygalacturonic acid content in pectin extracts by diffuse reflectance Fourier transform infrared spectroscopy

Abstract A simple, rapid diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) method was developed for pectin measurement. Pectin calibration standards were prepared by blending polygalacturonic acid with potassium bromide to cover a range of polygalacturonic acid concentrations (10–98%). A linear relationship between pectin content and total carbonyl absorption band area was found ( R 2 =0.982). Linearity was up to 80% pectin, since there was no significant difference in peak areas of 80% and greater. Pectin contents of various commercial pectin samples were calculated from the linear fit equation. Accuracy of the DRIFTS method was determined by comparing the pectin contents to the values obtained by colorimetric and HPLC methods. For four different sources of samples, the pectin contents by FTIR method were 78.2, 89.4, 65.9 and 67.1%, which were comparable to values obtained by colorimetric analysis (79.1, 87.9, 64.7 and 57.7%) and HPLC (84.1, 91.4, 69.5 and 67.9%).

The Freundlich Isotherm in Studying Adsorption in Oil Processing

The objective of this review is to discuss the history of the use of the Freundlich isotherm in investigating adsorption processing of vegetable oils and to evaluate its current value in adsorption studies. The Freundlich isotherm was originally developed to explain the adsorption of a single solute from solution. However, a similar adsorption pattern has been observed when studying a more complex system of adsorption of vegetable oil pigments onto bleaching clay during commercial bleaching of vegetable oils. The Freundlich isotherm has been useful for decades in finding the commercial value of adsorbents as long as a narrow experimental interval of adsorbate is used. More recent studies have shown that a complex series of interactions controls the adsorption process. While the isotherm summarizes these interactions, investigating them is vital to understand the physicochemical factors involved during adsorption. Statistical modeling and spectroscopy are useful in understanding the vegetable oil bleaching/refining process as a multiple-component adsorption system.

Mode of Oleic Acid Adsorption on Rice Hull Ash Cristobalite

Fourier transform infrared spectroscopy was used to investigate the adsorption of oleic acid (OA) onto dry rice hull ash (RHA) silica. Adsorption partially occurred by surface hydrogen bonding of the carboxylic acid. There was also formation of carboxylate ions by reaction of OA with residual potassium oxide. These ions were strongly bound by the ash. Isopropanol inhibited OA adsorption by H-bonding and encouraged desorption of H-bonded OA, but without itself being significantly bound. RHA with 40% moisture also adsorbed a small amount of OA by H-bonding and reacted with OA to form and adsorb carboxylate ions.

Soy hull carbon as an adsorbent of minor crude soy oil components

A carbon adsorbent was prepared from soy hulls. The adsorbent was used in a laboratory study to examine its performance under commercial soy oil adsorption bleaching conditions. Phospholipids, peroxides, and free fatty acids were effectively removed from the soy oil with little effect on carotenoid content. There may be competitive adsorption between oil components, the rank of the affinity of oil components for soy carbon was phospholipid>peroxides>free fatty acid>lutein.

Rapid equilibrium extraction of rice bran oil at ambient temperature

Rapid equilibrium extraction of soybean flour has been effective in obtaining an oil with reduced phospholipid content. This technique was examined to obtain a low phospholipid and low free fatty acid rice bran oil (RBO). The amount of RBO extracted with hexane from 1 g of rice bran at 22°C was measured over a 10-min period. The amount of oil extracted from variable amounts of bran with a fixed volume of solvent was also studied. Ninety percent of the oil was extracted in one minute, with 93% of the total RBO being extracted after ten minutes. This compares with the 98% yield obtained from soy flour, but increasing the amount of bran used did not reduce the extraction rate. This extraction method produced a good quality RBO with low phospholipid, low free fatty acid and low peroxide values.

Diffuse-reflectance Fourier-transform infrared spectroscopy of vegetable oil triglyceride adsorption on silicic acid

The adsorption of triglyceride by silicic acid from hexane miscellas was observed with diffuse-reflectance Fouriertransform infrared spectroscopy. Triglyceride was adsorbed by hydrogen bonding to silanol groups through the ester carbonyl group. Addition of isopropanol (IPA) to the triglyceride-hexane solution prior to adsorption resulted in unchanged triglyceride adsorption on silicic acid despite IPAs ability to adsorb on silicic acid and hydrogen-bond with triglyceride. Washing the triglyceride, adsorbed on silicic acid, with hexane containing IPA resulted in partial desorption of the triglyceride and a small amount of IPA being adsorbed. Triglyceride desorption into fresh hexane-IPA is due to the establishment of a new equilibrium of lipid and IPA between hexane and silicic acid. The relative strengths of all the possible pairwise interactions among triglyceride, IPA and silicic acid are revealed by the relative amounts of adsorption under various conditions.