Enzymatic degradation of esters of dichloropropanols: removal of chlorinated glycerides from processed foods

The esters of dichloropropanols from the byproduct of hydrolysates during food processing were degraded by the cell-free extracts of a dichloropropanol-assimilating bacterium of Pseudomonas sp. OS-K-29. 1-Acyloxy-2,3-dichloropropane was hydrolysed into the corresponding carbonic acid and 2,3-dichloropropanol, and then the dichloropropanol was dechlorinated. The esterase activity of the cell-free extracts was effective for the esters of the dichloropropanols and monoacylglycerides, but not for hydrolysing the lipase substrates such as triacylglycerides and Tween 60. A comparative study using a series of octanoyl glycerides and the esters of the dichlopropanols showed that the substrate specificities of the cell-free extracts were similar to the monoacylglyceride lipase from Penicillium camembertii.     

柠檬酸甘油单,二酸酯合成过程中沉淀物的分析

对柠檬酸和单甘酯酯化反应制取柠檬酸甘油单、二酸酯过程中产生的沉淀进行了红外光谱分析，并对沉淀产物的原因提出了合理的解析。     

Characterization of vegetable oils‐alumina membranes interactions by diffuse reflectance Fourier transform infrared spectroscopy

Adsorption of vegetable oil components, either as pure molecules or as mixtures, on alumina membranes was investigated by diffuse reflectance Fourier transform infrared spectroscopy. All tested compounds displayed very similar spectra. Triolein and diolein physically adsorb onto alumina by hydrogen bonding with the carbonyl groups of the carboxylic ester and surface hydroxyls. Monolein most likely interacts with glycerol hydroxyls, while phospholipids appear to adsorb either by the ester carbonyl or charged phosphate group. Due to the catalytic properties of alumina some hydrolysis takes place during treatments. The resulting oleic acid, most likely chemisorbs by ionic interactions with the carboxylic C=O bond of the alumina. The fact that no change in the symmetric and asymmetric CH₂ stretches is noticed in comparison with the free (unbound) form indicates that the molecules are not parallel, but at an angle to the surface. When alumina comes into contact with increasing amounts of crude vegetable oils a broadening of the band at 3280 cm^‐1 indicates an increasing adsorption of molecules with free hydroxyls, such as mono‐ and di‐acylglycerols or phospholipids. Among all oil components, sodium oleate seems to adsorb preferentially to alumina. However, a subsequent adsorption of a lipidic monolayer at the membrane surface or even inside the pores, is not consistent with the drastic flux reduction observed in previous studies during microfiltration, and could only initiate formation or/and deposition of macromolecular structures inside membrane pores.     

Separation of oil constituents in organic solvents using polymeric membranes

Different types of commercial nonporous (reverse osmosis and gas separation) polymeric membranes were screened for their abilities to separate FFA, MG, DG, and TG from a lipase hydrolysate of high-oleic sunflower oil after diluting it with organic solvents (ethanol and hexane). Cellulose acetate (CA) (NIR-1698) membrane gave the largest difference in rejection between FFA and glycerides and high flux in oil/ethanol mixtures. In the hexane system, the values of permeate flux and rejection were generally lower than those in the ethanol system. The silicone-polyimide composite membrane (NTGS-2100) gave the highest flux and rejections of solutes (70.2% for FFA, 94.4% for TG) in oil/hexane mixtures. In the ethanol system with the CA membrane, TG had the highest rejection (98%) followed by DG (90%) and MG and FFA (50–70%) when the oil concentration was varied from 6.3 to 45.8%. A discontinuous diafiltration process (16 batches) using the CA membrane with ethanol changed the composition of the oil from 31∶28∶9∶32 TG/DG/MG/FFA to 65∶30∶1∶4. The results of this study showed that oil constituents can be separated in suitable solvents using appropriate nonporous membranes.     

马尾松磨木浆经脂肪酶处理后树脂中甘油三酸酯的变化

利用DEAE-Sephadex离子交换色谱、GC、13C-NMR、1H-NMR和IR分析技术对马尾松磨木浆经来自Candidallipolytica的脂肪酶处理后树脂中甘油三酸酯的变化进行了研究。结果表明，脂肪酶处理可以降低纸浆中甘油三酸酯的含量；而树脂中的其它化学组分则未发现变化.     

Synthesis of medium-chain glycerides using lipase from Candida rugosa

Enzymatic synthesis of medium-chain glycerides (MCG) from capric acid and glycerol was studied using lipase from Candida rugosa. The effects of various reaction parameters such as time, molar ratio of substrates (mmol capric acid/mmol glycerol), amount of lipase, type of organic solvents, and initial water activity (a _w ) were studied. The best conditions tested for MCG synthesis at 37°C were, respectively, time, 24 h; molar ratio of substrates, 2.5; and amount of lipase, 100.0 mg. The use of organic solvents greatly influenced the activity of lipase in the synthesis of MCG. Generally, activity of lipase was high in nonpolar solvents with log P values from 3.50 to 4.50, where P is the partition coefficient between water and 1-octanol. The enzymatic synthesis of MCG was preferably carried out at an initial a _w of 0.328, which resulted in maximal yield. Analysis of the products of reaction using gas chromatography showed that lipase from Candida rugosa seemed to produce more dicaprin and tricaprin than monocaprin.     

Comparison of lipase-transesterified blend with some commercial solid frying shortenings in Malaysia

A transesterified experimental solid frying shortening was prepared from a palm stearin/palm kernel olein blend at 1∶1 ratio (by weight) by using Rhizomucor miehei lipase at 60°C for 6 h. The fatty acid (FA) and triacylglycerol compositions, polymorphic forms, melting and cooling characteristics, slip melting point (SMP), and solid fat content (SFC) of the transesterified blend were then compared with five commercial solid frying shortenings (three domestic and two imported) found in Malaysia. All the domestic shortenings contained nonhydrogenated palm oil or palm olein and palm stearin as the hard stock, whereas the imported frying shortenings were formulated from soybean oil and cottonseed oil and contained high level of β′ crystals. Trans FA were also found in these samples. The lipase-transesterified blend was found to be more β′-tending than the domestic samples. The SMP of the transesterified blend (47.0°C) fell within the range of the domestic samples (37.8–49.7°C) but was higher than the imported ones (42.3–43.0°C). All samples exhibited similar differential scanning calorimetry cooling profiles, with a narrow peak at the higher temperatures and a broad peak at the lower temperatures, even though their heating thermograms were quite different. Imported samples had flatter SFC curves than both the experimental and domestic samples. The domestic samples were found to have better workability or plasticity at higher temperatures than the imported ones, probably because they were formulated for a tropical climate.     

Characterisation of acylglycerol synthesis in aqueous foams by lipases

Low water systems have become important for organic synthetic reactions catalysed by enzymes. Esterification reactions could be catalysed by lipase in multiphasic reaction media, such as foams, containing excess water. The esterification of glycerol with oleic acid catalysed by lipase in aqueous foams has been characterised. More than 80% of the oleic acid was converted to glycerides within 10 h. Preliminary characterisation of the reaction with respect to time, pH and temperature indicate that acylglycerol synthesis in foam media as similar to hydrolysis by the same lipase. The observed high K_m of glycerol for the esterification reaction may be due to poor surface active properties of glycerol. The unique advantages of foam as a medium to conduct lipase reactions are discussed. © 1999 Society of Chemical Industry     

Oligopolymer,diglyceride and oxidized triglyceride contents as measures of olive oil quality

The objective of this study was to test the qualities of olive oils of different commercial grades by quantifying oligopolymer compounds by high-performance size-exclusion chromatography (HPSEC). The method required no sample manipulation and was accurate and rapid. The mean level of oligopolymers in refined olive oils was 0.70% and was more than twice as high in refined olive pomace oils. Conversely, edible virgin olive oils had no oligopolymer compounds. HPSEC analyses of polar compounds by silica gel column chromatography also allowed determination of oxidized triglycerides and partial glycerides, which help define levels of oxidative degradation and hydrolysis. Research supported by National Research Council of Italy, Special Project RAISA, Sub-project 4, Paper No. 321.     

Preparative separation of phenylpropenoid glycerides from the bulbs of Lilium lancifolium by high-speed counter-current chromatography and evaluation of their antioxidant activities

Preparative separation of seven phenylpropenoid glycerides from the bulbs of Liliumlancifolium (lily), was conducted by high-speed counter-current chromatography (HSCCC) with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-0.05% aqueous trifluoroacetic acid (TFA) (3:5:3:5, v/v/v/v). These phenylpropenoid glycerides were identified as 1-O-feruloylglycerol (1), 1-O-p-coumaroylglycerol (2), 1-O-caffeoyl-3-O-p-coumaroylglycerol (3), 1,2-O-diferuloylglycerol (4), 1,3-O-diferuloylglycerol (5), 1-O-feruloyl-3-O-p-coumaroylglycerol (6), and 1,3-O-di-p-coumaroylglycerol (7), respectively, by ESI-MS, ¹H NMR and ¹³C NMR. Their antioxidant activities were evaluated by DPPH radical scavenging activity, ABTS radical cation scavenging activity, and ferric-reducing antioxidant power (FRAP). The trend in antioxidant capacity was similar in all the three assays, with 3 > 1, 4, 5, 6 > 2, 7. This is the first report on simultaneous separation of seven antioxidantive phenylpropenoid glycerides from L. lancifolium by HSCCC.