DAG Oil Research Articles

Insights into the difference between diglyceride-oil based and triglyceride-oil based oleogels: Physical property, crystal structure and stability

This paper investigated the differences in the structure and properties of diglyceride (DAG) oleogels (DAG as the oil phase) and triglyceride (TAG) oleogels (TAG as the oil phase) with different gelator concentrations of beeswax (BW) and monoacylglycerol (MAG). When BW was used as gelator, compared with TAG oleogels, the mass of β′ crystals in DAG-oil based oleogels increased, the crystal network stability improved, and the G′ increased. In addition, the DAG-oil based oleogels prepared with BW showed hydrogen bonds. When MAG was used as gelator, the G′, the thermal and crystal network stability of DAG-oil based oleogels decreased compared to TAG oleogels, and large number of crystal clusters were formed. In addition, DAG-oil based oleogels showed lower oxidative stability than TAG oleogels. These results contribute to a better understanding the properties of DAG oil based oleogels and facilitate the development of low-fat functional plastic products.

Assessing the effectiveness of peanut diacylglycerol oil-ethylcellulose/monoglyceride-based oleogel in sponge cake as a margarine replacer

The aim of this research was to partially substitute margarine with peanut diacylglycerol oil-ethylcellulose/monoglyceride (DAG-EC/MG) oleogel and assess its effect on the texture of sponge cake. Fourier transform infrared spectrometry analysis showed that the carboxyl headgroups of MG could induce van der Waals forces in polar DAG oil, while the glycerol headgroups of MG could induce hydrogen bond interactions with EC in TAG oil. The oil binding capacity (OBC) indicated that all OBC values of DAG-based oleogels were above 95%, which was approximately 20% higher than that of TAG-based oleogels. The morphological analysis showed that the DAG-based oleogel exhibited thinner crystals than the TAG-based oleogel. Differential scanning calorimetry (DSC) analysis demonstrated that the addition of MG could enhance the thermal resistance of DAG-based oleogels. Rheological analysis showed that MG with carboxyl headgroups tended to produce soft gels in polar DAG oil. The hardness of the DAG-based oleogel cake decreased by 88.54% from 20.42 to 2.34 N with the addition of MG, which indicated that MG compensated for the negative influence of EC on the hardness of the DAG-based oleogel cake. The sponge cake with 50% substitution by DAG-based oleogel exhibited satisfactory texture profiles. Additionally, no difference in the overall acceptability was observed between DAG-based oleogels commercial margarine-based cakes. Consequently, DAG-based oleogel cakes are promising bakery products that possess a solid fat content reduction of up to 50% while maintaining bakery product sensory properties.

The effect of DAG oil replacing TAG oil on weight control and glycolipid metabolism: A meta-analysis of randomized controlled trials

• DAG oil intake reduces body weight and body mass index in healthy people. • Intake of DAG oil has a specific effect on reducing WC and serum TC. • The duration of eating DAG oil is significantly related to the effect of weight loss. • The longer the intake of DAG oil, the better the weight loss effect. The primary objective of this study is to summarize the effect of diacylglycerol (DAG) oil consumption on weight loss, glucose and lipid metabolism. The weighted mean difference (WMD) with 95% CI’s was calculated using the generic inverse variance approach. Heterogeneity was assessed and analyzed using the Cochran Q-statistic. In the overall analysis, intake of DAG oil can significantly reduce body weight (BW), body mass index (BMI), waist circumference (WC) in healthy people, and serum triacylglycerol (TAG) in people with diseases related to glucose and lipid metabolism, but has no significant effect on blood glucose (BG). Meta-regression analysis based on duration of intervention was significant for BW, BMI, and WC. The longer the intake of DAG oil, the better the weight loss effect. Pooled analyses show that DAG oil consumption has health advantages in maintaining a healthy weight, BMI, WC, serum TAG, and BG levels.

The digestion of diacylglycerol isomers by gastric and pancreatic lipases and its impact on the metabolic pathways for TAG re-synthesis in enterocytes

The specific activities of gastric and pancreatic lipases were measured using triacylglycerols (TAG) from rapeseed oil, purified 1,3-sn-DAG and 1,2(2,3)-sn-DAG produced from this oil, as well as a rapeseed oil enriched with 40% w/w DAG (DAGOIL). Gastric lipase was more active on 1,3-sn-DAG than on 1,2(2,3)-sn-DAG and TAG, whereas pancreatic lipase displayed a reverse selectivity with a higher activity on TAG than on DAG taken as initial substrates. However, in both cases, the highest activities were displayed on DAGOIL. These findings show that DAG mixed with TAG, such as in the course of digestion, is a better substrate for lipases than TAG. The same rapeseed oil acylglycerols were used to investigate intestinal fat absorption in rats with mesenteric lymph duct cannulation. The levels of TAG synthesized in the intestine and total fatty acid concentration in lymph were not different when the rats were fed identical amounts of rapeseed oil TAG, 1,2(2,3)-sn-DAG, 1,3-sn-DAG or DAGOIL. Since the lipolysis of 1,3-sn-DAG by digestive lipases leads to glycerol and not 2-sn-monoacylglycerol (2-sn-MAG) like TAG lipolysis, these results suggest that the re-synthesis of TAG in the enterocytes can entirely occur through the “glycerol-3-phosphate (G3P)” pathway, with the same efficiency as the 2-sn-MAG pathway predominantly involved in the intestinal fat absorption. These findings shed new light on the role played by DAG as intermediate lipolysis products. Depending on their structure, 1,2(2,3)-sn-DAG versus 1,3-sn-DAG, DAG may control the pathway (2-sn-MAG or G3P) by which TAG are re-synthesized in the enterocytes.

Two-step enzymatic synthesis of α-linolenic acid-enriched diacylglycerols with high purities from silkworm pupae oil.

In this study, α-linolenic acid-enriched diacylglycerols (ALA-DAGs) were prepared via a two-step enzymatic way by combi-lipase using silkworm pupae oils as substrates. Firstly, several factors including temperature, mass ratio of water to oil, pH and enzyme loading were optimized for the hydrolysis of silkworm pupae oil. The maximum fatty acid content (96.51%) was obtained under the conditions: temperature 40°C, water/oil 3:2 (w/w), pH 7, lipase TL100L loading 400U/g, lipase PCL loading 30U/g. Then, ALA was enriched by urea inclusion, with an increased ALA content of 82.50% being obtained. Secondly, the ALA-enriched silkworm pupae DAG oil (SPDO) was prepared by lipase PCL-catalyzed esterification reaction. After molecular distillation, the final SPDO product contained contents of DAGs (97.01%) and ALA (82.50%). This two-step enzymatic way for production of ALA-DAGs was successfully applied in a 100-fold scale-up reaction. Overall, our study provides a promising way for the preparation of ALA-DAGs.

Novel structured diacylglycerol (DAG) rich oleo formulations activate the Nrf2 pathway and impedes NF-κB translocation to mitigate pre-clinical conditions of hypertension

Abstract The objective of the present work was to assess the ameliorative potential of two novel edible diacylglycerol oil-formulations comprising caprylic acid, C8:0 or capric acid, C10:0 in treating CdCl2 induced in vivo hypertension at molecular level. Male Wistar rats were randomly divided into 4 groups (1) control; (2) DAG oil-treated group (2 gm/day DAG oil); (3) hypertensive group (1.0 mg/kg of CdCl2 for 2 weeks, i. p); and (4) hypertensive/DAG oil-treated group (2 gm/day DAG oil) (14 days). Hematological, biochemical and molecular parametric tools were performed to evaluate the protective efficacy of DAG oils against CdCl2-induced hypertension. Systolic blood pressure (SBP) measured non-invasively using BIOPAC-MP36 system (BIOPAC System Inc., USA). It was found that the pretreatment of DAG oil provided a significant improvement in renal antioxidant status, reduced the lipid peroxidation and the levels of inflammatory markers that were aggravated due to induced CdCl2-toxicity. Further, results of protein expression showed that DAG oil pretreatment normalized the renal expression of Nrf2/Keap1 and its downstream regulatory proteins in CdCl2-treated rat kidney. DAG oils also effectively attenuated CdCl2-induced renal apoptosis by the up-regulation of anti-apoptotic proteins such as Bcl-2 and down-regulation of Bax, caspase-3, caspase-9 and Cytochrome c. Histological and immunohistochemical observations provided further evidence that the DAG oils effectively protected the kidney from CdCl2-mediated oxidative damage. The results suggest that DAG oils ameliorated CdCl2-induced oxidative renal injury by activating the Nrf2/Mn-SOD pathway and inhibiting the ROS/NF-κB pathway. Evidences have revealed that Cy-DAG exhibited better efficacy than the Cp-DAG against induced hypertensive conditions.

Retardation Mechanism of Crystallization of Diacylglycerols Resulting from the Addition of Polyglycerol Fatty Acid Esters

Edible oils containing high concentrations (>80%) of diacylglycerols (DAG oil) have beneficial health effects on obesity and obesity-related diseases; however, at low temperature, undesired precipitation of high-melting fractions in DAG oil can occur. Thus, preventing the precipitation of high-melting saturated fatty acid moieties in DAG oil is crucial for its expanded use. In this study, we investigated the mechanism of retardation of crystallization of DAG oil through the addition of polyglycerol fatty acid esters (PGFEs). We observed the occurrence of birefringence under polarized crossed-Nicols conditions in the PGFE-added DAG oil. We also found that prior to the crystallization of high-melting DAG fractions, PGFE-added DAG oil showed shear-rate-dependent changes in viscosity, providing strong evidence for the existence of self-assembled structures that lead to the birefringence. Furthermore, small- and wide-angle X-ray diffraction patterns suggest the formation of a supramolecular assembly comprising...

지방산 종류에 따른 Diacylglycerol의 효소적 개질 연구

Abstract : Diacylglycerol-oil (DAG oil) and four kinds of fatty acids〔C16:0, C18:0, perillar oil-hydrolyzate(C18:3, 59.7%) and docosahexaenoic acid(DHA, C22:6, 63.7%)〕 were enzymatically esterified with 1:0.5, 1:1 and 1:1.5 molar ratio (DAG oil: fatty acids) to produce structured DAG. The reaction mixture were catalyzed by addition of sn-1,3 specific Lipozyme RMIM with 10 wt% of total substrates, and reacted for 1, 3, 6 and 24 hr at 62℃ with 220 rpm on the shaking water bath. The produced DAG were analyzed by TLC. In the result, the proportion of each fatty acid〔(C16:0, C18:0, perilla oil-hydrolysate(C18:3, 59.7%) and DHA(C22:6, 63.7%)〕on DAG products were increased as molar ratios of substrate increased. Among them, DHA showed the least reaction rate in which 24.2 % of DHA was found in the structured DAG molecules after 24 hr reaction with 1:1.5 molar substrate amount ratio. Key words : Enzymatic modification, Diacylglycerol, Fatty acids *Corresponding author: Tel: +82-42-821-6729E-mail address: ktlee@cnu.ac.kr

Retardation of Crystallization of Diacylglycerol Oils Using Polyglycerol Fatty Acid Esters

AbstractLiquid oil containing high concentrations of diacylglycerols (DAG > 80 %, hereafter referred to as DAG‐rich oil) is generally more likely to cause precipitation at chilled temperatures (clouding phenomena) than triacylglycerol‐based oil. The clouding phenomena that occur during long‐term storage of DAG‐rich oil are unwanted in consumer products and therefore, must be prevented. In the present study, we attempted to retard precipitation by adding food emulsifiers, polyglycerol fatty acid esters (PGFE) containing different fatty acid moieties. DSC, polarized optical microscopy, and X‐ray diffraction studies revealed that the addition of 0.2 % PGFE containing palmitic and oleic acid moieties very effectively retarded precipitation in the DAG‐rich oil. To confirm these observations, we prepared a model DAG oil to mimic DAG‐rich oil and examined the retardation behavior of high‐melting DAG fractions using PGFE. The results are discussed in terms of the effects of PGFE additives on the pre‐nucleation processes of high‐melting fractions in DAG‐rich oil.

The sound velocity measurement in diacylglycerol oil under high pressure

In this article, the influence of high pressure on sound velocity at 293 K has been presented. The investigated diacylglycerol oil (DAG – [D82T18]AG) was composed of 82% DAGs and 18% triacylglycerols. The variation of sound velocity with hydrostatic pressure for DAG was evaluated up to 400 MPa. The phase transformation in DAG has been observed as a discontinuity of the dependence of sound velocity on pressure. The sound velocity during the phase transition has shown distinct increment. Also the volume changes have been measured. It has shown the rapid drop of the volume at the phase transformation pressure due to the possible crystallization of DAG oil.

Measurement of glycidol hemoglobin adducts in humans who ingest edible oil containing small amounts of glycidol fatty acid esters

Hemoglobin (Hb) adducts are frequently used to address and/or monitor exposure to reactive chemicals. Glycidol (G), a known animal carcinogen, has been reported to form Hb adducts. Here, we measure G adduct levels in humans who daily ingest DAG oil, an edible oil consisting mainly of diacylglycerol. Since DAG oil contains a small amount of glycidol fatty acid esters (GEs), possible exposure to G released from GEs has been raised as a possible concern. For measurement of Hb adducts, we employed the N-alkyl Edman method reported by Landin et al. (1996) using gas chromatography–tandem mass spectrometry with minor modifications to detect G-Hb adducts as N-(2,3-dihydroxy-propyl)valine (diHOPrVal). Blood samples were collected from 7 DAG oil users and 6 non-users, and then G-Hb adduct levels were measured. G-Hb adducts were detected in all samples. The average level of diHOPrVal was 3.5±1.9pmol/g globin in the DAG oil users and 7.1±3.1pmol/g globin in the non-users. We conclude that there is no increased exposure to G in individuals who daily ingest DAG oil.

Abstract 2474: Increased PKC expression in diacylglycerol-induced mammary carcinogenesis in the human c-Ha-ras proto-oncogene transgenic rat

Abstract Protein kinase C (PKC) is implicated in cell proliferation and tumor promotion. PKC is activated by 1, 2-diacylglycerol (1, 2-DAG). An edible oil that includes 70% 1,3-DAG and 30% 1,2-DAG is commercially available in Japan, USA, and European countries. To examine whether the DAG oil enhances mammary carcinogenesis and to measure whether DAG affects the levels of PKC expression, we carried out this study with human c-Ha-ras proto-oncogene transgenic (Hras128) rats that are highly susceptible to mammary carcinogenesis. Hras128 rats (6-week-old) were randomly assigned into four experimental groups. DAG oil was administered to the rat as oral drops. Group 1 (G1): 0.5 mL triacylglyceraol (TAG) x2/week, Group 2 (G2): 0.5 mL DAG x2/week, Group 3 (G3): 0.5 mL TAG x1/week plus 0.5 mL DAG x1/week, Group 4 (G4): 0.5 mL DAG x1/2 weeks + 0.5 mL TAG x3/2 weeks. Experiment was terminated after 15 weeks. Mammary tumors were histologically identified as adenocarcinoma. Tumor incidence of G2 (77%) and G3 (77%) was significantly higher than G1 (22%). Tumor multiplicity of G2 (1.3 ± 1.1) was significantly higher than the other 3 groups (G1, 0.4 ± 1.0; G3, 0.9 ± 0.6; G4, 0.7 ± 1.0). In tumor samples, the mRNA expression levels of 6 PKC isoforms (α, δ, ε, η, λ, ν) increased compared to the adjacent normal tissues. In a parallel study, we also examined the levels of PKC expression in normal mammary tissues of Hras128 rats treated with either TAG or DAG oils alone for 4 weeks. The mRNA expression levels of 5 PKC isoforms (δ, ε, η, λ, θ) significantly increased in the DAG-treated normal tissues compared to the TAG-treated normal tissues. These findings provide evidence that treatment of Hras128 rats with DAG oil may promote mammary carcinogenesis by inducing expression of several PKC isoforms. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2474.

Possible enhancing activity of diacylglycerol on 4-nitroquinoline 1-oxide induced carcinogenesis of the tongue in human c-Ha- ras proto-oncogene transgenic rats

1,2-Diacylglycerol (1,2-DAG) is involved in cell proliferation as an activator of protein kinase C (PKC) and has been shown to stimulate growth of cancer cells, raising the possibility of a role in tumor promotion. Ingested DAG oil, containing 70% 1,3-DAG and 30% 1,2-DAG, is digested and considered to be safe as edible oil. However, DAG may directly contact with oral cavity mucosa in undigested form. The present study was conducted to examine the effects of DAG oil on carcinogenesis in c-Ha- ras proto-oncogene transgenic (Tg) rats administered 4-nitroquinoline 1-oxide (4NQO, 10 ppm) in their drinking water for 10 weeks for initiation of mainly upper digestive organs. DAG oil added in basal diet at 5.5%, 2.75%, 1.38% and 0% with total fat made up to 5.5% with triacylglycerol (TAG) was administered during the initiation and post-initiation period. The study was terminated at week 12 (Tg females) and 20 (Tg males, wild females and males). The fatty acid composition of DAG oil was similar to TAG (linoleic acid 46.6% and oleic acid 38.9%). In Tg male rats, DAG oil administration was associated with significant increase ( P < 0.05) in the incidence of squamous cell carcinomas (SCC) of the tongue (5.5% DAG, 43.8%; 2.75% DAG, 20%; 1.38% DAG, 14.3%; 0%, 12.3%) with the Cochran–Armitage trend test and also number of tumors in coefficients for linear contrast trend tests. Tongue SCC induction of wild males and all females was not significant. The present results suggest that DAG oil may have enhancing and/or promotion potential for tongue carcinogenesis in male Tg featuring elevated ras expression.

Diacylglycerol Oil Does Not Affect Portal Vein Transport of Nonesterified Fatty Acids but Decreases the Postprandial Plasma Lipid Response in Catheterized Pigs

Studies have shown several beneficial effects of dietary diacylglycerol oil (DAG oil), but the mechanism behind these effects is still not clear. One hypothesis is that an increase in portal vein transport of nonesterified fatty acids (NEFA) with subsequent oxidation in the liver might be responsible for the positive effects. We examined the portal vein transport of NEFA and other lipid related variables, in response to DAG and triacylglycerol (TAG) bolus feeding and a bolus of standard pig feed in 4 portal vein and mesenteric artery catheterized pigs. Also, the effect of the boluses on postprandial lipid variables was examined. Portal vein transport of NEFA did not differ when pigs were administered the 2 oil bolus diets, consistent with the similar portal plasma concentrations of oleic and linolenic acids during h 1 after feeding. Glycerol, on the contrary, was transported by the portal vein to a much higher degree after intake of DAG oil (P < 0.001; 20, 40, and 60 min). The postprandial arterial TAG response at 5 and 6 h postprandially was significantly lower after the DAG bolus intake. Analysis of Delta AUC for the 6-h postprandial period of selected and total fatty acids showed a lower concentration of vaccenic acid (P = 0.002) after the DAG bolus diet. In conclusion, DAG bolus feeding did not increase the portal transport of NEFA, but it did increase the portal transport of glycerol and lower the postprandial lipid concentration in arterial plasma.

Effect of diacylglycerol on the development of impaired glucose tolerance in sucrose‐fed rats

The effects of DAG oil and TAG oil on impaired glucose tolerance in rats that were fed a diet containing high levels of sucrose were compared. Male Wistar rats (8 wk old and 32 wk old) were fed either high-sucrose (57.5% sucrose w/w) or control diets containing either 10% (w/w) DAG or TAG oil with a similar FA composition for 48 wk in 8-wk-old rats and for 24 wk in 32-wk-old rats. Plasma lipids, the size of the islets of Langerhans, and insulin, glucose, and adipocytokine levels were measured. An oral glucose tolerance test (OGTT) was carried out during the study period. For rats in both age groups that were fed a high-sucrose diet, the DAG oil group had lower plasma glucose and insulin response in an OGTT, and lower homeostasis model assessment-R levels, than the TAG oil group. Furthermore, in 8-wk-old rats that were fed a high-sucrose diet, the DAG oil group accumulated less visceral fat and showed suppressed decreases [corrected] of plasma adiponectin and [corrected] increases of plasma insulin, leptin, and the size of islet of Langerhans compared with the TAG oil group. No difference in the OGTT was found between the DAG and TAG oil groups in either age group of rats fed a control diet. In conclusion, these results suggest that DAG oil ingestion prevents the high-sucrose-diet-induced development of impaired glucose tolerance compared with TAG oil ingestion.

Oxidative stability of diacylglycerol oil and butter blends containing diacylglycerols

AbstractDiacylglycerol (DAG) oils produced from sunflower oil and traditional sunflower oil were stored for 20 wk at 38 °C, and their oxidative stability was measured. Moreover, two butter blends were produced containing 40 wt‐% DAG oil made from sunflower oil or rapeseed oil, respectively, as well as two control butter blends with sunflower oil or rapeseed oil. Their oxidative stability during storage at 5 °C for up to 12 wk was examined by similar means as for the pure oils. The storage study of the oils indicated that the DAG oil was oxidatively less stable as compared to sunflower oil, but that they had similar sensory quality. Storage of the butter blends revealed that blends with the two types of rapeseed oil (triacylglycerol (TAG) or DAG oil) were oxidatively more stable than the blends containing oils from sunflower. There was no unambiguous indication of DAG butter blends having a different stability than their respective control TAG blends. However, they had a significantly less salty and buttery flavour, which was ascribed to a much smaller water droplet size causing a delayed sensory perception in the mouth. The butter blend with DAG oil from rapeseed had a very neutral flavour. On the contrary, the butter blend with DAG oil from sunflower had a more rancid aroma and flavour than its control blend with sunflower oil.

Lipolysis of different oils using crude enzyme isolate from the intestinal tract of rainbow trout,Oncorhynchus mykiss

Crude enzyme isolate was prepared from the intestine of rainbow trout. Positional specificity of the crude enzyme isolate was determined from both 1(3)- and 2-MAG products after in vitro lipolysis of radioactive-labeled triolein. The ratio of 2-MAG/1(3)-MAG was 2:1, suggesting that the overall lipase specificity of the enzyme isolate from rainbow trout tended to be 1,3-specific; however, activity against the sn-2 position also was shown. In vitro lipolysis of four different unlabeled oils was performed with the crude enzyme isolate. The oils were: structured lipid [SL; containing the medium-chain FA (MCFA) 8:0 in the sn-1,3 positions and long-chain FA (LCFA) in the sn-2 position], DAG oil (mainly 1,3-DAG), fish oil (FO), and triolein (TO). MCFA were rapidly hydrolyzed from the SL oil. LCFA including n-3 PUFA were, however, preserved in the sn-2 position and therefore found in higher amounts in 2-MAG of SL compared with 2-MAG of FO, DAG, and TO. Lipolysis of the DAG oil produced higher amounts of MAG than the TAG oils, and 1(3)-MAG mainly was observed after lipolysis of the DAG oil. The positional specificity determined and the results from the hydrolysis of the different oils suggest that n-3 very long-chain PUFA from structured oils may be used better by aquacultured fish than that from fish oils.

Metabolities of dietary triacylglycerol and diacylglycerol during the digestion process in rats

The present study investigated the metabolic fate of dietary TAG and DAG and also their digestion products in the stomach and small intestine. A diet containing 10% TAG or DAG oil, enriched in 1,3-DAG, was fed to Wistar rats ad libitum for 9 d. After 18 h of fasting, each diet was re-fed ad libitum for 1 h. The weights of the contents of the stomach and small intestine were measured, and the acylglycerol and FFA levels were analyzed by GC at 0, 1, and 4 h after the 1-h re-feeding. The amounts of re-fed diet ingested and the gastric and small intestinal content were not different between the two diet groups. In the TAG diet group, the main products were TAG and DAG, especially 1(3),2-DAG. In addition, 1,3-DAG and 1(3)-MAG were present in the stomach, and the 1,3-DAG levels increased over time after the re-feeding period. In the DAG diet group, the main products in the stomach were DAG, MAG, FFA, and TAG. There were significantly greater amounts of 1,3-DAG, 1(3)-MAG, and FFA in the DAG diet group in the stomach compared with the TAG diet group. The amount of FFA in the stomach relative to the amount of ingested TAG plus DAG in the DAG diet group was higher than that in the TAG diet group. Acylglycerol and FFA levels were considerably lower in the small intestine than in the stomach. These results indicate that, in the stomach, where acyl migration might occur, the digestion products were already different between TAG and DAG oil ingestion, and that DAG might be more readily digested by lingual lipase compared with TAG. Furthermore, almost all of the dietary lipid was absorbed, irrespective of the structure of the acylglycerol present in the small intestine.

Characterization of diacylglycerol oil mayonnaise emulsified using phospholipase A2‐treated egg yolk

AbstractMayonnaise samples were prepared using DAG oil as the oil phase; the properties and stability were compared with mayonnaise samples prepared from TAG oil. Normal (nontreated) egg yolk and phospholipase A2 (PLA2)‐treated egg yolk were used as emulsifiers. The DAG oil mayonnaise prepared with nontreated egg yolk (DAG‐M) was unstable, with cracks forming within 4 wk at 40°C. This type of fracture was not observed for TAG oil mayonnaise prepared with nontreated egg yolk (TAG‐M). 31P NMR and quantitative analyses of phospholipids suggested that the phospholipids of egg yolk lipoprotein were dissolved in DAG‐M oil droplets, which might result in the coalescence and fracture of the DAG‐M. Phospholipids were not dissolved in TAG‐M oil droplets. No crack formation was observed for DAG oil mayonnaise prepared with PLA2‐treated egg yolk (DAG‐PLM) after storage for more than 4 wk at 40°C. 31P NMR spectroscopy and quantitative analyses of phospholipids indicated that the dissolution of phospholipid molecules into the oil droplets was almost prevented in DAG‐PLM. The stability of DAG‐PLM is improved probably because the PLA2 treatment changes the molecular polarity of egg yolk phospholipids and prevents them from dissolution into the DAG oil droplets from oil/water interface.

Digestion and assimilation features of dietary DAG in the rat small intestine.

Several recent studies have demonstrated that dietary DAG oil rich in 1,3-species suppresses the postprandial increase of serum TAG level and decreases body fat accumulation, compared with TAG oil. To clarify the mechanisms underlying the beneficial effects of DAG, we investigated the metabolic features of DAG in the small intestine with regard to the digestion pathway in the lumen and the TAG-synthesis pathway in the mucosa. When intraduodenally infused as an emulsion, TAG was digested to 1,2-DAG, 2-MAG, and FFA, whereas 1,3-DAG was digested to 1(3)-MAG and FFA. When assessed by the incorporation of [1-14C]linoleic acid in lipids, the mucosal TAG-synthesis was significantly reduced by DAG infusion compared with TAG infusion. However, the mucosal 1,3-DAG synthesis was remarkably increased in the DAG-infused rats. The total amount of mucosal 1,3-DAG was also increased (4.5-fold) after DAG infusion compared with that after TAG infusion. Next, we examined the synthesis pathway of 1,3-DAG. In cultures of the everted intestinal sacs, 1,3-DAG production required the presence of 1-MAG, suggesting that the 1,3-DAG synthesis was due to acylation of 1(3)-MAG in the DAG-infused rats. Furthermore, measurements of DAG acyltransferase activity indicated that 1,3-DAG was little utilized in TAG synthesis. These findings suggest that features of 1,3-DAG digestion and assimilation in the intestine may be responsible for the reduction of the postprandial serum TAG level by dietary DAG.