Corn Oil Emulsion Research Articles

Learned Suppression of Intake Based on Anticipated Calories: Cross-Nutrient Comparisons

Warwick, Z. S., K. J. Bowen and S. J. Synowski. Learned suppression of intake based on anticipated calories: Cross-nutrient comparisons. Physiol Behav 62(6) 1319–1324, 1997.—Following training with distinctively flavored solutions which differ in calories and thus in their postingestive effects, rats demonstrate flavor–postingestive consequence learning by preferentially consuming one of the flavors in two-bottle tests (both flavors presented in nutrient-identical solutions). The direction of the preference—for the flavor previously paired with more calories (F-hi) or for the flavor previously paired with fewer calories (F-lo)—depends critically upon the magnitude of postingestive effects experienced during training. The most frequent and more thoroughly investigated observation has been preferential consumption of F-hi (conditioned flavor preference). However, when relatively concentrated solutions (e.g., 5% and 30% sucrose) are used as the training nutrients, F-lo is preferentially consumed in two-bottle tests. This lesser intake of F-hi presumably reflects its previous association with the more potent satiating effect of the highly concentrated nutrient: conditioned satiety. The present series of experiments explored conditioned satiety across nutrient types. In each experiment, rats consumed 30 mL of distinctively flavored nutritive solution per day, alternating between a distinctively flavored high-calorie (1.6 kcal/mL) solution and a lower calorie (0.2 kcal/mL) solution containing a different flavor. Two-bottle testing evaluated whether conditioned satiety was evident. Experiment 1 found that rats trained with sucrose, fructose, glucose, maltodextrin, or saccharin-sweetened medium-chain triglyceride oil emulsion preferentially consumed F-lo in two-bottle tests. In contrast, rats trained with corn oil emulsions tended to preferentially consume F-hi. In Experiment 2, increasing the number of corn oil calories associated with F-hi produced a tendency toward preferential intake of F-lo in two-bottle tests. In Experiment 3, rats consumed a high-fat maintenance diet; sucrose-trained rats again consumed more F-lo than F-hi, whereas rats trained with corn oil emulsions showed a tendency (nonsignificant) to consume more F-lo in two-bottle tests. In Experiment 4, however, adding saccharin to corn oil emulsions did produce conditioned satiety. These findings demonstrate conditioned satiety as a robust phenomenon across various nutrient types; however, corn oil calories entrain conditioned satiety only under certain conditions.

Effect of oral versus gastric delivery on gastric emptying of corn oil emulsions.

Several studies have shown that fluids delivered to the stomach tend to empty more rapidly than when ingested by mouth. To better characterize the "delivery route effect" for corn oil, rats received intragastric or intraoral infusions matched for concentration and for the rate and duration of stimulus delivery. We showed, first, that more than twice as much oil emptied by the end of 12-min intragastric versus intraoral infusions but that the emptying curves remained roughly parallel for 1 h after infusion offset. Remaining experiments therefore focused on stimulus parameters of relevance to emptying control during stomach fill. Emptying during intragastric infusions approximately doubled with doublings of oil concentration (25-50%), infusion duration (6-12 and 12-24 min), and infusion rate (0.5-1.0 ml/min). Emptying during intraoral infusions, by contrast, was entirely unaffected by these manipulations. Unlike oil emptying, glucose emptying did not vary as a function of delivery route. The nutrient specificity of the delivery route effect cannot be explained in terms of energy density, as the effect was obtained for oil but not for glucose when their energy densities were equated (50% glucose, 25% corn oil). In discussion, we suggest that the oral influence on corn oil emptying during stomach fill is a gating factor that enables the expression of inhibition derived from postgastric nutrient stimulation.

Antioxidant activity of green teas in different lipid systems

AbstractDifferent commercial green teas from Japan, China, and India, were compared in different lipid systems. Green teas were active antioxidants in bulk corn oil oxidized at 50°C but were prooxidant in the corresponding oil‐in‐water emulsions. Green teas also were active antioxidants in soybean lecithin liposomes oxidized at 37°C in the presence of cupric acetate as catalyst. At 50°C, however, three of the samples of green tea were active antioxidants in the absence of copper catalyst, and two samples showed prooxidant activity in the presence of copper catalyst. The marked variation in activity among green tea samples may be due partly to differences in their relative partition between phases in different lipid systems. The improved antioxidant activity observed for green teas in lecithin liposomes compared to corn oil emulsions can be explained by the greater affinity of the polar tea catechin gallates for the polar surface of the lecithin bilayers, thus affording better protection against oxidation. Liposomes may thus be appropriate lipid models to evaluate antioxidants for foods containing phospholipids.

Preparation and properties of a stable intravenous lorazepam emulsion.

Lorazepam is normally administered as a solution in organic solvents such as propylene glycol. This type of formulation is undesirable. This study describes the development of a parenteral emulsion formulation for lorazepam. The stability of lorazepam in the emulsion was examined. Ten per cent corn oil emulsions stabilized with egg lecithin, Pluronic F68 and Pluronic F88 were used. The incorporation of lorazepam does not appear to destabilize the emulsion, and lorazepam itself appears to be stable for at least 1 year in this liquid formulation. Haemolysis caused by emulsion formulations containing lorazepam and different emulsifiers was evaluated using human and rabbit blood to assess their safety as parenteral drug carriers. The results show that the emulsions did not have any significant haemolytic activity whereas organic solvents and solutions of lorazepam in organic solvents caused substantial haemolysis.

Influence of Unrefined Corn Oil and Surface-active Agents on the Germination and Infectivity of Alternaria helianthi

A dew immediately after inoculation is normally required for the mycoherbicidal activity of Alternaria helianthi on common cocklebur. The formulation of A. helianthi conidia in an emulsion of unrefined corn oil enabled the pathogen to infect the weed, regardless of whether dew was immediate or delayed for 24 h. Corn oil emulsion and the surface-active agents Tween 20, 40, 60 and 80 maintained the germination ability of 14-day-old conidia to some degree for up to 4 days in suspension. Both the corn oil emulsion and Silwet stimulated the germination of A. helianthi on common cocklebur leaves, but Silwet did not enhance infectivity when dew was delayed. Unrefined corn oil enhanced mycoherbicide efficacy by protecting the conidia during a dew-free period and by stimulating germination when a dew occurred. Corn oil emulsion, Silwet and Tween 20, 40, 60 and 80 reduced the dew period required for disease activity. Unrefined corn oil emulsion has potential as a formulation for the application of this mycoherbicide in the field because it maintained the germination ability and virulence of conidia on the weed during a dew-free period.

The composition of the maintenance diet alters flavor-preference conditioning by intragastric fat infusions in rats

Prior studies indicate that intragastric (IG) fat infusions condition only weak flavor preferences in chow-fed rats using brief daily training sessions. The present study attempted to facilitate fat conditioning by feeding rats a high-fat maintenance diet or by adding an oily flavor to the conditioning stimuli. In Experiment 1, rats were fed restricted rations of either a chow-corn oil mixture (48% energy as fat, HF group) or regular chow (12% fat, LF group). During 1-bottle training sessions, drinking a flavored (CS+, e.g., cherry) saccharin solution was paired with IG fat (7.1% corn oil emulsion). On other days, an alternate flavor (CS−, e.g., grape) was paired with IG water. In subsequent 2-bottle tests between the CS+ and CS− flavors, the HF rats displayed a stronger CS+ preference than the LF rats (90% vs. 62%). Experiment 2 tested the effect of a semisynthetic HF maintenance diet (48% fat energy), using a conditioning procedure similar to that of Experiment 1. The rats displayed only a moderate (72%) CS+ preference. When switched to the chow-oil maintenance diet and retrained with new CS flavors, they developed a 90% CS+ preference. In Experiment 3, chow-fed rats were trained and tested with oily CSs (i.e., 2% corn oil was added to flavored saccharin solutions). They failed to show a preference for the CS+ paired with IG oil. Thus, increasing the level of fat in the maintenance diet can greatly enhance preference conditioning with IG fat, but the amplitude of the effect is influenced by the composition of the high-fat food. In contrast, adding a fatty flavor to the conditioning stimuli did not improve fat conditioning.

Capsaicin attenuates feeding suppression but not reinforcement by intestinal nutrients.

During and after a meal, the presence of nutrients in the intestine can be rapidly detected and signaled to the brain via visceral afferents. Intestinal infusions of carbohydrate and fat suppress food intake, and this satiety action is inhibited by capsaicin, a neurotoxin that produces a partial visceral deafferentation. This study determined if the postingestive reinforcing action of nutrients is also suppressed by capsaicin treatment. Food-restricted control and capsaicin-treated rats were trained to drink a flavored solution paired with intraduodenal infusions of carbohydrate (Polycose solution) on some days and, on other days, a differently flavored solution paired with intraduodenal water infusions. In a choice test, both groups displayed a strong preference for the Polycose-paired flavor. In a subsequent satiety test, however, intraduodenal Polycose suppressed sucrose sham feeding in the controls but not in capsaicin-treated rats. The same rats were next trained to associate new flavors with intraduodenal fat (corn oil emulsion) and intraduodenal water infusions. During training, oil infusions reduced oral intakes in the controls much more than in the capsaicin-treated rats. Both groups reliably preferred the oil-paired flavor in the subsequent choice test. These results indicate that, unlike the satiating effect of intestinal carbohydrate and fat, the reinforcing actions of these nutrients are not mediated by capsaicin-sensitive visceral afferents. The data also imply that the postingestive reinforcement produced by nutrients is not dependent on the nutrients' satiating quality.

Effect of pH on Antioxidant Activity of α-Tocopherol and Trolox in Oil-in-Water Emulsions

The pH had a more significant effect on the antioxidant activity of Trolox than α-tocopherol in corn oil emulsified with Tween 20 at 60 °C. Although with increasing pH the oxidative stability of corn oil emulsions decreased, the antioxidant activity of α-tocopherol increased. Initially, Trolox and α-tocopherol were similar in inhibiting hydroperoxide formation with or without phosphate buffers at pH 3−7, but at later stages α-tocopherol was more effective than Trolox at pH 3, 4, 5, and 7 but not at pH 6. In contrast, α-tocopherol inhibited hexanal formation better than Trolox during the entire oxidation period. Trolox was more stable than α-tocopherol in bulk corn oil but less stable in Tween 20 solutions at different pH. Both antioxidants in Tween 20 solutions were most stable at pH 3 and least stable at pH 7. Although more Trolox partitioned into the oil phase and the oil−water interfaces at pH 3−4, its antioxidant activity was lower than at pH 5−6. The overall antioxidant activities of α-tocopherol and...

Antioxidant Activity of Carnosic Acid and Methyl Carnosate in Bulk Oils and Oil-in-Water Emulsions

This study was aimed at evaluating the antioxidant activities of carnosic acid and its methyl ester, methyl carnosate, in inhibiting the formation and decomposition of hydroperoxides in bulk and emulsified corn oil triglycerides at 60 °C. In both lipid systems, methyl carnosate was a better antioxidant than carnosic acid, and both were more active than α-tocopherol. The difference in antioxidant activity between methyl carnosate and carnosic acid was greater in emulsion than in bulk systems. Carnosic acid was less stable than methyl carnosate and α-tocopherol in bulk corn oil and 1% Tween 20 micelle solution. The partitioning of carnosic acid into the water phase may explain its low activity in emulsions. The measurement of antioxidant depletion may not be a valid method to evaluate antioxidant activities because the antioxidant activities of carnosic acid and methyl carnosate were not related to their oxidative stability in bulk oil and Tween 20 solution. Keywords: Antioxidants; carnosic acid; methyl carnosate; α-tocopherol; corn oil triglycerides; emulsion; mechanism; interfacial oxidation; hydroperoxides; hexanal; partition coefficient; oxidative stability of antioxidants

Subject index

‘Granny Smith’ apples (Malus x domestica Borkh) and ‘Beurre d'Anjou’ pears (Pyrus communis L.) were dipped in a 2.5, 5, or 10% stripped corn oil (α-tocopherol <5 mg kg−1) emulsions, 2000 mg l−1 diphenylamine (DPA), respectively, at harvest and stored in air at 0°C for 8 months. Untreated fruit served as controls. In oil-treated apples and pears, ethylene and α-farnesene production rates were lower in early storage and higher in late storage than in controls. Untreated ‘Granny Smith’ apples and ‘d'Anjou’ pears developed 34 and 23% superficial scald, respectively, after 6 months storage, whereas fruit treated with oil at 5 or 10%, or with DPA at 2000 mg l−1 were free from scald. After 8 months storage, oil at 10% was as effective as DPA in controlling scald in pears, whereas in apples, fruit treated with 10% oil developed 18% scald and DPA-treated fruit were scald free. DPA-treated apples, however, developed 32% senescent scald, while 5 or 10% oil-treated fruit had none. Oil-treated fruit were greener, firmer and contained more titratable acidity after 8 months of storage than control or DPA-treated apples and pears. In ‘Granny Smith’, 100% of the controls and 79% of the DPA-treated fruit developed coreflush after 8 months of storage, but in 10% oil-treated fruit, coreflush was eliminated. In ‘d'Anjou’, 34% of the controls and 27% of the DPA-treated fruit showed decay after 8 months of storage, compared with 5% decay in 5% oil-treated fruit, and no decay in 10% oil-treated fruit.

Interaction between orosensory and postingestional stimulation in the control of corn oil intake by rats

The microstructure of the ingestive behavior of rats ingesting corn oil emulsions was analyzed to describe quantitatively how postingestional stimulation interacts with orosensory stimulation to control the intake of corn oil. Seventeen hour food deprived rats were given 30-min access intake tests with corn oil emulsions ranging in concentration from 0.125% to 64%. The volume ingested showed an inverted U shaped function over this concentration range. The Weibull function fitted to the rate of licking function showed that the initial rate of licking was an increasing linear function of the log of the concentration of corn oil. The slope of the licking rate function was an increasing curvilinear function of the log of corn oil concentration. Together these results indicate that the negative feedback effect of corn oil in the gastrointestinal tract increases more rapidly at the higher concentrations of corn oil than does its orosensory stimulating effect resulting in a decrease in the volume ingested. Unlike carbohydrates, where the increase in the initial rate of licking is a result of an increase in the size of the clusters, the increase with concentration in the initial rate of ingesting corn oil was caused by an increase in the number of clusters rather than their size. This study provides a quantitative analysis of the interaction between orosensory and postingestional stimulation, two variables that play an important role in the control of ingestion of corn oil.

Water-Corn Oil Emulsion Enhances Conidia Germination and Mycoherbicidal Activity ofColletotrichum truncatum

A water-corn oil (unrefined) emulsion has promise as a carrier for application of the mycoherbicide,Colletotrichum truncatum.We investigated this formulation (normal emulsion; oil in water) for influences on conidia germination, appressoria formation, and mycoherbicidal activity ofC. truncatum.Germination of conidia after application to hemp sesbania leaves was increased from 30% in water alone to 92% in the water-corn oil emulsion (water:oil, 1:1, by vol). The emulsion did not affect appressoria formation. of the several other oils tested, safflower seed oil enhanced in vitro germination but did not enhance germination and mycoherbicide activity when the conidia-emulsion formulation was applied to hemp sesbania leaves. Application ofC. truncatumconidia in the unrefined corn oil emulsion to hemp sesbania seedlings resulted in 89 to 97% control of the weed after a 24 to 72 h dew delay. The emulsion enhanced mycoherbicide efficacy by stimulating conidia germination by protecting the conidia during a dew-free period, hence, increasing weed infection when a dew occurred.

Evaluation of oral contrast agents for abdominal magnetic resonance imaging

We evaluated the efficacy of six available oral contrast agents in improving visualization of bowel and surrounding structures on magnetic resonance imaging of the abdomen and pelvis. Five volunteers were examined without oral contrast (baseline) and, on separate occasions, after ingestion of 600–900 cc of two positive contrasts [12.5% weight-to-volume (w/v) corn oil emulsion (COE), Redi Cat (EZ-Em Corp., Westbury, NY) mixed with 1% ferric ammonium citrate (FAC)] and four negative contrasts [220%, 105%, 85%, 60% w/v barium sulfate (Liquid HD, Liquid Polybar Plus, HD 85, reconstituted EZ Pake; EZ-Em Corp., Westbury, NY)]. Spin-echo axial and coronal T 1-weighted and axial T 2-weighted images were obtained in the abdomen and pelvis. Three radiologists blindly graded the images for improved visualization of bowel and surrounding structures. Data were analyzed for statistical significance using the General Linear Models algorithm. In the upper abdomen (stomach, duodenum, liver, and pancreas), COE yielded the highest mean scores ( p < .0001), followed by 220% w/v barium. For the lower abdomen (ileum, colon), 220% w/v barium yielded the highest scores ( p < .0001) and COE was much worse. The higher density barium preparations (220% and 105% w/v) yielded higher scores than their lower density counterparts (85% and 60%). All contrasts improved visualization of the retroperitoneum and spleen, but no one agent was best. All agents tested are superior to no agent at all. For visualization of the upper abdomen, 12.5% COE performed best. For visualization of the lower abdomen, 220% w/v barium performed best. For concurrent evaluation of both areas with one agent, 220% w/v barium performed best.

Acute blockade of gastric emptying and meal size in rats

To investigate the functional capacity of the combination of pregastric and gastric satiating stimuli for the control of meal size, rats were surgically implanted with a pyloric cuff that could be inflated to prevent gastric emptying. After 0.5 or 19 h of food deprivation, rats were given access for 30 min to three concentrations of sucrose (0.8, 0.4, and 0.2 M) and of corn oil emulsions (100%, 50%, and 25%) in descending order. There were only two significant changes in intake between cuff-open and cuff-closed tests and both occurred after 19 h of food deprivation: 1) meal size of 50% corn oil with the cuff closed was significantly larger than meal size of 50% corn oil with the cuff open on the preceding day; 2) meal size of 0.8 M sucrose with the cuff closed was significantly larger than meal size with the cuff open on the next test day. These results provide new experimental evidence that when ingested food is prevented from emptying from the stomach acutely, the satiating effect of food stimuli acting at pregastric and gastric sites is sufficient to produce meals of normal size under many, but not all, experimental conditions.

Lymph Chylomicron Size is Modified by Fat Saturation in Rats

Mesenteric lymph chylomicrons were characterized during and after the establishment of steady-state triglyceride transport. Chylomicrons were isolated from lymph at 0, 2, 4, 6, 8 and 12 h after the start of an 8-h infusion of triglyceride emulsion (prepared using either corn or butter oil) at 160 μmol/(kg·h). Lymph flow was not influenced by triglyceride source. Output of triglyceride, measured both in whole lymph and in the chylomicron fraction, was not significantly affected by triglyceride source. Butter oil infusion produced a higher output of chylomicron phospholipid and unesterified cholesterol than was observed in response to corn oil emulsion. Ratios of transported phospholipid to triglyceride for butter oil chylomicrons were higher (1.3- to 1.7-fold) than those for corn oil chylomicrons at every time point examined after the start of lipid infusion. No other compositional differences in chylomicrons due to triglyceride source were observed. These results support the hypothesis that differences in efficiency of absorption and transport between saturated and unsaturated fat are sufficient to explain size differences in secreted chylomicrons in response to corn and butter oil infusions, and suggest that chylomicron number may be influenced by dietary fat saturation.

Lymph Chylomicron Composition and Size are Modified by Level of Intestinally Infused Cholesterol and Triglyceride Source in Rats , ,

Mesenteric lymph chylomicrons were characterized following acute continuous intestinal infusion of triglyceride emulsions in rats. Emulsions were prepared using corn, olive or butter oils with graded doses of cholesterol (0, 3, 10, 20, 30, 60, 100 mg/g triglyceride) added to each. Chylomicron cholesterol content varied directly with dose of cholesterol infused, ranging from ∼1.5% (by weight) with no added cholesterol to 5–10% at 100 mg cholesterol/g triglyceride. Minimum effective dose for increasing chylomicron cholesterol content (about twofold) was 20 mg/g triglyceride regardless of the triglyceride source. Esterified cholesterol accounted for most of the increase in chylomicron total cholesterol with corn oil infusion, whereas increases in the unesterified fraction accounted for 10–30% of the increase in total cholesterol during infusion of olive or butter oils. The effect of infused cholesterol on chylomicron lipid composition was dependent on triglyceride source: no effect on phospholipid:triglyceride ratio with corn and butter oils, but increased phospholipid:triglyceride ratio with olive oil at cholesterol doses >20 mg/g triglyceride. Infusion of butter emulsions produced smaller chylomicrons than those produced during infusion of corn or olive oil emulsions.

Cholecystokinin antagonist and lipid intake as a function of caloric density and familiarity

The effect of treatment with the cholecystokinin antagonist L364,718 on intake of different dilutions of corn oil emulsion was tested under two levels of familiarity with the oil emulsion. No increase in intake was observed. To see if the CCK antagonist was effective under our conditions, exogenous CCK was administered under the same conditions. A complete suppression of the large reduction produced by CCK on intake was found.

Intake of different concentrations of sucrose and corn oil in preweanling rats.

To investigate the orosensory control of ingestion in preweanling rats, we infused one of the following liquids continuously through anterior sublingual intraoral catheters for 20 min: sucrose solutions (5, 10, 20, and 40%) and corn oil emulsions (6.25, 12.5, 25, 50, and 100%). Pups were tested at 7, 14, 21, and 28 days of age. Each pup was tested only once. Intake of sucrose and of corn oil became increasingly correlated with concentration from 7 to 21 days. Sucrose elicited more intake than water by day 7, whereas corn oil did not until day 14. Low concentrations of sucrose had differential effects on intake by day 14, but low concentrations of corn oil emulsions did not have differential effects on intake until day 21. At all ages, the peak intake of sucrose was significantly larger than the peak intake of corn oil. These differences are probably not based on prior experience because each test of ingestion represented a first exposure to the stimulus. Thus we suggest that the differences are due to the maturation of the orosensory control of ingestion by sucrose and corn oil.

Computed Tomography of the Abdomen with Fat Density Oral Contrast Medium

A 12.5% corn oil-emulsion (COE) was tested as an oral contrast agent for abdominal computed tomography (CT) examinations in 100 patients. The results were compared with those obtained from another group of patients who received a conventional, high-density, oral contrast agent (2-3% iodinated solution). There was no statistically significant difference in the subjects' tolerance to the two agents (P greater than 0.05). There was, however, a significant improvement in image quality with COE (P less than 0.05). Gastrointestinal tract discrimination, and mucosal and mural visualisation was of higher quality with fat density oral contrast medium than with the high-density contrast agent. These data suggest that COE should be considered for routine use as an alternative to conventional high density oral contrast agents in upper abdominal CT.

Sham-feeding sucrose or corn oil stimulates food intake in rats

In separate experiments, rats with open gastric cannulas were sham-fed either 32% sucrose solution or 15% corn oil emulsion. The rats' cannulas were then closed, and food intake was measured for 2 h. Food intake was greater after sham-feeding either fluid than after tests when no fluid was available. These results suggest that the oral stimulation produced by ingestion of sweet or oily fluids can stimulate appetite in the rat.