Diets enriched with palm olein, cocoa butter, and extra virgin olive oil exhibited similar lipid response: a randomized controlled study in young healthy adults.

Vegetable oils having unsaturated fatty acids in the sn-2 position of triglyceride (TG) backbone might not raise serum cholesterol levels. We investigated the chronic effects of diets enriched with palm olein (IV64) (PO), cocoa butter (CB), or extra virgin olive oil (EVOO) with oleic acid primarily at the sn-2 position (66%, 75%, 87% sn-2 oleic acid, respectively) of the TG molecule in 40 healthy volunteers participated in this randomized, controlled, single-blinded, crossover trial. Following a 2-week run-in period, the subjects were given standardization meals (breakfast, lunch, and dinner) cooked with palm olein (IV72). Subjects were randomized to 1 of the 3 intervention groups; receiving baked products (brownies for breakfast and cookies for teatime) prepared with respective test fats accompanied with standardized low-fat meals for breakfast, lunch, and dinner prepared with palm olein (IV72) for all groups for 4 weeks in a crossover manner with 2-week washout period (given standardization meals). Anthropometric measurements, blood samples, and dietary intakes were measured before run-in and pre- and post-intervention. No significant difference was observed on the primary outcome of the study total: high-density lipoprotein cholesterol. All 3 test fats were found to exhibit similar lipid responses (total cholesterol, TG, lipoprotein (a), apolipoprotein-A1, apolipoprotein-B/A-1). Statistical difference was found on low-density lipoprotein cholesterol (CB>EVOO by 0.3 mmol/L, P = .003), high-density lipoprotein cholesterol (PO>CB by 0.04 mmol/L, P = .02) and apolipoprotein-B (EVOO

Predicting the viscosity of digesta from the physical characteristics of particle suspensions using existing rheological models.

The measurement of the viscosity of digesta is complicated by settling and compositional changes that accompany digestion. The current work determined whether the apparent and relative viscosities (ηa and ηr) of digesta could be accurately determined from the actual and maximum solid volume fractions (ϕ and ϕmax, respectively) using the Maron-Pierce equation. The rheological properties of digesta from the small intestine of six pigs were determined at a shear rate of 1 s-1 at 37°C. A series of suspensions of plant fibre in a Newtonian liquid (70% aqueous fructose) were made at viscosities similar to pig digesta by adjusting ϕ The relationships between the apparent and relative viscosities (ηa and ηr) and the plant fibre properties; aspect ratio (AR) and ϕ and ϕmax were then determined for digesta and the suspensions. The ARs for the digesta and plant fibre particles were determined using image analysis of scanning electron micrographs and ηa from rheometric flow curves at 37°C, ϕ from image analysis and gas pycnometry, and ϕmax from AR and suspension viscosity. The ηr of pig digesta and the test suspensions calculated using the Maron-Pierce equation were, with the exception of two outliers, in proportion with ηa determined using a rheometer, indicating that ηr could be successfully predicted from the Maron-Pierce equation.

Does viscosity or structure govern the rate at which starch granules are digested?

The rates of in vitro digestion of incompletely or fully gelatinised potato and corn starch were measured at 37 °C over 20 min in a rheometer fitted with cup and vane geometry at shear rates of 0.1, 1 and 10 s(-1). Shear rate did not influence the rate of starch digestion provided it was close to physiological levels. However, rates of digestion were significantly reduced when shear rates were below the physiological range (0.1 s(-1)) or when gelatinisation was incomplete. At physiological shear rates the relationship between starch digestion and viscosity was sigmoid in form and following a short initial slow phase a rapid decline in viscosity occurred as starch was digested and the structural integrity of the granules was lost. Conversely, when shear rate was reduced below physiological levels or gelatinisation was incomplete, digestion was hindered, granule integrity was maintained and the relationship between starch and viscosity became linear.

The effect of fibre and gelatinised starch type on amylolysis and apparent viscosity during in vitro digestion at a physiological shear rate.

An in vitro system was used to determine if the addition of insoluble or soluble fibre to aqueous suspensions of gelatinised starch affected the rate at which the starch was digested. Pre-gelatinised potato or corn starch suspensions were digested with porcine pancreatic amylase in the presence of either finely milled insoluble fibres from various sources or with guar gum. In vitro digestion was conducted at 37°C in a rheometer at a low and constant shear rate of 10s(-1) and the quantity of glucose released measured. The rates of starch digestion and suspension viscosity declined asymptotically and were unaffected by the addition of wheat fibre, but were considerably reduced by the addition of wood and AllBran(®) fibre and to a much greater extent (60%) by the addition of guar. The latter effect may be due to inhibition of amylase activity by non starch polysaccharide sequences.

The partitioning of water in aggregates of undigested and digested dietary particles.

The hydration of fibre particles derived from wheat and wood was quantified, before and after in vitro digestion, and compared with fibre particles from the colonic digesta of pigs and from human faeces. Total water and the extra- and intra-particulate water components were determined using a combination of centrifugation, drying, gas pycnometry and image analysis. The water of saturation (WS) of wood particles and AllBran® measured after in vitro digestion was up to double that of wheat fibres after in vitro digestion, and increased with particle size and loss of soluble material, but was not associated with the chemical composition of the fibres. Fibre that had undergone in vitro gastric digestion and that had been recovered from the colon or faeces, sequestered about 3% of the Ws into intra-particulate spaces, the remainder occupying extra-particulate spaces. The authors speculate that large quantities of fibre must be eaten to sequester toxins that locate into the intra-particulate space.