Annette Fillery-Travis

Effect of intragastric acid stability of fat emulsions on gastric emptying, plasma lipid profile and postprandial satiety

Fat is often included in common foods as an emulsion of dispersed oil droplets to enhance the organoleptic quality and stability. The intragastric acid stability of emulsified fat may impact on gastric emptying, satiety and plasma lipid absorption. The aim of the present study was to investigate whether, compared with an acid-unstable emulsion, an acid-stable fat emulsion would empty from the stomach more slowly, cause more rapid plasma lipid absorption and cause greater satiety. Eleven healthy male volunteers received on two separate occasions 500 ml of 15 % (w/w) [13C]palmitate-enriched olive oil-in-water emulsion meals which were either stable or unstable in the acid gastric environment. MRI was used to measure gastric emptying and the intragastric oil fraction of the meals. Blood sampling was used to measure plasma lipids and visual analogue scales were used to assess satiety. The acid-unstable fat emulsion broke and rapidly layered in the stomach. Gastric emptying of meal volume was slower for the acid-stable fat emulsion (P < 0.0001; two-way ANOVA). The rate of energy delivery of fat from the stomach to the duodenum was not different up to t = 110 min. The acid-stable emulsion induced increased fullness (P < 0.05), decreased hunger (P < 0.0002), decreased appetite (P < 0.0001) and increased the concentration of palmitic acid tracer in the chylomicron fraction (P < 0.04). This shows that it is possible to delay gastric emptying and increase satiety by stabilising the intragastric distribution of fat emulsions against the gastric acid environment. This could have implications for the design of novel foods.

A critical review of executive coaching research: a decade of progress and what's to come

This paper aims to summarise the current state of coaching research as a basis for future studies. It seeks to provide a frame of reference for researchers and reflective practitioners interested in research to ensure that future studies build on previous work and add to our knowledge and understanding of coaching as a unique domain of practice. The paper is divided into three sections. The first two sections review the state of coaching research over the past 100 years, with a greater focus on the past decade when the number of studies published has accelerated. The paper divides the recent research into categories: the nature of coaching, coach behaviour studies, client behaviour studies, relationship studies and executive coaching impact studies and discusses research methods including Interpretative Phenomenological Analysis, Grounded Theory and Discourse Analysis, randomised controlled trials, meta-analysis and mixed methods research. The third section considers the future direction research may take. It identifies key themes and sample research questions which the authors believe could be the focus of future research. The paper concludes by noting that coaching research is likely to continue to grow over the coming decade, and this growth offers an opportunity for the research–practitioner partnership to be strengthened and maintained.

Solubilization of carotenoids from carrot juice and spinach in lipid phases: II. Modeling the duodenal environment

Our understanding of the factors determining the bioavailability of carotenoids from fruits and vegetables is poor. The apolar nature of carotenoids precludes their simple diffusion from the food structure to the absorption site at the enterocyte. Therefore, there is interest in the potential pathways for solubilization in the gut before absorption. We have studied the transfer of carotenoids from carrot juice and homogenized spinach into lipid phases that mimic the intestinal lumen at the start of digestion. In this paper we report on their transfer into olive oil under conditions pertaining to the gastric environment. A comparison between preparations of raw spinach and of carrot, in which the intact cells have been largely broken, suggests that the membrane-bound carotenoids of spinach are more resistant to transfer than the crystalline carotenoids of carrot. Lowering the pH and pepsin treatment enhance the transfer from raw vegetables. The process of blanching and freezing spinach destroys the chloroplast ultrastructure and leads to (i) a substantial increase in transfer of the carotenoids to oil and (ii) an attenuation or reversal of the enhancement of transfer seen with reduced pH or with pepsin treatment. Similar effects are seen after blanching carrot juice. Our results show that removal of soluble protein and denaturation of membrane proteins enhances the partition of carotenoids into oil. For both vegetables there is no evidence of preference in the extent of transfer of one carotenoid over another. This suggests that partitioning into oil under gastric conditions is not the stage of digestion that could lead to differences in carotenoid bioavailability.

Effect of carrot (Daucus carota) microstructure on carotene bioaccessibilty in the upper gastrointestinal tract. 1. in vitro simulations of carrot digestion

Studies investigating carotene bioaccessibility (release from the food matrix to a solubilized form) directly from plant material during the process of digestion are scarce, mainly due to the difficulties associated with obtaining such material. Therefore, this paper examines the relationship between tissue microstructure and carotene bioaccessibility using an in vitro digestion model. Dietary oil provides a pool for the initial solubilization. Therefore, carotene partitioning into an emulsified oil phase was assessed using raw carrot tissue and carrot tissue subjected to various degrees of heating and particle size reduction and, in all cases, was found to be greatly reduced compared with juiced carrot. Carotene bioaccessibility was found to be greater from raw tissues than heated tissues of the same size. This is because heating increases the propensity for intact cells to separate, effectively encapsulating the carotene. Although the gross structure of the tissues was found to be relatively unaffected by in vitro digestion, at the cellular level some cell-wall swelling and cell death were observed, particularly close to the surfaces of the tissue. This study suggests that cell-wall rupture prior to digestion is an absolute requirement for carotene bioaccessibility in the upper intestine and that heating does not enhance carotene release from intact cells.

Effect of Carrot (Daucus carota) Microstructure on Carotene Bioaccessibility in the Upper Gastrointestinal Tract. 2. In Vivo Digestions

Nutrient bioaccessibility and subsequent absorption will be directly influenced by changes in food structure during gastrointestinal processing. The accompanying paper (Tydeman et al. J. Agric. Food Chem. 2010, 58, doi: 10.1021/jf101034a) reported results on the effect of carrot processing on the release of carotene into lipid phases during in vitro gastric and small intestinal digestions. This paper describes results from in vivo digestion of two of the types of processed carrot used previously, raw grated carrot and cooked carrot mashed to a puree. Ileostomy effluents from human volunteers fed meals containing the carrot material were used to study tissue microstructure and carotene release. Raw carrot shreds and intact cells that had survived the pureeing process were identifiable in ileal effluent. The gross tissue structure in the shreds had not changed following digestion. Carotene-containing particles remained encapsulated in intact cells, but were absent from ruptured cells. Microscopy revealed marked changes to the cell walls including swelling and pectin solubilization, which increased in severity with increasing residence time in the upper gut. These observations were entirely consistent with the in vitro observations. It was concluded that a single intact cell wall is sufficient to reduce carotene bioaccessibility from a cell by acting as a physical barrier, which is not broken down during upper gut digestion.

A physicochemical investigation of two phosphatidylcholine/bile salt interfaces: implications for lipase activation.

Within the gastrointestinal tract ingested lipids are broken down into their constituent mono-acylglycerides and fatty acids by the enzyme family of lipases. In this study we have investigated the interfacial composition and structure of two phospholipid/bile salt (BS) systems that display significant differences in the duration of the lag phase of porcine pancreatic lipase kinetics. The interfacial tension of the single BSs, and their binary mixtures with phospholipid is reported at an n-tetradecane/water interface as a function of phospholipid mole fraction and total surfactant concentration. The structuring of the interface was probed by characterisation of the thin liquid film formation, thickness and stability. Lateral interactions were quantified by measurement of the diffusion coefficient of a probe fluorophore. We conclude that interfacial tension was not a factor in lag time duration as there was no significant difference in the minimum interfacial tension for the phosphatidylcholine (PC)/sodium taurocholate and the PC/sodium taurodeoxycholate system. No correlation was found between lag phase duration and the physiochemical properties of the interface, i.e. lateral diffusion, thin liquid film formation or interfacial tension. This is in agreement with our previous study that the lag time duration was directly related to the phospholipid content of the interface.

STABILITY OF EMULSIONS STABILISED BY TWO PHYSIOLOGICAL SURFACTANTS : L-ALPHA -PHOSPHATIDYLCHOLINE AND SODIUM TAUROCHOLATE

The emulsion phase formed within the stomach and duodenum during digestion of a fatty meal has been modelled using two physiological surfactants, the phospholipid L-alpha-phosphatidylcholine (PC) and the bile salt sodium taurocholate (NaT). Upon dilution of the phospholipid stabilised emulsions with a solution of NaT the bile salt became incorporated into the oil/water interface imparting a negative charge to the droplet surface. The magnitude of the droplet microelectrophoretic mobility for the mixed PC and NaT system was 47% of that found for emulsion droplets stabilised by NaT alone. But the electrostatic repulsion between droplets was not sufficient to account for the observed improvement in emulsion stability to coalescence. It is suggested that a residual liquid crystalline phospholipid interface is present imparting a significant steric component to the stabilisation of the emulsions droplets.

Low pH Enhances the Transfer of Carotene from Carrot Juice to Olive Oil

A current model for carotenoid transport and absorption in the gut proposes an initial solubilization in the oil phase of dietary emulsions followed by incorporation of the carotenoids in mixed bile salt micelles. To assess the relevance of the first stage of this model to what is observed in vivo we have examined the transfer of carotene from carrot juice to olive oil. Increased acidity enhanced the transfer from both whole juice and carotene crystals isolated from both whole juice and carotene crystals isolated from carrot chromoplasts. The transfer was significantly slower from whole juice. By using exogenous β-carotene and measuring its transfer to oil in the presence and absence of carrot juice we have demonstrated that the inhibition of the transfer in juice arises, at least in part, from soluble juice factors. The inhibition is relieved by a fall in pH, which leads to lowering of the electric potential at the oil/aqueous phase interface and aggregation of carrot tissue including crystalline carotene. Under conditions of low pH, oil droplets adhere to the tissue aggregates, allowing carotene to pass into the oil. Our results provide an explanation for why carotene absorption in vivo is depressed by conditions of low gastric acidity.

Rotational spectrum, H, 19F spin–spin and D–nuclear quadrupole coupling constants, and molecular geometry of the sulphur dioxide–hydrogen fluoride dimer

The ground state rotational spectra of three isotopic species 32SO2⋅⋅⋅HF, 32SO2⋅⋅⋅DF, and 34SO2⋅⋅⋅HF of a dimer formed between sulphur dioxide and hydrogen fluoride have been detected and measured using a pulsed‐nozzle, Fourier‐transform microwave spectrometer. An analysis of observed nuclear hyperfine structure leads to the H, 19F nuclear spin–nuclear spin coupling constants DHFaa =−190(2) kHz and (DHFbb−DHFcc) =−57(4) kHz for 32SO2⋅⋅⋅HF, and to the D‐nuclear quadrupole coupling constants χaa =227(3) kHz and (χbb−χcc) =68(13) kHz for 32SO2⋅⋅⋅DF. Rotational and centrifugal constants have been determined for all three isotopic species, with the following values for 32SO2⋅⋅⋅HF: A0=16 502.775(4) MHz, B0=2100.308(1) MHz, C0=1853.642(1) MHz, ΔJ =18.31(2) kHz, ΔJK =−521.78(4) kHz, and δJ =4.37(3) kHz. The rotational constants for the three isotopic species are interpreted in terms of a planar geometry in which hydrogen fluoride forms a cis hydrogen bond to one of the oxygen atoms of SO2. Assuming a linear hydro...

The geometries of the heterodimers SO2⋯HF and SO2⋯HCl as determined by rotational spectroscopy

Abstract The rotational spectra of the hydrogen-bonded heterodimers SO 2 ⋯HF and SO 2 ⋯HCl in their vibrational ground states have been observed by pulsed-nozzle, Fourier-transform microwave spectroscopy. Rotational constants A 0 , B 0 and C 0 , centrifugal distortion constants Δ j , Δ jk and δ j , and Cl-nuclear coupling constants X aa and X bb have been determined. The spectroscopic constants are interpreted in terms of a geometry in which the subunits are coplanar and in which the HX molecule forms a hydrogen bond to one of the oxygen atoms of SO 2 . The observed geometries are compared with those predicted from electrostatic models of the intermolecular interaction.