| 1. |
- Andersson, Kristina E, et al.
(author)
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Effects of oats on plasma cholesterol and lipoproteins in C57BL/6 mice are substrain specific.
- 2010
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In: British Journal of Nutrition. - 1475-2662. ; 103, s. 513-521
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Journal article (peer-reviewed)abstract
- Cholesterol-lowering effects of oats have been demonstrated in both animals and human subjects. However, the crucial properties of oat-containing diets that determine their health effects need to be further investigated to optimise their use. A mouse model would be a valuable tool, but few such studies have been published to date. We investigated the effects of oat bran on plasma cholesterol and lipoproteins in two substrains of C57BL/6 mice. Western diet was made atherogenic by the addition of 0.8 % cholesterol and 0.1 % cholic acid. After 4 weeks on atherogenic diet, total plasma cholesterol had increased from 1.86-2.53 to 3.77-4.40 mmol/l. In C57BL/6NCrl mice, inclusion of 27 and 40 % oat bran reduced total plasma cholesterol by 19 and 24 %, respectively, reduced the shift from HDL to LDL+VLDL and caused increased faecal cholesterol excretion. There was no effect of oat bran on plasma levels of the inflammatory markers fibrinogen, serum amyloid A or TNF-alpha. Contrary to findings in C57BL/6NCrl mice, there was no sustained effect of oat bran (27 or 40 %) on plasma cholesterol in C57BL/6JBomTac mice after 4 weeks of feeding. Thus, C57BL/6NCrl mice fed an atherogenic diet are a good model for studies of physiological effects of oats, whereas a substrain derived from C57BL/6J, raised in a different breeding environment and likely possessing functional genetic differences from C57BL/6N, is considerably less responsive to oats. The present finding that two substrains of mice respond differently to oats is of practical value, but can also help to elucidate mechanisms of the cholesterol-lowering effect of oats.
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| 2. |
- Immerstrand, Tina, et al.
(author)
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Characterization of the properties of Pediococcus parvulus for probiotic or protective culture use.
- 2010
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In: Journal of Food Protection. - 0362-028X. ; 73:5, s. 960-966
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Journal article (peer-reviewed)abstract
- Pediococcus parvulus 2.6 (previously Pediococcus damnosus 2.6, here confirmed as P. parvulus by 16S DNA sequencing) displayed antibacterial activity toward several bacterial species, including isolates found as contaminants in oats, herein genetically identified as Bacillus cereus. No inhibition of Listeria monocytogenes was found under the conditions used. Antibacterial activity was retrieved after ammonium sulfate or acetone precipitation showed it to be peptide mediated. P. parvulus 2.6 has previously shown good technological properties in oat-based products. This, together with the currently found inhibition of food spoilage microorganisms like B. cereus, makes it suitable as a food protective culture. Survival trials of P. parvulus 2.6 at conditions mimicking the gastrointestinal tract were prompted by previously found cholesterol-lowering effects in humans after consumption of oat products cofermented by using P. parvulus 2.6 and Bifidobacterium spp. Viability was measured with in vitro, gutlike simulations at 37 degrees C. High survival was shown under two of three conditions (gastric juice, bile, and small intestine juice), defined as main obstacles of the gastrointestinal tract. The critical step was bile exposure. At a concentration of 20%, viability was low, but 0.3% bile (mean concentration in the intestine) did not have a major influence on growth. Viability of P. parvulus 2.6 was significantly decreased in gastric juice at pH 1.5 (with pepsin), but it was not significantly affected at pH 2.5, and was also improved at a lower pH in 20% oat milk. Viability was judged sufficient for colonization at gutlike conditions, qualifying the strain for further probiotic studies.
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| 3. |
- Immerstrand, Tina
(author)
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Cholesterol-lowering properties of oats: Effects of processing and the role of oat components
- 2010
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Doctoral thesis (other academic/artistic)abstract
- The cholesterol-lowering effect of oats has been studied for almost fifty years. The effect has hitherto essentially been associated with its content of β-glucans, the primary soluble dietary fibre in oats. Few studies have been published regarding the extent to which other oat components may contribute to the effect and how processing of oats may influence the cholesterol-lowering properties. The objective with the current thesis was to increase the knowledge in this area, and was intended to provide a basis for the development of new functional foods from oats, with optimised cholesterol-lowering properties. For this purpose, different oat products or fractions of oats were produced, characterised and evaluated in mice. The wild-type mouse strain C57BL/6 fed an atherogenic diet was shown to be an appropriate tool for evaluation of effects on plasma cholesterol, although substrain differences in response to oats were found. When oat bran was processed to different average molecular weight of β-glucans and then evaluated in C57BL/6NCrl mice, all products were found to lower plasma cholesterol to the same degree as untreated oat bran. This was also seen for a second mouse model (LDL-receptor deficient mice), although in this case there was a small but statistically significant decline in effect with reduced average molecular weight of β-glucans. It could, however, not be excluded that other components, apart from the β-glucans, might have contributed to the effects on plasma cholesterol in these studies. Indeed, the cholesterol-lowering effect of oat bran, was found to be attributed to two complementary fractions: an oat bran oil and a β-glucan containing fraction, which supported previously published studies that components other than β-glucan may be of importance. The effect of the oat bran oil was shown not to be caused by the content of unsaturated fatty acids, but by other components. An extraction method was developed in order to purify β-glucans from oat bran for studies in mice. The highest yield was obtained after a combined heat treatment and a starch digestion step followed by treatment with pancreatin. Using this method, about 80% of the β-glucans could be extracted. When purified β-glucans from oats were studied, the difference in purity, viscous properties and average molecular weight, seemed not to be crucial parameters for the cholesterol-lowering effect. Further studies are needed to investigate whether purified β-glucan products, with average molecular weights lower than 285 kDa, are able to lower plasma cholesterol and which components in the oat bran oil fraction that cause the effect on plasma cholesterol. The results should also be confirmed in human intervention studies.
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| 4. |
- Immerstrand, Tina, et al.
(author)
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Effects of oat bran, processed to different molecular weights of beta-glucan, on plasma lipids and caecal formation of SCFA in mice.
- 2010
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In: British Journal of Nutrition. - 1475-2662. ; 104:3, s. 364-373
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Journal article (peer-reviewed)abstract
- In the present study, we evaluated the cholesterol-lowering effects of different oat bran (OB) preparations, differing regarding their peak molecular weight (MWp) of beta-glucans (2348, 1311, 241, 56, 21 or < 10 kDa), in C57BL/6NCrl mice. The diets were designed to be atherogenic (0.8 % cholesterol and 0.1 % cholic acid), and they reflected the Western diet pattern (41 % energy fat). All OB preparations that were investigated significantly reduced plasma cholesterol when compared with a cellulose-containing control diet, regardless of the molecular weight of beta-glucan. Moreover, the difference in viscous properties between the processed OB (from 0.11 to 17.7 l/g) did not appear to play a major role in the cholesterol-lowering properties. In addition, there was no correlation between the molecular weight of beta-glucan and the amount of propionic acid formed in caecum. Interestingly, however, there was a significant correlation between the ratio of (propionic acid+butyric acid)/acetic acid and the MWp of beta-glucans: the ratio increased with increasing molecular weight. The results of the present study suggest that the molecular weights and viscous properties of beta-glucan in oat products may not be crucial parameters for their cholesterol-lowering effects.
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| 5. |
- Immerstrand, Tina, et al.
(author)
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Extraction of beta-Glucan from Oat Bran in Laboratory Scale
- 2009
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In: Cereal Chemistry. - 0009-0352. ; 86:6, s. 601-608
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Journal article (peer-reviewed)abstract
- Effects of various enzymes and extraction conditions on yield and molecular weight of beta-glucans extracted from two batches of commercial oat bran produced in Sweden are reported. Hot-water extraction with a thermostable alpha-amylase resulted in an extraction yield of approximate to 76% of the beta-glucans, while the high peak molecular weight was maintained (1.6 x 10(6)). A subsequent protein hydrolysis significantly reduced the peak molecular weight of beta-glucans (by pancreatin to 908 x 10(3) and by papain to 56 x 10(3)). These results suggest that the protein hydrolyzing enzymes may not be pure enough for purifying beta-glucans. The isolation scheme consisted of removal of lipids with ethanol extraction, enzymatic digestion of starch with alpha-amylase, enzymatic digestion of protein using protease, centrifugation to remove insoluble material, removal of low molecular weight components using dialysis, precipitation of beta-glucans with ethanol, and air-drying.
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| 6. |
- Ulmius, Matilda, et al.
(author)
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Gastrointestinal Release of beta-Glucan and Pectin Using an In Vitro Method
- 2011
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In: Cereal Chemistry. - 0009-0352. ; 88:4, s. 385-390
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Journal article (peer-reviewed)abstract
- The release of soluble dietary fiber is a prerequisite for viscous effects and hence beneficial health properties. A simple in vitro method was adapted to follow the release during gastrointestinal digestion, and the percentage of solubilized fiber was measured over time. beta-Glucan from oat bran was mainly released during gastric digestion while the release of pectin from sugar beet fiber continued in the small intestine. Unmilled fractions of sugar beet fiber released more soluble fiber than oat bran flakes, probably due to the porous structure of sugar beet fiber as a result of manufacturing processes, but also clue to differences in source. Milling to smaller fiber particles significantly improved releasability (from 20 to 55% released beta-glucan and from 50 to 70% released pectin, respectively, after digestion). When milled fibers were included in individual food matrices, the release was reduced by protein and starch matrices (5% beta-glucan and 35% pectin released, respectively) and slowed by fat (45% beta-glucan and 60% pectin released). This may result in a too low or too late release in the upper small intestine to be able to interfere with macronutrient uptake. The method may be suitable for predicting the gastrointestinal release of soluble dietary fibers from food matrices in the development of healthy food products.
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