Kirsi-Helena Liukkonen

Process-induced changes on bioactive compounds in whole grain rye.

Manufacturing of healthy wholegrain foods demands knowledge of process-induced changes in macro-, micro- and non-nutrients. The high content of dietary fibre is a challenge in relation to good product texture and sensory quality. The stability and bioavailability of bioactive compounds have a marked influence on the health effects of cereal foods. It was confirmed that sterols, folates, tocopherols and tocotrienols, alkylresorcinols, lignans, phenolic acids and total phenolics are concentrated in the bran layers of the rye grain, and are only present at low levels in the flour endosperm. The levels of folate and easily-extractable phenolic compounds increase in germination and sourdough baking, but there are negligible changes in the levels of sterols, lignans and alk(en)ylresorcinols. The levels of tocopherols and tocotrienols are reduced during the sourdough fermentation. In conclusion, many of the bioactive compounds in wholegrain rye are stable during food processing, and their levels can even be increased with suitable processing.

Effect of baking method and fermentation on folate content of rye and wheat breads

ABSTRACT The effect of baking method on folates of rye and wheat breads, as well as the effect of sourdough fermentation of rye, were examined. Sourdough fermentations were performed both with and without added yeast, and samples were taken throughout the baking process. Samples were analyzed microbiologically for their total folate content after trienzyme extraction. Individual folate vitamers were determined by HPLC after affinity chromatographic purification. The lowest folate contents for both rye and wheat breads were found from breads baked without added yeast. Total folate content increased considerably during sourdough fermentation due to increased amounts of 10-HCO-H2folate, 5-CH3-H4folate, and 5-HCO-H4folate. Bakers yeast contributed markedly to the final folate content of bread by synthesizing folates during fermentation. Proofing did not influence total folate content but changes in vitamer distribution were observed. Folate losses in baking were ≈25%. The variety of sourdoughs and baking pro...

A Psyllium Fiber-Enriched Meal Strongly Attenuates Postprandial Gastrointestinal Peptide Release in Healthy Young Adults

Dietary fiber (DF) and protein are essential constituents of a healthy diet and are well known for their high satiety impact. However, little is known about their influence on postprandial gastrointestinal (GI) peptide release. Our aim in this single-blind, randomized, cross-over study was to investigate the effects of DF and/or protein enrichments on satiety-related metabolic and hormonal responses. Sixteen healthy, nonobese volunteers participated in the study and ingested 1 of 5 isoenergetic test meals in a randomized order on separate days. The test meals were as follows: 1) low in protein (2.8 g) and fiber (7.6 g); 2) low in protein (2.6 g) and high in soluble fiber (psyllium, 23.0 g); 3) high in protein (soy, 19.7 g) and low in fiber (6.2 g); 4) high in protein (18.4 g) and fiber (23.0 g); and 5) white wheat bread. Serum insulin and plasma glucose, ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) concentrations were determined for 2 h following the meals. In addition, hunger and satiety ratings were collected. Postprandial glucose, insulin, ghrelin, GLP-1, and PYY responses all differed among the meals (P <or= 0.05). Fiber-enriched meals decreased glucose, insulin, ghrelin, and PYY responses; in addition, PYY secretion was prolonged compared with the other meals. The postprandial GLP-1 concentration was significantly suppressed after a fiber- and protein-rich meal, in contrast to the initial increases following the other meals. However, postprandial ratings of appetite were mostly similar after the test meals. In conclusion, solid meals enriched with psyllium fiber strongly modified postprandial signals arising from the GI tract.

Milling fractionation of rye produces different sensory profiles of both flour and bread

Rye grains of the cultivar Amilo were milled into five milling fractions, and three of the fractions were used for baking mixed wheat bread samples. The sensory profiles of the rye flours and those of the mixed wheat bread samples were determined. The results clearly demonstrated that both the sensory perception and the colour intensity are highly dependent on the milling fraction of rye. The innermost, endospermic part of the kernel had a very mild flavour, whereas the bitter, strong flavour and aftertaste were concentrated in the outermost bran layers. This sensory perception of the flours was consistent with the perception of the bread samples, where 20% of the wheat flour was replaced by the rye fraction. The endospermic fraction induced a very mild flavour in the mixed wheat bread, resembling pure wheat bread. The bitter, intense flavour and aftertaste were perceived as being most salient in the bread containing the bran fraction. The shorts, with high bioactivity, was the most important fraction, in producing a cereal-like but not bitter flavour in both flour and bread. The colour intensity of the bread samples increased from the endospermic layer to the bran layer.

Relationship between sensory perception and flavour-active volatile compounds of germinated, sourdough fermented and native rye following the extrusion process

Abstract Relation between sensory profiles and flavour-active volatile compounds was explored on six rye extrudates, representing two rye cultivars (Amilo and Akusti) and three pretreatments (germination, sourdough fermentation and milling), prior to the extrusion cooking. The processing method used before the extrusion cooking was shown to be very decisive for the perception; the germinated, sourdough fermented and milled rye extrudates clustered to cultivar pairs according to their pretreatment on the regression plot including the whole sample set. Germinated, extruded rye was cereal and fresh in flavour, and hard in texture, and dimethyl sulphide and 2-methylbutanal were highly related to these sensory attributes. Sourdough fermented, extruded rye had a sour, intense flavour and aftertaste, and porous texture, the most relevant volatile compounds being furfural, ethyl acetate, 3-methylbutanol and 2-methylbutanol. The extrudates prepared from rye flour were very mild in flavour and somewhat tough in texture, and 2-ethylfuran, 2-methylfuran, hexanal and pentanal were the dominating volatile compounds. The present study clearly demonstrated the effect of processing on adjusting the flavour of rye. Sensory perception and volatile compounds of germinated, sourdough fermented, and native rye were substantially different, and they remained variable after the second treatment, i.e. the extrusion process. The pretreatment process was shown to be most dominant in the formation of the flavour of the rye extrudates. The rye cultivar had an unsubstantial effect on the sensory profiles.

Effects of wheat pentosan and inulin on the metabolic activity of fecal microbiota and on bowel function in healthy humans

The effects of wheat pentosan and inulin on the metabolic activity of fecal microbiota and on bowel function were compared in healthy humans. In a parallel study 14 subjects consumed daily for three weeks 13 g of wheat pentosan or inulin baked in wheat bread. Activities of bacterial enzymes (β-glucuronidase, β-glucosidase, urease) and concentrations of bacterial metabolites (short chain fatty acids, phenol, p-cresol) in feces, bowel function and intestinal symptoms were measured at the beginning and end of the intervention period. Changes in most parameters studied were similar in subjects receiving pentosan or inulin bread, but pentosan increased total SCFA (P = 0.048) and butyrate (P = 0.009) concentrations in feces more than inulin. Pentosan also increased the occurrence of flatulence (P < 0.05). Pentosan appears to be more easily fermented than inulin, and due to the increase in the fecal butyrate concentration may have favourable effects on colonic health.

The effect of fibre amount, energy level and viscosity of beverages containing oat fibre supplement on perceived satiety

Background Soluble fibre has been proposed to suppress appetite-related perceptions and it could thus contribute favourably to the regulation of energy intake and the increasing obesity problem. Objective To investigate the effect of an oat ingredient rich in β-glucan on perceived satiety at different dietary fibre (DF) concentrations, energy levels and viscosity levels. Design A total of 29 healthy volunteers, age 19–39, mean BMI 23.2 kg/m2 participated in this study. Measurement of subjective perceptions (satiety, fullness, hunger, desire to eat something/the sample food and thirst) was performed during a 180-min period after ingestion of the sample. There were altogether six samples: two beverages without fibre at energy levels 700 and 1,400 kJ; two beverages containing 5 or 10 g oat DF (2.5 and 5 g oat β-glucan, respectively) at energy level 700 kJ, one beverage containing 10 g oat DF/1,400 kJ and one beverage containing 10 g enzymatically treated oat DF with low viscosity at energy level 700 kJ. Each beverage portion weighted 300 g. The order of the samples was randomised for each subject and evaluated during six separate days. The results are reported in three sets of samples: ‘fibre’, ‘energy’ and ‘viscosity’. Results In the fibre set, the beverages containing 5 or 10 g of fibre had a larger area under curve (AUC) for perceived satiety and smaller AUC for hunger compared to the beverage without fibre, but no significant dose–response relationship was detected. Increasing the energy content from 700 to 1,400 kJ in the energy set did not affect the satiety-related perceptions. In the viscosity set, the beverage with low-viscosity β-glucan increased satiety-related perceptions from no fibre containing beverage, but less compared to the beverage with the same amount of fibre and higher viscosity. Conclusions Addition of an oat ingredient rich in β-glucan and high viscosity of beverages enhance post-meal satiety induced by beverages. The effect was, however, not related to the amount of ingested fibre or energy.

Fibers with different solubility characteristics alter similarly the metabolic activity of intestinal microbiota in rats fed cereal brans and inulin

We compared the effects of different sources of fiber (rye-bran, oat-bran, wheat-bran) and inulin on the activity of fecal bacterial enzymes and concentration of short chain fatty acids (SCFA) in the colonic contents of rats. A diet without fiber was used as a control. The cereal brans and inulin had similar, increasing effect on the activities of β-glucuronidase and urease (P < 0.05). All bran diets also increased β-glucosidase activity while the increase by inulin was non-significant. Concentration of total SCFA was higher in the inulin and rye-bran groups compared to non-fiber and wheat-bran groups (P < 0.05). Concentration of butyrate was higher in rye-bran and inulin groups compared to the non-fiber group (P < 0.05), and that of propionate higher in the inulin group compared to non-fiber and wheat-bran groups (P < 0.05). The SCFA profile in the oat-bran group did not differ significantly from SCFA profile in the other groups. These findings indicate that the source of the fiber does not markedly affect the enzyme activities of the fecal bacterial microbiota, but may cause differences in the profile of SCFA in the rat colon.

Plasma ghrelin levels after two high-carbohydrate meals producing different insulin responses in patients with metabolic syndrome

Ghrelin is an orexigenic peptide produced in the stomach and its plasma levels are decreased acutely in response to ingested nutrients. To further clarify the role of insulin on ghrelin secretion, the present study was designed to investigate whether circulating ghrelin is affected differently by two mixtures of whole-grain breads known to produce low or high insulin responses in obese non-diabetic subjects with metabolic syndrome. After an overnight fast eight obese subjects with the metabolic syndrome (3 men and 5 women; BMI 33.7+/-0.7 kg/m(2); age 55.6+/-1.8 y) received two different meals consisting of whole-grain rye or wheat breads. The comparison group (3 men and 5 women; BMI 22.5+/-0.5 kg/m(2); age 26.0+/-0.9 y) received a wheat bread meal. Blood samples were collected postprandially at time intervals for 2 h. Feelings of hunger and satiety were analyzed using the visual analogue scales. Ghrelin concentrations decreased after bread meals in lean individuals, but not in obese individuals with the metabolic syndrome. Despite the difference in plasma insulin response, there was no difference in plasma ghrelin or feelings of hunger and satiety in patients with metabolic syndrome. After both rye and wheat bread meals, the decrease in ghrelin concentrations seen in normal-weight individuals after wheat bread meal was absent in subjects with metabolic syndrome. Despite the different plasma insulin response in obese patients, ghrelin levels did not change in response to either type of bread meals. In addition, ghrelin levels did not correlate with insulin, glucose, HOMA1-IR and satiety and hunger ratings in either study groups. This indicates that regulation of ghrelin might be altered in obese patients with metabolic syndrome independently of insulin.

Less Insulin is Needed for Regulation of Postprandial Glucose in Healthy Subjects after Wholekernel Rye Bread and Dark Durum Wheat Pasta than after Wheat Bread

Abstract Decreased glucose and insulin responses to carbohydrates are considered beneficial for health. Dietary fiber, structure of food, baking and processing influence these responses. Twenty subjects (10 men and 10 women, aged 28±1 y, BMI 22.9±0.7kg/m 2 ) with normal glucose tolerance were recruited. The test products were wholekernel rye bread (60% of whole kernels) containing lactic acid (Rye 1), wholemeal rye bread containing oat (β-glucan concentrate (Rye 2), dark durum wheat pasta and white wheat bread. The test portions contained 12.8, 17.0, 5.6 and 3.2g of dietary fiber, respectively. Each subject received five breakfasts (wheat bread twice) in random order during a period of 3 months. The breakfast contained the test product with 50g available carbohydrates, 3 dl non-caloric orange drink and 40g cucumber with breads or 19g tomato sauce with pasta. A fasting and 8 postprandial blood samples were collected at intervals of 15-30minutes during 3 hours. Glucose and insulin areas under the curve (AUC) were calculated. No significant differences in glucose AUC between the products were found, but insulin AUC of Rye 1 (P=0.001) and pasta (P=0.001) were significantly smaller than that of wheat bread. Maximal glucose response was lower to pasta than to wheat bread (P=0.006). Maximal insulin responses to Rye 1, Rye 2 and pasta were decreased compared to wheat bread (P=0.001, P=0.009, P=0.001, respectively). In conclusion, less insulin is required for the regulation of postprandial glucose after the wholekernel rye bread and dark durum wheat pasta than after the wheat bread. The way of processing and the structure of food may be more essential for the regulation of glucose and insulin metabolism than the amount of dietary fiber.