Olavi Myllymäki

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.

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.

Fructan Content of Rye and Rye Products

ABSTRACT The fructan content of Finnish rye grains (13 samples, seven cultivars, harvested in 1998-2000) varied at 4.6–6.6 g/100 g (db). Commercial whole grain rye flour and rye flakes had fructan content of 4 g/100 g, light refined rye flour had fructan content of 3 g/100 g, and rye bran had fructan content of 7 g/100 g. Fructan content as high as 23 g/100 g was detected in the water-extractable concentrate of rye bran. Finnish soft rye bread and rye crisp bread contained 2–3 g of fructan/100 g. According to the suggested new definition of dietary fiber, fructans are also classified as dietary fiber. This means that the dietary fiber content of some cereal foods such as rye products may be increased by as much as 20% due to the presence of fructans in the grain.

Physical properties of (1→3),(1→4)-β-D-glucan preparates isolated from finnish oat varieties

Abstract The β-glucan content in the groats of different Finnish oat varieties cultivated in Finland varied from 3.2 to 5.3% and, in the fibre concentrates obtained by dry milling and a further concentration step including hot ethanol treatment and wet milling, from 11.8 to 18.3%. The viscosities of the isolated crude extracts varied widely between the varieties. Stil, Puhti, Yty and Nasta formed the most viscous solutions and Pol, the typical feed oat, the least viscous solution. The more significant differences in the viscosities between the oat varieties when measured at the same β-glucan concentration could be explained in terms of differences in mean molecular weight. Trypsin decreased the viscosity and the molecular weight of β-glucan of all samples. The viscosity of the β-glucan solutions was independent of pH both before or after enzyme treatment indicating that the protein or peptide is firmly bound to β-glucan.

Mechanical and permeability properties of biodegradable extruded starch/polycaprolactone films

Barley starch and glycerol were mixed with polycaprolactone (PCL) powder in various combinations and plasticized in a twin-screw extruder. When possible, extrudates were processed into films in a single-screw extruder and subjected to an orientation process with the aim of improving the water durability and mechanical strength of the starch films. The mechanical properties, water vapour and oxygen permeabilities, sorption isotherms and solubility of the processed films were studied. The films containing 20% or more PCL achieved a tensile strength of 20 MPa or higher. Orientation of the film still further improved the tensile strength, and also the water vapour and oxygen barrier properties. With PCL contents of 0–20% the starch/PCL films proved to be excellent oxygen barriers. Increase in PCL content beyond this impaired the oxygen barrier properties, whilst improving the water barrier properties. Copyright

Relating microstructure, sensory and instrumental texture of processed oat

This study is a part of a larger project aiming to produce new, healthy, and tasty food ingredients from oat. Germination and different heating processes can be used to improve the texture and flavour of cereals. In this study effects of germination and wet and dry heating on the microstructure, instrumental structure and sensory properties of two oat varieties were assessed. The microstructure of native, germinated, autoclaved and extruded grains of the hulled cv. Veli and hull-less cv. Lisbeth was examined by light microscopy, the texture was measured by determining the milling energy and hardness of the grains and sensory characteristics were evaluated with descriptive sensory profile analysis. In cv. Veli the cells of the starchy endosperm were smaller than in cv. Lisbeth and β-glucan was concentrated in the subaleurone layer. In cv. Lisbeth β-glucan was evenly distributed in the starchy endosperm. The grains of cv. Lisbeth were more extensively modified in the germination process than the grains of cv. Veli, otherwise the effects of processing on the grains of the two cultivars were similar. Germination caused cell wall degradation, autoclaving and extrusion cooking caused starch gelatinization. Autoclaving resulted in the hardest perceived texture in oat. Gelatinization of starch appeared to contribute more to the hardness of oat groats than the cell wall structure. Of the instrumental methods used in this study the milling energy measurement appeared to be the most useful method for the analysis of the effects of processing on grain structure.

Bio)processing as Tool to Tailor Cereal Flavour

ABSTRACT Wholegrain products are regarded beneficial for health by reducing the risk of several chronic diseases. Certain cereal types have a typical flavour, which in some cases is not regarded attractive enough for consumers. The flavour of native, untreated grain is mild and bland. Generally, the cereal flavour forms during processing, especially in heat treatments. By applying different bioprocessing techniques the flavour and texture of the products may be adjusted into desired direction. Volatile and non-volatile compounds influence the perceived flavour directly or indirectly as flavour components or flavour precursors. Descriptive profiling is used to form a general view of the sensory characteristics in the product. To understand the chemistry behind the flavour, statistical multivariate techniques are used to relate sensory characteristics and chemical compounds. In this work the impact of germination, milling fractionation, sourdough technology and enzymatic treatments on cereal flavour formation and characteristics will be discussed. Germination-drying process was found to adjust effectively the perceived flavour and increase the flavour stability of oat. Sourdough fermentation increased the perceived sourness and flavour intensity, and the following heat-treatment induced the appearance of flavours and compounds originating from Maillard reaction. The fractions of rye kernel have their characteristic flavour: between the mild tasting endospermic part and the bitter tasting outermost bran fraction, a rye-like flavour without any obvious bitterness was observed. This fraction contains significant amounts of bioactive compounds, such as alkylresorcinols, lignans and phenolic acids. Enzymes were also investigated as tools to modify rye flour. As a result of protease treatment the intensive, bitter flavour of rye was increased indicating that certain small peptides and concomitantly released phenolic compounds had a role in the bitter flavour.