(Bio)technical tools to tailor cereal flavour Raija-Liisa Heiniö, Johanna Buchert, Anu Kaukovirta- Norja, Olavi Myllymäki, Kati Katina, Pekka Lehtinen, Emilia Selinheimo and Kaisa Poutanen VTT Technical Research Centre of Finland
CONSUMER-ORIGINATED PRODUCT DEVELOPMENT GOOD TASTE is the primary criterion for food choice, and essential for the success of a product in competitive markets Taste/ flavour vs. Health vs. Convenience Desired flavour can be actively designed by using different processing techniques to produce products that fulfill consumer expectations 2
FLAVOUR PERCEPTION IS BASED ON MULTIMODAL PERCEPTION BY USING SEVERAL SENSES Appearance SENSE OF VISION Colour Size Shape Texture SENSE OF HEARING Snapping Crispiness etc. SENSE OF TOUCH Burning Pungent Cold Warm etc. Taste SENSE OF TASTE Sour Sweet Salty Bitter Umami Metallic Flavour SENSE OF SMELL Volatile compounds Odour 3
Flavour-active compounds influence perceived flavour of a product, but All chemical compounds are not responsible for flavour sensation There are synergistic or suppressive effects of compounds Non-bound (free) compounds are most flavour-active In addition to volatile compounds, several non-volatile components affect perceived flavour 4
TOOLS FOR FLAVOUR DESIGN Sensory methods to measure sensory quality of products and determine the desired attributes Analysis of volatile and non-volatile compounds Relation of perceived flavour and chemical, flavour-active compounds by using statistical multivariate techniques (PCA, PLS regression) 5
CHEMISTRY BEHIND FLAVOUR FORMATION OF CEREAL MATERIALS Volatile compounds Amino acids, small peptides PERCEIVED FLAVOUR Phenolic compounds Fatty acids, lipids Sugars Perceived flavour is influenced by 1 - Flavour-active volatile compounds (odour) as such in the headspace of the cereal material (aldehydes, alcohols, ketones) 2 - Flavour-active non-volatile compounds (flavour) as such in the cereal material or as flavour precursors (amino acids, sugars, fatty acids, phenolic compounds) Acids 6
WHAT IS 'CEREAL-LIKE' FLAVOUR? Rye-like flavour ~ Flavour of rye bread? Oat-like flavour ~ Flavour of oat porridge? Each grain species, such as rye or wheat, has its characteristic flavour Grain cultivar, season and cultivation area influence flavour 7
SENSORY CONCERNS IN WHOLE GRAIN FOODS Dark (rye) or greyish (barley) colour (polyphenols, carotenoids) Bitter flavour (especially rye) (polyphenols, peptides) Hard like texture (lignocellulosic layers, large particles) 8
FORMATION AND MODIFICATION OF FLAVOUR OF CEREAL PRODUCTS Flavour of native grain is rather mild and bland Grain must be processed prior to use in human consumption Cereal flavour forms in processing Wheat Oat Rye Barley 9
TAILORING DESIRED FLAVOUR & TEXTURE OF CEREAL PRODUCTS Milling fractionation of grain Sourdough fermentation & baking Germination (malting) Enzymatic modifications Fermentation & germination increase amounts of health-beneficial phenolic compounds, concurrently influencing considerably perceived flavour Enzymes offer a tool for controlled flavour design Heat treatment: Extrusion, autoclave puffing, IR-roasting An important step for tailoring perceived flavour (Maillard reaction) 10
SOURDOUGH FERMENTATION AND BAKING Fermentation influences bread crumb flavour, and baking bread crust flavour Fermentation increases flavour intensities (sourness, bitterness and cereal-like flavour), and levels of lactic and acetic acids Sourness formed in fermentation does not disappear in heat treatment, such as baking or extrusion Amount of salt used in bread baking could be somewhat reduced through sourness formed in fermentation Baking produces Maillard reaction products (pyrazines, pyrrols, furfurals etc.), which often have a roasted note 11
GERMINATION AND HEAT TREATMENTS Germination mostly used for barley to produce malt for brewing Heat treatment used to halt germination is salient to flavour formation At high temperatures roasted, sweet, nutty flavour and crispy texture is formed (without Maillard reaction) Roasted, sweet, nutty flavour related to volatile compounds such as dimethyl sulphides and isobutanol Stability of cereal materials can be significantly improved by germination and subsequent heat treatment 12
ENZYMATIC FLAVOUR DESIGN Enzymes (lipases, esterases, proteases, amylases and glycosidases) used in food production include biochemical fermentation processes Curing of cheese, wine or bologna, sourdough fermentation of bread, brewing Enzymes provide novel, natural tools to tailor chemistry of raw materials present in food matrix, resulting in added value to the product or in improved processes Enzymes can be exploited in different stages of processing Tailored (bio)technologies to design cereal flavour in a controlled way Correlations between chemistry/ macromolecular characteristics of flavour and sensory profile of grain Role of food biopolymer matrix in sensory perception Targeted flavour boosting, stabilization or elimination in cereal material 13
ENZYMES IN FLAVOUR MODIFICATION Biopolymer matrix Hydrolytic enzymes Matrix opening Flavour release/ formation Low MW phenolics Polymerizing enzymes Flavour elimination Enzymatic deglycosylation Improved, modified flavour 14
Case studies 15
CASE 1 - DISTRIBUTION OF FLAVOUR AND BIOACTIVITY IN RYE GRAIN In mechanical milling fractionation rye kernel is separated into fractions, each of them having their characteristic flavour and phytochemicals Endosperm: Mild flavour Bran:Strong,bitter flavour Bitterness-Pinoresinol & syringic acid; Germ-like flavour-sinapic & ferulic acids, alkylresorcinols, except AlkrC23:0, syringaresinol Between mild-tasting innermost part and bitter-tasting outer bran fraction, rye-like flavour without bitterness is observed This shorts fraction contains significant amounts of health-beneficial, nonvolatile phenolic compounds (phenolic acids, alkylresorcinols and lignans), some of them having inpact on perceived flavour Heiniö R-L et al. LWT 2003a, JCS 2007 (subm.) Shorts: Rye-like flavour without bitterness Cereal flavour-vanillic & veratric acids, alkylresorcinol C23:0, lignans except pinoresinol 16
Case2: INFLUENCE OF PEELING AND FERMENTATION ON SENSORY PROFILING Breads containing native/ peeled, non-fermented/ fermented rye bran (20%) and white flour (80%) Sensory profiling of bran containing breads Trained panel (n=10-11), two replicate sessions Descriptive analysis with 8 sensory attributes; Vocabulary developed in round-table session Rating on verbally anchored, continuous unstructured, graphical intensity scales (0-10) Bread slices served to panellists coded and in random order Computerised data collection (Compusense) Statistical data analysis: Analysis of variance MANOVA & Tukey's test (SPSS) 17
10 9 8 7 6 5 4 3 2 1 FLAVOUR PROFILE OF BREADS BAKED WITH TWO DIFFERENT TYPES OF FERMENTED BRANS 0 Colour Springiness Coarseness Flavour pungency Flavour intensity Aftertaste bitterness Roasted flavour intensity* Wheat bread containing fermented native rye bran Wheat bread containing fermented peeled rye bran 18
SENSORY CHANGES INDUCED BY PEELING AND FERMENTATION Impact of peeling of grain Lighter colour Decreased coarseness of mouthfeel Tendency of decreased pungency, flavour intensity, aftertaste bitterness, significantly less roasted flavour Impact of fermentation of bran Fermentation of native bran tended to increase bitter flavour and flavour intensity Fermentation of peeled bran did not enhance undesired flavour characteristics Impact of combined peeling and fermentation of bran Lighter colour, less coarse crumb, milder flavour than in breads containing native bran 19
CASE 3 - STABILITY OF OATS Rancid, bitter flavour develops easily in oat during storage due to high fat content Oat stability can be significantly improved by germination-heat treatment process Bitter, rancid flavour resulting from lipid degradation appears in processed oat considerably later than in unprocessed Musty, earthy odour and bitter, rancid flavour of stored, deteriorated oat closely correlate with free fatty acids and volatile compounds related to lipid oxidation Phenolic compounds and volatile compounds derived from protein degradation are related to favourable roasted flavour Heiniö et al. Cereal Chem. 2002 20
CASE 3 - STABILITY OF OATS 1.5 PC2 X-loading Weights and Y-loadings 1.0 0.5 0-0.5 F-BITTER F-INTENSE O-MUSTY AFTER TASTE Native-12 Germinated-6 O-INTENSE Native-9 F-RANCID Germinated-9 F-MUSTY F-NUTTY Germinated-12 Pentanal F-ROASTED Native-6 n-butylfuran Pentylfuran O-EARTHY O-ROASTED 1-Hexanal F-CEREAL Phenyl acetate 1-Pentanol O-MOIST 3-Pentanone O-CEREAL 1-Hexanol Methylpropanal F-SWEET Germinated-0 Heptanal Methylbutanal Dimethylsulphide 2-Heptanone Belzaldehyde F-GERMLIKE 2-Ethylfuran Native-0-1.0 PC1-0.4-0.2 0 0.2 0.4 0.6 0.8 1.0 Heiniö et al. Cereal Chem. 2002 21
CASE 3 SEARCH FOR FLAVOUR ATTRIBUTES BY USE OF ENZYMES Intensive, bitter flavour of rye caused by small peptides and phenolic compounds Protease treatment resulted increase in intensive, bitter flavour of rye indicating that certain small peptides and concomitantly released phenolic compounds had a role in bitter flavour Heiniö R-L et al. 2005 22
NOVEL (BIO)PROCESSING TECHNOLOGIES FOR FLAVOUR DESIGN IN PLANT BASED FOODS 2006-2009 Whole grain cereal: Rye, Barley, Oats, Wheat Raw materials PROCESSING CHEMICAL AND SENSORY ANALYSIS Enzymes Starter cultures Thermal processing Physical/ mechanical processing CHEMICAL ANALYSIS GC-MS HPLC Spectrophotometry Capillary electroforesis SENSORY ASSESSMENT Descriptive profiling Flash profile Sorting GC-Olfactometry RELATION BETWEEN CHEMICAL AND SENSORY DATA PLS regression 23
CONCLUSIONS Cereal flavour is influenced by volatile and phenolic compounds, amino acids, sugars and fatty acids Flavour of native grain is mild (Bio)processing provides new tools for developing novel, palatable, healthbeneficial breakfast & snack applications from cereal Flavour components unevenly distributed in fractionated grain Sourdough fermentation strenghtens bitterness & rye-like flavour Germination-heat treatment results roasted, nutty, sweet flavour and crisp texture Enzymes offer potential for tailoring flavour to boost, stabilise or eliminate flavour atributes 24