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Quantitative Sensory Profiling of Cooked Oatmeal
Lebensm.-Wiss. u.-Technol., 33, 374}379 (2000)
Quantitative Sensory Pro"ling of Cooked Oatmeal Anja LapvetelaK inen* and Hanna Rannikko
Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku (Finland) (Received September 21, 1999; accepted April 20, 2000)
Sensory proxling of cooked oatmeal was carried out for rolled-oat process optimization and product characterization purposes. The main sensory properties of oatmeal (thickness, adherence to spoon, size of swollen yake particles, uniformity of mass, slipperiness, coarseness, darkness of colour) were included in the group of appearance and texture attributes. Odour and yavour were fairly weak, the terms most often used being toasted, sweet, cereal, and chemical. Rolled oats of xve various cultivars diwered in the oatmeal characteristics such as thickness, adherence to spoon, and size of swollen yake particle. Two commercial rolled-oat brands varying in their yake thickness (0.54 and 0.77 mm) and cooking time (10 and 15 min) resulted in oatmeals with diwerent texture proxles. Two cooking conditions also tested ~ adding the rolled oats either to cold or boiling water ~ profoundly inyuenced the texture characteristics quantixed.
2000 Academic Press Keywords: oatmeal; sensory properties; cultivar di!erences; e!ect of cooking conditions
Experimental
Introduction The optimization of rolled-oat production necessitates that the quality of the end product can be characterized, not only in physical and chemical, but also in sensory terms. The number of publications on sensory lexicons for cooked oatmeal, which is the primary use for rolled oats in Finland, is very limited. All sensory descriptions available concern #avour and are mostly aimed at describing the grain attributes (1}4) or extruded oat products (5,6). The aim of the present study was to develop a terminology for the odour, #avour, texture and appearance characteristics of oatmeal by means of generic descriptive analysis (7). The sensory terminology developed was further applied for analysing two sample sets. With the "rst set we aimed to "nd out whether the oat cultivar used for rolled-oat production has an in#uence on the sensory pro"le of oatmeal. With the second set, consisting of two commercial rolled-oat samples, we wanted to study the e!ect of two cooking conditions on the sensory properties of oatmeal. This was of interest since the procedures for preparing oatmeal in households vary from one country to another. For instance, rolled oats are commonly added to boiling water in Finland, but to cold water in Sweden. Information on the possible changes in the sensory properties due to cooking conditions is valuable, particularly for the manufacturers targeting rolled-oat products for the international market. * To whom correspondence should be addressed. Tel: #358-40-5212 639; fax: #358-2-333 6860; E-mail: anja.lapvetelainen@uku."
0023-6438/00/050374#06 $35.00/0 2000 Academic Press
Rolled-oat samples Cultivar rolled oats were manufactured by Melia Ltd. in a commercial oat mill located in Nokia, Finland, using grains (Avena sativa L.) of a single cultivar for each rolled-oat sample. The cultivar products were processed to a #ake thickness of 0.6 mm. Three of the cultivars (Veli, Virma, Yty) were Finnish and two (Salo, Freja) were of Swedish origin. All of them were cultivated by contract growers in southern Finland in 1995. A single cultivar grain batch (30,000}100,000 kg) was formed using grains from 2}6 growers. All the grains matched Melia Ltd.'s quality criteria for rolled-oat production. The sensory terminology was developed using nine Finnish commercial rolled-oat brands on the market in 1995. These were selected to represent a wide range of variation in terms of #ake thickness (0.3}0.8 mm) and recommended amount of rolled oats and length of cooking time given on the package instructions (Table 1). In addition, the samples from three cultivar rolled oats (Salo, Veli, Virma) were also used during the method development. The e!ect of cooking conditions was tested using two commercial rolled-oat brands: L and M (Table 1). Brand L represents most commonly used rolled-oat type in Finland and brand M an &old-fashioned' rolled-oat type having large, thick #akes and long cooking time. Storing of rolled-oat samples All commercial samples were purchased from the retail shops and stored in the original packages at room
doi:10.1006/fstl.2000.0675 All articles available online at http://www.idealibrary.com on
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Table 1 Amount of rolled oats and cooking time used for preparation of oatmeals of Finnish commercial brands characterized also in terms of #ake thickness Brand code K L M N O P Q R S
Flake thickness? Amount of rolled Cooking (mm) oats used (g/L water) time (min) 0.34 0.54 0.77 0.56 0.52 0.55 0.34 0.52 0.53
140 130 130 110 130 130 140 140 130
1 10 15 10 8 10 1 5 10
? mean of 10 measurements; coe$cient of variation 1.8}6.5%
temperature. To avoid #avour changes during storage, the cultivar rolled oats were packed in 200 g portions in 500 ml glass bottles, which were stored at !28 3C until analysis (within two months). By using a constant reference duo-trio test, the freezing procedure was checked to not cause detectable changes in the sensory quality of oatmeal. In this test, the unfrozen rolled oats were the constant reference sample. The glass bottles containing rolled-oat samples were removed from the freezer to room temperature 18}20 h before cooking.
Preparation of Oatmeal samples Oatmeals of commercial brands were prepared according to the instructions on the packages, the amount of rolled oats mixed into 1 L of boiling water varying between 110 and 140 g, and cooking time between 1 and 15 min depending on the brand (Table 1). The cultivar oatmeals were prepared by mixing 130 g of rolled oats (11% moisture basis) with 1 L of boiling water and cooking for 10 min. The tap water used for sample preparations was "ltered through a granular activated carbon cartridge (METEK, Sheboygan, WI, USA). Oatmeals were prepared in a cooking pot (stainless steel, 3 L, KombiDouble Pan, Opa, Mikkeli, Finland) comprising two parts, the lower one used as a boiling water bath and the upper as the actual cooking pot. After cooking, the oatmeal samples were served in random order from 40 mL glass cups with lids and coded with three-digit numbers. The samples were kept on hot portable plates (80 3C) until analysed. The assessors began the evaluations in 10 min and the evaluation of a single set including "ve cultivar samples took 15}20 min. During evaluation, the temperature of the samples was maintained at 60}70 3C. The assessors were given one steel spoon for each evaluated sample and asked to assess one sample at a time for all characteristics before continuing with the next sample. When the e!ect of cooking conditions was tested, the oatmeals were prepared by adding rolled oats to both cold and boiling "ltered tap water in a single cooking pot (stainless steel, 3 L, Hackman, Sorsakoski, Finland). In the former case, the rolled oats were added to cold water
and the mixture warmed to boiling and cooked for 5 min (counting commenced from boiling), whereas in the latter case the rolled oats were added to boiling water and cooked for the time given in Table 1. The samples were served to the assessors as described above.
Assessors The assessors were selected according to their willingness to participate in sensory evaluations, and tested for their ability to recognize selected taste and odour samples, and to detect certain #avour (sweetness, stale) and texture di!erences (uniformity of mass, adherence) in cooked oatmeals. The taste samples were: 0.6% sucrose (sweet); 0.04% and 0.08% citric acid (sour); 0.03 and 0.06% ca!eine (bitter). The odour samples were: 2% vinegar; vanillin; detergent/soap (a piece of Cussons Imperial Leather Soap); bitter almond; allspice; onion; oregano; curry; and stale. The stale extruded oat preparation was used for preparing the stale odour sample; all the other odour samples were prepared by using commercial spices or other products. The odour samples were weighed into brown 40 mL glass bottles which were wrapped with aluminium foil and topped with cotton wool to prevent visual recognition, sealed, and coded with three-digit numbers. From the total number of 28 candidates, 15 assessors were selected. This "nal sensory panel consisted of 12 female and 3 male assessors, in good health, from the sta! and students of the department between the ages of 21 and 50.
Development of terminology The assessors were "rst asked to describe all the sensory properties perceived in the samples. Odour and #avour were characterized in two one-hour sessions and appearance and oral texture during the two other one-hour sessions. In addition, four sessions (45 min) were conducted for discussions about the main characteristics and developing the evaluation procedures. The main sensory properties of oatmeal were found to be related to texture or appearance. The textural properties were grouped as manual (thickness, adherence to spoon) and oral characteristics (average size of swollen #ake particles, uniformity of mass, slipperiness, coarseness). During sample characterization, the most often used odour and #avour terms were toasted, sweet, cereal and chemical. In the group discussion, however, the odour and #avour of oatmeal were generally regarded as being fairly weak and neutral. Thus, a decision was made to quantify only the intensities of toasted odour and #avour, and the total intensities of odour and #avour, in the following sample sets. Based on the group discussions, the verbal de"nitions and reference substances at various intensity levels were preliminarily developed and suggested to the assessors by the authors. These were "nally agreed upon by the whole panel during two one-hour discussion sessions (Table 2). Colour was characterized with terms such as yellowish, brown, greyish brown, and grey. A single cooked oatmeal sample may exhibit notes of several hues depending
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Table 2 Main sensory characteristics of cooked oatmeal with de"nitions, verbal end anchors on the scale from 0 to 10, and reference substances. For reference oatmeal samples (R), the brand together with the amount of rolled oats (g/L of water) and cooking time used are listed below the scale anchors. Abbreviations for brands: EL"Elovena, AH"Aamun HyvaK , and IH"Iso Herkku, all manufactured by Melia Ltd (Finland) Characteristics Odour Overall intensity of odour Toasted odour
Manual texture Thickness
Adherence to spoon
Flavour Overall intensity of #avour Toasted #avour
Oral texture Average size of swollen #ake particles Uniformity of mass
Slipperiness
Coarseness
Verbal end anchors and reference substances used at the designated intensity levels
De"nitions The odour perceived immediately after removing the lid The odour related to toasted rolled oats; evaluated before mixing the sample
none P very strong * no references none P very strong R at 0.0}0.5"rolled oats, not steam-heated, 130 g, 10 min R at 7.5}8.0"toasted? EL, 130 g, 10 min
The force required to stir the sample with spoon. thin P very thick R at 0.0}0.5"EL, 90 g, 10 min R at 9.5}10"AH, 150 g, 1 min The amount of the sample adhering to the none P at least 1/2 of spoon "lled with the mass &inner side' of the spoon; evaluated by R at 0.0}0.5"EL, 90 g, 10 min taking a spoonful of sample and turning R at 9.5}10"AH, 150 g, 1 min the spoon over. After 5 s the adhered sample is observed The #avour evaluated orally after mixing the sample with a spoon The #avour related to toasted rolled oats: evaluated orally after mixing the sample with a spoon
none P very strong * no references none P very strong R at 0.0}0.5"rolled oats, not steam-heated, 130 g, 10 min R at 8.5}9.0"toasted? EL, 130 g, 10 min
The average size of swollen #ake particles in the mass; evaluated by pressing the sample with tongue against palate.
very small P very large R at 1.0}1.5"porridge prepared using oat bran@, 150 g, 15 min R at 8.0}8.5"IH, 130 g, 15 min not uniform/separate particles perceived P uniform R at 1.5}2.0"IH, 130 g 15 min R at 8.0}8.5"AH, 140 g, 1 min adhering/not slippery P very slippery R at 2.0}2.5"AH, 150 g, 1 min R at 9.5}10"EL 110 g#8 g added guar gumA
The uniformity of mass after 4}5 chews. The more uniform the mass, the less swollen #ake particles are perceived. The degree of slipperiness of the mass during chewing. The more slippery the mass, the less it adheres to the roof of the mouth or teeth. The degree of coarseness perceived on the surface of swollen #ake particles; evaluated during chewing.
Appearance Darkness of the colour
not coarse P very coarse R at 1.0}1.5"AH, 150 g, 1 min R at 9.5}10"EL 120 g, 8 min#wheat branB, 2 min Numerical scale (1}10) anchored with the oatmeal photographs representing the increasing levels of darkness at the values of 1, 4, 7 and 10.
? Toasting procedure: 200 g of rolled oats #4 g of sucrose toasted at 225 3C for 10 min @ Oat Bran, Melia Ltd, Finland A Supercol F, Berner Ltd B EL rolled oats cooked for 8 min, after which 15 g of wheat bran (Melia Ltd) is added and the mixture cooked for an additional 2 min
on its textural characteristics. Consequently, only the darkness of the colour was evaluated in the further sessions. The colour scale was anchored with the photographs as described below.
Evaluation of oatmeal characteristics After two additional training sessions, the intensities of the characteristics were evaluated in triplicate. The evalu-
ation data were collected via computer using The Compusense ,ve software (Compusense Inc., Guelph, Canada). The assessors indicated the intensities of their perceptions by clicking with the mouse on the line scale which ranged in value from 0 to 10. The verbal end anchors of the scales are given in Table 2. The quantitative evaluations of odour, #avour and texture were performed in individual assessing booths under #uorescent illumination.
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Evaluation of oatmeal colour The darkness of the colour was determined on the numerical scale (1}10) which was anchored with photographs representing the increasing levels of darkness at the values 1, 4, 7 and 10. The photographs were taken from an oatmeal sample (brand B) in a glass Petri dish. The increasing darkness in the pictures was generated upon development of the photographs. For colour evaluations, a three-digit numbered 50 mL beaker was "lled to the brim with cooked oatmeal, and the sample then covered with a watch-glass. The assessors were asked to place one sample beaker at a time on the rack located on the front wall of the booth, and give their judgement as to the darkness of the sample, using the above-mentioned scale presented on the front side of the rack, to enable easy comparison of the samples with the photographs. All assessors accomplished the colour evaluations in the same booth under #uorescent illumination (Philips TLD 18W/865, cool daylight 6500 K, 1400 lux). The samples were evaluated from a distance of 60 cm in random order in three replications.
Statistical analyses Quantitative sensory data were submitted to analysis of variance (SAS, ANOVA). For cultivar data, the model included three "xed main factors (assessors, samples, and replications) and their signi"cant (P(0.05) two-way interactions (assessor;sample, assessor;replication, sample;replication). Tukey's test was used for determining the di!erences among the means at P(0.05. For the data of two cooking conditions, the analysis was performed on three "xed main factors (assessors, samples and cooking conditions) and one interaction term (sample;cooking conditions).
Results Proxles of cultivar oatmeals Cultivar had an e!ect on the manual textural characteristics, thickness (P(0.01) and adherence to spoon (P(0.05), these attributes being the most intense in oatmeal of Swedish cultivar Freja (Fig. 1). Statistically, the cultivar oatmeals did not di!er signi"cantly in other oral textural characteristics, but did in size of swollen #ake particles (P(0.01), the range of which varied between 2.3 (Freja) and 3.3 (Veli). Four cultivar oatmeals (Salo, Virma, Yty, Freja) had very similar intensity levels for the odour and #avour characteristics, the means for the total intensity of odour, total intensity of #avour, intensity of toasted odour, and toasted #avour ranging at the level of 4.1}4.7, 3.7}3.9, 1.5}1.8 and 0.7}1.1, respectively. The mean intensities of all these attributes were signi"cantly higher (P(0.01) in Veli than in the other samples. The strong toasted odour and #avour of the Veli sample may partly be caused by the manufacturing conditions, although these were intended to be kept as unaltered as possible between the various cultivar batches. On the other hand, it is possible that some cultivars are more sensitive to the hydrothermic
Fig. 1 Sensory pro"les of cultivar oatmeals: means and standard deviations, n"39 (13 assessors;3 replications). Within an attribute, means designated with the same letter did not di!er at P(0.05. Abbreviations: TOT.OD."total intensity of odour, TOAST.OD."toasted odour, TOT.FLA."total intensity of #avour, TOAST.FLA."toasted #avour, ADH." adherence to spoon, THICK."thickness, U.M."uniformity of mass, SIZE OF SFP"size of swollen #ake particles, SLIP."slipperiness, COAR."coarseness. 䊏, Salo; 䊐, Veli; , Virma; k , Yty; n, Freja
treatments and form strong toasted characteristics faster than the others. Oatmeal Veli also had the darkest colour (mean 2.7$0.9) and in this respect di!ered signi"cantly from the cultivars Yty (mean 2.2$0.6) and Freja (mean 2.1$0.6).
Proxles of commercial samples The commercial oatmeals (brand L and M) di!ered in all textural characteristics (P(0.001, Fig. 2). When the rolled oats were added to boiling water, Brand L was perceived to be highly thick and adherent to spoon. In addition, its mass was considered much more uniform, with profoundly smaller size of swollen particles, than those of brand M. Brand M having larger and thicker #akes was perceived to be more slippery and coarse than brand L. The commercial brands did not di!er in terms of odour and #avour characteristics.
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ing conditions was brand dependent for three characteristics, indicated by a signi"cant interaction of sample by cooking conditions in Fig. 2. For two of these characteristics (thickness and size of swollen #ake particles), the trend of the change was the same for both brands. In the case of adherence to spoon, however, the brands showed opposite trends for the varied cooking conditions. When the #akes were added to cold water, the total intensity of #avour increased (P(0.001) and that of toasted #avour decreased (P(0.05), but the odour characteristics remained una!ected in the oatmeal samples (Fig. 2).
Discussion
Fig. 2 Sensory pro"les of oatmeals prepared using two commercial rolled-oat brands (L and M, Table 1) and two cooking conditions (addition of rolled oats to boiling or cold water): means and standard deviations, n"39 (13 assessors;3 replications). Within each attribute, signi"cancies for the sources of variance are given for two main e!ects (S"samples; C"cooking conditions) and their interaction term (S;C). n.s."not signi"cant, *P(0.05, **P(0.01, ***P(0.001. Abbreviations: TOT.OD."total intensity of odour, TOAST.OD. "toasted odour, TOT.FLA."total intensity of #avour, TOAST.FLA."toasted #avour, ADH."adherence to spoon, THICK."thickness, U.M."uniformity of mass, SIZE OF SFP"size of swollen #ake particles, SLIP."slipperiness, COAR."coarseness. 䊐, L added to boiling water; 䊏, L added to cold water; k, M added to boiling water; n, M added to cold water
Inyuence of cooking conditions The cooking conditions signi"cantly a!ected most of the textural characteristics of the oatmeal samples (Fig. 2). When the rolled oats were added to cold water, the resulting oatmeals were perceived to be signi"cantly thinner (P(0.01), lighter in colour, more uniform in mass, less slippery, less coarse, and smaller in terms of perceived swollen #ake particle size than the corresponding oatmeals prepared by adding the rolled oats to boiling water. This is most probably due to the di!erent modes of starch gelatination at varied temperature conditions upon the preparation of oatmeals. The in#uence of cook-
Standardization of cooking, sample presentation and evaluation procedure is of speci"c importance when oatmeal evaluations are carried out. Some alterations in the characteristics may occur even though the samples are kept at a constant temperature. Also in our study, some changes in characteristics may have occurred, although the sample cups were held on tempered plates throughout the evaluation session. The randomization of samples maintains the e!ect of this phenomenon even for all samples evaluated. Nevertheless, the alterations increase the deviation of collected data. By evaluating the samples at room temperature, changes in sensory attributes during evaluations could probably be avoided. This approach, however, would not give a realistic pro"le of the sensory properties of cooked oatmeal. In addition, assessors might "nd oatmeal evaluations at room temperature fairly uncomfortable. Assessors were a signi"cant source of variation (P(0.001) in both data sets, which is considered acceptable in most descriptive pro"ling procedures. For the cultivar data set, replications di!ered signi"cantly in evaluating slipperiness (P(0.001). This, and the signi"cant interactions of assessor by replication (for thickness, adherence to spoon and coarseness) and that of sample by replication (for uniformity of mass, slipperiness, coarseness and darkness of colour), may re#ect problems connected with the sample alterations described above. Overall, however, the panel performance was considered consistent, the assessor by sample interaction being signi"cant (P(0.001) only for toasted odour and toasted #avour (ANOVA, data not shown). There are several factors, e.g. manufacturing conditions, climate conditions during the crop year, soil, and use of fertilizers, which may cause variation within a single cultivar. Since the oat cultivars for this study were received from contract growers located fairly close to each other, the fertilizer level could be controlled and the in#uence of climate conditions remained low. As mentioned above, the manufacturing conditions may have caused some of the variation for cultivar samples in this study. The present terminology describes most suitably the sensory performance of unstored rolled oats. If the changes during storage are to be monitored, the odour/#avour characteristics such as rancid or stale/
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cardboardy should be involved in de"nitions. During lexicon development, some additional texture characteristics, such as gelatinousness and beadyness, were noted. Since these attributes were mainly connected to one particular brand (not involved in quanti"ed samples), they were not de"ned or quanti"ed in our further sessions. Selected oatmeal texture characteristics could possibly be measured mechanically (e.g. adherence to spoon) or instrumentally (e.g. thickness), which approach might result in smaller deviations and be more convenient for certain applications.
Conclusions The resulting emphasis of texture attributes in oatmeal matches well with the statement of Szczesniak (8): &texture is particularly important in foods that are bland in #avour'. Seven characteristics out of eleven evaluated were grouped by texture or appearance attributes. The present terminology aims to be used in product characterization, e.g. upon category survey, and/or product/process optimization. Cultivars vary in the selective physical and chemical parameters which determine their technological suitability for rolled-oat production (9). The present data showed that cultivars also result in di!erent sensory pro"les in cooked oatmeals, which deserves consideration during product optimization. Commercial rolled-oat products varying, e.g. in #ake thickness and size, di!ered profoundly, especially in terms of textural characteristics. These products may be directed at the di!erent target groups; the brand M, for instance, to the consumers favouring &old-fashioned, long-cooking-time, large-#ake-size' rolled oats. However, as shown in this study, the cooking conditions change the texture pro"les of the products. A manufacturer needs to take
this into account when he/she gives the product information to the consumers at the international market. Acknowledgements The authors wish to give sincere thanks to all sensory panel members. The "nancial support of Melia Ltd. (Finland) is gratefully acknowledged. References 1 HEYDANEK, JR., M. G. AND MCGORRIN, R. J. Oat #avor chemistry: principles and prospects. In: Webster, F. H. (Ed), Oats: Chemistry and ¹echnology. St. Paul, MN: American Association of Cereal Chemists, pp. 335}369 (1986) 2 MEILGAARD, M., CIVILLE, G. V. AND CARR, B. T. Sensory Evaluation Techniques, 2nd edn., Boca Raton, FL: CRC Press (1991) 3 SMITH, E. A., CHAMBERS IV, E. AND COLLEY, S. Development of vocabulary and references for describing o!-odors in raw grains. Cereal Foods =orld, 39, 495}499 (1994) 4 MOLTEBERG, E. L., SOLHEIM, R., DIMBERG, L. H. AND FR"LICH, W. Variation in oat groats due to variety, storage and heat treatment. II: Sensory quality. Journal of Cereal Science, 24, 273}282 (1996) 5 GUTH, H. AND GROSCH, W. Geruchssto!e von extrudiertem Hafermehl, VeraK nderungen bei der Lagerung. Zeitschrift fuK r Lebensmittel-Untersuchung und-Forschung, 196, 22}28 (1993) 6 GUTH, H. AND GROSCH, W. Aromasto!e in Haferextrudaten. Getreide, Mehl und Brot 48, 50}52 (1994) 7 LAWLESS, H. T. AND HEYMANN, H. Sensory evaluation of food. Principles and practices. New York: Chapman & Hall (1998) 8 SZCZESNIAK, A. S. Texture: is it still an overlooked food attribute? Food ¹echnology 44(9), 86}95 (1990) 9 LINDNER, B. AND TOG NNERFORS, U. An inventory of di!erent kinds of Swedish oats with regard to the degree of dehulling and "tness for making #akes. In: ICC 1991 Symposium, Cereal Based Foods: New Developments. Prag: ICSFR (1991)
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Quantitative Sensory Pro"ling of Cooked Oatmeal Anja LapvetelaK inen* and Hanna Rannikko
Department of Biochemistry and Food Chemistry, University of Turku, FIN-20014 Turku (Finland) (Received September 21, 1999; accepted April 20, 2000)
Sensory proxling of cooked oatmeal was carried out for rolled-oat process optimization and product characterization purposes. The main sensory properties of oatmeal (thickness, adherence to spoon, size of swollen yake particles, uniformity of mass, slipperiness, coarseness, darkness of colour) were included in the group of appearance and texture attributes. Odour and yavour were fairly weak, the terms most often used being toasted, sweet, cereal, and chemical. Rolled oats of xve various cultivars diwered in the oatmeal characteristics such as thickness, adherence to spoon, and size of swollen yake particle. Two commercial rolled-oat brands varying in their yake thickness (0.54 and 0.77 mm) and cooking time (10 and 15 min) resulted in oatmeals with diwerent texture proxles. Two cooking conditions also tested ~ adding the rolled oats either to cold or boiling water ~ profoundly inyuenced the texture characteristics quantixed.
2000 Academic Press Keywords: oatmeal; sensory properties; cultivar di!erences; e!ect of cooking conditions
Experimental
Introduction The optimization of rolled-oat production necessitates that the quality of the end product can be characterized, not only in physical and chemical, but also in sensory terms. The number of publications on sensory lexicons for cooked oatmeal, which is the primary use for rolled oats in Finland, is very limited. All sensory descriptions available concern #avour and are mostly aimed at describing the grain attributes (1}4) or extruded oat products (5,6). The aim of the present study was to develop a terminology for the odour, #avour, texture and appearance characteristics of oatmeal by means of generic descriptive analysis (7). The sensory terminology developed was further applied for analysing two sample sets. With the "rst set we aimed to "nd out whether the oat cultivar used for rolled-oat production has an in#uence on the sensory pro"le of oatmeal. With the second set, consisting of two commercial rolled-oat samples, we wanted to study the e!ect of two cooking conditions on the sensory properties of oatmeal. This was of interest since the procedures for preparing oatmeal in households vary from one country to another. For instance, rolled oats are commonly added to boiling water in Finland, but to cold water in Sweden. Information on the possible changes in the sensory properties due to cooking conditions is valuable, particularly for the manufacturers targeting rolled-oat products for the international market. * To whom correspondence should be addressed. Tel: #358-40-5212 639; fax: #358-2-333 6860; E-mail: anja.lapvetelainen@uku."
0023-6438/00/050374#06 $35.00/0 2000 Academic Press
Rolled-oat samples Cultivar rolled oats were manufactured by Melia Ltd. in a commercial oat mill located in Nokia, Finland, using grains (Avena sativa L.) of a single cultivar for each rolled-oat sample. The cultivar products were processed to a #ake thickness of 0.6 mm. Three of the cultivars (Veli, Virma, Yty) were Finnish and two (Salo, Freja) were of Swedish origin. All of them were cultivated by contract growers in southern Finland in 1995. A single cultivar grain batch (30,000}100,000 kg) was formed using grains from 2}6 growers. All the grains matched Melia Ltd.'s quality criteria for rolled-oat production. The sensory terminology was developed using nine Finnish commercial rolled-oat brands on the market in 1995. These were selected to represent a wide range of variation in terms of #ake thickness (0.3}0.8 mm) and recommended amount of rolled oats and length of cooking time given on the package instructions (Table 1). In addition, the samples from three cultivar rolled oats (Salo, Veli, Virma) were also used during the method development. The e!ect of cooking conditions was tested using two commercial rolled-oat brands: L and M (Table 1). Brand L represents most commonly used rolled-oat type in Finland and brand M an &old-fashioned' rolled-oat type having large, thick #akes and long cooking time. Storing of rolled-oat samples All commercial samples were purchased from the retail shops and stored in the original packages at room
doi:10.1006/fstl.2000.0675 All articles available online at http://www.idealibrary.com on
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Table 1 Amount of rolled oats and cooking time used for preparation of oatmeals of Finnish commercial brands characterized also in terms of #ake thickness Brand code K L M N O P Q R S
Flake thickness? Amount of rolled Cooking (mm) oats used (g/L water) time (min) 0.34 0.54 0.77 0.56 0.52 0.55 0.34 0.52 0.53
140 130 130 110 130 130 140 140 130
1 10 15 10 8 10 1 5 10
? mean of 10 measurements; coe$cient of variation 1.8}6.5%
temperature. To avoid #avour changes during storage, the cultivar rolled oats were packed in 200 g portions in 500 ml glass bottles, which were stored at !28 3C until analysis (within two months). By using a constant reference duo-trio test, the freezing procedure was checked to not cause detectable changes in the sensory quality of oatmeal. In this test, the unfrozen rolled oats were the constant reference sample. The glass bottles containing rolled-oat samples were removed from the freezer to room temperature 18}20 h before cooking.
Preparation of Oatmeal samples Oatmeals of commercial brands were prepared according to the instructions on the packages, the amount of rolled oats mixed into 1 L of boiling water varying between 110 and 140 g, and cooking time between 1 and 15 min depending on the brand (Table 1). The cultivar oatmeals were prepared by mixing 130 g of rolled oats (11% moisture basis) with 1 L of boiling water and cooking for 10 min. The tap water used for sample preparations was "ltered through a granular activated carbon cartridge (METEK, Sheboygan, WI, USA). Oatmeals were prepared in a cooking pot (stainless steel, 3 L, KombiDouble Pan, Opa, Mikkeli, Finland) comprising two parts, the lower one used as a boiling water bath and the upper as the actual cooking pot. After cooking, the oatmeal samples were served in random order from 40 mL glass cups with lids and coded with three-digit numbers. The samples were kept on hot portable plates (80 3C) until analysed. The assessors began the evaluations in 10 min and the evaluation of a single set including "ve cultivar samples took 15}20 min. During evaluation, the temperature of the samples was maintained at 60}70 3C. The assessors were given one steel spoon for each evaluated sample and asked to assess one sample at a time for all characteristics before continuing with the next sample. When the e!ect of cooking conditions was tested, the oatmeals were prepared by adding rolled oats to both cold and boiling "ltered tap water in a single cooking pot (stainless steel, 3 L, Hackman, Sorsakoski, Finland). In the former case, the rolled oats were added to cold water
and the mixture warmed to boiling and cooked for 5 min (counting commenced from boiling), whereas in the latter case the rolled oats were added to boiling water and cooked for the time given in Table 1. The samples were served to the assessors as described above.
Assessors The assessors were selected according to their willingness to participate in sensory evaluations, and tested for their ability to recognize selected taste and odour samples, and to detect certain #avour (sweetness, stale) and texture di!erences (uniformity of mass, adherence) in cooked oatmeals. The taste samples were: 0.6% sucrose (sweet); 0.04% and 0.08% citric acid (sour); 0.03 and 0.06% ca!eine (bitter). The odour samples were: 2% vinegar; vanillin; detergent/soap (a piece of Cussons Imperial Leather Soap); bitter almond; allspice; onion; oregano; curry; and stale. The stale extruded oat preparation was used for preparing the stale odour sample; all the other odour samples were prepared by using commercial spices or other products. The odour samples were weighed into brown 40 mL glass bottles which were wrapped with aluminium foil and topped with cotton wool to prevent visual recognition, sealed, and coded with three-digit numbers. From the total number of 28 candidates, 15 assessors were selected. This "nal sensory panel consisted of 12 female and 3 male assessors, in good health, from the sta! and students of the department between the ages of 21 and 50.
Development of terminology The assessors were "rst asked to describe all the sensory properties perceived in the samples. Odour and #avour were characterized in two one-hour sessions and appearance and oral texture during the two other one-hour sessions. In addition, four sessions (45 min) were conducted for discussions about the main characteristics and developing the evaluation procedures. The main sensory properties of oatmeal were found to be related to texture or appearance. The textural properties were grouped as manual (thickness, adherence to spoon) and oral characteristics (average size of swollen #ake particles, uniformity of mass, slipperiness, coarseness). During sample characterization, the most often used odour and #avour terms were toasted, sweet, cereal and chemical. In the group discussion, however, the odour and #avour of oatmeal were generally regarded as being fairly weak and neutral. Thus, a decision was made to quantify only the intensities of toasted odour and #avour, and the total intensities of odour and #avour, in the following sample sets. Based on the group discussions, the verbal de"nitions and reference substances at various intensity levels were preliminarily developed and suggested to the assessors by the authors. These were "nally agreed upon by the whole panel during two one-hour discussion sessions (Table 2). Colour was characterized with terms such as yellowish, brown, greyish brown, and grey. A single cooked oatmeal sample may exhibit notes of several hues depending
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Table 2 Main sensory characteristics of cooked oatmeal with de"nitions, verbal end anchors on the scale from 0 to 10, and reference substances. For reference oatmeal samples (R), the brand together with the amount of rolled oats (g/L of water) and cooking time used are listed below the scale anchors. Abbreviations for brands: EL"Elovena, AH"Aamun HyvaK , and IH"Iso Herkku, all manufactured by Melia Ltd (Finland) Characteristics Odour Overall intensity of odour Toasted odour
Manual texture Thickness
Adherence to spoon
Flavour Overall intensity of #avour Toasted #avour
Oral texture Average size of swollen #ake particles Uniformity of mass
Slipperiness
Coarseness
Verbal end anchors and reference substances used at the designated intensity levels
De"nitions The odour perceived immediately after removing the lid The odour related to toasted rolled oats; evaluated before mixing the sample
none P very strong * no references none P very strong R at 0.0}0.5"rolled oats, not steam-heated, 130 g, 10 min R at 7.5}8.0"toasted? EL, 130 g, 10 min
The force required to stir the sample with spoon. thin P very thick R at 0.0}0.5"EL, 90 g, 10 min R at 9.5}10"AH, 150 g, 1 min The amount of the sample adhering to the none P at least 1/2 of spoon "lled with the mass &inner side' of the spoon; evaluated by R at 0.0}0.5"EL, 90 g, 10 min taking a spoonful of sample and turning R at 9.5}10"AH, 150 g, 1 min the spoon over. After 5 s the adhered sample is observed The #avour evaluated orally after mixing the sample with a spoon The #avour related to toasted rolled oats: evaluated orally after mixing the sample with a spoon
none P very strong * no references none P very strong R at 0.0}0.5"rolled oats, not steam-heated, 130 g, 10 min R at 8.5}9.0"toasted? EL, 130 g, 10 min
The average size of swollen #ake particles in the mass; evaluated by pressing the sample with tongue against palate.
very small P very large R at 1.0}1.5"porridge prepared using oat bran@, 150 g, 15 min R at 8.0}8.5"IH, 130 g, 15 min not uniform/separate particles perceived P uniform R at 1.5}2.0"IH, 130 g 15 min R at 8.0}8.5"AH, 140 g, 1 min adhering/not slippery P very slippery R at 2.0}2.5"AH, 150 g, 1 min R at 9.5}10"EL 110 g#8 g added guar gumA
The uniformity of mass after 4}5 chews. The more uniform the mass, the less swollen #ake particles are perceived. The degree of slipperiness of the mass during chewing. The more slippery the mass, the less it adheres to the roof of the mouth or teeth. The degree of coarseness perceived on the surface of swollen #ake particles; evaluated during chewing.
Appearance Darkness of the colour
not coarse P very coarse R at 1.0}1.5"AH, 150 g, 1 min R at 9.5}10"EL 120 g, 8 min#wheat branB, 2 min Numerical scale (1}10) anchored with the oatmeal photographs representing the increasing levels of darkness at the values of 1, 4, 7 and 10.
? Toasting procedure: 200 g of rolled oats #4 g of sucrose toasted at 225 3C for 10 min @ Oat Bran, Melia Ltd, Finland A Supercol F, Berner Ltd B EL rolled oats cooked for 8 min, after which 15 g of wheat bran (Melia Ltd) is added and the mixture cooked for an additional 2 min
on its textural characteristics. Consequently, only the darkness of the colour was evaluated in the further sessions. The colour scale was anchored with the photographs as described below.
Evaluation of oatmeal characteristics After two additional training sessions, the intensities of the characteristics were evaluated in triplicate. The evalu-
ation data were collected via computer using The Compusense ,ve software (Compusense Inc., Guelph, Canada). The assessors indicated the intensities of their perceptions by clicking with the mouse on the line scale which ranged in value from 0 to 10. The verbal end anchors of the scales are given in Table 2. The quantitative evaluations of odour, #avour and texture were performed in individual assessing booths under #uorescent illumination.
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Evaluation of oatmeal colour The darkness of the colour was determined on the numerical scale (1}10) which was anchored with photographs representing the increasing levels of darkness at the values 1, 4, 7 and 10. The photographs were taken from an oatmeal sample (brand B) in a glass Petri dish. The increasing darkness in the pictures was generated upon development of the photographs. For colour evaluations, a three-digit numbered 50 mL beaker was "lled to the brim with cooked oatmeal, and the sample then covered with a watch-glass. The assessors were asked to place one sample beaker at a time on the rack located on the front wall of the booth, and give their judgement as to the darkness of the sample, using the above-mentioned scale presented on the front side of the rack, to enable easy comparison of the samples with the photographs. All assessors accomplished the colour evaluations in the same booth under #uorescent illumination (Philips TLD 18W/865, cool daylight 6500 K, 1400 lux). The samples were evaluated from a distance of 60 cm in random order in three replications.
Statistical analyses Quantitative sensory data were submitted to analysis of variance (SAS, ANOVA). For cultivar data, the model included three "xed main factors (assessors, samples, and replications) and their signi"cant (P(0.05) two-way interactions (assessor;sample, assessor;replication, sample;replication). Tukey's test was used for determining the di!erences among the means at P(0.05. For the data of two cooking conditions, the analysis was performed on three "xed main factors (assessors, samples and cooking conditions) and one interaction term (sample;cooking conditions).
Results Proxles of cultivar oatmeals Cultivar had an e!ect on the manual textural characteristics, thickness (P(0.01) and adherence to spoon (P(0.05), these attributes being the most intense in oatmeal of Swedish cultivar Freja (Fig. 1). Statistically, the cultivar oatmeals did not di!er signi"cantly in other oral textural characteristics, but did in size of swollen #ake particles (P(0.01), the range of which varied between 2.3 (Freja) and 3.3 (Veli). Four cultivar oatmeals (Salo, Virma, Yty, Freja) had very similar intensity levels for the odour and #avour characteristics, the means for the total intensity of odour, total intensity of #avour, intensity of toasted odour, and toasted #avour ranging at the level of 4.1}4.7, 3.7}3.9, 1.5}1.8 and 0.7}1.1, respectively. The mean intensities of all these attributes were signi"cantly higher (P(0.01) in Veli than in the other samples. The strong toasted odour and #avour of the Veli sample may partly be caused by the manufacturing conditions, although these were intended to be kept as unaltered as possible between the various cultivar batches. On the other hand, it is possible that some cultivars are more sensitive to the hydrothermic
Fig. 1 Sensory pro"les of cultivar oatmeals: means and standard deviations, n"39 (13 assessors;3 replications). Within an attribute, means designated with the same letter did not di!er at P(0.05. Abbreviations: TOT.OD."total intensity of odour, TOAST.OD."toasted odour, TOT.FLA."total intensity of #avour, TOAST.FLA."toasted #avour, ADH." adherence to spoon, THICK."thickness, U.M."uniformity of mass, SIZE OF SFP"size of swollen #ake particles, SLIP."slipperiness, COAR."coarseness. 䊏, Salo; 䊐, Veli; , Virma; k , Yty; n, Freja
treatments and form strong toasted characteristics faster than the others. Oatmeal Veli also had the darkest colour (mean 2.7$0.9) and in this respect di!ered signi"cantly from the cultivars Yty (mean 2.2$0.6) and Freja (mean 2.1$0.6).
Proxles of commercial samples The commercial oatmeals (brand L and M) di!ered in all textural characteristics (P(0.001, Fig. 2). When the rolled oats were added to boiling water, Brand L was perceived to be highly thick and adherent to spoon. In addition, its mass was considered much more uniform, with profoundly smaller size of swollen particles, than those of brand M. Brand M having larger and thicker #akes was perceived to be more slippery and coarse than brand L. The commercial brands did not di!er in terms of odour and #avour characteristics.
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ing conditions was brand dependent for three characteristics, indicated by a signi"cant interaction of sample by cooking conditions in Fig. 2. For two of these characteristics (thickness and size of swollen #ake particles), the trend of the change was the same for both brands. In the case of adherence to spoon, however, the brands showed opposite trends for the varied cooking conditions. When the #akes were added to cold water, the total intensity of #avour increased (P(0.001) and that of toasted #avour decreased (P(0.05), but the odour characteristics remained una!ected in the oatmeal samples (Fig. 2).
Discussion
Fig. 2 Sensory pro"les of oatmeals prepared using two commercial rolled-oat brands (L and M, Table 1) and two cooking conditions (addition of rolled oats to boiling or cold water): means and standard deviations, n"39 (13 assessors;3 replications). Within each attribute, signi"cancies for the sources of variance are given for two main e!ects (S"samples; C"cooking conditions) and their interaction term (S;C). n.s."not signi"cant, *P(0.05, **P(0.01, ***P(0.001. Abbreviations: TOT.OD."total intensity of odour, TOAST.OD. "toasted odour, TOT.FLA."total intensity of #avour, TOAST.FLA."toasted #avour, ADH."adherence to spoon, THICK."thickness, U.M."uniformity of mass, SIZE OF SFP"size of swollen #ake particles, SLIP."slipperiness, COAR."coarseness. 䊐, L added to boiling water; 䊏, L added to cold water; k, M added to boiling water; n, M added to cold water
Inyuence of cooking conditions The cooking conditions signi"cantly a!ected most of the textural characteristics of the oatmeal samples (Fig. 2). When the rolled oats were added to cold water, the resulting oatmeals were perceived to be signi"cantly thinner (P(0.01), lighter in colour, more uniform in mass, less slippery, less coarse, and smaller in terms of perceived swollen #ake particle size than the corresponding oatmeals prepared by adding the rolled oats to boiling water. This is most probably due to the di!erent modes of starch gelatination at varied temperature conditions upon the preparation of oatmeals. The in#uence of cook-
Standardization of cooking, sample presentation and evaluation procedure is of speci"c importance when oatmeal evaluations are carried out. Some alterations in the characteristics may occur even though the samples are kept at a constant temperature. Also in our study, some changes in characteristics may have occurred, although the sample cups were held on tempered plates throughout the evaluation session. The randomization of samples maintains the e!ect of this phenomenon even for all samples evaluated. Nevertheless, the alterations increase the deviation of collected data. By evaluating the samples at room temperature, changes in sensory attributes during evaluations could probably be avoided. This approach, however, would not give a realistic pro"le of the sensory properties of cooked oatmeal. In addition, assessors might "nd oatmeal evaluations at room temperature fairly uncomfortable. Assessors were a signi"cant source of variation (P(0.001) in both data sets, which is considered acceptable in most descriptive pro"ling procedures. For the cultivar data set, replications di!ered signi"cantly in evaluating slipperiness (P(0.001). This, and the signi"cant interactions of assessor by replication (for thickness, adherence to spoon and coarseness) and that of sample by replication (for uniformity of mass, slipperiness, coarseness and darkness of colour), may re#ect problems connected with the sample alterations described above. Overall, however, the panel performance was considered consistent, the assessor by sample interaction being signi"cant (P(0.001) only for toasted odour and toasted #avour (ANOVA, data not shown). There are several factors, e.g. manufacturing conditions, climate conditions during the crop year, soil, and use of fertilizers, which may cause variation within a single cultivar. Since the oat cultivars for this study were received from contract growers located fairly close to each other, the fertilizer level could be controlled and the in#uence of climate conditions remained low. As mentioned above, the manufacturing conditions may have caused some of the variation for cultivar samples in this study. The present terminology describes most suitably the sensory performance of unstored rolled oats. If the changes during storage are to be monitored, the odour/#avour characteristics such as rancid or stale/
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cardboardy should be involved in de"nitions. During lexicon development, some additional texture characteristics, such as gelatinousness and beadyness, were noted. Since these attributes were mainly connected to one particular brand (not involved in quanti"ed samples), they were not de"ned or quanti"ed in our further sessions. Selected oatmeal texture characteristics could possibly be measured mechanically (e.g. adherence to spoon) or instrumentally (e.g. thickness), which approach might result in smaller deviations and be more convenient for certain applications.
Conclusions The resulting emphasis of texture attributes in oatmeal matches well with the statement of Szczesniak (8): &texture is particularly important in foods that are bland in #avour'. Seven characteristics out of eleven evaluated were grouped by texture or appearance attributes. The present terminology aims to be used in product characterization, e.g. upon category survey, and/or product/process optimization. Cultivars vary in the selective physical and chemical parameters which determine their technological suitability for rolled-oat production (9). The present data showed that cultivars also result in di!erent sensory pro"les in cooked oatmeals, which deserves consideration during product optimization. Commercial rolled-oat products varying, e.g. in #ake thickness and size, di!ered profoundly, especially in terms of textural characteristics. These products may be directed at the di!erent target groups; the brand M, for instance, to the consumers favouring &old-fashioned, long-cooking-time, large-#ake-size' rolled oats. However, as shown in this study, the cooking conditions change the texture pro"les of the products. A manufacturer needs to take
this into account when he/she gives the product information to the consumers at the international market. Acknowledgements The authors wish to give sincere thanks to all sensory panel members. The "nancial support of Melia Ltd. (Finland) is gratefully acknowledged. References 1 HEYDANEK, JR., M. G. AND MCGORRIN, R. J. Oat #avor chemistry: principles and prospects. In: Webster, F. H. (Ed), Oats: Chemistry and ¹echnology. St. Paul, MN: American Association of Cereal Chemists, pp. 335}369 (1986) 2 MEILGAARD, M., CIVILLE, G. V. AND CARR, B. T. Sensory Evaluation Techniques, 2nd edn., Boca Raton, FL: CRC Press (1991) 3 SMITH, E. A., CHAMBERS IV, E. AND COLLEY, S. Development of vocabulary and references for describing o!-odors in raw grains. Cereal Foods =orld, 39, 495}499 (1994) 4 MOLTEBERG, E. L., SOLHEIM, R., DIMBERG, L. H. AND FR"LICH, W. Variation in oat groats due to variety, storage and heat treatment. II: Sensory quality. Journal of Cereal Science, 24, 273}282 (1996) 5 GUTH, H. AND GROSCH, W. Geruchssto!e von extrudiertem Hafermehl, VeraK nderungen bei der Lagerung. Zeitschrift fuK r Lebensmittel-Untersuchung und-Forschung, 196, 22}28 (1993) 6 GUTH, H. AND GROSCH, W. Aromasto!e in Haferextrudaten. Getreide, Mehl und Brot 48, 50}52 (1994) 7 LAWLESS, H. T. AND HEYMANN, H. Sensory evaluation of food. Principles and practices. New York: Chapman & Hall (1998) 8 SZCZESNIAK, A. S. Texture: is it still an overlooked food attribute? Food ¹echnology 44(9), 86}95 (1990) 9 LINDNER, B. AND TOG NNERFORS, U. An inventory of di!erent kinds of Swedish oats with regard to the degree of dehulling and "tness for making #akes. In: ICC 1991 Symposium, Cereal Based Foods: New Developments. Prag: ICSFR (1991)
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