This article was downloaded by: [Nofima] On: 02 January 2013, At: 03:43 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK International Journal of Fruit Science Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/wsfr20 Quality of Highbush Blueberry (Vaccinium corymbosum L.) and Bilberry (Vaccinium myrtillus L.) Jam Marit R dbotten a, Berit Karoline Martinsen a, Hans J. Rosenfeld b, Per Lea a & Karin Haffner c a The Matforsk AS, Norwegian Food Research Institute, Osloveien 1, N-1430, Ås, Norway b The Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Ås, Norway c The Department of Chemistry, Biotechnology and Food Science, Agricultural University of Norway, P.O. Box 5003, N-1432 Ås, Norway Version of record first published: 12 Oct 2008. To cite this article: Marit R dbotten, Berit Karoline Martinsen, Hans J. Rosenfeld, Per Lea & Karin Haffner (2005): Quality of Highbush Blueberry (Vaccinium corymbosum L.) and Bilberry (Vaccinium myrtillus L.) Jam, International Journal of Fruit Science, 5:2, 61-71 To link to this article: http://dx.doi.org/10.1300/j492v05n02_07 PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: http://www.tandfonline.com/page/termsand-conditions
This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Quality of Highbush Blueberry (Vaccinium corymbosum L.) and Bilberry (Vaccinium myrtillus L.) Jam Marit Rødbotten Berit Karoline Martinsen Hans J. Rosenfeld Per Lea Karin Haffner ABSTRACT. Jam from wild bilberries and from the blueberry cultivars Bluecrop and Berkeley were analyzed by means of sensory profiling and by instrumental measurement of anthocyanins, color, ph and soluble solids. The study shows that bilberry jam has more bluish black color, compared to a more reddish-blue color and glossy surface of the jam from cultivated blueberries. Bilberry jam was less smooth and higher in viscosity and berry density as well as less distinct in flavor of flowers and fruits, while the blueberry flavor and odor were more distinct in the bilberry jam than that made of highbush blueberries. Analysis of color by means of sensory hue and instrumental α Hunter lab corresponded well, as did saturation measured by the sensory method and chroma instrumentally measured. [Article copies available for a fee from The Haworth Document Delivery Service: 1-800-HAWORTH. E-mail address: <docdelivery@ haworthpress.com> Website: <http://www.haworthpress.com> 2005 by The Haworth Press, Inc. All rights reserved.] Marit Rødbotten, Berit Karoline Martinsen and Per Lea are Researchers at the Matforsk AS, Norwegian Food Research Institute, Osloveien 1, N-1430, Ås, Norway. Hans J. Rosenfeld is Researcher in the Department of Plant and Environmental Sciences, Agricultural University of Norway, P.O. Box 5003, N-1432 Ås, Norway. Karin Haffner is Researcher in the Department of Chemistry, Biotechnology and Food Science, Agricultural University of Norway, P.O. Box 5003, N-1432 Ås, Norway. International Journal of Fruit Science, Vol. 5(2) 2005 Available online at http://www.haworthpress.com/web/ijfs 2005 by The Haworth Press, Inc. All rights reserved. doi:10.1300/j492v05n02_07 61
62 INTERNATIONAL JOURNAL OF FRUIT SCIENCE KEYWORDS. Blueberry, bilberry, Bluecrop, Berkeley, jam, processing, color, total pigments, sensory quality, Vaccinium INTRODUCTION Blueberry jams are very popular in Scandinavia. The jams are dark blue, almost black in color, and have a typical sweet-sour blueberry flavor with a convenient consistency, which makes blueberry jam attractive for the consumers. Blueberry jam is popular as a bread-spread at breakfast meals and especially when served with pancakes. Today, all blueberry jam in Scandinavia is produced using bilberries. During the last 15 years, highbush blueberry plantings have been established in the Southern part of Norway. Both blueberry growers and the jam industry are interested in research comparing bilberries and highbush blueberry cultivars as raw material for blueberry jam. Bluecrop, Patriot and Hardyblue are important cultivars in Norway that are mainly grown for the fresh market. Berkeley is another cultivar included in the research fields at the Agricultural University of Norway. Bluecrop is described as a productive cultivar with large, firm and slightly aromatic berries with an attractive light blue color. Berkeley has very large, firm berries, with a light blue color (Eck and Childers, 1989). The blue color in Vaccinium corymbosum is concentrated in the skin of the berries. When harvested in 2002 the berry weight was on average 1.9 g for Bluecrop and 2.4 g for Berkeley. The bilberry plants of Scandinavian origin produce small berries with a dark blue color throughout the whole fruit (Figure 1). The flavor is rich and delicious, but not as sweet as the cultivated blueberries. In particular, the European blueberry (V. myrtillus L.) is known as an ancient medical plant (Ulltveit, 1998), and the wild blueberries of North America (V. angustifolium) have their color concentrated in the skin. The berries are rich in flavonoids and other phenolics. It is likely that these components have positive effect in the prevention of coronary diseases and some types of cancer. In addition blueberries are thought to improve night vision (Hollman and Katen, 1998). The color of blueberries is rather intense due to the high amount of anthocyanins. During jam processing and storage, the anthocyanins will
Rødbotten et al. 63 FIGURE 1. Vaccinium myrtillus L. on the left and Vaccinium corymbosum L. on the right. (Photo: Finn Måge) undergo degradation. In strawberry jam we can easily see the effect of this discoloration, but in blueberry jam almost 90% of the anthocyanins must degrade before the change can be readily perceived by humans (Skrede et al., 1992). In general, the jam quality is dependent on the quality of the raw material, the jam recipe, the processing procedure, the storage conditions and the storage duration (Haffner et al. 2003, Redalen and Haffner, 2002). The aim of the present investigation was to study the differences in sensory and instrumental quality of jam made from bilberries and highbush blueberries. MATERIALS AND METHODS Fruit Material The highbush blueberry cultivars Bluecrop and Berkeley were harvested in the research fields of the Agricultural University of Norway, in the southeastern part of Norway (59 40 N) during August 2002. Fruits were picked at processing maturity and frozen at 20 C, until processing in October the same year. The wild blueberries Vaccinium myrtillus were bought from Norwegian jam industry and were delivered frozen in 10 kg closed buckets.
64 INTERNATIONAL JOURNAL OF FRUIT SCIENCE Jam Processing The jam was processed in a laboratory. The frozen berries (2 kg) were thawed for 45 minutes at room temperature in a kettle. Water (200 ml) was added to the berries, and sugar (2.35 kg) was added at a temperature of 10 C. Temperature was raised to 80 C within 10 minutes. Pectin LM101 (30 g) dissolved in distilled water (350 ml) was added, and the temperature raised to 90 C and kept at this level for three minutes. Sodium benzoate (1.5 g), potassium-sorbate (2 g), and citric acid (70 ml of 25%) were added after lowering the temperature to 80 C. The jam was stirred for 10 min before cooling to 60 C, and finally filled in transparent glass jars and closed with a metal lid. Further cooling was done for two hours until the temperature had reached 20 C. The jams were then stored in a refrigerator. The process was repeated once. Sensory Analysis The sensory panel consisted of 12 well-trained assessors screened for sensory ability (basic tastes, color vision, odor detection, tactile sensibility) as well as ability to communicate sensory descriptions of products as recommended in ISO 8586-1:1993. The assessors developed the list of attributes for the project by describing samples from different cultivars of blueberry, and agreed on a consensus list of attributes for profiling and on the definition of each attribute. The sensory panel was trained in the use of the rating anchors by pre-testing samples expected to be different in the intensity of various attributes. The evaluation of the color was conducted according to the Natural Color System (NCS) using the attributes lightness, hue and saturation. No information was given to the panelists about the purpose of the project. The study was carried out using a profile of 19 sensory attributes (Table 1). The sensory laboratory was designed according to guidelines in ISO 8589-1988 with separate booths treated with neutral, gray paint. Each booth was equipped with an instrument for electronic registration of data (CSA, Compusense Five, Version 3.80, Canada, 1999). The sensory laboratory had a uniform artificial light source, with a correlated color temperature of approximately 650 K, similar to northern daylight. Sample Preparation for Sensory Assessment Each jam, produced from bilberries or highbush blueberry cultivars, was produced in two batches. For sensory assessment the two batches
Rødbotten et al. 65 TABLE 1. Sensory attributes and their definitions used in the experiment. Sensory attributes Color: Glossiness: Lightness Hue Saturation Odor: Intensity of odor Flower Fruit Chemical Berry Flavor: Intensity of flavor Acidic Sweet Sour Bitter Texture: Smoothness Viscosity Hardness of skin Berry density Definition Degree of shiny appearance Pale color or addition of black/clear color in the sample Red/blue to blue (NCS R-70-B to R-90-B) Degree of clear color, or addition of white/black contribution Intensity of sum of all odors Odor of fresh flowers Odor of fresh fruits Odor of artificial product, like in medicine Odor of fresh, wild berries Intensity of sum of all flavors Flavor of fruity/fresh and sour/sweet Taste of sugar Complex sensation due to presence of organic acids Flavor of bitter substance, like quinine Perception of size and shape of particles in the product Force required to draw a liquid from a spoon Force required to achieve a given deformation or penetration of the skin Perception of berries in relation to juice or jelly in the jam were cautiously mixed into one sample and served in portions of 25 g per sample. At the time of assessment the samples had a temperature of approximately 20 C. Sensory Procedure Each of the three jam types was assessed in triplicate and samples were served in coded plastic dishes in random order. For rinsing the
66 INTERNATIONAL JOURNAL OF FRUIT SCIENCE mouth between samples, water and bland crackers were available to the assessors. The panelists evaluated the samples at individual speed on a 15-cm non-structured continuous scale with the left side of the scale corresponding to the lowest intensity and the right side corresponding to the highest intensity. The results were recorded directly on a computer registration system. The computer transformed the responses into numbers between 1 = low intensity and 9 = high intensity. Instrumental Analysis Analysis of Pigments Anthocyanins were analyzed according to the AOAC official method (2001.0X), the ph Differential Method. The pigments were extracted from the jam by acidified methanol. An average of 4 g jam was homogenized with 15 ml acidified methanol (0.84 ml concentrated HCl was added to 1 L methanol) by a Polytron PT 3000 Kinematic homogeniser in one minute before centrifuging at 27,200 G in 15 minutes. The supernatant was filtered and transferred to a 50-ml volumetric flask. The extraction was repeated twice on the precipitate. The volumetric flask was filled to volume with acidified methanol. Monomeric anthocyanin pigments reversibly change color with ph, the colored oxonium form existing at ph 1.0 and the colorless hemiketal form predominating at ph 4.5. The difference in absorbance at the wavelength of maximum absorption for the pigments (520 nm) is proportional to the pigment concentration. Content of anthocyanins is expressed as pelargonidin-3-glucoside, with molar absorbance 22,400 and molecule weigh 433.2 g/mol. As the jam only contained 40% berries in the end product, the results from the measurements were adjusted to 100% berries. Analysis of Color Color measurements were performed using a full-scanning spectra colorimeter (Hunter Lab, LabScan XE, Reston, VA, USA). The equipment measures color units (L*, α and β) and spectral data with intervals of 10 nm from 400 to 700 nm. The α and β data were used to calculate
2. Hue is the attribute of color perception by means of which an object is judged to be red, blue, green, yellow and so forth. Chroma correlates saturation, expressed on a scale extending from zero for gray to a maximum of about 20. the hue-angle (arctan (β/α)) and the chroma 2 ( α ) + ( β ) Analysis of ph and Soluble Solids ( Brix) Rødbotten et al. 67 Measurement of ph was performed using a Thermo Orion ph-meter, model 420A and electrode Thermo Orion 9102AP. The content of soluble solids ( Brix) was measured on a Mettler Toledo RE40 refractometer (Mettler-Toledo GmbH, Analytical, CH-8603 Schwerzenbach). RESULTS AND DISCUSSION The Natural Color System describes color appearance by using the attributes lightness, hue and saturation. The jam samples in this study had very low intensity of lightness, and thus appeared to be very dark in color. The samples varied in hue on the NCS scale between R70B (blue/ red) and R90B (more plain blue). The jam from the cultivated samples was significantly more intense in color, had more lightness and was more red than the jam from bilberry samples (Table 2). The samples with the highest intensity of gloss were those made from Berkeley and Bluecrop and were significantly more glossy than those made of bilberry (Figure 2). Results from sensory and instrumental measurements corresponded on some of the measured parameters. Analysis of color by means of sensory hue and instrumental α corresponded well, showing the bilberry jam to be less red than the jam from the cultivated berries. Results from saturation measured by sensory method and chroma measured instrumentally corresponded well for the jam made of bilberries in comparison with the jam from Bluecrop and Berkeley. The bilberry jam was the sample with the least clear color, and thus the sample with the most gray contribution in the blue color. Anthocyanin content and sensory hue corresponded with high values for bilberry jam (dark blue), and bilberry jam was significantly darker than the jam made from cultivated berries. The samples were described to be different in odor, with the bilberry sample being highest in berry odor. The two highbush blueberry jams
68 INTERNATIONAL JOURNAL OF FRUIT SCIENCE TABLE 2. Sensory attributes and instrumental measurements of blueberry and bilberry jam as mean values and results from ANOVA, with Tukey s multiple comparison tests. For each row, mean values superscripted with the same letter are not significantly different at the 0.05 level. Rows without superscripts represent non-significant ANOVAs. Sensory attributes: Bilberry Bluecrop Berkeley Glossiness 4.89 b 7.67 a 7.98 a Lightness 1.03 b 2.09 a 2.34 a Hue 7.20 a 5.37 b 4.89 b Saturation 4.23 b 5.74 a 6.27 a Odor intensity 6.78 a 6.13 b 6.37 ab Flower odor 1.96 b 2.68 ab 3.00 a Fruit odor 1.98 b 3.12 a 3.47 a Chemical odor 1.53 a 2.46 a 2.39 a Berry odor 7.42 a 3.36 b 3.06 b Flavor intensity 7.21 a 6.63 b 6.57 b Acidic flavor 5.85 a 4.61 b 4.33 b Sweet taste 6.02 b 7.03 a 7.23 a Sour taste 3.06 a 2.64 ab 2.14 b Bitter taste 3.57 a 3.75 a 3.62 a Smoothness 3.20 b 5.44 a 5.76 a Viscosity 8.51 a 5.36 b 5.04 b Hardness of skin 3.77 b 4.69 ab 5.56 a Berry density 8.59 a 4.71 b 3.93 c Instrumental measurements: L* - value 2.97 b 4.24 a 3.06 b - value 0.70 c 4.43 a 2.26 b - value 1.07 a 1.18 a 0.68 b Hue 1.05 a 0.27 b 0.30 b Chroma (color saturation) 0.72 b 5.20 a 1.54 b Anthocyanins (mg/100g jam) 429.4 a 87.2 b 137.5 b ph 2.49 b 2.77 a 2.77 a Soluble solids ( Brix) 56.8 b 57.9 a 56.6 b : Although the ANOVA was significant at the 0.05 level, Tukey s test was unable to pinpoint significantly different means. had a more distinct odor of fruits than the bilberry jam and jam from Berkeley had significantly more flavor of flowers than jam from bilberry. The definition of berry odor was odor of fresh berries, meaning naturally growing blueberries. The sample with the highest intensity of
Rødbotten et al. 69 FIGURE 2. Jam made from Bilberry, Berkeley and Bluecrop. (Photo: Kjell Merok) berry odor was the one with the lowest intensity of fruit odor and flower odor, which is the most important explanation for the odor differences between the cultivated samples compared with the wild growing sample. There was also a difference in flavor, mainly between the bilberry jam and the jam from the cultivated berries. The bilberry jam had the highest intensity of flavor. This can be explained by the fact that this jam also had the highest intensity of acidic flavor. The two samples described to have the most odor of flowers and fruits were less intense in overall flavor. Results show a correspondence between sensory measured sourness (acidic flavor and sour taste) and instrumentally measured ph. Bilberry jam in both cases was the sourest sample of the three samples analyzed. Sensory perception of texture of the jams was dominated by the difference in the moisture content in the berries. The bilberry jam was more compact than the two other jams. That is shown in all the measured texture attributes, and most so in the attributes viscosity and berry density. The most viscous (the thickest) sample was bilberry jam, which was significantly more viscous than Bluecrop jam and Berkeley jam. The attribute berry density gave the same conclusion of differences, as the bilberry jam had a significantly higher density of berries than the two other samples, and the jam from Berkeley had significantly lower density of berries than the two other samples. The sample with
70 INTERNATIONAL JOURNAL OF FRUIT SCIENCE the toughest skin was the Berkeley jam having significantly higher intensity than the bilberry jam. CONCLUSIONS The present study shows that highbush blueberries are well suited as raw material for the production of jam. Jam made from cultivated berries is not today available for purchase in Scandinavia. Jam from bilberries is very popular even if the consumers find the jam to have a major disadvantage, namely eating the jam results in coloring of teeth and lips, which is not a problem with the jam made from highbush blueberry cultivars. The present study also shows that bilberry jam has a more bluish black color, compared to a more blue-reddish color and glossy surface of the jam from cultivated blueberries. The differences in color may be explained by a higher anthocyanin content in bilberries. Bilberry jam was less smooth and higher in viscosity and berry density than the jam from cultivated berries. The jam from bilberries was also less distinct in flavor of flowers and fruits, while the blueberry flavor and odor were more distinct in the jam from the wild growing berries. Highbush blueberries are available from July to September in the Northern Hemisphere and from December to February in the Southern Hemisphere, depending on cultivar. As the fresh market prefers large blueberries, smaller berries might have a future as raw material for the jam industry which would be economically advantageous for growers. Further research on consumer preference will perhaps give an answer to this question. REFERENCES Eck, P. and N. F. Childers. 1989. Blueberry culture, 378 pp. Rutgers University Press, New Brunswick and London. Haffner, K., M. B. Finstad Bye, H. J. Rosenfeld, and G. Skrede. 2003. Color of raspberry jam as influenced by cultivar, temperature and light during storage. Proc. XXVI IHC Issues and advances. In Postharvest Hort. Acta Hort. 628: 829-834. Hollman, P. C. H. and M. B. Katan. 1998. Bioavailability and health effects of dietary flavonols in man. Arch. Toxicol. Suppl. 20: 237-247. ISO. 1988. Sensory analysis General guidance for the design of test rooms. ISO, 8598: 1988, ISO, Geneva.
Rødbotten et al. 71 ISO. 1993. Sensory analysis General guidance for selection, training and monitoring of assessors. ISO 8586-1: 1993, ISO, Geneva. NCS Natural Color System, 2000, Scandinavian Color Institute B, Stockholm, Sweden. Redalen, G. and K. Haffner. 2002. Quality of raspberry jam of individual cultivars after one year of storage. Acta Hort. 585: 525-530. Skrede, G., R. E. Wrolstad, P. Lea, and G. Enersen. 1992. Color stability of strawberry and blackcurrant syrups. J. Food Sci. 57: 172-177. Ulltveit, G. 1998. Ville bær (Wild berries). 2nd ed. N. W. Damm Søn A. S.-Teknologisk forlag, Oslo, Norway. p. 166.