International Journal of Biosciences IJB ISSN: 2220-6655 (Print), 2222-5234 (Online) http://www.innspub.net Vol. 6, No. 7, p. 7-17, 2015 RESEARCH PAPER OPEN ACCESS The effect of roasting method and conditions on physic chemicals and sensory properties of sunflower seed kernels Shiva Mirzaei Soleimanieh 1, Mohammadreza Eshaghi 1*, Zahra Piravi Vanak 2 1 Department of Food Science and Technology, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran 2 Assistant Proffesor Faculty of Food Industry and Agriculture.Standard Research Institute, Karaj, Iran Key words: Sunflower seed kernel, Roasting, Microwave, Electrical oven, physicochemical properties. http://dx.doi.org/10.12692/ijb/6.7.7-17 Article published on April 10, 2015 Abstract Sunflower seed kernel is a popular food with various applications. The aim of this study was to investigate the effect of roasting method and conditions on some physicochemical properties of sunflower seed kernel. Sunflower seed kernels were roasted under two different conditions, i.e. by microwave at 2450 MHz and 900 W and by electrical oven at 190C for different time periods. The changes in color texture firmness, moisture content, and percententage of extracted oil as well as acidity, peroxide sensory properties and fatty acid composition were studied. The results showed that roasting had significant effect on color as the kernels became darker over time. Roasting resulted in reduced moisture content extracted oil percentage and hardness of the kernels while acidity and peroxide values increased as the time of roasting was prolonged. Fatty acid composition was found within the standard range for both methods. Regarding the sensory property, the kernels roasted by electrical oven showed more total acceptability than microwave roasted ones. * Corresponding Author: Mohammadreza Eshaghi mr.eshaghi@yahoo.com 7 Soleimanieh et al.
Introduction Nuts kernel is rich in phosphorous which help osteogenesis and dental strength. Nuts also are a good source of magnesium which plays an important role in balancing the functions of muscles and nerves. Linolenic acid contained in these edible kernels also may be useful for skin health and hormonal balance. They also contain dietary fibers. These foods thus have relatively high nutritional value and are healthful if consumed in proper amounts (Anonymous, 1984). Sunflower seed is one of the most nutritious and healthful foods with commercial value together with the oil. Sunflower seeds are rich in vitamin E. the vitamin may help improving the function of blood circulation system. The seeds also have sedative effect because they are a good source of amino acid tryptophan. Roasting is one of preparation methods and a kind of dry heat cooking carried out for development of more desirable aroma and taste. Application of very height temperature may result in reduced nutrients content in the kernels. Thus optimum roasting temperature and time are necessary in addition to desirable flavor and aroma. Roasted sunflower seed kernel is a product obtained through sifting dehulling washing and roasting by heating with or without oil under optimal manufacture conditions (Anonymous, 2012). Roasting is one of processing steps for edible seeds mostly performed for improving nutritional value taste color, texture, appearance and flavor of the product (Nikzadeh & sedaghat, 2008; Perren & Escher, 1996; Robertson et al., 1985). The purpose of this process is to increase total acceptability of the product. Roasting considerably changes flavor, Color, texture and appearance of nuts. The changes generally improve the desirability of nuts mainly due to non enzymatic browning (Bhattacharya & Prakash, 1997; Kita & Figiel, 2007; Ozdemir, 2001). During roasting process the kernels become more crisp which is considered a basic property of these products. Crisp texture of the roasted kernels makes them more delicious. Drying occurs during roasting process contributing to the texture changes. Moisture content decreases during roasting because of high temperature (>100ºC) despite insignificant initial moisture contained in nut kernels being generally 5-9% (Askari et al., 2005). The changes occurring in color flavor texture and appearance of nut kernels during roasting are caused by non enzymatic browning reaction. Non enzymatic browning reaction may be divided into three primary reactions resulting in developed color and flavor: Millard, Strecker and sugar caramelization (Buckholz et al., 1980). Radfar et al., (2003) studied the favorable roasting conditions in order to prevent oxidation of hazelnut and peanut oil. The results suggested the effect of roasting in preventing oil oxidation which was enhanced at high temperature over time. However this effect was considerable for peanut oil but mot for hazelnut. Nikzadeh et al., (2011) investigated the variations of moisture texture and sensory properties of pistachio influenced by roasting temperature and time and concluded that hardness breakage force, and rigidity all increased for all samples over time. Also the moisture content of roasted pistachio increased over storage. As the temperature was raised moisture content hardness and breakage force significantly reduced. The highest total acceptability was found for samples roasted at 120 C. the results also showed that there was a significant correlation between sensory and system properties. Habibi Nodeh et al., (2010) examined the effect of microwave treatment on the quality of extracted rapeseed oil. As the results showed it may be concluded that using microwave treatment before extraction by cold pressing may improve rapeseed oil extraction yield quality and increased components. Ozdemir et al., (2001) studied the effect of roasting on some nutrients of hazelnut (corylus avellena). The 8 Soleimanieh et al.
results revealed that roasting had considerale effect on peroxide index free fatty acids thiamin riboflavin and amino acid composition of Giresun and Akcakoca hazelnuts. Kita and figiel (2007) investigated the effect of roasting temperature (100-180ºC) and time (5-30 min) and the heating method (hot air or boiling vegetable oil) on physical and sensory properties of walnut. The results showed that the properties of walnut depended on roasting temperature and time as the moisture reduced when roasting temperature and time increased. Also nuts roasted in oil were darker than those roasted by hot air and they became darker as roasting temperature and time increased. The samples roasted in oil showed a firmer texture than those roasted by hot air. The samples roasted at 130-150ºC for 15-20 min exhibited the best sensory properties for both treatments. Nikzadeh et al., (2008) studied the effect of roasting temperature and storage time on texture moisture and sensory properties of pistachio. Texture properties including hardness breakage force, and firmness of salted roasted pistachio were determined over three month storage. The results revealed that hardness and breakage force increased as the storage time was prolonged. In addition the moisture content of roasted pistachio increased over storage. Using high temperature roasting resulted in considerably reduced stability, moisture content hardness and breakage force. Given the fact that sunflower seeds have high nutritional value it is necessary to conduct comprehensive research on the effects of roasting on physicochemical and sensory properties of the kernels. Roasting is one of the most important steps of processing of nuts. In Iran and some countries, the production and processing of the nuts is more traditional and less attention has been paid to the optimization of processing conditions. Therefore optimization and modification of this process in order to improvement of the quality and taste of nuts is very important (Jafari et al.,2012). Thus the objective of this study was to examine the effect of roasting and roasting time on the physic chemical as well as sensory properties of sunflower seed kernels. Materials and methods Materials Two cultivars of sunflower kernels Dor sefid and Azargol, were obtained from Varamin Agricultural Jihad. All used chemicals were obtained from merc company, Germany. Preparation of sunflower seed kernels Samples preparation Sunflower seeds were refrigerated until processing. Before any treatment, the samples were kept at ambient temperature to reach 25±2C. The seeds were shelled by a sheller before roasting. Samples roasting: samples were divided into seven parts. Parts 1, 2 and 3 were one layer roasted in solardom microwave system (LG, model SD 38555SCR, Korea) at 900 w and 2450 MHz for 5, 7 and 10 min, respectively. Parts 4, 5 and 6 were one layer roasted in an electrical oven (model UNB-300, 220V, memmert Co., Germany) at 190ºC for 7, 10 and 15 min respectively. Control sample (part7) also was evaluated. The time periods were selected based on test and error (preliminary study). Cooling: The roasted samples were cooled to ambient temperature (25 ±2ºC). To conduct the experiments each part was sampled individually. The treatments used in this study were prepared according to table 1. Tests Calorimetric: The color of samples was evaluated after each step of roasting process. Color measurement was done by a colorimeter (model color flex, U.S.A) using Hunter parameters and expressed as brightness (L*) redness greenness (a*) and blueness yellowness (b*). Total color difference (ΔE) was calculated by use of relation (1) and used for estimation of color variation during roasting (Edalatian et al., 2007). (1) 9 Soleimanieh et al.
Texture test: Hardness was evaluated by Instron system (Hounsfield Co., UK). According to definition, texture hardness is the required force over compression test. To do so three perfect samples from each treatment were tested based on the following settings: It was done by GC (model youngling, Korea) characterizes by Varian capacity column cp-sill for fame the column length width and diameter were 60 m, 0.25 mm and 0.2 µm respectively temperatures of column injector and detector were 175, 280 and 300ºC respectively. Load cell used for this test was 250N, the diameter speed and penetration index of the probe were 32mm, 5mm/min and 50% of the kernel thickness respectively. Moisture content measurement: The moisture content was measured after roasting according to Iranian national standard N. 8034 (Anonymous 2, 2004). Acidity was determined according to Iranian national standard No 8617 (Anonymous 1, 2004). Sensory assessment was of single tasting type performed for five characteristics color, flavor, odor, hardness and total acceptance. The assessment was done by a 11- member panel from Iranian industrial research and standard. Sensory test was based on 5- point hedonic scale. Data analysis All experiments were laid out in completely randomized block design with three replications. For comparison of data means multiple range Duncan test at 0.05 level was used. Peroxide was determined according to Iranian national standard No. 4179 (Anonymous, 2008). For data analysis software SPSS was used and the graphs were drawn by software Excel. Oil extraction percentage was determined according to Iranian national standard No. 1771 (Anonymous, 1996). Fatty acid composition was determined according to Iranian national standard N 1771 (Anonymous, 1984). Results and discussion Moisture Figure 1 shows the means comparison for the effect of roasting method and time on the moisture content of sunflower seed kernels. Table 1. Studied treatments this research. Explanations Sunflower seed kernels roasted by microwave for 5 min. Sunflower seed kernels roasted by microwave for 7 min. Sunflower seed kernels roasted by microwave for 10 min. Sunflower seed kernels roasted by oven for 7 min. Sunflower seed kernels roasted by microwave for 10 min. Sunflower seed kernels roasted by microwave for 15 min. Unroasted (raw) sunflower kernels. Treatments S1 S2 S3 S4 S5 S6 B The initial moisture content was about 4% which reduced to 0.75-1.66% after roasting by either roasting methods. As shown in the figure roasting by either method for a longer time resulted in significant (p 0.01) decrease in moisture with the electrical oven having more pronounced effect. This moisture reduction was probably due to the temperature of either method. According to Iranian national standard maximum permitted level of moisture for roasted sunflower kernels is 3%, thus all roasted 10 Soleimanieh et al.
samples showed a moisture content within the standard range. Our results were in agreement with the results obtained by Nikzadeh et al., (2009), Kita & Figiel (2007), Nikzadeh & Sedaghat (2008), Shakerardakani et al., (2011), Kahyaoglu & Kaya (2006) and Bhattacharya & Prakash (1997) who stated that as the time of roasting was prolonged, the moisture content decreased. Table 2. Results of colorimetry of L, a, b values in roasted sunflower seed kernels. Treatment L-Value a-value b-value B 58.83±0.009 a 2.19±0.006 g 11.17±0.015 f S1 S2 S3 S4 S5 S6 57.79±0.003 b 2.86±0.006 f 14.88±0.009 d 54.61±0.007 d 3.98±0.006 e 16.98±0.017 b 48.69±0.007 f 6.08±0.003 a 17.51±0.068 a 54.82±0.035 c 5.56±0.006 d 17.06±0.018 b 52.71±0.006 e 5.65±0.012 c 15.54±0.018 c 48.42±0.006 g 5.76±0.017 b 14.78±0.003 e In each line, means with at least one common letter are not different at significance level of 1% according to Duncan test. 7min), S3 (sample roasted by microwave for 10min) (sample roasted by electrical oven for 10min), S6 Table 3. The results of comparison of fatty acids mean in roasted and control sunflower seed kernels. Treatment B S1 S2 S3 S4 S5 S6 Fatty acids C14:0 0.10±0.00 0.08±1.017 0.13±0.033 0.10±0.00-0.13±0.033 0.10±0.00 C16:0 7.17 ±0.033 b 6.43±0.033 de 7.53±0.033 a 6.73±0.033 c 6.33±0.033 e 6.47±0.033 d 6.43±0.033 de C16:1t 0.10±0.00 a 0.12±0.017 a 0.10±0.00 a 0.13±0.033 a 0.13±0.033 a 0.13±0.033 a 0.13±0.033 a C16:1c 0.10±0.00 a 0.10±0.00 a 0.08±0.017 a 0.10±0.00 a 0.13±0.033 a 0.13±0.033 a 0.13±0.033 a C18:0 4.83±0.033 cd 4.77±0.033 d 4.88±0.017 c 4.57±0.033 e 5.27±0.033 a 5.17±0.033 b 5.33±0.033 a C18:1 21.07±0.033 e 21.33±0.033 d 20.50±0.00 f 22.67±0.033 a 21.57±0.033 c 21.13±0.033 e 21.73±0.033 b C18:2 66.13±0.033 c 66.67±0.033 a 66.38±0.00 b 65.17±0.033 f 66.07±0.033 cd 66.17±0.00 d 65.65±0.033 e C18:3 0.27±0.033 ab 0.20±0.00 bc d 0.13±0.033 d 0.23±0.033 abc 0.17±0.033 cd 0.30±0.00 a 0.23±0.033 abc C20:0 0.23±0.033 c 0.30±0.00 abc 0.27±0.033 bc 0.30±0.00 abc 0.33±0.033 ab 0.37±0.033 a 0.27±0.033 bc In each line, means with at least one common letter are not different at significance level of 1% according to Duncan test. Texture hardness Figure 2 shows the means comparison for the effect of roasting method and time on the texture hardness of sunflower kernels where the effect was significant (p 0.01). the initial hardness was 273.33N which decreased to 87.66-224N after roasting indicating that prolonged roasting time resulted in reduced hardness in either treatment with the electrical oven having more pronounced effect. The reason may be the heat penetration into the kernel thereby reducing 11 Soleimanieh et al.
the moisture content and making the kernels crispy. The oven roasted kernels showed more crispy texture than those roasted by microwave likely because when homogenous rectangle shaped foods are heated by microwave they show higher temperature in the edges and angles since multiple direction microwave energy strengthens the waves resulting in heterogeneous heat distribution. In contrast in the oven hot air reduces the moisture from food surface resulting in crisp textured kernels with less texture hardness. The results were consistent with the reports of Nikzadeh et al., (2011), Edalatian et al., (2007) and Kahyaoglu and Kaya (2006) who concluded that traditional roasting of sesame seeds reduced the hardness. Table 4. Results of compare sensory properties of roasted and control sunflower seed kernels. Property Color Odor Firmness Taste Total acceptance Treatment B 2.36±0.432 c 1.73±0.348 c 2.09±0.315 c 1.55±0.207 b 1.82±0.263 c S1 3.18±0.377 ab 3.18±0.352 ab 3.09±0.315 b 3.00±0.330 a 3.09±0.315 ab S2 3.90±0.314 ab 3.50±0.307 ab 3.60±0.267 ab 3.50±0.373 a 3.60±0.267 a S3 3.09±0.285 bc 3.18±0.296 ab 3.73±0.195 ab 2.91±0.285 a 3.00±0.270 ab S4 4.27±0.195 a 3.91±0.285 a 3.91±0.163 a 3.55±0.312 a 3.73±0.304 a S5 4.27±0.141 a 4.00±0.191 a 4.00±0.243 a 3.64±0.310 a 3.82±0.226 a S6 2.64±0.364 c 2.91±0.315 b 3.27±0.273 ab 2.00±0.234 b 2.36±0.279 bc In each line, means with at least one common letter are not different at significance level of 1% according to Duncan test. 7min), S3 (sample roasted by microwave for 10min) (sample roasted by electrical oven for 10min), S6 Peroxide index As shown in figure 3, peroxide index significantly increased (p 0.01) as the time of roasting was prolonged for both treatments. Peroxide index of control sample was 0.90±0.003 while samples roasted by either method showed peroxide index of 5.31±0.003 and 7.41±0.006 meq/kg. Peroxide index of roated sunflower seed kernels must not exceed 10mEq/kg. Thus all samples exhibited peroxide values within the standard range. Peroxide index fluctuates during processing. Increased peroxide index after roasting suggests some oil deterioration (Gardner, 1979). The results are in consistent with reports of Kashani and Valadon (1983) who stated that roasting pistachios at 145ºC had significant effect on increasing peroxide index. Ozdmir et al., (2001) also showed that hazelnut roasted at high temperatures exhibited significantly increased peroxide value. Acidity As shown in figure 4, acidity significantly increased (p 0.01) for both treatments as the time of roasting was prolonged. Acidity value of control sample was 0.18±0.003 whereas samples roasted by both treatments showed acidity values of 0.26±0.003 and 0.61±0.003% (based on oleic acid). Maximum permitted level of acidity in sunflower oil is 2%. All samples thus are within the standard range. Increased amounts of free fatty acids suggest the hydrolysis phenomenon in sunflower oil. Lipase and sterase cause oxidative reactions of enzyme catalase. These two enzymes separate fatty acids from lipids and release them consequently free fatty acids may act as a substrate for oxidative reactions. 12 Soleimanieh et al.
These findings are consistent with the results obtained by Sedaghat & Nikzadeh (2009) who reported that an increase in roasting temperature resulted in increased free fatty acids based on linoleic acid. brown pigments getting involved in development of dark color in the product. Sugar caramelization heat dehydration and sugar decomposition also result in produced brown pigments together with organic acids aldehydes and ketons (ozdemir, 2001). Fig. 1. Effect of roasting method and different time periods on moisture content of roasted sunflower seed kernels. Colorimetry According to the results of colorimetry test by Hunter system presented in Table 1, for both treatments as the time of roasting increased, L* value decreased while a* value increased with the electrical oven having more pronounced effect. Also prolonged roasting time by microwave increased b* value whereas it reduced b* value for oven roasted samples. In general prolonged roasting time by both methods (oven and microwave) increased total color difference (ΔE) (figure 5). Enhanced color of samples roasted by both treatments may be due to the fact that non enzymatic browning reaction mediated roasting increased the number of pigments thereby improving total desirability of the product. The products resulted from millard, strecker and non enzymatic browning reaction have a complex structure mostly being unsaturated. Double bonds present in these structures absorb light thus act as Fig. 2. Effect of roasting method and different time periods on texture firmness of roasted sunflower seed kernels. The presence of lower reducing sugars content in some samples and smaller sized products decelerates browning reaction and thus may cause a difference in the rate of reaction in different parts of sample local development of millard reaction and / or development of lighter color in smaller sized samples (Danehy, 1986). Oil percentage As shown in figure 6 roasting resulted in slightly decrease in oil percentage in sunflower seed kernels. Indeed as roasting time increased for both treatments the extracted oil reduced when compared to control sample as control treatment and treatment S6 showed the highest and the lowest oil content respectively (p 0.01). As the time of roasting increased the extracted oil slightly decreased. It seems to be due to the amount of oil left over the roasting pan. 13 Soleimanieh et al.
composition and the amount of fatty acids was found within the standard range. Fig. 3. Effect of roasting method and different time periods on peroxide index of roasted sunflower seed kernels. Fig. 5. Effect of roasting method and different time periods on total color variations in roasted sunflower seed kernels. Fig. 4. Effect of roasting method and different time periods on acidity of roasted sunflower seed kernels. Fatty acid composition As indicated in Tables 3 and 4 prolonged roasting time did not considerably change fatty acid Sensory assessment The mean scores given to sensory properties were compared and the results are presented in Table 2. Given the obtained results the scores ranged from 2.36 to 2.64. Treatments S4 and S5 showed the highest scores for color and the lowest scores were observed for control sample followed by S6 (p 0.01). The low score found for S6 seems to be due to excess heat processing making the product unacceptable by the consumer. Negative point found for control sample may be the result of rawness of the kernels. Roasting resulted in improved aroma for roasted kernels as compared to the control. Likely because of rawness the lowest aroma score was observed for the control followed by S6 (p 0.01) which seems to be due to excess heat processing. For hardness the highest scores were given to S5 followed by S4 likely because of a crispy texture and the lowest score was found for the control (B) followed by S1 likely due to the rawness of the samples. There was no significant 14 Soleimanieh et al.
difference between the treatments (p 0.01). The scores assigned to flavor ranged from 1.55 to 3.64. The lowest score was found for the control because of rawness, followed by S6 due to bitterness caused by excess roasting. The highest score was observed for S5. There was no significant difference between the treatments except for control and S6 (p 0.01). As shown in Table 2, the scores given to total acceptance ranged 1.82-3.82. The lowest scores were found for control followed by S6 because of rawness and excess roasting as previously stated. The highest score was given to S5. The reason seems to be that all parameters were considered by the panelists. insignificant occurring within the standard range. The results of assessment of sensory properties of roasted sunflower seed kernels conducted by the panelists revealed that all sensory properties (color, odor, hardness, flavor and total acceptance) of the roasted kernels were more desirable than the control. Among the samples roasted by microwave S2 was the best treatment and from the samples roasted by oven S5 was reported as the best one for organoleptic characteristics. Acknowledgment The authors express their gratitude to Dr. Leila Nateghi at the Department of Food Science and Technology, Varamin-Pishva Branch, Islamic Azad University, Varamin, Iran, for editing the manuscript. References Anonymous. 2012. Iranian industrial research & standard institute. Standard N. 14615. Roasted sunflower seed kernels. Test qualities and method. 1 st edition. Anonymous 1. 2004. Iranian industrial research & standard institute. Standard N. 8617. Oil seeds acidity measurement 1 st edition. Fig. 6. Effect of roasting method and different time periods on oil percentage of roasted sunflower seed kernels. Conclusion Given the obtained results it can be concluded that prolonged roasting time results in reduced moisture hardness and oil percentage of sunflower seed kernels roasted by two methods microwave and electrical oven with the oven having more pronounced effect. In addition as the roasting time increased acidity peroxide index and darkness of samples increased. The changes in fatty acid composition were Anonymous 2. 2004. Iranian industrial research & standard institute. Standard N. 8034. Oil seeds moisture and volatiles measurement. 1 st edition. Anonymous. 2008. Iranian industrial research & standard institute. Standard No. 41179. Vegetable and animal fats and oils peroxide measurement by Iodometry 0 1 st revision. Anonymous. 1996. Iranian industrial research & standard institute. Standard 661. Test of oil seeds 3 rd edition. Anonymous, 1984. Iranian industrial research & standard institute. Standard N. 1771. Determination of fatty acid composition by gas chromatography. 1 st edition. Askari GH, Emamjome Z, Ebrahimzadeh 15 Soleimanieh et al.
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