APTEFF, 42, (2011) UDC: : DOI: /APT P BIBLID: (2011) 42, Original scientific paper

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1 STATISTICAL ANALYSIS OF THE INFLUENCE OF WHEAT BLACK POINT KERNELS ON SELECTED INDICATORS OF WHEAT FLOUR QUALITY Verica D. Petrov a and Nada K. Filipović b a Ţitoprodukt, Bolniţka 7, Zrenjanin, Serbia b University of Novi Sad, Faculty of Technology, Bulevar cara Lazara 1, Novi Sad, Serbia The influence of wheat black point kernels on selected indicators of wheat flour quality farinograph and extensograph indicators, amylolytic activity, wet gluten and flour ash content, were examined in this study. The examinations were conducted on samples of wheat harvested in the years 2007 and 2008 from the area of Central Banat in four treatments-control (without black point flour) and with 2, 4 and 10% of black point flour which was added as a replacement for a part of the control sample. Statistically significant differences between treatments were observed on the dough stability, falling number and extensibility. The samples with 10% of black point flour had the lowest dough stability and the highest amylolytic activity and extensibility. There was a trend of the increasing 15 min drop and water absorption with the increased share of black point flour. Extensograph area, resistance and ratio resistance to extensibility decreased with the addition of black point flour, but not properly. Mahalanobis distance indicates that the addition of 10% black point flour had the greatest influence on the observed quality indicators, thus proving that black point contributes to the technological quality of wheat, i.e.flour. KEY WORDS: wheat, wheat flour, black point INTRODUCTION Impurities in wheat are known as the most important elements for the technological quality of wheat. It is significant for the processing industry to differentiate the foreign materials in wheat bulk which are easily separable and those that are inseparable (hard separable) (1). The foreign materials of hard separable category, i.e. the foreign materials that, by geometrical and weight characteristics, have healthy grain characteristics but due to damage at waxy stage of maturity, caused by wheat bugs or attack of field moulds (Fusarium spp., Alternaria spp., etc.), show changed technological quality, in case of larger quantity of particular categories, have a negative effect on particular aspects of the kernel mass technological quality (2). Kernels with black point are also inseparable * Corresponding author: Verica D. Petrov, Ţitoprodukt, Bolniţka 7, Zrenjanin, Serbia, kurjaki@ptt.rs 111

2 ingredients. Black point kernels have characteristically distinctive dark germ and/or part of endosperm, and they appear due to the growing of Dematiaceae family moulds (1). These are filamentous fungi that form black-brown conidia and conidiophores, due to the presence of pigments, which are secondary metabolites of fungi (3). The appearance of black point is conditioned by seasonal climatic conditions. When the weather during the period of grain filling and maturing is humid, the intensity of black point increases (4). If it is moist and warm weather, the grain can be completely darkened. After a rainy season when drought occurs, black bars appear on the grains, since the growth of fungi has been stopped (5). When grain moisture content exceeds 20%, combined with the relative humidity above 90%, the amount of black point kernels increases dramatically (6). In Australia and New Zealand the problem of wheat black point kernels is highly present. Rees et al. (4), based on the experiment of 12 wheat black point samples found that at the level of 10-50%, stated that the falling number and dough stability were statistically significant lower in samples with greater share of black point, while water absorption and flour colour grade increased. Dexter and Preston (7) found that the increase of water absorption and dough development time resulted from larger black point quantities. In his experiments Lorenz (5) worked with tested 2 wheat varieties, highly sensitive to black point, and determined that amylolytic activity increased with the increase of black point level. Testing 4 wheat varieties in the Volga Region, Krupnova et al. (8) obtained statistically significant higher alpha-amylase activity of black point kernels compared to kernels without black point (healthy kernels). According to their findings, there were no differences in the protein content and content of wet and dry gluten of black point kernels as compared to healthy kernels. In the early 70's of the last century, in this growing area, Pastornaţki et al. (9) investigated the changes of wheat quality of black point kernels of old varieties Aurora and Kavkaz. Also, an increasing trend of farinograph water absorption and 15 min drop was proved, while the quality number was in decrease. The protein content in flour, and wet gluten content generally showed an increasing trend with a higher level of black point kernels compared to healthy kernels. In comparison to the fraction without black point, in the black point fraction an increased activity of proteolytic enzymes was noted, but not in such an extend to destroy protein complex structure. The amylolytic activity of black point flour fractions was also increased, but not significantly related to healthy kernel flour. Due to water absorption increase and increased enzyme amylolitic activity, in some cases, a small amount of black point kernels can positively effect the technological quality of wheat. In modern cereal screenrooms in mills, there are devices that are able to detect and remove a substantial share of black point kernels and thus eliminate them from further processing (10,11). Unfortunately, a small number of mills are equipped in this way, so black point kernels arrive to first break. In our country the examinations of wheat black point are mainly related to test their mycological and toxicological properties, and little is known about their impact on the technological quality of wheat. The aim of this study was to examine the effect of wheat black point kernels on selected indicators of wheat flour quality in the conditions of production in the area of Central Banat. 112

3 EXPERIMENTAL The survey includes samples of the wheat crop 2007 and 2008 from the area of Central Banat. The experiments were conducted in the laboratory of "Ţitoprodukt" Zrenjanin. In 2007, testings were conducted on 3 samples of wheat with 4 treatments and 3 replications. For the purposes of the examination in 2008, 4 wheat samples with 4 treatments in 3-4 replicates were tested. Each wheat sample came from a single manufacturer, from a single lot. Sample preparation Black point kernels were manually separated from average samples of wheat crop 2007 and 2008 from the area of Central Banat, collected at the entrance to the silo "Ţitoprodukt" Zrenjanin. Black point grains were further grinded. Grinding Prepared wheat samples (sound or black point fraction) were individually tempered overnight (14h) at 14% moisture and milled in the Brabender mill Quadrumat junior. Flour of 60% extraction (12) was manually homogenized. In each year of study, wellhomogenized samples of wheat flour were used for making 4 sub-samples. The first sample was further used as a control one - flour from sound grains, while to the other three samples 2, 4 or 10% of black point flour was added as a substitute for part of the control sample. Dough rheology tests (farinogram and extensogram) were made on standard Brabender equipments, according to the Serbian Rules on methods of physical and chemical analyses designed for quality control of wheat, milling- and bakery products, pasta and frozen dough (13). Wet gluten content and falling number according to Hagberg were determined according to the procedure described by KaluŤerski and Filipoviš (12). Moisture and flour ash content were determined, according to Rules on methods of physical and chemical analyses designed for quality control of wheat, milling- and bakery products, pasta and frozen dough (13). The average values of 25 replicates were statistically analyzed and tested by multivariate MANOVA and discriminative analysis, while as the univariant procedures ANOVA and t-test were used (14). At the testing of the hypothesis, a critical p value was used, which poses a risk of conclusion. If p > 0.1, the differences are not significant. If 0.1 > p > 0.05 the existence of significant differences with increased risk of reasoning is accepted, whereas in the case when p<0.05 there are significant differences. By finding the coefficient of discrimination, the features determining the specificity of the addition of black point flour were distinguished. Calculating Mahalanobis distance between samples with the addition of black point flour another indication of similarity or difference was obtained, since the distances of different areas can be compared. Statistical designing and data processing were done according to the methodology of the agency "Smartline" Novi Sad, using the program package Microsoft Excel 2003 version. The discrimination coeffi- 113

4 cient and Mahalanobis distance are calculated according to Anderson (14), while the figures showing the confidence intervals of the selected quality indicators were prepared in Grapher Six program, Golden Software, Inc., 2005 version. RESULTS AND DISCUSSION Tables 1 and 5 show the central and dispersive parameters of the tested quality indicators for control samples and the samples with 2, 4 and 10% black point flour added, and the statistically significant differences between the sample groups are marked with an asterisk (*) and the alphabet letters. The adding of black point flour affected the farinograph indicators (Table 1). Table 1. The influence of the addition of black point flour on farinograph indicators FARINOGRAPH average standard variation confidence min max INDICATORS deviation coefficient interval control (without black point flour) a Water absorption (%) Dough development (min) Dough stability (min) 1.33 *ad min drop (FU) Number of quality with 2% of black point flour b Water absorption (%) Dough development (min) Dough stability (min) 1.46 *bc,bd min drop (FU) Number of quality with 4% of black point flour c Water absorption (%) Dough development (min) Dough stability (min) min drop (FU) Number of quality with 10% of black point flour d Water absorption (%) Dough development (min) Dough stability (min) min drop (FU) Number of quality 68, * significant difference, alphabet letters in the superscript indicate groups of samples among which significant differences were observed 114

5 The addition of black point flour lead to a slight increase in the water absorption. The dough stability showed a decreasing trend with larger quantities of black point flour, while the 15 min drop was increasing. Regarding the dough development time and quality number there were no significant changes with the addition of black point flour. Table 2. Statistical analysis of the influence of addition of black point flour on farinograph indicators Analysis n (Number of quality indicators) F (Fisher test) p (Confidence of the test) MANOVA Discriminative Statistical analysis (Table 2) showed that, based on the value p=0.000 (MANOVA analysis) and p=0.000 (discriminative analysis), there is a difference and clearly defined borderline between the samples with the addition of black point flour and confirmed the strong influence of black point kernels on the farinograph indicators of flour quality. Table 3. The significance of differences between samples with the addition of black point flour in relation to the farinograph indicators (ANOVA test and coefficient of discrimination) F (Fisher test) p (Confidence of the test) Coefficient of discrimination Water absorption Dough development (min) Dough stability * min drop Number of quality * - significant difference The ANOVA test showed a significant difference between the dough stabilities of some samples, with the addition of black point flour, in relation to the farinograph indicators (Table 3). The coefficient of discrimination indicates that the largest contribution to the discrimination between samples with addition of black point flour is associated with the number of quality, followed by dough stability and 15 min drop. The level of black point flour affected the increase in the water absorption (Table 1), which is a prerequisite for obtaining a higher yield of dough and bread. In the case of water absorption, there are no significant differences between control and samples with addition of black point flour, as confirmed by p> 0.1 (Table 3). This is in accordance with the findings of Rees et al. (4). The differences in dough development time are minor, while in the case of dough stability the existence of significant differences between groups of samples (p<0.05, Table 3) was noticed. The effect of black point flour showed 115

6 up with the addition of 4%, while 10% of black point flour significantly affected reduction of dough stability, which is consistent with the literature data (4). The share of black point flour contributed to the increased 15 min drop. More precisely, 2% and 4% caused an approximate effect, while the sample with 10% of black point flour differs significantly compared to the control sample. Although, regarding the 15 min drop, a statistically significant difference between samples with different levels of black point flour is not obtained, the trend of increasing 15 min drop with the increase of black point flour is evident (Figure 1), which is in agreement with the results obtained by Pastornaţki et al. (9). The coefficient of discrimination indicates that the influence of black point kernels on 15 min drop is a bit smaller than the effect on dough stability. Figure 1. Confidence intervals for dough stability and 15 min drop of samples with addition of black point flour (Legend: control (1), 2% of black point flour (2), 4% of black point flour (3), 10% of black point flour (4)) Regarding the farinograph number of quality, there has been a slight, but irregular, trend of increase parallel to the added amount of black point flour. The coefficient of discrimination points at the greatest contribution to the difference between samples though these differences were not statistically significant. The Mahalanobis distance (Table 4) indicates that, in terms of farinograph indicators, the influence of the black point flour increases with the increase of its level and is the highest with the addition of 10%. Concerning the variety of farinograph indicators, statistical analysis shows that the addition of black point flour had the most influence on dough stability. According to Table 1, significant difference exists in the dough stability between control and samples with 10% of black point flour. Dough stability of the sample with 2% of black point flour was significantly higher than in samples with 4 and 10% of black point flour. 116

7 Table 4. Mahalanobis distance between the samples with addition of black point flour in relation to the farinograph indicators Control 2% bpf 4% bpf 10% bpf Control % bpf % bpf % bpf bpf black point flour The addition of black point flour also affected the extensograph indicators, amilolytic activity, wet gluten and flour ash content (Table 5). Tabela 5. The influence of addition of black point flour on certain flour characteristics QUALITY INDICATORS Average Standard deviation min max Variation coefficient Confidence interval Control (without black point flour) a Area (cm 2 ) Resistance (EU) Extensibility (mm) Ratio number Falling number (s) *ad Wet gluten content (%) Flour ash (% d.m.) With 2% of black point flour b Area (cm 2 ) Resistance (EU) Extensibility (mm) Ratio number Falling number (s) Wet gluten content (%) Flour ash (% d.m.) With 4% of black point flour c Area (cm 2 ) Resistance (EU) Extensibility (mm) Ratio number Falling number (s) Wet gluten content (%) Flour ash (% d.m.) With 10% of black point flour d Area (cm 2 ) Resistance (EU) Extensibility (mm) *da Ratio number Falling number (s) , Wet gluten content (%) Flour ash (% d.m.) * significant difference, alphabet letters in the superscript indicate the groups of samples among which significant differences were observed 117

8 Based on the values p=0.000 (analysis MANOVA) and p=0.000 (discriminative analysis) (Table 6), the existence of differences and clearly defined borderlines between the samples with the addition of black point flour in relation to extensograph indicators, amilolytic activity, wet gluten and flour ash content is observed. However, ANOVA (Table 7) did not prove significant differences between the samples with different ratio of black point flour as it was registered in the individual cases, referring the falling number and extensibility (Table 5). Extensograph indicators change in terms of decreasing area and ratio number, considering to the resistance decrease with black point flour level increase. The lowest area and dough resistance were recorded at the level of 4% black point flour addition. The addition of 4% black point flour caused a slight increase in extensibility, which, at the level of 10%, became statistically significantly different compared to the control (Table 5). Coefficients of discrimination (Table 7) indicate that the falling number (0.557) and wet gluten content (0.333) proved to be influenced by the level of black point in the samples. Table 6. Statistical analysis of the influence of black point flour addition in relation to certain flour characteristics Analysis n F p (Number of quality indicators) (Fisher test) (Confidence of the test) MANOVA Discriminative Table 7. The significance of differences between samples with the addition of black point flour in relation to certain flour characteristics (ANOVA test and coefficient of discrimination) F p Coefficient of (Fisher test) (Confidence of the test) discrimination Area Resistance Extensibility Ratio number Falling number Wet gluten content Flour ash The falling number decreases with the increase of the share of black point flour (Figure 2). The sample with 10% of black point flour has the lowest value of falling number, or the highest amylolytic activity, which is consistent with the findings of Rees et al. (4), Lorenz (5) and Krupnova et al. (8). A significant difference in falling numbers was observed between control and samples with 10% of black point flour (Table 5). In terms of wet gluten content, a decreasing trend with the increase of the level of black point flour (Figure 2) was observed, which is not in agreement with Pastornaţki et al. (9). 118

9 Statistical analysis confirmed that the addition of black point flour had no effect on flour ash content. Figure 2. Confidence intervals for falling number and wet gluten content of samples with the addition of black point flour (Legend: control (1), 2% of black point flour (2), 4% of black point flour (3), 10% of black point flour (4)) Table 8. Mahalanobis distance between the samples with the addition of black point flour in relation to certain flour characteristics Control 2% bpf 4% bpf 10% bpf Control % bpf % bpf % bpf bpf black point flour The values of Mahalanobis distances between samples confirmed the observed changes of the extensograph indicators, amilolytic activity, wet gluten and flour ash content (Table 8). With the increase of black point flour level, the Mahalanobis distance increases, too, which indicates that the addition of 10% of black point flour has the greatest influence on the change of quality indicators. CONCLUSION The applied statistical analysis indicated the similarities and differences between the earlier and contemporary findings concerning the influence of wheat black point level on the technological characteristics of flour. 119

10 Based on the results of this study, it could be concluded that the addition of black point flour effected most the dough stability and dough development time, 15 min drop and falling number, with the peak values at 10% share. The findings that are not in accordance with literature data can be interpreted as a result of temporal distance (test performed in the 70's) and/or different conditions of production. As climatic conditions are the most important factor for the black point occurrence, the influence of black point kernels on the technological quality of wheat production per year should be reviewed. Also, it should be checked if in a specific production year the small share present of black point kernels can effect the improvement of particular wheat quality indicators (if the grain mass is being healthy safe from mycological and toxicological aspects). Further research should deal with both the effect of black point kernels on baking properties of wheat and the enzyme (proteolytic and amilolytic) activity of black point kernels. To solve partly the problem of black point kernels, the further research should include the resistance of wheat varieties to the black point and, regarding it, take care of the proper variety choice at the seeding time, as well as treat wheat with fungicides during the blooming period and to modernize cereal screenrooms in mills with the equipment for colour wheat impurities separation. 120 REFERENCES 1. Šariš, M., Psodorov, Đ., Ţivanţev D. and Košutiš, M.: Uticaj neodvojivih primesa na promene tehnološkog kvaliteta pšenice. Ţasopis za procesnu tehniku i energetiku u poljopriverdi (PTEP) 8, 1-2 (2004) Šariš, M., Šariš-Konc, N., Gnip M. and Psodorov, Đ.: Sorta kao faktor obezbeťenja tehnološkog kvaliteta merkantilne pšenice. Ţito-hleb 29, 2 (2002) Ellis, M.B.: Dematiaceous Hyphomycetes, Commonwealth Mycological Institute, Kew & Surrey, England (1971). 4. Rees, R.G., Martin, D.J. and Law, D.P.: Black point in bread wheat: effects on quality and germination, and fungal associations. Australian Journal of Experimental Agriculture and Animal Husbandry 24 (1984) Lorenz, K.: Effects of blackpoint on grain composition and baking quality of New Zealand wheat. New Zealand Journal of Agricultural Research 29 (1986) Toklu, F., Akgül, D.S, Biçici, M. and Karaköy, T.: The relationship between black point and fungi species and effects of black point on seed germination properties in bread wheat. Turk. J. Agric. For. 32 (2008) Dexter, J.E. and Edwards N.M.: The implications of frequently encountered grading factors on the processing quality of common wheat. research-recherche/dexter/gfqw-cfab/gfqw-cfab-4-eng.htm (accessed 12 July 2010). 8. Krupnova, O.V., Krupnov, V.A. and Antonov, G.Yu.: Black point: influence on bread-making quality. Annual Wheat Newsletter 51 (2005) (accessed 9 May 2011). 9. Pastornaţki, Đ., Petriš, D. and Šariš, M.: Tamnokliţnost pšenice semenski i tehnološki kvalitet. Ţito-hleb 1, 1 (1974) Udicki, D.: Efikasnost SORTEX Z+ ureťaja u fazi izdvajanja primesa, I deo. Mlinpek Almanah (2010)

11 11. Udicki, D.: Efikasnost SORTEX Z+ ureťaja u fazi izdvajanja primesa, II deo. Mlinpek Almanah (2010) KaluŤerski, G. and Filipoviš, N.: Metode ispitivanja kvaliteta ţita, brašna i gotovih proizvoda, Tehnološki fakultet, Zavod za tehnologiju ţita i brašna, Novi Sad (1998). 13. Pravilnik o metodama fiziţkih i hemijskih analiza za kontrolu kvaliteta ţita, mlinskih i pekarskih proizvoda, testenina i brzo smrznutih testa, Sluţbeni list SFRJ 74 (1988) Anderson T.W.: An introduction to Multivariante Statistical Analysis, second edition, John Wiley&Sons, USA (1984). СТАТИСТИЧКА АНАЛИЗА УТИЦАЈА ТАМНОКЛИЧНИХ ЗРНА ПШЕНИЦЕ НА ОДАБРАНЕ ПОКАЗАТЕЉЕ КВАЛИТЕТА ПШЕНИЧНОГ БРАШНА Верица Д. Петров а и Нада К. Филиповић б а Житопродукт, Болничка 7, Зрењанин, Србија б Универзитет у Новом Саду, Технолошки факултет, Булевар цара Лазара 1, Нови Сад, Србија У раду је испитан утицај тамнокличних зрна на одабране показатеље квалитета пшеничног брашна фаринографске и екстензографске показатеље, амилолитичку активност, садржај влажног глутена и пепела брашна. Испитивања су обављена на узорцима пшенице рода и са подручја Средњег Баната, у 4 третмана контрола (без тамнокличног брашна) и са 2, 4 и 10% брашна од тамнокличних зрна које је додавано као замена дела контролног узорка. Статистички значајне разлике међу третманима уочене су по стабилитету, броју падања и растегљивости. Узорци са 10% тамнокличног брашна имали су најмањи стабилитет и највећу амилолитичку активност и растегљивост. Уочен је тренд пораста степена омекшања и моћи упијања воде са порастом удела тамнокличног брашна. Енергија по екстензограму, отпор и однос отпора према растегљивости се смањују при додатку тамнокличног брашна, иако не правилно. Махаланобисова дистанца указује да је додатак 10% тамнокличног брашна испољио највећи утицај на посматране показатеље квалитета, тиме потврђујући да тамнокличност утиче на технолошки квалитет пшенице, односно брашна. Кључне речи: пшеница, пшенично брашно, тамнокличност Received 7 June 2011 Accepted 8 August