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Chemical composition of small white (navy) beans
Lebensm.-Wiss.u.-Technol., 28, 272-278 (1995)
Chemical Composition of Small White (Navy) Beans* G.R. Kereliuk* and G.C. Kozub
Agriculture and Agri-Food Canada, Research Centre, RO. Box 3000 - Main, Lethbridge, Alberta, T1J 4Bl(Canada) (Received August 22, 1994; accepted October 17, 1994)
The chemical composition of small white (navy) beans grown in Ontario and at two locations in Alberta was compared to see (f chemical composition was influenced by environment. The Ontario-grown beans had more starch and less protein than beans grown in Alberta. Of the fiber components, only enzyme-extractable pentosan was higher in beans from Alberta compared to beans from Ontario. Most Other chemical components had similar levels in both environments. Simple and partial correlations revealed the relationships among a number of the chemical components. However, the effect of chemical composition on maturity was not obvious and may be complex.
Introduction Dry Beans (Phaseolus vulgaris L.) are an important food source for many human populations. In North America, beans canned in thick tomato sauce, called 'beans with pork' are popular. Previous work showed differences among small white (navy) beans grown in Alberta and those grown in Ontario (1). After processing, Alberta beans had a greater tendency to mat in the can and a lower alcoholinsoluble solids content, making them less desirable than Ontario beans for commercial canning. The longer growing season in Ontario was considered to be a factor resulting in more physiological maturity in Ontario beans compared to those from Alberta (1). This study was conducted to determine which chemical components of small white beans are associated with the regional differences in quality. The nature of the associations among the components was also studied to identify their influence on quality and maturity.
Materials and Methods
Crops and Horticultural Research Center in Brooks, Alberta. Dry bean samples were ground through a 0.5 mm screen and moisture determined at 130°C (2) in order to calculate the results on a dry weight basis. All analyses were done in triplicate.
Protein and phosphorus
The protein (N × 6.25) and the phosphorus content were determined from a single sample digest by an automated colorimetric procedure (3).
Sugars
Sugars were determined after extraction with 800 mL/L ethanol (4). Reducing sugar was determined colorimetrically using p-hydroxybenzoic acid hydrazide (5) and total sugar using phenol/sulfuric acid (6). After extraction with 800 mL/L ethanol, the residue was extracted with 100 mL/L ethanol, to extract higher molecular weight sugars. Reducing and total sugars in this extract were determined as for the 800 mL/L ethanol extraction.
Materials and handling
Samples of four bean cultivars, Northland, Pulsar, Sanilac and Seaforth, grown in 1985 under normal field conditions were obtained from the Agriculture and Agri-Food Canada Research Centre, Harrow, Ontario. Samples of these cultivars grown under irrigation in 1985, and of Northland, Pulsar, Aurora and Seafarer grown in 1986 were obtained from the Alberta Special *LRC Contribution No. 3879463 tTo whom correspondence should be addressed
Starch
Starch was determined by a modification of the method of Rasmussen and Henry (7). G r o u n d bean samples (50 mg) were weighed into 16 x 125 mm culture tubes. The sugars were removed by adding 10 mL of 800 mL/L ethanol, heating at 80°C for 10 min, cooling to room temperature, centrifuging for 15 min at 1200 x g and discarding the supernatant. The procedure was
0023-6438/95/030272 + 07508.00/0 01995 Academic Press Limited
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repeated at room temperature with stirring for 20 min. The residues were air-dried at room temperature, 0.5 mL of dimethyl sulfoxide was added to each tube, and the samples stirred and heated at 100°C for 10 min. Tris maleate buffer, 4.5 mL, 0.01 mol/L, pH 6.7 in calcium chloride, 2.5 mmol/L was then added with stirring. The temperature was reduced to 80°C, and 20 ~tL of heat stable a-amylase, Termamyl 120L, (Novo Industrials A/S, Lachine, PQ), diluted 25 times, was added and the temperature maintained at 80°C for 30 min. After cooling to room temperature, 5 mL of sodium acetate buffer, 0.2 mol/L, pH 4.5 and 50 IxL of amyloglucosidase, 5 mg/mL in water (6 U/mg lyophilisate, Boehringer Mannheim, Laval, PQ) were added and held overnight (18 h) at 60°C. The samples were then cooled to room temperature and centrifuged for 15 min at 1200 x g. The supernatants were collected and analysed for glucose using glucose oxidase and the amount of starch calculated.
Pentosans
1000 x g for 15 min and the supernatants removed by aspiration. The residues were air-dried, if necessary overnight. After the addition of 0.7 mL sulfuric acid, 12 moi/L, the samples were kept at 35°C for 1 h. Then 7.3 mL of water was added, and the tubes heated and stirred at 100°C for 2 h. An aliquot (3 mL) was taken from each sample after 1 h for uronide analysis. The remaining hydrolysate was saved for total fiber, pentosan and cellulose analysis. Total uronide was determined using the method of Scott (11). Total fiber was determined using phenol/ sulfuric acid (6). Cellulose was determined by glucose analysis using glucose oxidase (7). Pentosan associated with fiber was determined using orcinol (9). To determine if any other fiber components were present, the sum of uronide, pentosan and cellulose was subtracted from total fiber and the difference called unknown fiber.
Alcohol-insoluble solids
Soluble, enzyme-extractable and total pentosans were determined as described by Hashimoto et al. (8), except that enzyme-extractable pentosan was extracted for 24 h with cellulase, Type V (Sigma Chemical Co, St. Louis, MO). Also, residual glucose was removed from the hydrolysed soluble and enzyme-extractable pentosans using 1 mg of glucose oxidase to 20 mL of neutralized hydrolysate and incubating at 37°C for 2 h. The colorimetric analysis of pentosan was based on the difference in absorbance between 670 and 600 nm
(9).
The procedure for alcohol-insoluble solids (12,13) was adapted for dry ground sample as follows. Ground bean samples (0.5 g) were weighed into 125-mL erlenmeyer flasks, 60 mL of 800 mL/L ethanol added and heated to near boiling for 30 min. After cooling, the samples were vacuum filtered through dried, weighed Whatman No. 3, 7 cm filter paper. The residue on the filter paper was washed twice with 20 mL of hot 800 mL/L ethanol, twice with 10 mL of cold absolute ethanol, and dried overnight (18 h) at 95°C, then placed in a desiccator for 0.5 h to cool, and weighed.
Fiber
Total fiber and its constituents, pentosan, uronide (pectic substances) and cellulose were determined as described by Faulks and Timms (10) with modifications. Ground samples (100 mg) were weighed into 16 × 125 mm culture tubes, 3.3 mL of Tris maleate buffer, 0.1 mol/L, pH 6.7 containing calcium chloride, 2.5 mmol/L added and heated with stirring at 100°C for 10 min. Seventy ~tL of Termamyl 120L (Novo Industrials A/S, Lachine, PQ), diluted 25 times, was added and heating continued for 15 min at 100°C. After cooling to room temperature, 13.3 mL of ethanol (950 mL/L) was added. The samples were cooled at 0°C for 30 min, centrifuged at 1000 x g for 15 min, and the supernatants were removed by aspiration. The residues were suspended in 0.7 mL of dimethyl sulfoxide by vortexing, and heated with stirring at 100°C for 5 min. Upon cooling to room temperature, 2.7 mL of acetate buffer, 0.1 mol/L, pH 4.6 and 60 ~tL of amyloglucosidase, 12 mg/mL in water (6 U/mg lyophilisate, Boehringer Mannheim, Laval, PQ) were added. After 35 min at 37°C with vortexing every 10 min, the incubation was ended by adding 13.0 mL of 950 mL/L ethanol and cooling at 0°C for 30 min. The tubes were centrifuged at
Statistical methods
Analyses of variance (14) were carried out on the data for each chemical component. The statistical model included effects of environment and cultivar, with the environment - cultivar interaction being used to estimate error variance. Cultivar and error variations were pooled when their mean squares were of similar magnitude to increase the precision for comparing the environments. A contrast was included in the analysis to compare the means of the samples from Alberta with those from Ontario. Simple correlations were calculated between all pairs of chemical components after effects due to environment were taken into account (15). However, the effect of chemical composition on quality and maturity may not be evident from simple correlations alone. To determine whether other intercorrelated variables were affecting the magnitudes of the simple correlations, partial correlations were also determined (14) to provide further insight into the relationships between chemical composition and quality. The GLM and CORR procedures of SAS (16,17) were used to perform the statistical analyses.
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Table 1 Selected nutrient components of small white (navy) beans (g/kg of dry weight) Component h Sample ° Ontario 1985 1 2 3 4 Alberta 1985 5 6 7 8 Alberta 1986 9 10 11 12 Grand Mean
PROT
PH OS
RS80
TS80
RS 10
TS 10
STAR
234 245 248 233
5.26 4.07 5.16 5.69
1.5 1.6 1.4 1.3
73.9 73.4 76.3 71.3
1.4 1.0 1.0 1.1
24.1 22.4 25.0 24.1
387 378 376 404
254 242 265 247
5.75 5.96 6.43 6.48
1.3 1.7 2.5 2.1
76.1 80.0 85.0 77.7
0.5 0.9 1.1 1.0
21.0 21.8 22.4 21.8
367 358 363 371
265 271 264 266
6.88 7.10 6.41 7.09
1.6 1.6 2.3 1.8
73.0 80.1 77.9 74.8
1.2 1.0 0.9 1.3
23.9 22.7 28.9 23.3
349 352 337 353
253
6.02
1.7
76.6
1.0
23.5
366
a T h e samples are Northland (1, 5, 9), Pulsar (2, 6, 10), Sanilac (3, 7), Seaforth (4, 8), Aurora (11) and Seafarer (12). b P R O T = protein (N × 6.25); PHOS = phosphorus; RS80 and TS80 = reducing and total sugars, respectively, extracted with 800mL/L ethanol; RS10 and TS10 = reducing and total sugars, respectively, extracted with 100mL/L ethanol; S T A R = starch.
Table 2
S t r u c t u r a l c a r b o h y d r a t e s a n d a l c o h o l - i n s o l u b l e s o l i d s in s m a l l w h i t e ( n a v y ) b e a n s ( g / k g o f d r y w e i g h t ) Component b
Sample a
SOPE
EEPE
TOPE
FPEN
URON
CELL
TFIB
XFIB
AISS
SUM
5.4 3.9 5.3 4.9
29.6 21.0 27.3 26.1
111 108 108 109
84.1 88.1 88.9 87.1
24.2 25.7 23.1 24.7
32.6 34.8 30.9 30.6
181 194 174 174
39.9 45.0 30.8 31.1
852 838 823 854
931 937 923 933
Ontario 1985 1 2 3 4 Alberta 1985 5 6 7 8 Alberta 1986 9 10 11 12
4.6 5.7 4.9 5.3
27.3 30.5 31.8 31.3
115 113 99 102
83.1 88.3 84.4 88.6
20.5 24.3 22.8 23.0
35.1 31.8 33.3 33.5
180 178 168 181
41.2 33.4 27.7 35.7
882 870 868 867
936 910 924 917
7.3 6.8 11.8 7.3
34.6 29.8 42.8 33.6
104 106 98 103
86.4 96.9 89.4 90.0
19.9 25.0 23.4 22.5
28.9 31.5 30.0 25.0
174 179 180 168
38.4 26.0 37.1 30.8
862 860 826 841
909 921 903 904
Grand Mean
6.1
30.5
106
87.9
23.3
31.5
177
34.8
854
921
See Table 1 for the description of the samples. b SOPE, E E P E and T O P E = soluble, enzyme-extractable and total pentosans, respectively; FPEN = pentosan associated with fiber; U R O N = uronide; C E L L = cellulose; TFIB = total fiber; XFIB = total fiber (TFIB) less the sum of FPEN, U R O N and CELL: AISS = alcoholinsoluble solids: S U M = s u m of P R O T + PHOS + TS80 + TS10 + STAR, all from Table 1 and T O P E + U R O N + C E L L + XFIB.
Results and Discussion The main nutritional components in the beans were starch (337 to 404 g/kg) and protein 233 to 271 g/kg (Table 1). The total fiber content was (168 to 194 g/kg), consisting of total pentosan predominantly (98 to 115 g/kg), cellulose (25.0 to 35.1 g/kg) and uronides or pectic substances (19.9 to 25.7 g/kg) (Table 2). There were no significant differences among the cultivars Northland, Pulsar, Sanilac and Seaforth for any of the nutrient or fiber components. However, environmental effects were evident (Table 3). The mean protein and phosphorus contents of Ontario beans (240 g/kg and 5.05 g/kg, respectively) were lower (P < 0.01) than those of the Alberta beans (260 and 6.58 g/kg, respectively) (Table 3). Total sugars extracted by 800 mL/L ethanol were also lower (P < 0.01) in Ontario
(73.7 g/kg) than in Alberta beans (78.2 g/kg). However, reducing sugars extracted in 800 mL/L ethanol were not significantly different for the environments. The sugars extracted in 800 mL/L ethanol had a very low reducing power, slightly more than 2%, suggesting a small nonreducing sugar, probably sucrose. Reducing sugars extracted in 100 mL/L ethanol were small and not different between environments (Table 3). Total sugars extracted in 100 mL/L ethanol were higher (P < 0.10) for the Ontario beans (23.9 g/kg) than in Alberta beans (22.6 g/kg). The reducing power of the sugars extracted in 100 mL/L ethanol was small, around 4%, suggesting large oligosaccharides. The mean starch content was significantly higher (P<0.01) in Ontario beans (386 g/kg) than Alberta beans (358 g/kg) (Table 3). Alberta beans had similar starch levels in both 1985 and 1986.
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Table 3
The effect of environment on the chemical components in small white (navy) beans (g/kg of dry weight) Environment Variable"
PROT PHOS RS80 TS80 RS10 TS10 STAR SOPE EEPE TOPE FPEN URON CELL TFIB XFIB AISS SUM
O n t a r i o 1985
A l b e r t a 1985
A l b e r t a 1986
.~
Sx
.~
Sx
.~
240 b 5.05b 1.5 a 73.7 b 1.1 a 23.9 a 386 a 4.9 b 26.0 b 109 a 87.1 a 24.4 a 32.2 a 180 a 36.7 a 842 b 931 a
4h 0.26 0.2 1.7 0.1 0.4 5 0.3 1.5 3 1.8 0.9 0.8 4 3.4 5 5
252 a b 6.16 a 1.9 a 79.7 a 0.9 a 21.8 b 365 b 5.1 b 30.2ab 107 a 86.1 a 22.7 a 33.4 a 177 a 34.5 a 872 a 922a
4 0.26 0.2 1.7 0.1 0.4 5 0.3 1.5 3 1.8 0.9 0.8 4 3.4 5 5
268 a 6.99a 1.6 a 76.6ab 1.1 a 23.3ab 351 b 7.1 a 32.2 a 105 a 91.7 a 22.5 a 30.2 a 177 a 32.2 a 861 ab 915a
Sx
6 0.36 0.3 2.4 0.2 0.6 6 0.4 2.1 4 2.6 1.3 1.2 5 4.8 7 6
u P R O T = p r o t e i n (N x 6.25); P H O S = p h o s p h o r u s ; RS80 and TS80 = r e d u c i n g and total sugars, respectively, e x t r a c t e d with 8 0 0 m L / L e t h a n o l ; R S I 0 and T S I 0 = r e d u c i n g a n d total sugars, r e s p e c t i v e l y e x t r a c t e d with 100mL/L e t h a n o l ; S T A R = starch; S O P E , E E P E and T O P E = soluble, e n z y m e - e x t r a c t a b l e and total p e n t o s a n s , respectively; F P E N = p e n t o s a n a s s o c i a t e d with fiber; U R O N = u r o n i d e ; C E L L = cellulose: T F I B = total fiber; X F I B = total fiber ( T F I B ) less the s u m of F P E N , U R O N and C E L L ; A I S S = a l c o h o l - i n s o l u b l e solids; S U M = P R O T + P H O S + TS80 + TS10 + S T A R + T O P E + U R O N + C E L L + XFIB. b M e a n (,~') e S t a n d a r d E r r o r (sx) (7df.) using cultivars N o r t h l a n d . Pulsar, Sanilac 1985 a n d A l b e r t a 1985, and the cultivars A l b e r t a 1986. M e a n s f o l l o w e d by the s a m e significantly d i f f e r e n t ( P > 0.05).
from a n a l y s i s of v a r i a n c e and S e a f o r t h for O n t a r i o N o r t h l a n d and P u l s a r for l e t t e r within rows are not
In general, as the starch content increased, protein, phosphorus and total sugars soluble in 800 mL/L ethanol decreased, suggesting that with maturity, starch content increased. As a result, the proportions of protein, phosphorus and total sugars soluble in 800 mL/ L ethanol were smaller. The mean soluble pentosan content for the Ontario beans (4.9 g/kg) was the lowest (Table 3). However, the means were significantly different between the two Alberta years (5.1 and 7.1 g/kg), despite similar levels of other chemical constituents (Tables 1 and 2). The mean enzyme-extractable pentosan content was significantly lower for Ontario (26 g/kg) than Alberta beans grown in 1986 (31.2 g/kg) but not 1985 (30.2 g/kg) (Table 3). However, Alberta beans were not significantly different from each other. The total pentosan content was not significantly different for the two environments (Table 3). The values for pentosan associated with fiber were lower than those for total pentosan. Possibly, some pentosan is lost in the extraction of fiber resulting in smaller than expected values for fiber-associated pentosan. The means for pentosan associated with fiber, uronide, cellulose, total fiber and unknown fiber were not significantly affected by environments. Since pentosan is partially water soluble, it may have an effect of the viscosity of canned beans.
The mean for alcohol-insoluble solids for the Ontario beans (842 g/kg) was significantly lower than that for the Alberta beans grown in 1985 (872 g/kg) but not in 1986 (861 g/kg) (Table 3). The means for the Alberta samples were not significantly different. This was in contrast to a previous report that alcohol-insoluble solids were lower in Alberta beans (721 g/kg) than in Ontario beans (776 g/kg) (1). However, Kaldy (1) used canned beans in which the breakdown of structural components during the severe thermal treatment of processing may have differed for beans from the two environments. The proportions of material in the beans accounted for by the chemical analyses were similar, indicating that the analyses were consistent. Correlations among the variables following the removal of the variation due to growing environment are presented in Table 4. Correlations that are significant at the 10% level were identified to show relationships which may be present and are not significant at a lower level because of the limited number of samples. Partial correlations are given in Table 5 to demonstrate associations that may be obscured because of interactions among variables. For selected pairs of variables, the largest correlation when a third variable is held constant is given. Protein was positively correlated with total sugar extracted in 800 mL/L ethanol (r = 0.58; P < 0.10) (Table 4), suggesting these two components may be synthesized at about the same time. The partial correlation of protein with soluble pentosan was -0.71 (P<0.05) when total sugar extracted in 100 mL/L ethanol was held constant (Table 5). Protein was not correlated with starch. Total sugar extracted with 800 mL/L ethanol was positively correlated with similarly extracted reducing sugar (r=0.57; P<0.10) (Table 4), and the partial correlation was similar when pentosan associated with fiber (r= 0.63) was held constant (Table 5). The simple correlation of reducing and total sugar extracted with 100 mL/L ethanol was not significant (Table 4). However, the partial correlation was -0.85 (P < 0.01) when enzyme-extractable pentosan was considered (Table 5). Enzyme-extractable pentosan strongly influences the reducing and total sugars extracted in 100 mL/L ethanol, indicating that they all may be produced at around the same time. A significant (P<0.05) simple correlation between starch and phosphorus was evident (r = 0.68) (Table 4). When partial correlations were calculated using the other variables, a significant positive association between starch and phosphorus was still evident (Table 5). This indicates that the correlation between starch and phosphorus was not influenced by other variables. When the partial correlation was determined for starch and total sugar extracted in 800 mL/L ethanol, the correlation was significant (P<0.05) when unknown fiber ( r = - 0 . 7 6 ) and phosphorus (r =-0.67) were taken into consideration. This suggests that as starch is produced, the sugar content decreases.
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Iwt/vol. 28 (19951 No. 3 Table 4
C o r r e l a t i o n coefficients of the various chemical c o m p o n e n t s of beans" Correlation coefficients PROT h PHOS
PROT PHOS RS80 TS80 RSI0 TSI0 STAR SOPE EEPE TOPE FPEN URON CELL TFIB XFIB AISS SUM
--0.16 0.26 0.58* -0.17 -0.11 -0.32 -0.30 -0.28 -0.35 0.06 -0.12 0.29 -0.12 -0.24 -0.24 0.38
RS80
-0.00 -0.08 0.57* 0.55 0.41 -0.06 0.55* 1/.68"* -0.33 -0.15 0.47 0.15 0.56* -41.19 -0.92*** 1/.11 -4/.03 --0.06 0.33 -0.52 0.110 -41.75"* -0.05 -41.73"* -0.14 0.27 -0.59* -0.13 -0.37
TS80
RS10 TSI()
STAR SOPE
EEPE TOPE FPEN
-0.13 - 0.25 -0.13 - -0.44 0.23 -0.41 -11.16 -0.16 0.96*** -0.42 - 0.16 0.22 11.91"** -0.27 0.89*** -0.44 -0.40 -4).45 0.12 -0.30 0.41 -0.16 -41.23 -0.01 -41.17 0.50 0.05 -0.03 -0.06 0.10 0.17 -0.48 -0.06 -0.22 -0.113 -0.15 -0.44 -0.12 -41.32 0.05 -41.59"-0.27 0.01 -0.27 0.13 -41.39 11.12 -0.64** 11.66"* -0.61" -4).08 -0.39 -0.49 0.37 -0.51
URON CELL TFIB XFIB AISS SUM
--0.45 -4).38 0.00 - 0.74** - -41.11 -0.14 0.13 0.18 -41.24 0.07 0.24 0.35 -41.26 0.20 0.24 -11.50 -41.31 0.01 -41.15 0.50 0.53 -0.15 -0.06 -0.60* 0.31 -0.03
0.76** 0.42 0.22 0.65**
-0.68** - 0.03 11.1/8 0.29 0.15 0.61" - -
" Average within environment correlations. b PROT = protein (N x 6.25): PHOS = phosphorus: RS80 and TS80 = reducing and total sugars, respectively, extracted with 800mL/L ethanol: RSI0 and TSI0 = reducing and total sugars, respectively, extracted with 100mL/L ethanol: STAR = starch: SOPE. EEPE and TOPE = soluble, enzyme-extractable and total pentosans, respectively: FPEN = pentosan associated with fiber: URON = uronide: CELL = cellulose: TFIB = total fiber: XFIB = total fiber (TF1B) less the sum of FPEN, URON and CELL: AISS = alcohol-insoluble solids: SUM = PROT + PHOS + TS80 + TS10 + STAR + TOPE + URON + CELL + XFIB. * ** *** Significant at the 10%, 5% and 1% levels, respectively. Table 5
Partial c o r r e l a t i o n coefficients of the various chemical c o m p o n e n t s of b e a n s Variable"
Correlation
X
Y
Z
Partial u (r,.:)
Simple (r,,)
PROT RS80 RSI0 STAR STAR SOPE SOPE EEPE AISS AISS AISS AISS
SOPE TS80 TS10 PHOS TSS0 EEPE PHOS PHOS STAR TS10 SOPE EEPE
TS10 FPEN EEPE TS80 XFIB RSI0 EEPE SOPE CELL FPEN PROT PROT
-41.71 ** 0.63* -4).85*** 0.79** -0.76** 11.96"** -4).65* 11.65" 0.75** -0.711"* -4/.74"* -41.61 *
-41.30 11.57" -41.13 0.68** -41.44 11.89"** -41.15 11.15 0.66** -41.64"* -41.61* -41.50
" PROT = PROTEIN (N x 6.25): PHOS = Phosphorus: RS80 and TSS0 = reducing and total sugars, repectively, extracted with 800mL/ L ethanol: RS10 and TSI0 = reducing and total sugars, respectively, extracted with 100 mL/L ethanol: STAR = starch: SOPE and EEPE = soluble and enzyme-extractable pentosans, respectively: FPEN = pentosan associated with fiber: URON = uronidc: CELL = cellulose:TFIB = total fiber: XFIB = total fiber (TFIB) less the sum of FPEN, URON and CELL: AISS = alcohol-insoluble solids. h Maximum partial correlation between variables X and E * ** *** = significant at the 10%, 5% and 1% level, respectively.
T h e t o t a l s u g a r e x t r a c t e d w i t h 100 m L / L e t h a n o l correlated highly with both soluble and enzymee x t r a c t a b l e p e n t o s a n s ( r = 0 . 9 6 a n d 0.91, r e s p e c t i v e l y : P<0.01) ( T a b l e 4). T h e s e c o m p o n e n t s m a y a l s o b e p r o d u c e d in b e a n s at a b o u t t h e s a m e t i m e . S o l u b l e pentosan correlated strongly with enzyme-extractable pentosan (r=0.89: P<0.01) since soluble pentosan constitutes about 20% of enzyme-extractable pentosan. Partial correlations between soluble and enzymeextractable pentosans were also high and significant w h e n v a r i a b l e s s u c h as p h o s p h o r u s , r e d u c i n g s u g a r e x t r a c t e d in 100 m L / L e t h a n o l , p e n t o s a n a s s o c i a t e d w i t h fiber, u r o n i d e , c e l l u l o s e , t o t a l f i b e r a n d u n k n o w n
fiber were taken into account. However, the correlation d i s a p p e a r e d w h e n t h e e f f e c t o f t o t a l s u g a r e x t r a c t e d in 100 m L / L e t h a n o l w a s c o n s i d e r e d , r e f l e c t i n g t h e s t r o n g correlations of soluble and enzyme-extractable pentosans with this variable. Soluble pentosan correlated negatively with phosphorus (r=-0.65: P<0.10) when enzyme-extractable pent o s a n w a s c o n s i d e r e d ( T a b l e 5), a l t h o u g h t h e s i m p l e correlation was not significant. Similarly, the simple correlation between enzyme-extractable pentosan and phosphorus was not significant but when soluble pentosan was taken into account, the partial correlation w a s 0.65 ( P < 0 . 1 0 ) . Total pentosan had a strong negative correlation with reducing sugar extracted with 800 mL/L ethanol ( r - - - 0 . 9 2 : P < 0.01 ) ( T a b l e 4), s u g g e s t i n g t h a t as p e n t o s a n is p r o d u c e d in t h e cell, t h e s u g a r c o n t e n t decreases. Uronide was positively correlated with pentosan associated with fiber (r= 0.74:P<0.051 ( T a b l e 4), p o s s i b l y because both are fiber constituents. However, uronide did not strongly correlate with other fiber variables s u c h as c e l l u l o s e a n d t o t a l fiber. Total fiber showed a positive correlation with cellulose (r=0.76: P<0.05) ( T a b l e 4). T o t a l f i b e r a l s o h a d positive correlations, though not significant, with total pentosan, fiber associated with pentosan and uronide, as w a s a n t i c i p a t e d , s i n c e t h e s e v a r i a b l e s a r e c o m p o n e n t s o f t o t a l fiber. T o t a l f i b e r h a d a s t r o n g n e g a t i v e correlation with phosphorus (r=-0.75; P<0.05), sugg e s t i n g t h a t as f i b e r is p r o d u c e d in t h e cell, t h e proportion of phosphorus decreases. The unknown fiber constituents correlated positively with total fiber (r=0.68:P<0.051 since total fiber was u s e d t o c a l c u l a t e u n k n o w n f i b e r ( T a b l e 4). H o w e v e r , none of the other fiber components correlated. The unknown fiber correlated negatively with phosphorus
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(r = -0.73; P < 0.05) and total sugar extracted in 800 mL/ L ethanol (r=-0.59; P<0.10), probably because of the strong correlation of unknown fiber with total fiber. Alcohol-insoluble solids correlated positively with starch (r = 0.66; P < 0.05) (Table 4), and the correlation was similar when cellulose (Table 5), phosphorus, total pentosan, pentosan associated with fiber, total fiber and unknown fiber were held constant. Alcohol-insoluble solids correlated negatively with reducing sugar extracted in 800 mL/L ethanol (r=-0.59; P < 0.10), total sugar extracted in 100 mL/L ethanol (r=-0.64; P<0.05), and soluble pentosan r =-0.61: P<0.10) (Table 4). The partial correlations of alcohol-insoluble solids with total sugar extracted in ethanol (100 mL/L) were similar when other variables were considered, and largest when pentosan associated with fiber was held constant (Table 5). The partial correlations of alcohol-insoluble solids with soluble pentosan were also similar when other variables were considered, and the largest when protein was held constant (r =-0.74; P < 0.05). The correlation between alcohol-insoluble solids and enzyme-extractable pentosan was not significant but was significant when protein or pentosan associated with fiber was held constant (P<0.10; Table 5). Sugars and soluble and enzyme-extractable pentosans, which correlate negatively with alcohol-insoluble solids, are removed during the preparation of alcohol-insoluble solids. The components starch and total pentosan, correlated positively with alcohol-insoluble solids, of which they are constituents. However, other components, such as uronide, cellulose and total fiber, which we expected to be positively associated with alcoholinsoluble solids, showed no significant correlations, possibly due to the limited number of samples. The correlations with the sum of the recovered constituents indicate which constituents contribute to recovery. The components correlating positively with the sum were cellulose (r = 0.65: P < 0.05) and alcoholinsoluble solids (r=0.61; P<0.10) (Table 4). A significant negative correlation was found between the sum and enzyme-extractable pentosan (r=-0.60; P < 0.10). Generally, we expected larger components to contribute most to the recovery and, consequently, the correlation. This proved true for alcohol-insoluble solids but not for starch and protein. We examined many components of beans but in a relatively small number of samples. Comparable data on navy and small white beans has been compiled for protein and neutral detergent fiber (18). The levels for protein (194 to 220 g/kg) are similar to our study (233 to 271 g/kg) while the levels for neutral detergent fiber (98 to 104 g/kg) are lower than our levels for total fiber (168 to 194 g/kg).
Conclusions Bean samples grown in Ontario tended to be higher in starch and lower in protein and phosphorus than those grown in Alberta probably because the longer growing
season in Ontario results in more starch production. The amounts of total sugars extracted by 800 and 100 mL/L ethanol were different for the Ontario samples than those from Alberta. The only fiber components that appeared to be affected by environment were soluble and enzyme-extractable pentosans which tended to be lower in the Ontario bean samples. Differences in soluble and enzyme-extractable pentosan may affect canning quality. In soft white wheat flour, pentosans correlated negatively with cake-baking quality probably by increasing the viscosity of the batter (19). In a similar manner, soluble and enzymeextractable pentosans may increase the viscosity of canned beans, resulting in matting. Statistical comparisons of the various chemical components detected correlations among some of them. As anticipated, starch and total pentosan, constituents of alcohol-insoluble solids, correlated positively with alcohol-insoluble solids. Components such as reducing sugars extracted in 800 mL/L ethanol, total sugars extracted in 100 mL/L ethanol, and soluble and enzyme-extractable pentosans, which are lost in the preparation of alcohol-insoluble solids, correlated negatively with it. The decrease in total sugars extracted in 800 mL/L ethanol as starch increased was expected as glucose is the precursor of starch. Total sugars extracted in 100 mL/L ethanol correlated positively with soluble and enzyme-extractable pentosans suggesting that these components may be synthesized at about the same time. The influence of chemical composition on canning quality is not obvious and may be complex. Apparently, during canning of Alberta beans, some component, probably carbohydrate, is broken down or released because of the severe thermal treatment, and is then involved in matting. Further work with processed beans is required to determine the chemical component involved.
Acknowledgements We thank R.G. Gaudiel from the Alberta Special Crops and Horticultural Research Center in Brooks, Alberta, and S.J. Park from the Agriculture and Agri-Food Canada Research Centre in Harrow, Ontario, for providing the bean samples. The assistance of B.J. Nishiyama with the statistical analysis is appreciated.
References 1 KALDY, M. S. Matting characteristics
of small white (navy) beans. Journal of Food Quality, 9, 161-165 (1986) 2 AACC. Approved Methods of the AACC. Method 44-15A. St. Paul, MN: The American Association of Cereal Chemists (1983) 3 TECHNICON INDUSTRIAL SYSTEMS. I n d i v i d u a l / s i m u l t a n e o u s
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determination of nitrogen and/or phosphorus in BD acids digests. Technicon AutoAnalyzer II. Industrial Method No. 334-74 W/B. Tarrytown, NY: Technicon Inc. (1973)
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4 HENRY, R.J. A comparison of the non-starch carbohydrates in cereal grains. Journal of the Science of Food and Agriculture, 36, 1243-1253 (1985) 5 BLAKENEY,A. B. AND Mu'rrON, L. L. A simple colorimetric method for the determination of sugars in fruit and vegetables. Journal of the Science of Food and Agriculture, 31, 889-897 (1980) 6 DUBOlS, M., GILLES, K.A., HAMILTON, K., REBERS, P.A. AND SMITH, E Colorimetric method for determination of sugars and related substances. Analytical Chemistry, 28, 350-356 (1956) 7 RASMUSSEN,T. S. AND HENRY, R. J. Starch determination in horticultural plant material by an enzymic-colorimetric procedure. Journal of the Science of Food and Agriculture, 52, 159-170 (1990) 8 HASHIMOTO~ S., SHOGREN, M.D. AND POMERANZ, Y. Cereal pentosans: their estimation and significance. I. Pentosans in wheat and milled wheat products. Cereal Chemistry, 64, 30-34 (1987) 9 KUNERTH, W. H. AND YOUNGS, V. L. Modifications of the anthrone, carbazole, and orcinol reactions for quantitation of monosaccharides. Cereal Chemistry, 61, 344-349 (1984) 10 FAULKS, R.M. AND TIMMS, S.B. A rapid method for the determining the carbohydrate content of dietary fibre. Food Chemistry, 17, 273-287 (1985) 11 SCOTt, R.W. Colorimetric determination of hexuronic
acids in plant materials. Analytical Chemistry, 51, 936-941 (1979) 12 AOAC. Official Methods of Analysis of the Association of Official Analytical Chemists. No. 32.012 Washington, DC: Association of Official Agricultural Chemists (1980) 13 KERTESZ, Z. I. The chemical determination of the quality of canned green peas. New York State Agriculture Experimental Station Bulletin, No. 233 (1935) 14 STEEL, R. G. D. AND TORRm, J.H. Principles and Procedures of Statistics, 2nd Edn. New York: McGraw-Hill (1980) 15 DRAPER, N. R. AND SMITH, H. Applied Regression Analysis, 2nd Edn. New York: John Wiley and Sons (1981) 16 SAS INSTITUTE. SAS/STAT User's Guide, Version 6, 4th Edn. Cary, NC: SAS Institute, Inc. (1989) 17 SAS INSTITUTE. SAS Procedures Guide, Version 6, 3rd Edn. Cary, NC: SAS Institute, Inc. (1990) 18 AUOUSTIN, J. AND KLEIN, B.E Nutrient composition of raw, cooked, canned, and sprouted legumes. In: MATTHEWS, R.H. (Ed.), In: Legumes Chemistry, Technology and Human Nutrition. New York: Marcel Dekker, Inc. (1989) 19 KALDY, M.S., RUBENTHALER, G.I., KERELIUK, G.R., BERHOW, M. A. AND VANDERCOOK, C. E. Relationships of selected flour constituents to baking quality in soft white wheat. Cereal Chemistry, 68, 508-572 (1991)
278
Chemical Composition of Small White (Navy) Beans* G.R. Kereliuk* and G.C. Kozub
Agriculture and Agri-Food Canada, Research Centre, RO. Box 3000 - Main, Lethbridge, Alberta, T1J 4Bl(Canada) (Received August 22, 1994; accepted October 17, 1994)
The chemical composition of small white (navy) beans grown in Ontario and at two locations in Alberta was compared to see (f chemical composition was influenced by environment. The Ontario-grown beans had more starch and less protein than beans grown in Alberta. Of the fiber components, only enzyme-extractable pentosan was higher in beans from Alberta compared to beans from Ontario. Most Other chemical components had similar levels in both environments. Simple and partial correlations revealed the relationships among a number of the chemical components. However, the effect of chemical composition on maturity was not obvious and may be complex.
Introduction Dry Beans (Phaseolus vulgaris L.) are an important food source for many human populations. In North America, beans canned in thick tomato sauce, called 'beans with pork' are popular. Previous work showed differences among small white (navy) beans grown in Alberta and those grown in Ontario (1). After processing, Alberta beans had a greater tendency to mat in the can and a lower alcoholinsoluble solids content, making them less desirable than Ontario beans for commercial canning. The longer growing season in Ontario was considered to be a factor resulting in more physiological maturity in Ontario beans compared to those from Alberta (1). This study was conducted to determine which chemical components of small white beans are associated with the regional differences in quality. The nature of the associations among the components was also studied to identify their influence on quality and maturity.
Materials and Methods
Crops and Horticultural Research Center in Brooks, Alberta. Dry bean samples were ground through a 0.5 mm screen and moisture determined at 130°C (2) in order to calculate the results on a dry weight basis. All analyses were done in triplicate.
Protein and phosphorus
The protein (N × 6.25) and the phosphorus content were determined from a single sample digest by an automated colorimetric procedure (3).
Sugars
Sugars were determined after extraction with 800 mL/L ethanol (4). Reducing sugar was determined colorimetrically using p-hydroxybenzoic acid hydrazide (5) and total sugar using phenol/sulfuric acid (6). After extraction with 800 mL/L ethanol, the residue was extracted with 100 mL/L ethanol, to extract higher molecular weight sugars. Reducing and total sugars in this extract were determined as for the 800 mL/L ethanol extraction.
Materials and handling
Samples of four bean cultivars, Northland, Pulsar, Sanilac and Seaforth, grown in 1985 under normal field conditions were obtained from the Agriculture and Agri-Food Canada Research Centre, Harrow, Ontario. Samples of these cultivars grown under irrigation in 1985, and of Northland, Pulsar, Aurora and Seafarer grown in 1986 were obtained from the Alberta Special *LRC Contribution No. 3879463 tTo whom correspondence should be addressed
Starch
Starch was determined by a modification of the method of Rasmussen and Henry (7). G r o u n d bean samples (50 mg) were weighed into 16 x 125 mm culture tubes. The sugars were removed by adding 10 mL of 800 mL/L ethanol, heating at 80°C for 10 min, cooling to room temperature, centrifuging for 15 min at 1200 x g and discarding the supernatant. The procedure was
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repeated at room temperature with stirring for 20 min. The residues were air-dried at room temperature, 0.5 mL of dimethyl sulfoxide was added to each tube, and the samples stirred and heated at 100°C for 10 min. Tris maleate buffer, 4.5 mL, 0.01 mol/L, pH 6.7 in calcium chloride, 2.5 mmol/L was then added with stirring. The temperature was reduced to 80°C, and 20 ~tL of heat stable a-amylase, Termamyl 120L, (Novo Industrials A/S, Lachine, PQ), diluted 25 times, was added and the temperature maintained at 80°C for 30 min. After cooling to room temperature, 5 mL of sodium acetate buffer, 0.2 mol/L, pH 4.5 and 50 IxL of amyloglucosidase, 5 mg/mL in water (6 U/mg lyophilisate, Boehringer Mannheim, Laval, PQ) were added and held overnight (18 h) at 60°C. The samples were then cooled to room temperature and centrifuged for 15 min at 1200 x g. The supernatants were collected and analysed for glucose using glucose oxidase and the amount of starch calculated.
Pentosans
1000 x g for 15 min and the supernatants removed by aspiration. The residues were air-dried, if necessary overnight. After the addition of 0.7 mL sulfuric acid, 12 moi/L, the samples were kept at 35°C for 1 h. Then 7.3 mL of water was added, and the tubes heated and stirred at 100°C for 2 h. An aliquot (3 mL) was taken from each sample after 1 h for uronide analysis. The remaining hydrolysate was saved for total fiber, pentosan and cellulose analysis. Total uronide was determined using the method of Scott (11). Total fiber was determined using phenol/ sulfuric acid (6). Cellulose was determined by glucose analysis using glucose oxidase (7). Pentosan associated with fiber was determined using orcinol (9). To determine if any other fiber components were present, the sum of uronide, pentosan and cellulose was subtracted from total fiber and the difference called unknown fiber.
Alcohol-insoluble solids
Soluble, enzyme-extractable and total pentosans were determined as described by Hashimoto et al. (8), except that enzyme-extractable pentosan was extracted for 24 h with cellulase, Type V (Sigma Chemical Co, St. Louis, MO). Also, residual glucose was removed from the hydrolysed soluble and enzyme-extractable pentosans using 1 mg of glucose oxidase to 20 mL of neutralized hydrolysate and incubating at 37°C for 2 h. The colorimetric analysis of pentosan was based on the difference in absorbance between 670 and 600 nm
(9).
The procedure for alcohol-insoluble solids (12,13) was adapted for dry ground sample as follows. Ground bean samples (0.5 g) were weighed into 125-mL erlenmeyer flasks, 60 mL of 800 mL/L ethanol added and heated to near boiling for 30 min. After cooling, the samples were vacuum filtered through dried, weighed Whatman No. 3, 7 cm filter paper. The residue on the filter paper was washed twice with 20 mL of hot 800 mL/L ethanol, twice with 10 mL of cold absolute ethanol, and dried overnight (18 h) at 95°C, then placed in a desiccator for 0.5 h to cool, and weighed.
Fiber
Total fiber and its constituents, pentosan, uronide (pectic substances) and cellulose were determined as described by Faulks and Timms (10) with modifications. Ground samples (100 mg) were weighed into 16 × 125 mm culture tubes, 3.3 mL of Tris maleate buffer, 0.1 mol/L, pH 6.7 containing calcium chloride, 2.5 mmol/L added and heated with stirring at 100°C for 10 min. Seventy ~tL of Termamyl 120L (Novo Industrials A/S, Lachine, PQ), diluted 25 times, was added and heating continued for 15 min at 100°C. After cooling to room temperature, 13.3 mL of ethanol (950 mL/L) was added. The samples were cooled at 0°C for 30 min, centrifuged at 1000 x g for 15 min, and the supernatants were removed by aspiration. The residues were suspended in 0.7 mL of dimethyl sulfoxide by vortexing, and heated with stirring at 100°C for 5 min. Upon cooling to room temperature, 2.7 mL of acetate buffer, 0.1 mol/L, pH 4.6 and 60 ~tL of amyloglucosidase, 12 mg/mL in water (6 U/mg lyophilisate, Boehringer Mannheim, Laval, PQ) were added. After 35 min at 37°C with vortexing every 10 min, the incubation was ended by adding 13.0 mL of 950 mL/L ethanol and cooling at 0°C for 30 min. The tubes were centrifuged at
Statistical methods
Analyses of variance (14) were carried out on the data for each chemical component. The statistical model included effects of environment and cultivar, with the environment - cultivar interaction being used to estimate error variance. Cultivar and error variations were pooled when their mean squares were of similar magnitude to increase the precision for comparing the environments. A contrast was included in the analysis to compare the means of the samples from Alberta with those from Ontario. Simple correlations were calculated between all pairs of chemical components after effects due to environment were taken into account (15). However, the effect of chemical composition on quality and maturity may not be evident from simple correlations alone. To determine whether other intercorrelated variables were affecting the magnitudes of the simple correlations, partial correlations were also determined (14) to provide further insight into the relationships between chemical composition and quality. The GLM and CORR procedures of SAS (16,17) were used to perform the statistical analyses.
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Table 1 Selected nutrient components of small white (navy) beans (g/kg of dry weight) Component h Sample ° Ontario 1985 1 2 3 4 Alberta 1985 5 6 7 8 Alberta 1986 9 10 11 12 Grand Mean
PROT
PH OS
RS80
TS80
RS 10
TS 10
STAR
234 245 248 233
5.26 4.07 5.16 5.69
1.5 1.6 1.4 1.3
73.9 73.4 76.3 71.3
1.4 1.0 1.0 1.1
24.1 22.4 25.0 24.1
387 378 376 404
254 242 265 247
5.75 5.96 6.43 6.48
1.3 1.7 2.5 2.1
76.1 80.0 85.0 77.7
0.5 0.9 1.1 1.0
21.0 21.8 22.4 21.8
367 358 363 371
265 271 264 266
6.88 7.10 6.41 7.09
1.6 1.6 2.3 1.8
73.0 80.1 77.9 74.8
1.2 1.0 0.9 1.3
23.9 22.7 28.9 23.3
349 352 337 353
253
6.02
1.7
76.6
1.0
23.5
366
a T h e samples are Northland (1, 5, 9), Pulsar (2, 6, 10), Sanilac (3, 7), Seaforth (4, 8), Aurora (11) and Seafarer (12). b P R O T = protein (N × 6.25); PHOS = phosphorus; RS80 and TS80 = reducing and total sugars, respectively, extracted with 800mL/L ethanol; RS10 and TS10 = reducing and total sugars, respectively, extracted with 100mL/L ethanol; S T A R = starch.
Table 2
S t r u c t u r a l c a r b o h y d r a t e s a n d a l c o h o l - i n s o l u b l e s o l i d s in s m a l l w h i t e ( n a v y ) b e a n s ( g / k g o f d r y w e i g h t ) Component b
Sample a
SOPE
EEPE
TOPE
FPEN
URON
CELL
TFIB
XFIB
AISS
SUM
5.4 3.9 5.3 4.9
29.6 21.0 27.3 26.1
111 108 108 109
84.1 88.1 88.9 87.1
24.2 25.7 23.1 24.7
32.6 34.8 30.9 30.6
181 194 174 174
39.9 45.0 30.8 31.1
852 838 823 854
931 937 923 933
Ontario 1985 1 2 3 4 Alberta 1985 5 6 7 8 Alberta 1986 9 10 11 12
4.6 5.7 4.9 5.3
27.3 30.5 31.8 31.3
115 113 99 102
83.1 88.3 84.4 88.6
20.5 24.3 22.8 23.0
35.1 31.8 33.3 33.5
180 178 168 181
41.2 33.4 27.7 35.7
882 870 868 867
936 910 924 917
7.3 6.8 11.8 7.3
34.6 29.8 42.8 33.6
104 106 98 103
86.4 96.9 89.4 90.0
19.9 25.0 23.4 22.5
28.9 31.5 30.0 25.0
174 179 180 168
38.4 26.0 37.1 30.8
862 860 826 841
909 921 903 904
Grand Mean
6.1
30.5
106
87.9
23.3
31.5
177
34.8
854
921
See Table 1 for the description of the samples. b SOPE, E E P E and T O P E = soluble, enzyme-extractable and total pentosans, respectively; FPEN = pentosan associated with fiber; U R O N = uronide; C E L L = cellulose; TFIB = total fiber; XFIB = total fiber (TFIB) less the sum of FPEN, U R O N and CELL: AISS = alcoholinsoluble solids: S U M = s u m of P R O T + PHOS + TS80 + TS10 + STAR, all from Table 1 and T O P E + U R O N + C E L L + XFIB.
Results and Discussion The main nutritional components in the beans were starch (337 to 404 g/kg) and protein 233 to 271 g/kg (Table 1). The total fiber content was (168 to 194 g/kg), consisting of total pentosan predominantly (98 to 115 g/kg), cellulose (25.0 to 35.1 g/kg) and uronides or pectic substances (19.9 to 25.7 g/kg) (Table 2). There were no significant differences among the cultivars Northland, Pulsar, Sanilac and Seaforth for any of the nutrient or fiber components. However, environmental effects were evident (Table 3). The mean protein and phosphorus contents of Ontario beans (240 g/kg and 5.05 g/kg, respectively) were lower (P < 0.01) than those of the Alberta beans (260 and 6.58 g/kg, respectively) (Table 3). Total sugars extracted by 800 mL/L ethanol were also lower (P < 0.01) in Ontario
(73.7 g/kg) than in Alberta beans (78.2 g/kg). However, reducing sugars extracted in 800 mL/L ethanol were not significantly different for the environments. The sugars extracted in 800 mL/L ethanol had a very low reducing power, slightly more than 2%, suggesting a small nonreducing sugar, probably sucrose. Reducing sugars extracted in 100 mL/L ethanol were small and not different between environments (Table 3). Total sugars extracted in 100 mL/L ethanol were higher (P < 0.10) for the Ontario beans (23.9 g/kg) than in Alberta beans (22.6 g/kg). The reducing power of the sugars extracted in 100 mL/L ethanol was small, around 4%, suggesting large oligosaccharides. The mean starch content was significantly higher (P<0.01) in Ontario beans (386 g/kg) than Alberta beans (358 g/kg) (Table 3). Alberta beans had similar starch levels in both 1985 and 1986.
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Table 3
The effect of environment on the chemical components in small white (navy) beans (g/kg of dry weight) Environment Variable"
PROT PHOS RS80 TS80 RS10 TS10 STAR SOPE EEPE TOPE FPEN URON CELL TFIB XFIB AISS SUM
O n t a r i o 1985
A l b e r t a 1985
A l b e r t a 1986
.~
Sx
.~
Sx
.~
240 b 5.05b 1.5 a 73.7 b 1.1 a 23.9 a 386 a 4.9 b 26.0 b 109 a 87.1 a 24.4 a 32.2 a 180 a 36.7 a 842 b 931 a
4h 0.26 0.2 1.7 0.1 0.4 5 0.3 1.5 3 1.8 0.9 0.8 4 3.4 5 5
252 a b 6.16 a 1.9 a 79.7 a 0.9 a 21.8 b 365 b 5.1 b 30.2ab 107 a 86.1 a 22.7 a 33.4 a 177 a 34.5 a 872 a 922a
4 0.26 0.2 1.7 0.1 0.4 5 0.3 1.5 3 1.8 0.9 0.8 4 3.4 5 5
268 a 6.99a 1.6 a 76.6ab 1.1 a 23.3ab 351 b 7.1 a 32.2 a 105 a 91.7 a 22.5 a 30.2 a 177 a 32.2 a 861 ab 915a
Sx
6 0.36 0.3 2.4 0.2 0.6 6 0.4 2.1 4 2.6 1.3 1.2 5 4.8 7 6
u P R O T = p r o t e i n (N x 6.25); P H O S = p h o s p h o r u s ; RS80 and TS80 = r e d u c i n g and total sugars, respectively, e x t r a c t e d with 8 0 0 m L / L e t h a n o l ; R S I 0 and T S I 0 = r e d u c i n g a n d total sugars, r e s p e c t i v e l y e x t r a c t e d with 100mL/L e t h a n o l ; S T A R = starch; S O P E , E E P E and T O P E = soluble, e n z y m e - e x t r a c t a b l e and total p e n t o s a n s , respectively; F P E N = p e n t o s a n a s s o c i a t e d with fiber; U R O N = u r o n i d e ; C E L L = cellulose: T F I B = total fiber; X F I B = total fiber ( T F I B ) less the s u m of F P E N , U R O N and C E L L ; A I S S = a l c o h o l - i n s o l u b l e solids; S U M = P R O T + P H O S + TS80 + TS10 + S T A R + T O P E + U R O N + C E L L + XFIB. b M e a n (,~') e S t a n d a r d E r r o r (sx) (7df.) using cultivars N o r t h l a n d . Pulsar, Sanilac 1985 a n d A l b e r t a 1985, and the cultivars A l b e r t a 1986. M e a n s f o l l o w e d by the s a m e significantly d i f f e r e n t ( P > 0.05).
from a n a l y s i s of v a r i a n c e and S e a f o r t h for O n t a r i o N o r t h l a n d and P u l s a r for l e t t e r within rows are not
In general, as the starch content increased, protein, phosphorus and total sugars soluble in 800 mL/L ethanol decreased, suggesting that with maturity, starch content increased. As a result, the proportions of protein, phosphorus and total sugars soluble in 800 mL/ L ethanol were smaller. The mean soluble pentosan content for the Ontario beans (4.9 g/kg) was the lowest (Table 3). However, the means were significantly different between the two Alberta years (5.1 and 7.1 g/kg), despite similar levels of other chemical constituents (Tables 1 and 2). The mean enzyme-extractable pentosan content was significantly lower for Ontario (26 g/kg) than Alberta beans grown in 1986 (31.2 g/kg) but not 1985 (30.2 g/kg) (Table 3). However, Alberta beans were not significantly different from each other. The total pentosan content was not significantly different for the two environments (Table 3). The values for pentosan associated with fiber were lower than those for total pentosan. Possibly, some pentosan is lost in the extraction of fiber resulting in smaller than expected values for fiber-associated pentosan. The means for pentosan associated with fiber, uronide, cellulose, total fiber and unknown fiber were not significantly affected by environments. Since pentosan is partially water soluble, it may have an effect of the viscosity of canned beans.
The mean for alcohol-insoluble solids for the Ontario beans (842 g/kg) was significantly lower than that for the Alberta beans grown in 1985 (872 g/kg) but not in 1986 (861 g/kg) (Table 3). The means for the Alberta samples were not significantly different. This was in contrast to a previous report that alcohol-insoluble solids were lower in Alberta beans (721 g/kg) than in Ontario beans (776 g/kg) (1). However, Kaldy (1) used canned beans in which the breakdown of structural components during the severe thermal treatment of processing may have differed for beans from the two environments. The proportions of material in the beans accounted for by the chemical analyses were similar, indicating that the analyses were consistent. Correlations among the variables following the removal of the variation due to growing environment are presented in Table 4. Correlations that are significant at the 10% level were identified to show relationships which may be present and are not significant at a lower level because of the limited number of samples. Partial correlations are given in Table 5 to demonstrate associations that may be obscured because of interactions among variables. For selected pairs of variables, the largest correlation when a third variable is held constant is given. Protein was positively correlated with total sugar extracted in 800 mL/L ethanol (r = 0.58; P < 0.10) (Table 4), suggesting these two components may be synthesized at about the same time. The partial correlation of protein with soluble pentosan was -0.71 (P<0.05) when total sugar extracted in 100 mL/L ethanol was held constant (Table 5). Protein was not correlated with starch. Total sugar extracted with 800 mL/L ethanol was positively correlated with similarly extracted reducing sugar (r=0.57; P<0.10) (Table 4), and the partial correlation was similar when pentosan associated with fiber (r= 0.63) was held constant (Table 5). The simple correlation of reducing and total sugar extracted with 100 mL/L ethanol was not significant (Table 4). However, the partial correlation was -0.85 (P < 0.01) when enzyme-extractable pentosan was considered (Table 5). Enzyme-extractable pentosan strongly influences the reducing and total sugars extracted in 100 mL/L ethanol, indicating that they all may be produced at around the same time. A significant (P<0.05) simple correlation between starch and phosphorus was evident (r = 0.68) (Table 4). When partial correlations were calculated using the other variables, a significant positive association between starch and phosphorus was still evident (Table 5). This indicates that the correlation between starch and phosphorus was not influenced by other variables. When the partial correlation was determined for starch and total sugar extracted in 800 mL/L ethanol, the correlation was significant (P<0.05) when unknown fiber ( r = - 0 . 7 6 ) and phosphorus (r =-0.67) were taken into consideration. This suggests that as starch is produced, the sugar content decreases.
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Iwt/vol. 28 (19951 No. 3 Table 4
C o r r e l a t i o n coefficients of the various chemical c o m p o n e n t s of beans" Correlation coefficients PROT h PHOS
PROT PHOS RS80 TS80 RSI0 TSI0 STAR SOPE EEPE TOPE FPEN URON CELL TFIB XFIB AISS SUM
--0.16 0.26 0.58* -0.17 -0.11 -0.32 -0.30 -0.28 -0.35 0.06 -0.12 0.29 -0.12 -0.24 -0.24 0.38
RS80
-0.00 -0.08 0.57* 0.55 0.41 -0.06 0.55* 1/.68"* -0.33 -0.15 0.47 0.15 0.56* -41.19 -0.92*** 1/.11 -4/.03 --0.06 0.33 -0.52 0.110 -41.75"* -0.05 -41.73"* -0.14 0.27 -0.59* -0.13 -0.37
TS80
RS10 TSI()
STAR SOPE
EEPE TOPE FPEN
-0.13 - 0.25 -0.13 - -0.44 0.23 -0.41 -11.16 -0.16 0.96*** -0.42 - 0.16 0.22 11.91"** -0.27 0.89*** -0.44 -0.40 -4).45 0.12 -0.30 0.41 -0.16 -41.23 -0.01 -41.17 0.50 0.05 -0.03 -0.06 0.10 0.17 -0.48 -0.06 -0.22 -0.113 -0.15 -0.44 -0.12 -41.32 0.05 -41.59"-0.27 0.01 -0.27 0.13 -41.39 11.12 -0.64** 11.66"* -0.61" -4).08 -0.39 -0.49 0.37 -0.51
URON CELL TFIB XFIB AISS SUM
--0.45 -4).38 0.00 - 0.74** - -41.11 -0.14 0.13 0.18 -41.24 0.07 0.24 0.35 -41.26 0.20 0.24 -11.50 -41.31 0.01 -41.15 0.50 0.53 -0.15 -0.06 -0.60* 0.31 -0.03
0.76** 0.42 0.22 0.65**
-0.68** - 0.03 11.1/8 0.29 0.15 0.61" - -
" Average within environment correlations. b PROT = protein (N x 6.25): PHOS = phosphorus: RS80 and TS80 = reducing and total sugars, respectively, extracted with 800mL/L ethanol: RSI0 and TSI0 = reducing and total sugars, respectively, extracted with 100mL/L ethanol: STAR = starch: SOPE. EEPE and TOPE = soluble, enzyme-extractable and total pentosans, respectively: FPEN = pentosan associated with fiber: URON = uronide: CELL = cellulose: TFIB = total fiber: XFIB = total fiber (TF1B) less the sum of FPEN, URON and CELL: AISS = alcohol-insoluble solids: SUM = PROT + PHOS + TS80 + TS10 + STAR + TOPE + URON + CELL + XFIB. * ** *** Significant at the 10%, 5% and 1% levels, respectively. Table 5
Partial c o r r e l a t i o n coefficients of the various chemical c o m p o n e n t s of b e a n s Variable"
Correlation
X
Y
Z
Partial u (r,.:)
Simple (r,,)
PROT RS80 RSI0 STAR STAR SOPE SOPE EEPE AISS AISS AISS AISS
SOPE TS80 TS10 PHOS TSS0 EEPE PHOS PHOS STAR TS10 SOPE EEPE
TS10 FPEN EEPE TS80 XFIB RSI0 EEPE SOPE CELL FPEN PROT PROT
-41.71 ** 0.63* -4).85*** 0.79** -0.76** 11.96"** -4).65* 11.65" 0.75** -0.711"* -4/.74"* -41.61 *
-41.30 11.57" -41.13 0.68** -41.44 11.89"** -41.15 11.15 0.66** -41.64"* -41.61* -41.50
" PROT = PROTEIN (N x 6.25): PHOS = Phosphorus: RS80 and TSS0 = reducing and total sugars, repectively, extracted with 800mL/ L ethanol: RS10 and TSI0 = reducing and total sugars, respectively, extracted with 100 mL/L ethanol: STAR = starch: SOPE and EEPE = soluble and enzyme-extractable pentosans, respectively: FPEN = pentosan associated with fiber: URON = uronidc: CELL = cellulose:TFIB = total fiber: XFIB = total fiber (TFIB) less the sum of FPEN, URON and CELL: AISS = alcohol-insoluble solids. h Maximum partial correlation between variables X and E * ** *** = significant at the 10%, 5% and 1% level, respectively.
T h e t o t a l s u g a r e x t r a c t e d w i t h 100 m L / L e t h a n o l correlated highly with both soluble and enzymee x t r a c t a b l e p e n t o s a n s ( r = 0 . 9 6 a n d 0.91, r e s p e c t i v e l y : P<0.01) ( T a b l e 4). T h e s e c o m p o n e n t s m a y a l s o b e p r o d u c e d in b e a n s at a b o u t t h e s a m e t i m e . S o l u b l e pentosan correlated strongly with enzyme-extractable pentosan (r=0.89: P<0.01) since soluble pentosan constitutes about 20% of enzyme-extractable pentosan. Partial correlations between soluble and enzymeextractable pentosans were also high and significant w h e n v a r i a b l e s s u c h as p h o s p h o r u s , r e d u c i n g s u g a r e x t r a c t e d in 100 m L / L e t h a n o l , p e n t o s a n a s s o c i a t e d w i t h fiber, u r o n i d e , c e l l u l o s e , t o t a l f i b e r a n d u n k n o w n
fiber were taken into account. However, the correlation d i s a p p e a r e d w h e n t h e e f f e c t o f t o t a l s u g a r e x t r a c t e d in 100 m L / L e t h a n o l w a s c o n s i d e r e d , r e f l e c t i n g t h e s t r o n g correlations of soluble and enzyme-extractable pentosans with this variable. Soluble pentosan correlated negatively with phosphorus (r=-0.65: P<0.10) when enzyme-extractable pent o s a n w a s c o n s i d e r e d ( T a b l e 5), a l t h o u g h t h e s i m p l e correlation was not significant. Similarly, the simple correlation between enzyme-extractable pentosan and phosphorus was not significant but when soluble pentosan was taken into account, the partial correlation w a s 0.65 ( P < 0 . 1 0 ) . Total pentosan had a strong negative correlation with reducing sugar extracted with 800 mL/L ethanol ( r - - - 0 . 9 2 : P < 0.01 ) ( T a b l e 4), s u g g e s t i n g t h a t as p e n t o s a n is p r o d u c e d in t h e cell, t h e s u g a r c o n t e n t decreases. Uronide was positively correlated with pentosan associated with fiber (r= 0.74:P<0.051 ( T a b l e 4), p o s s i b l y because both are fiber constituents. However, uronide did not strongly correlate with other fiber variables s u c h as c e l l u l o s e a n d t o t a l fiber. Total fiber showed a positive correlation with cellulose (r=0.76: P<0.05) ( T a b l e 4). T o t a l f i b e r a l s o h a d positive correlations, though not significant, with total pentosan, fiber associated with pentosan and uronide, as w a s a n t i c i p a t e d , s i n c e t h e s e v a r i a b l e s a r e c o m p o n e n t s o f t o t a l fiber. T o t a l f i b e r h a d a s t r o n g n e g a t i v e correlation with phosphorus (r=-0.75; P<0.05), sugg e s t i n g t h a t as f i b e r is p r o d u c e d in t h e cell, t h e proportion of phosphorus decreases. The unknown fiber constituents correlated positively with total fiber (r=0.68:P<0.051 since total fiber was u s e d t o c a l c u l a t e u n k n o w n f i b e r ( T a b l e 4). H o w e v e r , none of the other fiber components correlated. The unknown fiber correlated negatively with phosphorus
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(r = -0.73; P < 0.05) and total sugar extracted in 800 mL/ L ethanol (r=-0.59; P<0.10), probably because of the strong correlation of unknown fiber with total fiber. Alcohol-insoluble solids correlated positively with starch (r = 0.66; P < 0.05) (Table 4), and the correlation was similar when cellulose (Table 5), phosphorus, total pentosan, pentosan associated with fiber, total fiber and unknown fiber were held constant. Alcohol-insoluble solids correlated negatively with reducing sugar extracted in 800 mL/L ethanol (r=-0.59; P < 0.10), total sugar extracted in 100 mL/L ethanol (r=-0.64; P<0.05), and soluble pentosan r =-0.61: P<0.10) (Table 4). The partial correlations of alcohol-insoluble solids with total sugar extracted in ethanol (100 mL/L) were similar when other variables were considered, and largest when pentosan associated with fiber was held constant (Table 5). The partial correlations of alcohol-insoluble solids with soluble pentosan were also similar when other variables were considered, and the largest when protein was held constant (r =-0.74; P < 0.05). The correlation between alcohol-insoluble solids and enzyme-extractable pentosan was not significant but was significant when protein or pentosan associated with fiber was held constant (P<0.10; Table 5). Sugars and soluble and enzyme-extractable pentosans, which correlate negatively with alcohol-insoluble solids, are removed during the preparation of alcohol-insoluble solids. The components starch and total pentosan, correlated positively with alcohol-insoluble solids, of which they are constituents. However, other components, such as uronide, cellulose and total fiber, which we expected to be positively associated with alcoholinsoluble solids, showed no significant correlations, possibly due to the limited number of samples. The correlations with the sum of the recovered constituents indicate which constituents contribute to recovery. The components correlating positively with the sum were cellulose (r = 0.65: P < 0.05) and alcoholinsoluble solids (r=0.61; P<0.10) (Table 4). A significant negative correlation was found between the sum and enzyme-extractable pentosan (r=-0.60; P < 0.10). Generally, we expected larger components to contribute most to the recovery and, consequently, the correlation. This proved true for alcohol-insoluble solids but not for starch and protein. We examined many components of beans but in a relatively small number of samples. Comparable data on navy and small white beans has been compiled for protein and neutral detergent fiber (18). The levels for protein (194 to 220 g/kg) are similar to our study (233 to 271 g/kg) while the levels for neutral detergent fiber (98 to 104 g/kg) are lower than our levels for total fiber (168 to 194 g/kg).
Conclusions Bean samples grown in Ontario tended to be higher in starch and lower in protein and phosphorus than those grown in Alberta probably because the longer growing
season in Ontario results in more starch production. The amounts of total sugars extracted by 800 and 100 mL/L ethanol were different for the Ontario samples than those from Alberta. The only fiber components that appeared to be affected by environment were soluble and enzyme-extractable pentosans which tended to be lower in the Ontario bean samples. Differences in soluble and enzyme-extractable pentosan may affect canning quality. In soft white wheat flour, pentosans correlated negatively with cake-baking quality probably by increasing the viscosity of the batter (19). In a similar manner, soluble and enzymeextractable pentosans may increase the viscosity of canned beans, resulting in matting. Statistical comparisons of the various chemical components detected correlations among some of them. As anticipated, starch and total pentosan, constituents of alcohol-insoluble solids, correlated positively with alcohol-insoluble solids. Components such as reducing sugars extracted in 800 mL/L ethanol, total sugars extracted in 100 mL/L ethanol, and soluble and enzyme-extractable pentosans, which are lost in the preparation of alcohol-insoluble solids, correlated negatively with it. The decrease in total sugars extracted in 800 mL/L ethanol as starch increased was expected as glucose is the precursor of starch. Total sugars extracted in 100 mL/L ethanol correlated positively with soluble and enzyme-extractable pentosans suggesting that these components may be synthesized at about the same time. The influence of chemical composition on canning quality is not obvious and may be complex. Apparently, during canning of Alberta beans, some component, probably carbohydrate, is broken down or released because of the severe thermal treatment, and is then involved in matting. Further work with processed beans is required to determine the chemical component involved.
Acknowledgements We thank R.G. Gaudiel from the Alberta Special Crops and Horticultural Research Center in Brooks, Alberta, and S.J. Park from the Agriculture and Agri-Food Canada Research Centre in Harrow, Ontario, for providing the bean samples. The assistance of B.J. Nishiyama with the statistical analysis is appreciated.
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