Animal Feed Science and Technology, 27 (1990) 219-228 219 Elsevier Science Publishers B.V., AmsterdAm - - Printed in The Netherlands

The Nutr i t ive Value of Full-fat and Defatted Austral ian Rice Bran. I. Chemical Composit ion

B.E. WARREN and D.J. FARRELL

Department of Biochemistry, Microbiology and Nutrition, University of New England, Armidale, N.S. W. 2351 (Australia)

(Received 13 January 1988; accepted for publication 6 April 1989)

ABSTRACT

Warren, B.E. and Farrell, D.J., 1990. The nutritive value of full-fat and defatted Australian rice bran. I. Chemical composition. Anita. Feed Sci. Technol., 27: 219-228.

The chemical composition of rice bran from several rice cultivars, grown in Australia in different years, was examined. The quality of the rice bran, irrespective of cultivar or harvest, was reason- ably uniform. Crude protein ranged from 134 to 173 g kg -1 and ether extract from 204 to 234 g kg -1. Mean neutral detergent fibre was 256 g kg -1, acid detergent fibre 122 g kg -~, ash 105 g kg -1 and large particles ( > 1 ram) 80 g kg- 1. Calcium levels were very low ( < 0.4 g kg- 1 ), but phos- phorus was high at > 17 g kg -~. Over half of the phosphorus was in phytate form which was ~33 g kg- ~ of the rice brans examined. The amino-acid profiles showed relatively high concentrations of threonine (5.4-6.4 g kg- 1 ) and a good balance of other essential amino acids.

INTRODUCTION

Australia produces ~ 70 000 tonnes (t) of rice bran annually from a rice crop of ~ 700 000 t. Over 550 000 t is grown in southern New South Wales (N.S.W.) in a Mediterranean climate under irrigation from the one source, with 'Calrose' being the dominant cultivar. The remainder is grown in northern Queensland where two crops of the cultivar 'Starbonnet' are produced each year.

Reported chemical analysis of rice bran varies widely and Houston (1972), in a review of the rice-bran literature published between 1916 and 1970, found crude protein (CP) values of 98-154 g kg -1, lipid 77-224 g kg -1 and ash 71- 206 g kg-1. The wide range for each chemical component is probably caused by adulteration with rice hulls of little nutritive value. In parts of Asia the bran-hull mixture from single-pass mills is often classed as rice bran and in the U.S.A. some hulls may also be included in the bran. However, from Grist's

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220 B.E. WARREN AND D.J. FARRELL

(1965) definitions Australian rice bran consists of bran and polishings and includes embryos, inner and outer (true) bran layers, polish from the starchy endosperm and some broken endosperm, but few hulls. Australian rice bran is sometimes called rice pollard.

The apparent variability in chemical composition of rice bran often makes its efficient use as an animal feed difficult, although in developed countries much of the bran produced is used in feeds for the intensive animal industries. An increasing number of developing countries, as well as some developed coun- tries, are recovering the high-quality oil from the full-fat rice bran (FFRB) (Cornelius, 1980) although the rapid hydrolysis of rice-bran oil into glycerol and free fatty acids (FFA) by the very active rice-bran lipase, and often oxi- dative rancidity due to the presence of endogenous lipoxygenase, limited the recovery of food-grade oil under certain conditions (Barber and Benedito de Barber, 1980 ) and can reduce the feed value of the FFRB (Hussein and Kratzer, 1982 ). It has been shown (Fig. 1 ) that under normal, summer conditions as in Leeton (N.S.W.) ~10% of the oil in FFRB is broken down to FFA after I week, and after ~ 6 weeks, > 50% of the oil has been hydrolysed. However, the peroxide value remained relatively constant ( < 5) until Week 5, but increased rapidly to > 20 at Week 6 (Ricegrowers Co-operative Mills Pry Ltd., Leeton, N.S.W., unpublished data, 1979).

Therefore, the purpose of this work was to examine the chemical composi- tion, and subsequently the nutritional value for non-ruminants, of both full- fat and oil-extracted (defatted) rice bran (DFRB) from several rice cultivars grown in Australia.

4O

"- 3 0 u.

2 0

1 0

I I i 1 2 3 4 5 6

T IME (WEEKS)

3 0 6 0

I sol

2 0

~o

Fig. 1. The percentage of long chain fatty acids (m--m) from rice bran oil as free fatty acids and the peroxide value ( b--& ) of the oil as a function of storage time of full-fat rice bran (Rice- growers Co-operative Mills Ltd., Leeton. N.S.W. ).

NUTRITIVE VALUE OF FULL-FAT AND DEFATTED RICE BRAN. I. 221

MATERIALS AND METHODS

All FFRB samples used in the experimental series were freshly milled and transported rapidly to our laboratory where they were stored in sealed plastic containers at - 20 ° C until use. Time from milling to cold storage was usually less than 72 h. Large samples of DFRB were prepared by batch extraction of fresh FFRB samples with hexane. Small samples were prepared in the labo- ratory using a Soxhlet apparatus. Although containing < 10 g kg-1 residual oil, DFRB was stored at either 4°C for large samples, or - 2 0 ° C for smaller quantities ( < 10 kg).

Determinations of neutral detergent fibre (NDF), acid detergent fibre (ADF), insoluble ash and lignin (van Soest, 1963; van Soest and Wine, 1967 ) and proximate analysis (Association of Official Analytical Chemists, 1980) were performed on samples of rice bran. Nitrogen was determined by micro- Kjeldahl digestion and steam distillation (Ivan et al., 1974). Large particles ( > 1 ram) were separated by fractionation on a 1-mm screen. The fatty-acid profile of the oil extracted from three different rice brans by the method of Folch et al. (1957) was measured on a 1-/d sample by using gas chromato- graphy following esterification with 14% boron trifluoride in methanol.

Amino acids were measured on samples of 'Starbonnet' and 'Pelde' FFRB from the 1984 harvest using high-pressure liquid chromatography with the ap- propriate column (Waters Associates, Sydney, N.S.W. ) and on three replicate samples of 'Calrose' FFRB (1981 harvest) using an amino-acid analyser (Di- onex D-300). Hydrolysis of samples for each system was carried out by the methods of Taverner (1979) and Wallis and Balnave (1983), respectively.

Following acid digestion of samples, minerals were assayed by atomic ab- sorption spectrophotometry, with calcium and iron determined with an acet- ylene-nitrous oxide flame, and magnesium and zinc with an acetylene-air flame (Varian Technical Manual, 1979). Phosphorus was determined by a modified molybdate reaction using an analytical centrifuge (Cobas Bio, F. Hoffman- LaRoche and Co. Ltd., Basle, Switzerland) and a Lancer ® Phosphorus Auto/ Stat Diagnostic Kit. Phytate was determined by a method modified from Har- land and Oberleas (1977) and Ellis and Morris (1983). Gross energy was mea- sured in an adiabatic bomb calorimeter.

Data were examined statistically using analysis of variance techniques (Steel and Torrie, 1980).

RESULTS

Proximate components and particle size of FFRB are given in Table 1. The important differences appear to be in CP and ether extract. These varied both between season and variety. CP varied from 134 g kg-i (,inga,_1983) to 173 g

222

TABLE 1

B.E. WARREN AND D.J. FARRELL

Proximate analysis (g kg- 1) and particle size of full-fat rice brans from different cultivars of rice produced in Australia over two, three or four consecutive harvests

Year Variety Mean SE n 2

'Calrose' 'Inga' Mixed 1

Dry matter 1980 918 "a 933 Ab 920 ~ 926 A 4.6 20 1981 920 915 B 900 B 913 Bc 17.0 4 1982 908 906 Bc 901B 907 B 7.3 12 1983 925" 903 cb 912 ~b 914 c 10.0 9

Mean 914 a 925 b 913" 918 3.1 45 SE 5.3 5.0 3.4 3.1 n 18 17 10 45

Crude protein 1980 156 AB 149 A 154 152 A 9.7 20 (NX6.25) 1981 182 c 177 s 160 175 B 24.8 4

1982 175 Bca 146 Ab 168 ab 169 s 13.4 12 1983 151A 141A 144 146 A 20.0 9

Mean 168 149 154 154 5.5 45 SE 10.8 10.6 13.0 5.5 n 18 17 10 45

Ash 1980 109 109 104 108 2.8 20 1981 112 111 79 102 11.2 4 1982 111 94 78 105 10.0 11

Mean 110 107 95 105 3.8 35 SE 6.4 3.7 11.8 3.8 n 14 15 6 35

Ether extract 1980 218 223 A - 222 5.1 15 1983 234 a 204 Bb 212 b 216 10.6 7

Mean 222 a 221 ~ 212 b 220 4.2 22 SE 8.2 4.8 11.6 4.2 n 6 12 4 22

Particles 1980 77 71A - 73 6.0 10 > 1 mm 1983 62 ~ 98 sb 87 b 84 8.7 8

Mean 72 a 78 ab 875 78 4.8 18 SE 9.8 10.1 15.2 4.8 n 6 8 4 18

~Most of the 1982 and all of the 1983 samples included in the column are from 'Starbonnet ' rice from northern Queensland. The 1980 and 1981 samples were from unidentified southern N.S.W. cultivars. 2Number of observations in mean. 3Values in a column (A-C) or row (a-c) with the same or no superscript do not differ significantly

( P > 0.05).

NUTRITIVE VALUE OF FULL-FAT AND DEFATTED RICE BRAN. I. 223

kg-1 ('Calrose'-1981). The range of ether extract was small (204-234 g kg-1 ). Large particles ( > 1 mm) varied from 62 to 98 g kg- i

Fibrous fractions and acid-insoluble ash of FFRB and DFRB are given in Table 2. Removal of oil generally concentrated fibrous components. In both types of bran hemiceUulose comprised, on average, at least 50% of NDF. The effective mean increase in NDF due to defatting was similar to the fraction

TABLE 2

An analysis of the fibre component (g kg -1 DM) of four rice brans, before (FFRB) and after (DFRB) ether extraction of the bran

Rice cultivar Mean SE

'Calrose' 'Inga' 'Pelde' 'Star '1

NDF FFRB 222 ~ 201 ̂ 220 219 A 215 A 6.0 DFRB 292 ~ 272 Bb 239 ¢ 277 Bb 270 B 3.8

Mean 257 236 229 248 256 3.0

SE 7.4 10.6 10.8 7.7 3.0

ADF FFRB 116 ~ 94 A¢ 105 Ab 112 ~b 107 A 4.5 DFRB 140 s~ 116 Bb 125 Bb¢ 135 Ba¢ 129 B 2.2

Mean 128 105 115 129 122 1.5 SE 2.8 4.4 4.2 3.7 1.4

Lignin FFRB 41 30 29 53 38

DFRB 41 33 33 52 40

Mean

Acid insoluble ash

41 32 31 52 39

FFRB 12.1 ~ 8.3 ̂ b 7.4 b 7.3 b 7.7 A 1.24 DFRB 16.8 Ba 10.6 Bb 8.4 b 8.9 b 13.8 B 0.81

Mean 14.4 a 9.3 b 7.9 b 8.1 b 10.8 0.70

SE 1.21 1.40 1.68 2.41 0.70

Hemicellulose 3 FFRB 106 107 115 107 108

DFRB 152 156 114 142 141

1In this and following tables Star refers to bran from 'Starbonnet ' rice harvested in northern Queensland.

2Values in a column (A-B) or row (a-c) with the same or no superscript do not differ significantly (P>0 .05) . 3Calculated as the difference between NDF and ADF.

224 B.E. WARREN AND D.J. FARRELL

removed by ether extraction (204 vs. 207 g kg-1 ). The fatty-acid composition is given in Table 3. Oleic, linoleic and palmitic acids accounted for over 96% of the oil component.

The mineral content of FFRB is given in Table 4. Calcium varied from 0.27 to 0.51 g kg- 1 DM, and zinc from 44 to 54 mg kg- 1. The phytate content showed considerable variation in DFRB (Table 5 ), but was constant for the two sam- ples of FFRB tested. There was a small range in variety means and a larger

TABLE 3

Representat ive fatty acid ester composit ion (g kg-1 ) of oil extracted from single samples of three rice brans

Bran Year Fat ty acid

Palmitic Palmitoleic Stearic Oleic Linoleic Linolenic Arachidonic 16:0 16:1 18:0 18:1 18:2 18:3 20:0

'Calrose' 1982 158 Trace 14 422 384 19 3 'Calrose' 1983 153 1 14 420 400 13 Trace 'Star ' 1982 165 3 16 429 371 12 4

Mean 159 2 15 424 385 15 4

TABLE 4

Minerals in full-fat rice b ran samples (g kg -1 DM for calcium, phosphorus and magnesium, mg kg -1 DM for zinc and i ron) from three cultivars of rice harvested in different years

Mineral 'Calrose' ' Inga' 'S ta rbonne t ' Mean SE

1980 1981 1982 1981 1982 1983

n 1 4 3 3 4 4 3 21

Calcium 0.43 a2 0.38 b 0.51 c 0.385 0.405 0.27 d 0.39 0.013

Phosphorus nd 3 16.23 18.11 nd 17.07 nd 17.14 0.416 Magnesium 7.71 6.07 6.35 7.61 7.24 6.27 6.88 0.551 Zinc 44.2 a 52.5 ab 50.6 ab 44.3 a5 53.9 b 48.6 ~b 49.0 3.07

Iron 48.1 nd nd 42.5 37.9 nd 42.8 2.42

~Number of samples examined. 2Values in a row with the same (a -c ) or no superscript do not differ significantly ( P > 0.05 ). 3Not determined.

NUTRITIVE VALUE OF FULL-FAT AND DEFA'I'r,~0 RICE BRAN. I. 225

TABLE 5

Phytate content (g kg- I DM) of rice bran from four cultivars of rice, grown in one of two locations, over three years

Variety Year Phytate

Defatted 'Calrose' 1981 30.7AB 1 'Calrose' 1981 24.0 A 'Inga' 1981 30.7 AB 'Calrose' 1982 29.3 As 'Calrose' 1982 27.6 A 'Calrose' 1982 46.0 c 'Calrose' 1983 29.1A 'Starbonnet' 1983 29.3 As 'Pelde' 1983 29.6 ~

Full-fat 'Calrose' 1983 43.7 Bc 'Starbonnet' 1983 42.1Bc

Overall mean 32.9

Variety means 'Calrose' 33.0 'Starbonnet' 35.7 'Inga' 30.7 'Pelde' 29.6

Year means 1981 25.9 1982 36.2 1983 35.3

1Values with the same (A-C) or no superscript do not differ significantly (P > 0.05).

r ange for t he 3 years , a l t hough 'Ca l rose ' va lues for 1982 r anged f r o m 28 to 46 g k g - 1 D M .

T h e ind ispens ib le a m i n o - a c i d prof i le is g iven in Tab l e 6. T r y p t o p h a n a n d cys te ine were no t de t e rmined . Severa l a m i n o acids showed s ign i f ican t differ- ences be tween 'Pe lde ' a n d ' S t a r b o n n e t ' samples . 'Ca l rose ' was no t inc luded in t he s ta t i s t i ca l ana lys i s because a m i n o acids were d e t e r m i n e d wi th a d i f fe ren t ana ly t i ca l sys t em, bu t va lues were s imi l a r to those for 'Pe lde ' a n d ' S t a r b o n n e t ' . Desp i t e t he s l ight ly lower n i t rogen ( N ) c o n t e n t o f ' S t a r b o n n e t ' , e ssen t ia l a m i n o - a c i d c o n c e n t r a t i o n s t e n d e d to be h igher w h e n exp re s sed as g p e r 16.8 g N or g k g - 1 D M .

226 B.E, WARREN AND D.J. FARRELL

T A B L E 6

The indispensible amino-acid content of three full-fat rice brans reported as (A) g amino acid per 16.8 g N and (B) g amino acid kg -1 D M

Amino acid A B

'Pelde' ' S t a rbonne t ' SE 'Calrose '~ SE 'Pelde' 'Starbonnet' SE 'Calrose '2 SE

n 1 4 4 3 4 4 3

Asparticacid 11.4 ~a 12.5 a 0.30 9.9 1.15 15.9 ~ 16.3 a 0.40 14.4 1.74

Threonine 4.0 a 5.1 b 0.30 4.3 0.37 5.4 a 6.4 b 0.42 6.3 0.50

Valine 5.9 a 7.3 b 0.15 7.8 0,59 7.6 ~ 8.8 b 0.19 11.4 0.89

Methionine 1.8 a 3.4 a 0.89 1.6 0.06 2.4 a 4.3 a 1.24 2.4 0.12 Isoleucine 4.3 ~ 5.5 b 0.24 4.6 0.48 5.6 ~ 6.6 b 0.33 6.8 0.73

Leucine 7.3" 8.8 b 0.37 8.0 0.27 10.1 a 11.5 b 0.48 11.7 0.35

Tyrosine 3.7" 4.6 b 0.15 4.0 0.11 5.1 ~ 6.0 b 0.16 5.9 0.20

Phenylalanine 3.6" 4.5 b 0.15 5.2 0.13 5.0 a 5.9 b 0.22 7.6 0.21

Histidine 3.5" 4.7 b 0.37 3.1 0.33 4.8 ~ 6.1 b 0.54 4.6 0.46

Lysine 6.1 a 7.0 ~ 0.30 5.7 0.05 8.5 ~ 9.1" 0.37 8.2 0.08 Arginine 8.9 ~ 12.2 b 0.59 8.5 0.40 12.4 ~ 15.9 b 0.82 12.3 0.64

No. in sample (%) 2.3 2.2 2.5

INumber of samples hydrolysed. 2Analysed separately. 3Values within a row for the two rice brans, 'Pelde' and 'Starbonnet', with different superscripts are signifi- cantly different (P<0.05).

D I S C U S S I O N

The quality of rice bran produced in Australia, irrespective of cultivar or harvest, is reasonably uniform. Content of large particles ( > 1 mm) and ash are indicators of milling standards and variation in these components can in- dicate adulteration, particularly with hulls and broken rice grains (Spadaro et al., 1980). Unpublished data (B. Tangendjaja and J. Diment, 1984) from In- donesia showed that hull inclusion can be up to 300 g kg- 1 of rice bran. How- ever, the maximum ash content of 110 g kg -1 found here (Table 1) is about half the maximum reported by Houston (1972) of 206 g kg -1 and the lowest value found of 78 g kg-1 is almost as low as the minimum reported. As there was also only 80 g kg-1 of large particles in the brans analysed, these values suggest that hull inclusion and broken grains in the brans were very low and milling standards were good. The high ether extract is of good quality, because of its high oleic (420 g kg -1) and linoleic (390 g kg -1) acid contents. This makes FFRB an attractive by-product, and the oil, if extracted from bran soon after milling, a useful human food.

Although CP varied to some extent among rice brans, a mean value of 147 g kg- ~ is within the range reported by Houston (1972). The amino-acid profiles showed higher concentrations of lysine than reported by Houston (1972) and by Barber and Benedito de Barber (1980). An important indispensible amino

NUTRITIVE VALUE OF FULL-FAT AND DE, FATTED RICE BRAN. I. 227

acid is threonine, which is present in reasonably high concentrations (Table 6). Methionine showed quite wide variation, but this smlno acid is difficult to measure accurately. There may be some uncertainty with regard to the avail- ability of amino acids from rice bran. The high NDF and ADF suggest that amino acids may not be highly digestible. The removal of 220 g kg- I oil from rice bran did not always result in a cor-

responding increase in NDF or ADF. For example, NDF in 'Pelde' rice bran increased by only 10 g kg- i, and the mean increase in ADF was only 170 g kg- i for all samples surveyed (Table 2). There is no immediate explanation for these discrepancies, but the presence of starch may have had an influence. Mod et al. (1978) examined bran from four rice varieties for NDF and crude fibre. They found 447 g kg -1 NDF for 'Calrose' bran and 287 g kg -1 for 'Buzos'. The former value is about double that found in full-fat Australian 'Calrose' bran and may reflect adulteration with hulls.

Phytate is an undesirable component of rice bran, firstly because the phos- phorus in phytate is relatively unavailable to non-ruminants, and secondly because phytate may render other minerals poorly available. The high levels of phytate (24-46 g kg-1) and relatively high fibre found here are cause for concern, and indicate the need for further evaluation of rice bran in studies with animals.

A C K N O W L E D G E M E N T S

We wish to thank the Ricegrowers Co-operative Mills Ltd., Leeton, N.S.W., for financial support, and Barbara Ward and Amanda Choice for technical assistance.

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