Laboratory-made Kishk from wheat, oat and barley: 1. Production and comparison of chemical and nutritional composition of Burghol

Food Research International, Vol. 30, No. 5, pp. 311±317, 1997 # 1998 Canadian Institute of Food Science and Technology Published by Elsevier Science Ltd Printed in Great Britain PII: S0963-9969(97)00054-9 0963-9969/98 $19.00+0.00

Laboratory-made Kishk from wheat, oat and barley: 1. Production and comparison of chemical and nutritional composition of Burghol A. Y. Tamime,a* D. D. Muir,b M. N. I. Barclay,a M. Khaskhelia & David McNultyc a

SAC Auchincruive, Food Science and Technology Department, Ayr, KA6 5HW, UK b Hannah Research Institute, Ayr, KA6 5HL, UK c Biomathematics & Statistics Scotland (BioSS), University of Edinburgh, Edinburgh, EH9 3JZ, UK Kishk is a dried product usually made from yoghurt and parboiled `cracked' wheat (Burghol) and is widely used in the region between the eastern Mediterranean and the Indian sub-continent. To evaluate the contribution of the cereal component to the overall character of Kishk, di€erent cereal bases were prepared. Three varieties of barley and four of oats were processed in a manner similar to the production of Burghol. The traditional cracking process was successful for barley and oats, but it was very dicult to separate the husk from the oat product. The chemical composition of the `cracked' cereals were compared with that of the original grains (minus the bran), and with the traditional wheat product (i.e. Burghol). The overall ®bre content of the `cracked' barley was lower by 5.1% while the phytic acid and -glucan contents were higher than the corresponding original cereal grain by 0.03 and 0.36%, respectively. In comparison with the original grain, the overall ®bre content of the `cracked' oats was also lower by 1.43% while the -glucan content was 0.26% higher. The concentration of copper, calcium, zinc and manganese di€ered between the cereal grain and the `cracked' product ( p < 0.05). These di€erences emphasise the signi®cance of cereal type on the properties of Burghol. # 1998 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd Keywords: cereals, -glucan, phytic acid, minerals, Burghol, Kishk.

INTRODUCTION

with water and served as a hot gruel, but with the incorporation of vegetables, spices, garlic, herbs or dates, can form the base of savoury and sweet dishes (Kurmann et al., 1992). Various combinations of the fermented milk and cereal components of Kishk are found. For example, the yoghurt base may be made from bovine or caprine milk or from a mixture of both (Tamime et al., 1996). The e€ect of such di€erences on chemical, nutritional and sensory quality of Kishk has been studied in detail (Muir et al., 1995; Tamime et al., 1998a,b). However, little is known on the contribution made by the cereal component of Kishk to overall quality. Burghol (parboiled `cracked wheat'), crushed wheat or wheat ¯our are widely used as the cereal base (Tamime and O'Connor, 1995). However, in Sudan a closely related dried fermented milk product (Um-Kushuk) is made with de-hulled sorghum (Dirar, 1993), and

Fermented milks are inherently safe and have a wholesome, healthy image. Because of their high level of acceptability, the range of fermented milk products available to the consumer is becoming more diverse. Greek-style yoghurt, yoghurt ice-cream and yoghurts containing probiotic micro¯ora (Lactobacillus acidophilus and/or Bi®dobacterium sp.) are examples of `new' (or re-discovered) products with widespread consumer acceptance. The market is thus receptive to new ideas. One such example is KishkÐa dried mixture of fermented milk and cereal, widely consumed in the region between the eastern Mediterranean and the Indian sub-continent. Kishk is usually reconstituted *To whom correspondence should be addressed. Fax: 0044 1292 525071; e-mail: [email protected] 311

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laboratory-made Kishks using soya milk and chick-pea ¯our have been evaluated in Egypt (Hassan and Hussein, 1987). Burghol made from wheat is also popular in its own right, e.g. in Tabouleh (a salad dish) or as a substitute for boiled rice. Foods based on whole cereal grains ®nd a ready market because of their association with dietary `®bre' and hypocholesterolemic e€ects (De Groot et al., 1963). However, the dietary implications of consumption of whole grains and their components are complex and have been widely discussed elsewhere (Frolich and Nyman, 1988; Newman et al., 1989; Swain et al., 1990; Jenkins et al., 1993; Kritchevsky and Story, 1993; Spiller, 1993). Nevertheless, there are well-established di€erences between cereal types and the chemical composition and properties of barley (hordeum valgare) as a food grain were reviewed by Newman and Newman (1991) while Hutchison and Cook (1988) have examined the opportunities for alternative uses of oat and oatbased products. Because no data are available on the production of Burghol, four barley and four oat varieties were treated in a manner similar to that used for wheat in traditional Lebanese Burghol. The e€ect of such processing on the composition and nutritional value of barley and oats was evaluated. In a separate report, the chemical composition and the sensory properties of Kishk made with these cereals is also detailed. MATERIALS AND METHODS Materials Four varieties of non-waxy barley [Pastoral and Marinka (winter sown), Maghee and Camargue (spring sown)], and four varieties of oat [Matra and Adamo (early spring sown), Valiant and Dula (late spring sown)] were tested. The barley and oat varieties used were enclosed in the lemma and palea, and were grown in Scotland during 1991 (Alexander Harley Seeds, Milnathort KY13 7RF, Scotland, UK). One soft wheat grain (Salibi) and two Burghol samples (i.e. one coarse and the other ®ne) were also tested, and were obtained from Najar Granary Ltd., Chtoura, Bekka Valley, Lebanon. The bran layers and germ were removed by hand. The whole grains were milled for chemical analysis.

broken). The large grains were steeped continuously in boiling water for ca 1 h and dried in the sun for ca 2 days. The dried grains were re-hydrated (ca 20%), then cracked between two `star' wheels. Traditionally, Burghol is separated from the bran by winnowing (Tamime and O'Connor, 1995); however, under commercial operations a mechanised and enclosed winnowing machine made locally from wood (1.5  2±2.5  1.5 m) is used. Figure 1 illustrates schematically the separation of bran from the Burghol by using density fractionation. However, commercial Burghol from wheat was used as a control in the present study. Since the cracking machine for preparing the Burghol was not available in our laboratory, the samples of barley and oat varieties were prepared in Lebanon in the same process described above for the preparation of Burghol from wheat until the winnowing stage. The grains (each variety 15 kg) were ®rst cleaned by hand because the commercial rotary cylindrical machine was too large to handle such small volume. The cleaned grains were steeped in boiling water for 1 h followed by sun drying for ca 2 days. Fresh water was used during the steeping stage of each grain variety. The dried parboiled barley and oat kernels were moistened with water (ca 20%), cracked, dried and the bran was removed. In Scotland, husk separation from barley and oat was dicult. Several fractions were obtained from each cracked sample using a Dockage Tester, which uses sieves and air for cleaning grain (loaned from Rank Hovis, McDougall Research and Engineering Ltd, The Lord Rank Centre, Lincoln Road, High Wycombe, UK). The pool of husk-free fraction was selected for analysis. Four varieties of `cracked' barley and four varieties of `cracked' oats similar to Burghol were prepared. However, the grain samples of Maghee were lost in transit and, for this reason, comparative analysis was excluded, but the Burghol fraction was used for Kishk-making. Chemical analyses Protein and ash contents of whole grains and parboiled `cracked' cereals were estimated as described in British

Preparation of Burghol The commercial method for the preparation of Burghol from wheat in the Lebanon was described by Tamime and O'Connor (1995). In brief, the method is: threshed wheat, with a naked caryopsis, was cleaned of stalks, dirt and weed seeds using a rotary cylindrical machine known locally as a `ghorbal'. The `ghorbal' also sizes the wheat kernels into three fractions (i.e. large, small and

Fig. 1. Schematic illustration of a mechanically winnowing machine made locally in the Lebanon. (A): Low density fraction (husk), (B): high density fraction (cracked wheat), (D) and (E): collecting drawers for coarse and ®ne cracked wheat, respectively.

Laboratory-made Kishk from wheat, oat and barley: 1. Standards Institution (BSI, 1990, 1993). Fat, moisture and starch were determined by the methods described by Statutory Instruments (SI, 1982, 1985). The phytic acid, -glucan, dietary `®bre' and free sugar were measured using the methods described by Latta and Eskin (1985), McLeary and Glennie-Holmes (1985) (see also McLeary and Codd, 1991), Prosky et al. (1985) and Englyst and Hudson (1987), respectively. The mineral content of the grains (Ca, P, Mg, Zn, Fe, Cu, Mn, K and Na) and parboiled `cracked' cereals were measured using the nitric-perchloric acid digestion procedure according to the method described by the Ministry of Agriculture, Fisheries and Food (MAFF, 1986) followed by induction coupled plasma (ICP) emission spectrometry (Thermo Electron Ltd., Birchwood, Warrington, UK). The analyses were performed at the following ¯ow rates: (a) main argon of 15 l minÿ1, (b) nebulizer argon of 0.51 l minÿ1, and (c) sample of 0.8 ml minÿ1. The mineral eluates were monitored at di€erent wavelengths: 317.9 nm±Ca, 214.9 nm±P, 285.2 nm±Mg, 766.5 nm±K, 589.6 nm Na, 213.9 nm±Zn, 238.2 nm±Fe, 324.8 nm±Cu and 257.6 nm±Mn. All chemical analysis were carried out in duplicate on each sample. The percentage of phosphate associated with phytic acid was calculated by converting the phosphorus content to phosphate (i.e. P  3.065), then calculating the phosphate bound in phytic acid (hexaphosphate inositol) by multiplying the phytic acid content by 0.888. Internal quality control was maintained by using standards of known composition: Community Bureau Reference (CRM No 380) supplied by the Laboratory of the Government Chemist, Teddington, Middlesex, UK was used for protein, fat, ash and minerals; ®bre control from Sigma Chemical Company Ltd., Dorset, UK, and -glucan from Megazyme (Aust.) Pty Ltd., Sydney, New South Wales, Australia. External quality control was maintained by participation in the Food Analysis Performance Assessment Scheme (FAPAS) run by CSL±Food Services Laboratory, Norwich. Statistical analysis Analysis of variance (Genstat 5; release 3.1: copyright 1992; Lawes Agricultural Trust Rothampsted Experimental Station) was used to identify statistical signi®cance of e€ects due to cereal (barley/oat/wheat), treatment (grain/cracked product) and associated with the cereal  treatment interaction. Cereal varieties were used as a proxy for replicates. The interactions between compositional attributes were examined using principal Component Analysis (PCA) of the standardized variables, i.e. mean was centred and scaled to the unit variance. PCA of compositional and mineral data were carried out separately. The interpretation of the Principal Components was clari®ed by correlating the sample scores on each PC with the original attribute ratings.

313

RESULTS AND DISCUSSION A cracked product analogous to wheat was produced in the Lebanon from three varieties of barley and four varieties of oat. No diculties were experienced in produced the cracked products until husk removal. The husk of both barley and oat proved heavier than the bran of the wheat, and the oat husk or hull was particularly dicult to separate. The traditional winnowing method was tried in the Lebanon and was unsuccessful, and the locally made winnowing machines were too large to handle the small weight ( 15 kg) of each variety of barley and oat. Closer inspection of the whole oat kernel prior to cracking would have indicated that the separation of the husk from the grain was likely to be dicult. Conventional oatmeal production where the whole oat is roasted ®rst allows the groat to shrink away from the dry brittle hull and facilitate the hulling process. Even here, care is given to grading the grain sizes before hulling as separation is recognised as a problem. The cracking procedure would swell and gelatinise starch granules thus binding the groat more closely to the hull. Possibly the separated groat itself could be subjected to the cracking procedure, but it is more likely that this would produce gruel. Rolled oats are produced after limited treatment of groats with live steam at atmospheric pressure just prior to rolling. This limited access to heat and moisture softens the groats and allows ¯aking with minimum breakage or ¯our formation. A possible alternative would be the use of hull-less oats. The structure of barley allowed conventional cracking procedures to be adopted, and although dicult to separate using traditional Burghol winnowing equipment could be relatively separated. E€ect of processing on chemical composition content of `cracked' cereals The fat, protein and ash contents of barley, oats and wheat were compared (Table 1) for the original grain and its parboiled `cracked' product counterpart on dry matter basis (DMB). The fat content of barley and wheat grains was similar, but that of oat was higher (i.e. 2-fold more in three varieties and 10.5 g 100 gÿ1 in Adamo, Table 1). As a result, oats have a higher energy content and greater potential for fat degradation. The protein content of barley and oat varieties averaged 12.8 and 14.1 g 100 gÿ1 , respectively, compared to 16.8 g 100 gÿ1 for wheat. The ash content of all the tested grains was relatively similar, and ranged between 1.9±2.4 g 100 gÿ1 depending on cereal variety and strain (Table 1). In all the parboiled `cracked' products, the fat, protein and ash contents was reduced (Table 1) as a result of processing. The mean fat content in the cracked barley dropped from 3.5 to 3.1 g 100 gÿ1, protein 12.8 to 12.2 g 100 gÿ1 and ash 2.4 to 1.7 g 100 gÿ1, and the patterns in cracked oat and wheat were similar (Table 1).

314

A. Y. Tamime et al.

Table 1. Comparison of the chemical composition (g 100 gÿ1 DMB)a of the original and parboiled cracked grains of di€erent cereals Grain/ ANOVAb

Variety

Fat c

O

Barley

Pastoral Camargue Marinka

Oat

Matra Dula Valient Adamo

Wheat

Salibi

Cereal (barley/oat/wheat) Treatment (O/P) Cereal  treatment

Protein d

P

3.56 2.67 3.47 3.22 3.58 3.31 7.31 7.32 7.46 10.45

7.12 7.52 7.10 9.31

O

P

Ash O

P

Starch O

P

Free sugar O

P

O

P

Phytic acid O

-glucan

P e

O

P

12.60 12.76 2.43 1.79 61.99 66.50 0.80 12.51 10.90 2.51 1.69 61.38 70.34 0.64 13.26 13.06 2.13 1.64 61.25 66.90 1.31

0.40 23.32 21.76 1.22 (86) 0.24 23.73 15.29 1.18 (90) 0.26 23.35 18.17 1.16 (86)

1.27 (97) 1.16 (82) 1.22 (93)

2.90 3.18 3.02 3.30 3.54 4.06

13.87 14.22 13.82 14.28

0.14 0.14 0.24 0.26

1.36 1.50 1.34 1.38

3.11 3.32 3.69 3.83

14.13 14.21 13.53 13.77

1.93 2.14 1.97 2.00

1.96 2.01 1.85 1.95

67.70 65.29 65.90 63.11

66.17 66.22 67.69 65.62

0.94 0.82 0.94 0.50

3.63 2.82 (F)f 16.84 14.40 1.94 1.61 64.85 66.98 0.88 3.05 (C) 15.20 1.70 62.73 *** *

Fibre

*** * *

*** ***

* *

11.30 14.54 11.27 13.38

12.54 10.77 10.77 10.67

1.41 1.45 1.25 1.27

(69) (89) (77) (75)

0.34 12.62 13.31 1.20 (90) 0.30 14.84

***

***

(84) (90) (84) (84)

3.56 3.78 3.75 3.91

1.36 (100) 0.29 0.24 1.27 (100) 0.21 * *

*** **

a

All ®gures were calculated on dry matter basis (DBM). ANOVA: analysis of variance; signi®cance; *p  0.05, **p  0.01, ***p  0.001; n = 8. c Original cereal grain. d Parboiled cracked cereal. e Figures in parenthesis represent % of phosphate expressed as phytic acid. f F: ®ne; C: coarse. Results are average of replicate determinations on materials of each sample. b

Di€erences between the cereals in fat and protein contents were signi®cant ( p  0.001), but not ash. In addition, signi®cant di€erences were found between the original grain and the cracked product for fat and protein ( p  0.05), and for ash ( p  0.001). The only factors with a signi®cant cereal  treatment interaction were ash ( p  0.001), and protein ( p  0.05) (see Table 1). The carbohydrate fractions of the di€erent cereal varieties are also shown in Table 1. For barley, there was an apparent increase in starch content of the cracked product of 6.37 g 100 gÿ1. The average free sugar content of the barley was initially 0.92 g 100 gÿ1, but the hot water steeping process reduced the free sugar of the cracked product to an average of 0.30 g 100 gÿ1. Similarly, the ®bre content of the barley was reduced on processing from an average of 23.47 g to 18.41 g 100 gÿ1. The barley analysed as `original' has had its husk removed by hand so that this should not be the source of the reduction. It is more likely that some of the non-digestible starch (estimated as `®bre') in the original grain was rendered digestible by the cracking. An increase in starch content of the cracked oats (65.5 to 66.43 g 100 gÿ1) was evident (Table 1), while the free sugar content dropped from 0.8 to 0.2 g 100 gÿ1. The `®bre' content decreased in three of the varieties of oats studied, but increased slightly in Matra (11.3 to 12.54 g 100 gÿ1). The `®bre' content for oat was < wheat < barley. Again the average decrease was thought to be due to an increase in digestible starch. The phytic acid content of the parboiled `cracked' barley was increased from 5.0% to 6.6% of total `®bre'. Phytase (EC 3.1.3.8), present in the whole grain, was inactivated by heating prior to the cracking procedure.

The proportion of phosphorus to phytate was 87.6% and 90.6% in the original grain and cracked cereal, respectively. Such high levels of phytate phosphate would sequester most of the divalent cations making them unavailable for absorption. The phytic acid content of the oat in the original grain was higher (1.35 g 100 gÿ1) than that of barley (1.19 g 100 gÿ1). This was even greater in the cracked product as the oat phytate rose to 1.4 g 100 gÿ1. An average of 85.5% of the phosphorus present in the cracked oats was associated with phytic acid compared to 91 and 100% for barley and wheat products, respectively. The -glucan content of the barley increased on cracking (3.15 to 3.51 g 100 g, but this was probably due to the decrease of other contents. The level, as expected, was considerably higher than that of wheat (0.23 g 100 gÿ1). Similarly, the -glucan content of oat (Table 1) also increased on cracking from 3.59 g to 3.75 g 100 gÿ1. The di€erences between the cereals studied were signi®cant for phytic acid ( p  0.05), -glucan and `®bre' ( p  0.001), but not for starch or free sugar contents. In addition, di€erences between the original grains and cracked products were signi®cant for free sugar ( p  0.001), phytic acid and starch ( p  0.05) and glucan ( p  0.01), but not for ®bre (Table 1). The only carbohydrate fraction with a signi®cant interaction between cereal  treatment was for starch ( p  0.05). The overall relationship between the samples was analysed using Principal Component Analysis (PCA). The ®rst, second and third PCs accounted for 37, 25, and 21% of the variance, respectively. The samples scores for PCs 1 and 3, which are more readily interpretable, are shown in Fig. 2. As a result, a two-dimensional solution

Laboratory-made Kishk from wheat, oat and barley: 1.

315

Mineral content of the `cracked' cereals

Fig. 2. Principal Component Analysis of Chemical composition of di€erent cereals using correlation matrix.

using PCs 1 and 3 accounted to 58% of the variance. It is evident that the chemical composition data can be separated into original grain and parboiled `cracked' products. The original grain is associated with the free sugars and ash, while the parboiled product is associated with starch (see Fig. 2). Thus, the starch was highly correlated with free sugar (r = ÿ0.47, p  0.05), and with ash (r = ÿ0.68, p  0.01). By projecting the observations in Fig. 2 onto the separating line, it can be observed that the di€erent cereals (original grain and the parboiled products) can be distinguished by their fat, ®bre and phytic acid contents. Signi®cant correlations were noted between the di€erent attributes, and the results are shown in Table 2.

When the minerals were considered individually (Table 3), the calcium content of the barley varieties and wheat showed high losses after processing to the cracked products while the other elements decreased slightly. In total, these changes accounted for 60% of the ash loss. Chloride and other water soluble anions may account for the di€erences. However, calcium in the cracked oat products increased from 78.9 to 88.9 mg 100 gÿ1, but potassium and manganese content dropped after cracking. The iron content of all three cereal types increased in the cracked products (2.55 to 3.02 mg 100 gÿ1 in barley, 3.81 to 4.74 mg 100 gÿ1 in oat and 4.02 to 7.58 mg 100 gÿ1 in one wheat sample examined). The increase in iron content in the cracked product was the second most signi®cant change in the oat products. If this iron was available it would enhance the nutritional value. The di€erences of the mineral elements between the cereals were signi®cant for calcium, phosphorous and manganese ( p  0.001), copper ( p  0.01), and magnesium, potassium and zinc ( p  0.05), but not for sodium nor iron (Table 3). The di€erences between the original grain and the cracked products were signi®cant for only potassium ( p  0.01), copper and manganese ( p  0.05). The attributes with a signi®cant interaction between cereal  treatment were for calcium, zinc and manganese ( p  0.05), and copper ( p  0.01) (Table 3). PCA of the mineral data (Table 3) was carried out, ®rst and second PCs accounted for 45% and 24% of the variance, respectively. Each cereal had clustered di€erently according to the mineral component (Fig. 3)Ðin particular, oat contained high proportions of Mn, Ca, Mg, and P. The Cu and K contents were high in wheat, while the barley varieties appear de®cient in minerals when compared with the other cereals. Although the di€erent varieties of barley were clustered near the Na (Fig. 3), the di€erences in the Na content between the cereals were found to be insigni®cant. Signi®cant

Table 2. Matrices of signi®cant correlations for chemical and mineral attributes Correlation coecients (r) of attributes Chemical components

Starch

Ash Fibre Starch Protein Fat Mineral content K Zn P Mg Ca

±0.68**

*p  0.05, **p  0.01, ***p  0.001; n = 8.

Free sugar

±0.57* Cu 0.64**

K

Phytic acid

-glucan

Fibre

±0.66** 0.54* Mg

0.55* 0.48* ±0.60** P

±0.57* ±0.60** Zn

0.83**

±0.47* 0.88***

0.92** 0.66**

0.63** 0.64**

Mn 0.74** 0.88***

316

A. Y. Tamime et al. Table 3. Mineral content (mg 100 gÿ1 DMB)a of the original and parboiled cracked grains of di€erent cereals

Grain/ ANOVAb

Variety

Calcium

Barley Oat

Pastoral Camargue Marinka Matra Dula Valient Adamo

46.5 46.5 48.0 43.0 47.5 43.5 83.0 109.5 86.5 86.0 70.5 80.5 75.5 79.5

Wheat

Salibi

80.5

c

O

Cereal (barley/oat/wheat) Treatment (O/P) Cereal  treatment

P

d

Magnesium

Phosphorus

Sodium

O

P

O

P

O

127.0 126.0 114.5 143.5 146.0 132.0 148.0

125.0 125.0 112.0 146.0 146.0 128.0 141.0

406.5 381.0 388.0 482.5 484.5 472.0 494.5

383.0 408.0 375.0 469.0 484.0 455.0 479.5

*

***

*

O

P

Copper O

Zinc

Iron

Manganese

P

O

‹

O

P

O

P

0.47 0.46 0.32 0.35 0.26 0.38 0.25

1.97 1.67 2.87 3.35 3.26 3.64 2.64

1.87 1.83 2.50 3.75 3.43 3.51 2.73

2.34 2.15 3.17 3.35 4.17 4.32 3.41

2.85 2.90 3.31 3.62 4.96 5.01 4.38

1.66 1.22 1.76 5.33 6.11 6.16 4.33

0.93 1.16 1.10 5.37 4.83 5.22 3.76

3.5 575.5 453.5 0.91 0.51 3.87 3.04 4.02 3.36 6.79 4.5 476.5 0.57 3.26 11.80

2.39 2.78

7.5 3.5 550.5 468.5 0.45 7.0 6.0 682.5 430.5 0.56 6.5 8.0 486.0 422.5 0.34 2.5 10.5 459.5 334.0 0.36 4.0 4.0 473.0 416.5 0.33 4.0 5.5 470.5 394.5 0.45 3.5 4.0 448.0 425.5 0.46

65.0 (F)e 121.0 113.5 390.0 358.0 4.5 70.0 (C) 122.0 378.0 ***

P

Potassium

* ** **

** *** *

* *

*** *** *

a

All ®gures were calculated on dry matter basis (DBM). ANOVA: analysis of variance; signi®cance; *p  0.05, **p  0.01, ***p  0.001; n = 8. c Original cereal grain. d Parboiled cracked cereal. e Figures in parenthesis represent % of phosphate expressed as phytic acid. Results are average of replicate determinations on materials of each sample. b

the parboiled `cracked' products revealed signi®cant di€erences in the ®bre, carbohydrate and mineral content. Such di€erences would be anticipated to in¯uence the properties of food stu€s such as Kishk in which Burghol is an essential ingredient. ACKNOWLEDGEMENTS The authors thank Mrs I. Hamilton, Miss A. Mair and Mr T. McCreath for skilled technical assistance. SAC, HRI and BioSS receive ®nancial support from the Scottish Oce of Agriculture, Environment and Fisheries Department (SOAEFD), and Mr M. Khaskheli is indebted to The World Bank for ®nancial support.

REFERENCES

Fig. 3. Principal Component Analysis of mineral content of di€erent cereals using correlation matrix.

correlations were found for the di€erent attributes which are summarised in Table 2. CONCLUSIONS Preparation of Burghol from oats but, not barley or wheat was complicated by the adhesion of the husk to the grain. However, modi®cation of the traditional wheat processing method allowed Burghol to be successfully produced from oats. A detailed comparison of

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(Received 19 December 1996; accepted 24 August 1997)