J Sci Food Agric 1992, 60,419-423

Germination Alters the Chemical Composition and Protein Quality of Lupin Seeds Suzanne G Dagnia," David S Pettersoqb* Roma R Bellc and Frank V Flanagan" a Edith

Cowan University, Western Australia, Australia

Department of Agriculture, Baron Hay Court, South Perth, Western Australia 61 5 1, Australia Curtin University of Technology, Western Australia, Australia (Received 13 August 1991 ; revised version received 29 May 1992; accepted 18 September 1992)

Abstract: The chemical composition and protein quality of the kernels from

Lupinus angustijolius seeds were compared with that for sprouts after 6 days germination. Germination resulted in an apparent increase in protein content from 395 g kg-' to 435 g kg-' DM. Fat and carbohydrate contents decreased. The oligosaccharide content of the sprouted lupin fell to a negligible level, while the phytate and alkaloid concentrations fell from 4.7 g kg-' to 1.6 g kg-I and from 0.72 g kg-' to 0.16 g kg-'. respectively. The quality of lupin kernel protein was poor with a protein efficiency ratio (PER) of 1.45+0.15. Supplementation of kernel with DL-methionhe (2.0 g kg-') increased the protein quality (PER = 2.87k0.17) to that of casein (PER = 2.86k0.18). Germination reduced protein quality (PER = 0.44-tO.I6), and did not improve apparent protein digestibility (APD kernel = 80 f 4 YO; APD sprout = 77 f5 YO). Supplementation of sprout protein with DL-methionine (2.0 g kg-') increased the protein quality (PER = 2.57 020). The total sulphur-containing amino acid concentration of lupin kernel protein, 1.9 g per 16 g N was low. and decreased further to 1.3 g per 16 g N in the sprout, a drop of 32%. The results showed that germination of lupin seeds reduced the concentration of the anti-nutritive factors; however, it also reduced protein quality.

Key words: lupin, germination, protein quality, nutritional quality, artinutrients.

el a1 1986). The cell wall material from the lupin kernel has cholesterol lowering properties (Evans el al 1990). Therefore, research into the use of lupin as a human food seems warranted. It is a generally held belief that sprouting increases the nutritive value of legume seeds. Past research has determined that germination improves the nutritional value of Phaseolus radiatus, P angularis, Glycine hispida, G m a s (Lee and Karunanithy 1990), red kidney beans (El-Hag et a l l 9 7 8 ) and L albus (EJ-Habbal eta! 1987) by increasing the proportions of proteins and ascorbic acid, and/or by decreasing the content of anti-nutritive factors. However, the nutritional value of navy and pinto beans (P. uulgaris) was not improved following germination ; protein quality was unchanged, and trypsin inhibitor activity persisted (Chang and Harrold 1988). Although there was no information in the literature on the effect of germination on the nutritive value of L

INTRODUCTION Legumes are widely incorporated into human diets. The soya bean has been used for many thousands of years in the Orient as a vegetable, in beverages (especially as a 'milk') and as a base for fermented foods. It is also used in a wide range of processed foods in Western nations (Shurtleff and Aoyagi 1985). Seeds of Lupinus angusti$olius have an appearance and chemical composition similar to the soya bean. The kernels are high in protein, and Low in fat and anti-nutritive factors (Yanez ef al 1983; Lee 1986; Gross 1988; Petterson and Crosbie 1990). Lupin protein is low in the sulphur-containing amino acids. However, when supplemented with DLmethionine (1.0-2.0 g kg-'), protein quality is high (Sgarbieri and Galeazzi 1978; Yanez et al I983 ;Aguilera

* To whom correspondence should be addressed. 30

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J F A 60

S G Dugniu, D S Petterson, R R Bell, F V Flunugun

410

TABLE 1 PER, PER ratio. apparent NPU and A P D scores for lupin kernels and sprouts" Triwtiireiit

Divrorj. proii+i

grolrp

CIJllfC'Il l

PER

Ratio

NPU

.4 P D

507 (5.2)* 100.4 (5.8)** 100.0 (6.3)** 15.4 (5.6)*** 89.9 (7.0)****

0.43 (005)* 0.58 (0.03)**

080 (0.04)*

0.63 (0.04)** 0.44 (0.13)*

0.92 (0.01)** 0.77 (0.05)***

048 (0.09)* < 0.001

< 0~001

( N x 6.25) (g k g - ' )

I05 I10 I09

Kcrncls Kerncls"

Casciii Sprouts Sprouts"

83 x4

ANOVA'

1.45 ( 0 1 5 ) * 2.87 (0.I7)** 2.86 (0. I8)**

0.44 (016)*** 2.57 (020)**** < 0.001

< 0.001

I' Values arc means with standard deviations shown in brackets for 10 rats per group. Means for the same variable with a different nuinbsr of superscript asterisks are significantly different by Scheffe's test ( P < 0.05). I , Suppleincntcd with m-mcthionine (2 g kg I ) . ' ANOVA is one way analysis of variancc.

ringu.sri/dius. i t was thought likely that the concen-

trations of anti-nutritive factors would decrease and protein content would increase, thus improving the nutritional quality. This study aimed to determine whether germination would lead to a change in nutritive value of lupins with respect to concentration of anti-nutritional factors and to protein. in terms of both quantity and quality as measured by amino acid profile and digestibility.

MATERIALS AND METHODS Germination of seed

Lupin seeds ( L ungir.vt~foliuscv Gungurru) were soaked in tap water for 24 h and germinated under natural lighting at 30--25OC.The seeds were rinsed and drained daily over the 6 day germination period. A kernel sample was prepared by manually de-hulling lupin seeds. After germination any seeds that had not already shed their hulls were also de-hulled to provide a comparable sample for analysis. The lupin sprout and kernel samples were freeze-dried and milled prior to analysis. Seven batches of sprouts were prepared and sub-samples of each combined for analysis. Analytical methods

Nitrogen. potassium, sodium and phosphorus were determined by digesting the samples with sulphuric acid and hydrogen peroxide, and analysing the diluted digest through continuous flow colorimetry and flame photometry in a Leco four-channel autoanalyser. The fat content was determined using a Tecator Soxtec apparatus. using Shell X4 as the solvent. Phytate extraction and assay was by the rapid colorimetric procedure of

Latta and Eskin (1980). All of the above analyses were conducted in duplicate. Amino acids were separated by ion exchange chromatography and measured after reaction with ninhydrin. The method of analysis is based on Millipore-Waters manuals (Waters Associates 1984; Walker 1986). The samples were oxidised with performic acid, to ensure a good recovery of cystine and methionine, prior to hydrolysis at 110°C for 24 h in constant boiling hydrochloric acid under nitrogen. The values obtained for threonine, serine and isoleucine were corrected for incomplete hydrolysis and partial decomposition using results from standard ANRC casein. Tryptophan is not detected by this method. An extra hydrolysis, without performic acid, enabled determination of phenylalanine, tyrosine and histidine. Protein efficiency ratio (PER) followed AOAC methods (AOAC 1990). Apparent net protein utilisation (NPU) and apparent protein digestibility (APD) were calculated from nitrogen balance data obtained from metabolic collections conducted during the third week of the PER study. Experimental diet

Milled lupin kernels or spouts (with or without the addition of 2.0 g kg-' DL-methionhe) were incorporated into four diets to provide about 100 g of protein per kg of diet (the exact levels are shown in Table 1). The diets were adjusted to provide equal amounts of fat (80 g kg-'), crude fibre (10 g kg-I), moisture (100 g kg-I), and ash (50 g kg-'), based on proximate analyses of kernels and sprouts. Casein was used as the reference protein in the fifth diet. The diets were supplemented with vitamins and minerals according to AOAC (1990) procedures.

Germination and nutritional quality of lupin seed

42 1

TABLE 2 Chemical analysis of lupin and sprouts (g kg-') dry basis)"

'(YO) *

Analyte

sprouts (day

@

day adaptation period, experimental diets and water were fed ad libiizcnz. Body weight and feed consumption were recorded every 6 days, and on the 28th day of the study. Faeces and urine were collected for four consecutive days during the third week of the experiment.

_ _ ___.____

Protein Fat Ash Carbohydrate' Oligosaccharide Phytate Calcium Sodium Potassi um Phosphorus Alkaloid (total)

I .8