ABSTRACT

The study was carried out on three Polish varieties of winter canola seeds -Mar, Polo and Leo and their fractions, size 2,0-2,5 mm and 1,6-2,0mm. The mass of 1000 seeds and content of dry matter, oil, crude protein, glucosinolates, tannic acid, condensed tannins, phytates, iron, copper and zinc was investigated. Mass of 1000 seeds, content of oil, glucosinolates, tannins, phytates, iron, copper and zinc differ significantly among varieties. The fraction of big seeds (2,0-2,5 mm) compared to small seeds (1,6-2,0 mm) showed significantly (P=0,01) higher mass of 1000 seeds and contained more oil, crude protein and glucosinolates and less crude fibre. Content of hull depended on variety and size of seeds. The results do not allow to indicate one variety, which would have significantly higher content of desirable components and on the other hand, lower content of hull and undesirable components crucial to usefulness for dehulling. The big seeds are more useful for dehulling compared to small ones.

Introduction

Technological and feeding usefulness of canola/rapeseeds depends on their physico-chemical characteristic, especially content of basic components, such as dry matter, oil, protein, carbohydrates, content of non-nutritive components – glucosinolates, polyphenolic compounds, phytates, also some metals and shapeliness of seeds (Niewiadomski 1990, Bell 1993, Jensen et al. 1995). The components are not regularly distributed in seeds, considerable differences occur especially between cotyledons with embryo and hull, thus dehulling enables improvement of quality of meal and oil (Kozłowska et. al. 1988, Bell 1993). Despite of many technological problems, known also from the industrial installations (Signoret and Vermeersch 1988), potential benefits such as obtaining of high protein meal with lower content of fibre and oil of lighter colour and higher oxidation stability were encouragement to conduct further studies in this field.
The aim of this study was examination of three Polish winter canola seeds in view of their usefulness for dehulling. Content of hull and cotyledons with embryo and their physico-chemical characteristic, which is mass of 1000 seeds, content of oil, protein, crude fibre, glucosinolates, tannins, phytates, iron, copper and zinc was studied.

Experimental

Materials and the methods

The materials were cultivated seeds of three typical Polish winter canola varieties of Mar, Polo and Leo and their fractions, size 2,0-2,5 mm and 1,6-2,0 mm. During the experiments the seeds were stored at relative air humidity 75% and temperature 15°C. Analysis was carried out according to following methods:

• moisture and volatile matter content – drying method, at temperature 105°C, according to ISO 666:1977,

• oil content – extraction method, applying petroleum ether, according to ISO 734:1979,

• crude protein content – Kjeldahl method in Kjeltec apparatus (the results are given using conversion coefficient of nitrogen to protein 6,25),

• crude fibre content – gravimetric method, according to AOAC, 1978, no. 978.10,

• glucosinolates content – HPLC method, according to ISO 9167-1:1992,

• tannins content was determined according to two methods:

a) as tannic acid - spectrophotometric method, after reaction with Folin-Denis reagent, according to AOAC, 1965, no. 952.03, with initial extraction of tannins from defatted samples by two-hour boiling with distilled water, according to AOAC, 1965, no. 30.018.

b) as condensed tannins - modified Price vanillin method (1978), with initial extraction tannins by 70% acetone (Naczk et al.1994),

• phytates content – anion-exchange method, according to AOAC, 1990, no. 986.11,

• iron, zinc and copper contents – atomic absorption method, according to AOAC, 1996, no. 975.03.

Computer program Statgraphic 6.1 was used for statistical analysis. Procedure of One Way Anova – LSD test (α=0,05) was applied.

Results and discussion

Characteristics of seeds. Table 1 presents characteristics of examined seeds, and their statistical comparison. The typical content of seeds of examined varieties, characteristic for this raw material, was stated, and the content of each component did not differ from data quoted for canola/rapeseed varieties (Niewiadomski 1990, Griffith 1995). Mass of 1000 seeds and content of oil, glucosinolates, tannins, phytates, iron, copper and zinc differ statistically. The highest content of oil (48,9% ddm.) and protein (38,8% ddm.) and lowest of crude fibre (12,4% ddm.) showed variety Mar, however at the same time it also contained the highest content of glucosinolates (21,0 μM/1g ddm.), tannic acid (1,99 % ddm.), condensed tannins (364 mg catechin/100g ddm,) and phytates (4,69 % ddm.).

Tab. 1. Characteristics of rapeseeds varieties Mar, Polo and Leo.

(Values in rows with the same letter are not significantly different at α=0,05)

Characteristic of seeds fractions. The average values from three varieties were discussed because differences among them were negligible. Seeds fractions of diameter 2,0-2,5 mm and 1,6-2,0 mm selected from initial raw material were examined.

The statistical comparison of mean values showed statistically important differences between fractions in mass of 1000 seeds, content of oil, protein, crude fibre and glucosinolates. The big seeds (2,0-2,5 mm) compared to small ones showed significantly (P=0,01) higher mass of 1000 seeds and contained favourably more fat (2,5%), protein (2,6%), less crude fibre (3,1%), but also unfavourable more glucosinolates (by 10,4%). Similar tendencies were observed by Jensen et al.(1995) and Liu et al. (1995). Generally it means, that bigger seeds are more useful for dehulling compared to smaller seeds.

Tab. 2. Comparison of characteristics of seeds fractions 2,0-2,5 mm and 1,6-2,0 mm (n=18).

(Value in rows with the same letter are not significantly different at α=0,05)

Characteristic of hull and cotyledons with embryo. Seeds fractions were dehulling by hand and the hull and cotyledons with embryo were examined. Results are shown in table 3.
The small seeds contented more hull than big ones. The similar tendencies noticed also Liu et al.(1995) and Jensen et al.(1995). The lowest content of hull (13,8% ddm.) showed big seeds variety Polo. The decisive influence on composition of hull and cotyledons had the composition of whole seeds. The results indicate, that hull removing increases regardless their size, the concentration of oil, protein, glucosinolates, tannic acid, phytates and zinc and decreases content of crude fibre, condensed tannins, iron and copper.

Tab.3. The content and composition of hull and cotyledons with embryo depend of seeds fraction (n=9).

Conclusions

1. The Polish varieties winter canola seeds contain: oil - from 46,2 to 48,9 % dm., protein - from 38,1 to 38,8 % ddm., crude fibre - from 12,4 to 12,8 % ddm., glucosinolates - from 15,6 to 21,0 μM/1g ddm., tannic acid - from 1,72 to 1,99 % ddm., condensed tannins - from 266 to 364 mg catechin/100g ddm., phytates - from 3,41 to 4,69 % ddm., iron - from 82,5 to 98,8 mg/kg ddm., copper - from 5,6 to 7,0 mg/kg ddm., and zinc - from 49,5 to 65,6 mg/kg ddm. The results obtained do not allow to indicate one variety, with significantly higher content of desirable components and on the other hand, lower content of hull and undesirable components crucial to usefulness for dehulling.

2. The big seeds (2,0-2,5 mm) contain more oil - from 1,4 to 3,6%, protein - from 2,1 to 3,2%, glucosinolates - from 9,4 to 11,3% and less crude fibre - from 2,1 to 3,2% compared to small seeds (1,6-2,0 mm). The big seeds are more useful for dehulling.

3. The hull contains more crude fibre, condensed tannins, iron and copper and less oil, protein, glucosinolates, tannic acid and zinc compared to cotyledons and embryo. The removal of the hull should theoretically increase in meal the content protein by 13,9 %, glucosinolates by 11,0%, tannic acid by 15,6%, phytates by 15,5% and zinc by 13,4%, and decrease the content of crude fibre by 47,1%, condensed tannins by 44,9%, iron by 5,3% and copper by 11,8%.

References

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