Short communication
Nutritional value of rapeseed meal containing
lecithin gums precipitated with citric acid
B. Pastuszewska
a,*, G. Jabøecki
b, E. SÂwie,ch
a,
L. Buraczewska
a, A. OchtabinÂska
aaThe Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences,
05-110 Jabøonna, Poland
bThe Warsaw Oil Factory, 122 RadzyminÂska Street, 03-574 Warsaw, Poland
Received 1 November 1999; received in revised form 23 March 2000; accepted 25 May 2000
Abstract
The composition and nutritional value of 00-type industrial rapeseed meals containing lecithin gums either precipitated with citric acid (meal ALAC) or removed from oil by hydration (meal BLH) were determined. Control meals without lecithin (A and B) were included in the study. The ether extract content was over 20 g/kg greater, while the protein content was slightly lower in meals containing lecithin gums. The amino acid composition (g/16 g N) of all meals was uniform while the FDNB-available lysine content was lower in the meal with acidi®ed lecithin than in the control meal without lecithin and in the meal with hydrated lecithin gums (4.85 versus 5.16 and 5.28 g/ 16 g N in ALAC, A and BLHmeals, respectively). Meal ALAChad a lower pH and lower solubility in KOH than other meals. Neither the two indices determined in vitro simulating energy digestibility and ileal protein digestibility for pigs, nor indices of protein value determined in rats were affected by the type of lecithin added to the meal. Feed intake and body gain of rats tended to be slightly lower on the diet containing acidi®ed lecithin than on other diets.# 2000 Elsevier Science B.V. All rights reserved.
Keywords:Rapeseed lecithin gums; Meals; Composition; Rats; Protein value; Digestibility
1. Introduction
Rapeseed oil produced either by expelling or solvent extraction contains 10±20 g impurities per kilogram, composed mainly of phospholipids (lecithin gums) and minor
86 (2000) 117±123
*Corresponding author. Tel.:48-22-782-44-22; fax:48-22-774-20-38.
E-mail address: in®zyz@atos.warman.com.pl (B. Pastuszewska)
quantities of other seed components. Removal of phospholipids by degumming processes consists of water treatment (hydration) followed by centrifugation. The gums are usually blended back into the meal (Carr, 1995). Gums can also be removed from oil by precipitation with acids, either inorganic (usually phosphoric acid) or organic.
Observations on the degumming of rapeseed oil with citric acid have shown that it is an ef®cient method of removing phospholipids allowing for a decreased use of adsorbent without deterioration of oil quality (Jabøecki, unpublished data). As the effects of including acidi®ed lecithin gums on rapeseed meal quality are unknown, a study was undertaken to compare the nutritional value of meals containing gums obtained by the standard hydration method or precipitated with citric acid.
Chemical and amino acid compositions were determined and indices of nutritional value were assayed by in vitro methods and in tests with rats.
2. Material and methods
2.1. Meals
The meals were produced in the oil factory in Warsaw under standard processing conditions. Flaked seeds of commercial 00-type rapeseed were heated for 50 min at 908C in open conditioners, prepressed to about 18% oil content and extracted with hexan-like solvent. The meal was then toasted for 50 min from 70 to about 1158C. During toasting, the meal was blended with lecithin gums obtained either by precipitation with 0.3% citric acid added to oil (meal ALAC) or by hydration (meal BLH). Each meal sample was prepared by pooling three sub-samples taken at regular intervals. For technical reasons, the meals containing different type of lecithin were produced within a 2-day period so the reference samples of the respective meals without lecithin were taken to check the possible differences between the batches of processed seeds. Thus, the whole material under study comprised four samples: sample of meal without and with acidi®ed lecithin produced at time A (meals A and ALAC, respectively), and of meal without and with standard-hydrated lecithin produced at time B (meals B and BLH, respectively). The total amount of lecithin gums obtained from the extracted oil was added to the meals but the exact quantities were not measured. The estimated content of citric acid in the meal with acidi®ed lecithin (ALAC) was 0.3%.
2.2. Chemical analysis
The chemical composition of meals, diets and rat faeces were determined according to AOAC (1990). Amino acids in meals were analyzed with a Beckman 6300 amino acid analyzer according to Buraczewska and Buraczewski (1984), after acid hydrolysis except tryptophane. Methionine and cystine were determined after oxidation with performic acid and tryptophane after hydrolysis with BaOH. FDNB-available lysine content was determined according to Booth (1971). Protein solubility in KOH was measured as described by Pastuszewska et al. (1998) and the pH of a water extract of meal was measured on Beckman 71 pH meter.
2.3. In vitro assay
The in vitro indices of nutritional value of meals for pigs comprised energy digestibility in total digestive tract and ileal protein digestibility determined using the methods of Boisen and Fernandez (1995, 1997). The method simulating energy digestion in total tract consists of a three-step enzymatic incubation corresponding to the digestion in the stomach, small intestine and hind-gut (Boisen and Fernandez, 1997) while the prediction of the ileal protein digestibility is based on a two-step incubation and includes the correction for endogenous protein loss (Boisen and Fernandez, 1995).
2.4. Rat experiments
In an N-balance experiment, true digestibility (TD), biological value (BV), and net protein utilization (NPU) of the meal protein were determined by the Thomas±Mitchell method according to the procedure described by Smulikowska et al. (1997). Semisynthetic diets contained the evaluated meals as the only source of protein at a level corresponding to 95 g crude protein/kg. The composition of the diets is given in Table 1. Each diet was fed to eight male IFz:JAZ rats of initial mean body weight 77 g. After the conclusion of the N-balance experiment, the same diets were fed to rats for the next 11 days and apparent digestibility of nutrients was determined based on analysis of faeces pooled from two animals.
The growth experiment was performed on male IFz:JAZ rats weighing about 53 g, eight rats per treatment. The animals were fed for 3 weeks on the same diets as those used in the balance experiment; feed intake and body weight were recorded weekly.
The results of N-balance and growth experiments were analyzed by one-way variance analysis using `Statgraph. Plus var. 7' Software.
Table 1
Composition of the experimental diets (g/kg)
Ingredient Diet
A ALAC B BLH
Meal A without lecithin 283 ± ± ±
Meal A with acidi®ed lecithin ± 291 ± ±
Meal B without lecithin ± ± 287 ±
Meal B with lecithin obtained by hydration ± ± ± 294
Sucrose 120 120 120 120
Corn starch 515 514 513 513
Soya oil 32 25 30 23
Mineral premixa 30 30 30 30
Vitamin mixtureb 20 20 20 20
aPer kg diet: CaHPO
4, 22.1 g; K2HPO4, 2.5 g; K2SO4, 2.0 g; NaCl, 0.9 g; CaCO3, 0.6 g; Na2HPO4, 0.6 g;
MgO, 0.7 g; ferric citrate, 0.167 mg; ZnCO3, 24 mg; MnCO3, 126 mg; CuCO3, 9 mg; KJ, 0.3 mg; citric acid,
274 mg.
bPer kg diet: vitamin A, 20.000 IU; vitamin D
3, 2.000 IU; vitamin E, 100 IU; vitamin K, 5 mg; choline,
2.0 g; p-aminobenzoic acid, 100 mg; inositol, 100 mg; niacin, 40 mg; ribo¯avin, 8 mg; thiamine, 5 mg; pyridoxine, 5 mg; folic acid, 2.0 mg; biotin, 0.4 mg; vitamin B12, 0.03 mg; starch, ad 20 g.
3. Results and discussion
The chemical composition of meals (Table 2) was fairly uniform except that the meals with added lecithin gums contained more fat and slightly less protein than those without lecithin, and meals B and BLHcontained more ®bre than meals A and ALACwhich may indicate for a difference in the composition of seeds processed ad time A and B. The increment of ether extract level due to addition of both gums was similar (26 and 23 g in meal ALACand BLH, respectively) which may indicate a comparable quantity of products obtained in different ways.
The amino acid composition of meals (Table 3) was typical of rapeseed meal protein and did not differ between the meals, the only difference was a slightly lower FDNB-available lysine content in ALACthan in A meal (4.85 versus 5.16 g/16 g N) and than in other meals.
The indices of protein value (Table 4) point to a somewhat lower protein solubility in KOH of meals with both added types of lecithin, but particularly with acidi®ed lecithin (44.7 versus 50.4% in ALAC and A, respectively). This may be explained rather by a lower ef®ciency of KOH in meals containing greater amount of fat and by binding of Table 2
Chemical composition of rapeseed meals (g/kg DM)
Meal Dry
A (without lecithin) 907 370 76 31 124 5.94
ALAC(with acidi®ed lecithin) 901 362 76 57 116 5.81
B (without lecithin) 907 364 76 40 140 5.97
BLH(with lecithin obtained by hydration) 903 357 75 63 140 5.97 aOf water extract.
Table 3
Amino acid composition of rapeseed meals (g/16 g N)
Amino acid Rapeseed meals
A ALAC B BLH
Lysine 5.55 5.49 5.51 5.49
FDNB-available lysine 5.16 4.85 5.13 5.28
Methionine 2.00 2.04 2.05 2.01
KOH by citric acid in ALACmeal (the pH of this meal was over 0.1 lower than of other meals), than by a direct negative effect of lecithin on protein solubility. However, the lower lysine availability in ALACthan in all other meals may indicate a negative effect of acidi®ed gums.
The ileal protein digestibility of meals for pigs determined in vitro was uniform and did not depend on either the type of lecithin or batch of meal (Table 4). Also, the indices of protein value determined in rats (protein digestibility, biological value and net utilization) were not affected by lecithin (Table 4) but a tendency was observed towards lower true digestibility of protein in both B than A meals (0.815 versus 0.834,p0.05 and 0.806 versus 0.821,p>0.05 in B versus A and BLHversus ALAC, respectively). This difference may be ascribed to a slightly higher crude ®bre level in meals B than A and Ð probably Ð to the greater proportion of ®bre-bound protein, having a lower faecal and ileal digestibility, as reported by Bjergegaard et al. (1991), Buraczewska et al. (1998), and Grala et al. (1999). Lower apparent protein digestibility of both meals B than A was not con®rmed in the experiment on older rats (Table 5) but crude ®ber digestibility also was lower on both B than A meals.
Supplementation of meals with lecithin did not increase fat digestibility, which in the group fed on diet BLH tended to be even lower than on respective B without lecithin (Table 5). This does not indicate that rapeseed lecithin gums have emulsifying properties and is in contrast with the results of Smulikowska et al. (1992) who found a signi®cant Table 4
Indices of nutritional value of rapeseed meal protein determined in rats and in vitro (meansS.D.)
Meal Ratsa In vitro
aValues with the same superscript are not different atp0.05. bApparent ileal values according to Boisen and Fernandez (1995).
Table 5
Apparent digestibility of dietary nutrients determined in rats (meansS.D.) and energy digestibility measured in vitroa
aValues with the same superscript are not different atp0.05. bAccording to Boisen and Fernandez (1997).
positive effect of 1% crude rapeseed lecithin in chickens when the diets were either not supplemented with fat or supplemented with 9% tallow. The different response to rapeseed lecithin found in chicken and rats may be ascribed to different fat content (9% versus 4%) and type of fat (tallow versus plant oil). In Smulikowska's study, nitrogen retention in chicks was also increased by lecithin, while in our experiment net protein utilization was not affected by either lecithin gum.
Growth performance of rats did not differ signi®cantly between the groups (Table 6) but a tendency was observed towards a greater feed intake of diets containing meals B and BLH than A and ALAC. This is in agreement with greater content of ®bre and its lower digestibility in meals B than A resulting in their lower energy concentration and compensatory consumption. The lowest feed intake, body gain and feed ef®ciency in animals fed acidi®ed lecithin was not con®rmed statistically and may be treated only as an indication needing further studies.
From this preliminary experiment, it may be concluded that precipitation of phospholipids with citric acid does not negatively affect the nutritional value of rapeseed meal containing acidi®ed gums, except for a slight decrease of available lysine content. However, a small effect of acidi®ed gums on feed intake cannot be excluded.
References
Association of Of®cial Analytical Chemists (AOAC), 1990. Of®cial Methods of Analysis, 15th Edition. AOAC, Washington, DC.
Bjergegaard, C., Eggum, B.O., Jensen, S.K., Sùrensen, H., 1991. Dietary ®bre in oilseed rape: physiological and antinutritional effect in rats of IDF and SDF added to a standard diet. J. Anim. Physiol. Anim. Nutr. 66, 69±79.
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Boisen, S., Fernandez, J.A., 1997. Prediction of the total tract digestibility of energy in feedstuffs and pig diet by in vitro analyses. Anim. Feed Sci. Technol. 68, 277±286.
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Table 6
Growth performance of rats fed on experimental diets during 21 days, g (meansS.D.)a
Diet with meal Feed intake Body weight gain Feed/gain (g/g)
A 256a39.8 86a17.6 3.02a0.16
ALAC 245a32.8 79a13.8 3.13a0.16
B 276a32.4 92a16.7 3.04a0.29
BLH 271a39.1 92a18.6 2.99a0.19
aValues with the same superscript are not different atp0.05.
Carr, R.A., 1995. Processing the seed and oil. In: Kimber, D., McGregor, D.J. (Eds.), Brassica Oilseeds. Production and Utilization, pp. 267±290.
Grala, W., Verstegen, M.W.A., Jansman, A.J.M., Huisman, J., van Leeuwen, P., 1999. Apparent protein digestibility and recovery of endogenous nitrogen at the terminal ileum of pigs fed diets containing various soybean products, peas or rapeseed hulls. Anim. Feed Sci. Technol. 80, 231±245.
Pastuszewska, B., Buraczewska, L., OchtabinÂska, A., Buraczewski, S., 1998. Protein solubility as an indicator of overheating rapeseed oilmeal and cake. J. Anim. Feed Sci. 7, 73±82.
Smulikowska, S., Chibowska, M., Alloui, O., Minorska, A., 1992. Studies on feeding value for chickens of raw and hydrolyzed rapeseed lecithin. Oil Crops XIV, 348±357 (in Polish).
Smulikowska, S., Pastuszewska, B., Mieczkowska, A., OchtabinÂska, A., 1997. Chemical composition, energy value for chickens, and protein utilization in rats of rapeseed expeller cakes produced by different pressing technologies. J. Anim. Feed Sci. 6, 109±121.
