Downes, T.E.H.

Hastings, J.W.

Nourse, L.D.

Siebrits, F.K.

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The relative nutritive value of irradiated spray-dried blood powder and heat-sterilizedblood meal as measured in combination with whey proteinT.E.H. Downes*, L.D. Nourse, F.K. SiebritsAnimal and Dairy Science Research Institute, Private Bag X2, Irene, 1675 Republic of South AfricaJ.W. HastingsRadiation Technology Division, Nuclear Development Corporation of South Africa (Pty) Ltd.A method of processing blood meal in which the nutritive value of the protein is preserved is described, sinceappreciable losses occur in the nutritive value of the protein when prepared by heat sterilization with drying atatmospheric pressure in steam jacketed vessels. Blood was spray dried and irradiated at an intensity of 10 kGy.Collectively the heat of spray drying and irradiation was effective in killing both the virus plaque-forming unitsand the bacteria, thus producing a commercially acceptable sterile product of higher nutritive value. The relat-ive nutritive values (RNV) of 50:50 protein mixtures were 0,56 for whey protein concentrate plus heat-sterilizedblood meal and 0,90 for whey protein concentrate plus irradiated spray-dried blood powder. Whey protein con-centrate used as a control has a RNV of 1,0.Omdat die hitte-sterilisasieproses in die vervaardiging van bloedmeel die voedingswaarde van die protei'enaansienlik verlaag, is 'n alternatiewe manier van prosessering getoets. Bloed is gesproeidroog en bestraal met 'nintensiteit van 10 kGy en daar is gevind dat die proses voldoende was om bakteriee en virusse te vernietig son-der strawwe hittebehandeling. Op die manier was dit moontlik om die relatiewe voedingswaarde van die bloed-protei'en te verhoog van 0,56 vir gewone bloedmeel en weiprotei'en, tot 0,90 wanneer in 50:50 mengsels sproei-gedroogde bloed- en weiprotei'en gevoer word, teenoor die kontrole van weiprotei'en alleen van 1,0.IntroductionIt has been shown that vat-dried blood meal (Preparedby heat sterilization with drying at atmospheric pressurein steam-jacketed vessels) has a nutritive value much lessthan would be expected from an analysis of the aminoacid content of fresh blood because the biological valueof both lysine and methionine were reduced to between0-43% of total lysine and methionine values (Waibel,Cuperlovic, Hurrell & Carpenter, 1977). It wouldappear that a similar deterioration pertains in the com-mercially prepared blood meals in South Africa. Un-published work carried out at the Animal and DairyScience Research Institute by G.A. Smith showed that30 - 40% of the nutritive value was lost when comparedto spray-dried blood powder (SDBP) in commercial feedpreparations containing heat-processed blood powder(L.D. Nourse, unpublished observations 1975- 1981). Anegative protein efficiency ratio (PER) results whenblood protein is used as a sole source of protein in a dietdue mainly to a low isoleucine content. When fed in a50:50 protein mixture with whey protein a positive PERof 2,99 was obtained (Downes, Cruywagen, Smith &Pelster, 1882).In the commercial process blood meal is sterilized be-cause of the temperature conditions used. Spray-driedblood powder is not subjected to high temperatures dur-ing preparation. Under commercial abattoir conditions itis not possible to collect blood only from healthy ani-mals, unless an elaborate system of blood collection is in-stalled, so an alternative method of sterilization involv-ing irradiation was tried. The purpose of this project wasthus to test the efficiency of spray drying and irradiationon the relative nutritive value (RNV) and sterility ofblood protein.Materials and MethodsPreparation of spray-dried protein sourcesWhey protein was produced by removing a large pro-portion of the lactose by ultrafiltration and spray dryingthe resultant protein concentrate. Blood was spray driedat an air-inlet temperature of 160°C and outlet temp-erature of 80°C. During spray drying the temperatureof the blood does not exceed the outlet temperature ofthe dryer due to the rapid evaporation of water in thewarmer parts of the dryer. The powder is therefore ex-posed to a temperature of 80°C for a few seconds duringthe process.Stock cultures of Bacillus subtiJis ATCC 6633 weremaintained on Nutrient Agar (Difco) slants, which wereincubated at 37°C for 2 days and stored at 4°C untilneeded. Spore suspensions of these were prepared ac-cording to Busta (1966) and added in a concentration ofbetween 8 x 103 and 1 x 104 per ml before spray drying.These organisms were chosen as marker organisms be-cause of their very high resistance to destruction by heattreatment (van der Heever, personal communication).The blood powder produced was then irradiated at levelsof 10, 20, 45 and 50 kGy and tested for survival of theBacillus organisms. It is, however, known that virusesare very resistant to irradiation but more sensitive toheat treatment. For this reason blood was contaminatedwith 1 x 103 Bluetongue virus (vaccine strain 8) and 1 x104 Banzi virus plaque-forming units per ml before spraydrying and irradiation. The blood powders were thentested for bacterial and virus sterility before and afterirra'diation.Bacterial enumerationStandard plate counts were made in accordance with thestandard method of the International Dairy Federa-tion(IDF, 1981) and the plates incubated for 72 h at30°C. Spore suspensions were subjected to heat treat-ment of 80°C for 10 min and the total aerobic sporescounted on nutrient agar (Biolab) after 72 h at 30°C.Brewer's Thioglycollate medium (Merck) was used fortotal anaerobic spore counts. Plates were Incubated inBBL anaerobic jars (Gas Pak Anaerobic System) at37°C for 72 h. The coliform count was determined onviolet red bile-lactose agar (Biolab) after incubation ofplates at 30°C . Faecal streptococci were counted oncitrate-azide-tween-carbonate agar (Merck) and incuba-ted at 30°C for 72 h. For Salmonella 10 g of the bloodpowder was placed in lactose broth (Merck) for 4 h at30°C. 10 ml of this broth was then dispensed into 90 mlof Selenite enrichment broth (Merck) and incubated at34°C for 72 h. Every 24 h a loopful was streaked ontoxylose-lysine-deoxycholate (Merck), and Salmonella-Shigella media (Merck), incubated at 37°C for 48 handobserved for typical colonies.The products were tested for virus survival by titrationin cell cultures and intracerebrally in day-old mice.Determination of relative nutritive value (RNY)The multi-point slope ratio assay of Hegsted, Neff &Worcester (1968) as described by Siebrits, Esterhuyse &Kemm (1986) with male Wistar rats was used. Bodycomposition was determined by the method of Bell &Stern (1977), without the removal of intestinal contents.Body protein gain was chosen as a measure of responseto dietary protein. At 28 days of age 65 rats were fastedfor 24 h, after which 11 were asphyxiated and used to de-termine the initial body composition. The remaining 54rats were divided into 13 groups of equal mass, onegroup consisted of six rats and received a protein-freediet, while the remaining 12 groups of four rats eachwere allocated to the four sources of protein under test,the diets from each source being formulated to contain3,0; 6,0 and 9,0% protein. The proteins used were wheyprotein alone (control), and 50:50 protein combinationsof protein from whey with either abattoir blood meal,SDBP or irradiated SDBP. The diets were formulated tobe isocaloric at the 3,0; 6,0 and 9,0% protein levels. Toobtain the 50:50 protein mixtures of the blood proteinsand whey proteins, 282 g of SDBP (84,06% protein) and518 g of whey protein concentrate (45,8% protein) weremixed. Similarly an amount of 325,5 g of abattoir bloodmeal (73,0% protein) was mixed with 524,5 g whey pro-tein concentrate. The composition of the various diets ispresented in Table 1.These experimental diets were fed ad libitum from 29to 41 days of age, whereafter the rats were again fastedfor 24 h, asphyxiated, and their body composition deter-mined. The experimental period lasted 14 days insteadof 21 days as the rats on the poor protein diets becamevery weak.The rats were individually housed in metabolismcages, enabling daily collection of faeces and spillage.The differences between the regression lines were deter-mined by analysis of covariance as described by Siebrits,et al. (1986).Results and DiscussionBacterial counts were carried out in two independentlaboratories and the results were similar. Spray dryingwas not effective in killing all of the bacteria present oradded to the blood before it was spray dried as shown inTable 2 under the column of zero irradiation where it isseen that faecal Streptococci and B. subtilis are still pre-sent. Coliforms and Salmonella sp. do however appearto be absent after spray drying. Radiation was, however,effective in removing all the bacterial strains present inor added to the blood, even at the lowest dosage tried, asshown in Table 2.The two virus strains added to the blood, namely theProtein sourceSource A & B Source C Source DDietary component 3% 6% 9% 3% 6% 9% 3% 6% 9% 0%SDBP + whey protein concentrate 5,06 10,12 15,18Blood meal + whey protein concentrate 5,31 10,62 15,93Whey protein concentrate 6,55 13,10 19,65Starch 79,44 74,88 69,82 79,69 74,38 69,07 78,45 71,90 65,35 85Maize oil 10 10 10 10 10 10 10 10 10 10Vitamins and mineral premix 5 5 5 5 5 5 5 5 5 5Source A & B - SDBP and irradiated SDBP plus whey protein concentrateSource C - Abattoir blood meal and whey protein concentrateSource D - Whey protein concentrateS.Afr.J.Anim.Sci.1987,17(2)Table 2 Bacterial counts in spray-dried blood protein(SDBP) before and after irradiation at four levels oftreatmentRadiation dosage (kGy)0 10 20 45 60Bacterial group Counts (per g sample)Total aerobes 1,0 x 10-' <10 <10 <10 <10Total aerobic spores 9 x 103 <10 <10 <10 <10Total anaerobic spores <10 <10 <10 <10 <10Faecal streptococci 3,7 x 102 <10 <10 <10 <10Coliforms <10 <10 <10 <10 <10Salmonella sp. 0 0 0 0 06,0 X 104B. subtilis 7,0 x 104 0 0 0 0Table 3 The relative nutritive values (RNV) of the dietsof proteins processed by the various treatments incombination with whey proteinWhey protein concentrateSDBP + whey protein concentrateIrradiated SDBP + whey protein concentrateAbattoir blood meal + whey proteinconcentrate0,8541" 0,4735 1,000,7148b 0,4531 0,84O,nOlb 0,2993 0,90Different superscripts denote significantly (P<0,05) different slopesSE-Standard error of regression coefficienthardy Bluetongue virus (vaccine strain 8) and the morefragile Banzi virus, were completely inactivated duringthe spray-drying process because neither could be de-tected in SDBP, before and after irradiation, by titrationin cell cultures or intracerebrally in day-old mice. Thisresult indicates that this heat treatment of 80°C for afew seconds was sufficient to inactivate the virus plagues.The results obtained on the determination of RNV ofdifferent proteins are presented in Table 3. Whey pro-tein had a significantly better RNV (P<O,05) than theSDBP, both with and without irradiation. The RNV ofthe abattoir blood meal protein was significantly lower(P<O,05) than any of the other protein sources.The slightly higher RNV of the irradiated SDBP pro-tein over non-irradiated SDBP protein was not signifi-cant but demonstrates that irradiation does not alter thenutritive value. The criticism discussed by McLauglan &Keith (1975) against including a zero-protein group inthe calculation of the respective slopes due to cur-vilinearity does not affect the present results since nosignificant curvilinearity was found and thus it was de-cided to include the data of the protein-free group. Thisalso increased the range of protein intake since the palat-ability of the abattoir blood meal was low.The indications are that palatability is a problem withthe whey-abattoir blood meal diet as the rats showed im-mediate rejection when changed to this diet, with onlylimited acceptance thereafter. This did not occur withthe SDBP diets. It also resulted in a lower protein intakeas illustrated in Figure 1.The severe heat treatment of abattoir blood meal re-sulted in such a dramatic reduction in the nutritionalvalue that 2,25 g of blood meal protein plus 2,25 g ofwhey protein resulted in a loss of body protein whereas2,25 g of whey protein alone gave a gain in body protein(Figure 2).119.2'0 7~:lIIIc:0 !Ju.: ;'.. ;'2 3,;'D. ,;,;3 6Protein in diet (X)Figure 1 Influence of protein source on protein consumption(-- Whey + irradiated SDBP; ------ whey + SDBP; - --whey; - - - whey + abattoir blood meal)32~;;;;;;;;;;;;;~;;;;.: I Initial bode 0 IIQ. I>- I --~ -1 II ~I.S: I /I& I //-=-2 Ic: IIVI /.I:u -_/-30 2 3 4 5 6Figure 2 Comparison between blood meal + whey protein andwhey protein alone in relation to protein consumption andchanges in body protein (------ Whey protein; - - - bloodmeal + whey protein)ConclusionsThe results of this investigation revealed that spray dry-ing plus irradiation at 10 kGy, results in a commerciallysterile product, and due to the great improvement in therelative nutritive value in using this technique, the reg-ulations prohibiting the use of non heat-sterilized bloodmeal in animal nutrition should be changed. This is ofimportance due to the anticipated shortage of protein inSouth Africa in the future. The cost of production ofirradiated SDBP would be higher than that of con-ventional blood meal, but the increase in RNV would re-sult in an increase of the nutritive value of the product,which according to present estimates, would more thancompensate for the increased cost of production. Fur-thermore abattoir blood meal, although useful as asource of protein for ruminants, has very little value inthe nutrition of monogastric animals, but spray-driedblood could be very useful for the latter.A further possibility is that the blood be separated intoplasma and blood cells by centrifugation and then treat-ed separately by the same process. The plasma powderwould have a value comparable to soya isolate or sodiumcaseinate in the production of processed meats.In the separation into plasma and blood cell fractions,60% plasma with a solids content of 8% and 40% cor-puscles with a solids content of 38% is obtained. There-fore, from 100 kg of blood 4,8 kg of plasma powderwould be produced plus 15,2 kg corpuscle powder.Blood cell powder has a lower isoleucine content (0,6%in the protein) than whole blood protein (1,04% in theprotein) so that in using blood cell powder for animalnutrition more isoleucine-rich sources of protein will beneeded to balance the essential amino acid compositionof the diet.AcknowledgementsDr B.J. H. Barnard of the virology department of theVeterinary Research Institute, Onderstepoort, isthanked for his advice, the supply of virus material andS.-Afr.Tydskr. Veek.1987, 17(2)subsequent analysis of the product, while Dr LF. Mos-tert, Senior Research Officer of the Microbiology Sec-tion of the ADSRI is also thanked for the preparation ofthe culture of B. subtiJis and the bacterial analysis of theproduct. The assistance of Mr J. C. Pelster, also of theADSRI, in preparing the blood and whey protein pow-ders was very much appreciated.ReferencesBELL, E.G. & STERN, J.S. 1977. Evaluation of bodycomposition of young obese and lean Zucker Rats. Growth41,63.BUSTA, F.F. 1966. Milk components inhibitory to Bacillusstearothermophilus. 1. Dairy Sci. 49, 351.DOWNES, T.E.H., CRUYWAGEN, e.W .. SMITH, G.A. &PELSTER, J.e. 1982. The use of whey, whey proteinconcentrate and spray dried blood powders in themanufacture of milk replacers for calves. S. Afr. J. DairyTechn. 14, 81.HEGSTED, D.M., NEFF, R. & WORCESTER, J. 1968.Determination of the relative nutritive value of proteins.Factors affecting precision and validity. J. Aqric. Foodc"'hem. 16,190.IDF, 1981. Enumeration of microorganisms colony counttechnique at 30°e. Provisional IDF Standard 100: 1987.International Dairy Federation, Square Vergote 41, 1040Brussels.McLAUGLAN, J.M. & KEITH, M.O. 1975. Bioassays forprotein quality. In: Protein Nutritional Quality of Foodsand Feeds. Part 1. Ed. Mendel Friedman. New York:Marcel Dekker, Inc.SIEBRITS, F.K., ESTERHUYSE, e.D. & KEMM, E.H.1986. The relative nutritive value of lucerne leaf proteinconcentrate (LPC) coagulated by means of steam or hotwater. S. Afr. J. Anim. Sci. 16, 143.WAIBEL, P.E., CUPERLOVIC, M., HURRELL, R.F. &Carpenter, K.J. 1977. Processing damage to lysine andother amino acids in the manufacture of blood meal. J.Agric. Food Chem. 25, 171.

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The relative nutritive value of irradiated spray-dried blood powder and heat-sterilized blood meal as measured in combination with whey protein

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The relative nutritive value of irradiated spray-dried blood powder and heat-sterilized blood meal as measured in combination with whey protein

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