Ondetstepoott Journal of rf'tuinwy Sc£ence and Animal lndu.stry, Volume 15, ,\'umbers 1 and 2, Iuly and October, 1940.
Printed in the linion of South Afriea by the Gon~rnment Printer, Pretoria.
The Biological Value of the Proteins of Maize and Maize Supplemented with Lysine
and Tryptophane.
By J. S. U . .YIARAIS aurl D. B. S:YH;Ts, S<\dion of Nutrition, 0 n der~t epoort.
I~ the continuatiou of lHH ~tudie . ..; on the nutritiYe Yalut> of tht>
different plant protei11s, the protein~ of maize were itn-e,-tig-ated by means of tbe Thoma>i-.Mitl'hell methotl fOl' (letermiuing the lJiO!log-icnl Yalues of proteins.
AH n feeding-stuff lllaize OL·cupie" a uuiL1ue positiou .in thi..; country in that it i . ., the cheapest aucl mo,.:t extensively gro"·u animal fee1l, which provides both the nutritional elements now know11 to he
seriou~ly defil'ie11t in the natural pastnres of the summer rainfall arPa (turing- t.he wiui.er ..;easous. Although maize i~ richest in nnhoh:vrhaie and hence ]Jrovide;; an ex('ellent ..;ouree of energy during "·inter sup]llementation, it ha:3 abo been ~ho1Y11 to proYide sutticieni protein for the maintenance requin•Jue11b of animals whtm fed in the correct
qu.antitie.~. In mai?:e, therefon•, this (:ountry pos..;l'Si\Ps a valuabile animal feed which should be utili~ed to it...; fullest extent. It is, therefore, essential that a 1letailed lmo,dedge about. its nutrihonar qualities ,,hould be available. Fur thi,.; reason a special study has been undertaken to inYestigate the proteill of maize in OrOer to .a;;certaiJJ to what extent it ean bt~ 111ili~ed hv the .animal and whid1 components limit its utilization so that, if pc;;;,;ible, these deficiencies can be elimi11atel or rectified in pr<H~tice hy ;;eit•ntific 811pplemeutatiou. Aeeording to Osborne <lll1l .YJeudel (.1914) ~ein the mo~t impor- tant of the mai~e proteins is deficient in the essential amino acicls lysine and tryptophane. Zeill "UPlJlementerl wii.h iryptophaue is capable of supplying the nwintenanee requirements of rats, but growth t:an only take place after fm-ther supplementation with lysine.
A similar deficiency ha:; also been est a blisherl by Hogan (1917) for the proteins of the whole maize. ln tlw~e experinwnis conducted by him the protein intakes were not eq ua lizNl. 'L'hus it is d ifficuilt to as~ess
the true n1lue of these re::mlts. Ke,-ertheless. the reactions on growth, after supplementing with these amino acids, were sharp enough to justify the given interpretation. The results of Hogan do not conform "·ith those of :Mitchell and Smut:; (l9a2). Ar~('orrling:
197
BIOLOGiCAL VALUE OF PiUJTElXS.
to the latter workers 110 S1l}JplemeHtatiou oc-eunecl when tryptoplwne alone "'"as a deled and only a slight impro\·ement after lysine supple·
mentation. .\ markell improvement wa:-;, however, obtained by su pplemen ti 11 g with lysine an cl tryptophane si m ultaneou6ily.
~ ohYi thiil au ding theoe a mi11o ac·id deficiem·ies of maize proteins Contesco and Howan (19:jf)) succeeded in keeping
42
months old pigc;in excellent condition on a mai:1:e ration without the occurrence of :llly sign~ of ill-health. An average clail.v gain of 0 · 417 Kg. per head was obtained. It is well known that the different proteins of the maize kernel supplement en<'h other. The protein containc·d in thP embryo improves that of the rest. For t ht- whole maize a biological value of 69 has been determined hy Laporta and eo-\\orkPr,; (19:171.
'vhiilst tlw biological value of thP proteius without the embryo is only .jO. Similarly maize supplt•mented by a gluten lJrepara tion gi n•,_;
excellent grmYth with y<nmg· pigs according· to Hart and 1fd'ollum (1!!14). .
The biological value~ of maizP, with rat~ as PXperimental animals, are, as reported by }fitchell (19;.?4) at 5 and 10 per cent.
p1·oteins levels, 72 and 60 respec.ti vely. \Yi th pigs on a [J per cent.
levE'l Mitehell and Kick (1927) found a ntlut' of 54, whilsi Gaudwr and Popov (193(i) obtained a slig·htly lower ntlue of 49. Boas Fixse11 ancl Jackson (19:32) experimenting with rats found a biological value of 67 for whole yellow maize at a 7-R per cent. protein level. Au exeeptionally high biological value of 9R bas been estahllished hy Smuts (19:HJ) for sheep on a maintPuance ration.
ExPEROlKX'L\L.
Rats were used as experiuJPntal animals. AJl cletenni11atious were c:arried out according to the method of Mitchell (1924). Onl~
onp biological value was determined on a series of six rats. Th<·
nitrog·en low period was conducted Pither prior to or after the protein period. Six to seven day periocls were allowed on a nitrogen ao\\
ration to establish eonstant nitrogen exeretion. For the protein periods at least 10 days were allowed. Collection periods were of
~even day's duration. Fe203 was used a~ faeeal markers. The urine was colleetecl in aeid and the daily faeees digested by the Kjeld.ahl method. The week's digests of faeee:-; >vere made up to volumH and aliquots distilled for nitrogen determination. The urine coUeeted over the period was made up to a known volume and aliquot~
analy~ed for nitrogen. The rations were made up so as to contain approximately 8 per cent. protein. The percentage eomposition of the different rations is tabulatefl in Table I. Analvses were made of all rations after eareful mixing·. To prevent d~terioration, the rations \Vere stored in an ice ehest.
RESULTS.
The nitrogen metabolism data as well as the calculation of the biollogical values are given in Table II. The standardizing periods on the nitrogen low ration preeeded the protein feeding periorls in the three cases of yellow 1naize supplemented with lysine and tr,yptophane
W8
J. S. C. MARAIS ASD D. B. S~IUTS.
separately and yellow maize ~npplemente(l w.ith lysine and trypto- phane simultaneously. For t.he yellow and wh.ite maize periods the nitrogen low period ·was conducted after the protein periods.
The caleulation of the biologica!l values is l1a,:ed on thP principles as expounded by Mitchell (1924) namdy that the metabolic faecal nitrogen is proportional to the flry matter intake and that t.he endogenous urinary nitrogen is proportional to the body ''eight.
TARLE I.
Perr:entage Compost:tion of the Ration$.
==-:::== = ====c== = ===:==== == ··-· -
I '
I Whole ·I ':Yhole~
WholeIngredients.
Whole white maize meal. .......
Whole yellow maize meal. ......
d-Lysine-di-hydrochlori<lt· ....... Tryptophane .............
Butter fat (1) •..•. . . ... • •
Cod liver oil. .......
Sucrose ..............
Harris' Vitamin B complex (2) ..
Salt mixture (Hubbel etc.) (3) •••
\Vhole egg white (4 ) •• . • • • • • • .••
NaCI. .............. · · · Agar ..... Starch ( dextrinized) ...
TOTAL .....
.PERCilKTAGE N ......
- - --- -- - -- -- - - -
Whole v\"h I Y ll - "Yellow y ello"-
r 11
°
c I "'Ie .0" I 1Iaize ~ J'Iaize -'-- 'X. Low. \\'hite LC ow , d a1ze , . iL .· ..L}[a.ize. 1faize. , - ' • , -·- 1 ysme •
I
8·0 2·0 10-0 :2·0 :2·0 3·R 1·0 :2·0
' 69·2
- - - - 100·0
0·67
I Lnine. . 1 , Irypto-phane. Trypto-phane.
----~--- --~
___
. - --81·6
84·2 8:hi 82·8 81·1
0·2 0·2
0·15 0·15
8·0 8·0 8·0 8·0 8·0
2·0 2·0 2·0 2·0 2-·0
3·4 0·8 :2·3 2·0:) 3·55
2·0 2·0 2·0 2·0 2-0
2·0 2·0 2·0 Z·O i 2-0
l·O 1·0 1·0 1·0 1·0
100·0 100·0 100·0 lCH.)·O 100·0 1·44 1-44 1·59 1·51
J
1·49(')The butter fat has been filtered through a course filter paper to remove a-ny casein.
(2
) The Ha-rris' Vitamin B complex is a prepara-tion of "The Ha-rrir; Laboratm·ics ", Tuckahoe, :New York.
(3) A new salt mixture described by Hubbel, R., l\'Iendel, J. B. and ''\'akeman, A . . 1.
(1937) J. N1ttr. Vol. 14, pp. 273-285.
('1) The whole egg white has been dried on a watcrbath and extmcted with ether.
As can be seen from these tables a significant difference is mani- fested between the biological values of whole white maize and whole yelilow maize, the values being 76 ± 1· 91 and 67 ± 0 · 98. The rlifference of 10±2·15 which gives a t value for N ±10 of 4·66 denotes a significant difference at p ± 0 · 001. No signifinant difference is manifested between yellow maize and yellow maize supplemente(l separately with lysine and tryptophane. The biological values for the supplementations are 70 ± 2 · 63 and 66 ± 0 · 75 respectively. The differences are 3
±
2 · 63 and 1±
1· 23, which gives t values for n = 10 of 1·14 and 0·81 respectively. These t values denote that. the differences are insignificant. The simultaneous suppilementation with the amino acids, however, enhanced the biological value to 81 ±0·61, which means a difference o£ 14+1·15 and therefore a t value for11 ,= 10 of 12 ·15 makiug thiR result highly significant at p
=
0 · 001.199
~ 0 0
..; ..; ,.Q .~ ,.Q bO
"
·:;;:::
0::: " .
bO-+'> z ] ~ I~]o
-+'> =a~
al > " ~ l H "'if:: gm. gm. gm. 1 179 185 183 2 210 210 210 3 157 155 156 4 170 174 173 5 149 150 150 6 164 160 162 1 168 190 179 3 210 220 315 3 140 158 149 4 157 175 166 5 143 150 146 6 150 164 157 13 318 216 217 14 156 160 158 15 181 188 185 16 188 190 189 17 198 196 197 18 147 149 148 13 200 216 208 14 142 164 153 15 170 194 182 16 184 198 191 17 185 301 193 18 140 158 149 ---TABLE II. Nitrogen ilf etabolism Data and the Calculation of the Biological Value. N-Low PERIOD.
I
Endogenous Metabo1ie h
z z
'"0z
N. ai 0z .s "
0 '"0 ---1 '"0 ;::: R· za5 >=i"
~r g .
.l.s "
Zoo I,.0 ~
"
h~.s
h~ h~ 5b,j .-o" .... p.,al -::::: .-oa5 ~2 ~2 :-;::::~ [ .... h 0 g 0 ~::: 8)~ o.S al >='< '"0 00 ·~ ·c .... . -+'> al al "0 "al 0 al ,.0 " s 0 ...."
~~ ~~ ~R P-<R p..,~ RR <li ~p P-<bO p..,~ RP ~ z gm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. mgm. 14·1 -49·6 3·53 ---33·6 13·0-
-- 12·3 -36·3 2·94 ---23·6 13·0 -- 10·7 -34·4 3·21 --- -
24·0 15·4 ---- 11·1 -36·4 3·38 ---20·8 12·1 ----
ll·9 -37·8 3·18 ---24·8 16·5 ---- 12·1 -41·4 3·42 ---27·6 17·0 --- WHOLE WHITE MAIZE PERIOD (1·44 PER CENT. 16·7 240·5 56·0 3·52 58·8 -3·8 240·5 71·6 13·0 23·3 48·3 192·2 +112·9 17·4 ?50·6 41·3 2·94 51·2 10·0 350·6 107·6 17·0 36·6 71·0 179·6 +101·8 15·4 221·8 38·0 3·21 49·4 -11·4 231·8 72·8 15·4 22·9 49·9 171·9 ±111·0 14·6 210·2 40·0 3·28 47·9 -7·9 310·2 79·2 12·1 20·1 59·1 151·1+
91·0 12·1 174·3 30·4 3·18 38·5 -8·1 174·2 53·2 16·5 24·1 29·1 145·1+
90·6 15·3 230·3 48·0 3·42 52·3 -4·3 230·3 87·2 17·0 26·7 60·5 159·8+
85·1I
N-Low PERIOD. 14·3-
49·8 3·48 -- -
30·8 14·2-
---
12·9-
44·2 3·43-
--21·2 13·4-
---
14·6 --l8·4 3·32 -- -
30·0 16·2--
---
12·6-
44·0 3·49 -- -
30·4 16·1-
---
13·3-
41·4 3·11- -
-28·8 14·6-
---
12·4-
45·6 3·68 -- -
32·4 21·9-
---
-WHOLE YELLOW MAIZE PERIOD (1·44 PER CENT. N.) 18·1 260·6 49·6 3·48 63·0 -13·4 260·6 114·0 14·2 29·5 84·5 176·1 ± 97·0 17·0 244·8 44·0 3·43 58·3 -1<'·3 244·8 104·8 13·4 20·5 84·3 160·5 ± 96·0 18·1 260·6 38·4 3·32 60·1 -21·7 260·6 112·0 16·2 29·5 82·5 178·1 ±110·2 14·2 204·5 36·0 3·49 49·6 13·6 204·5 106·4 16·1 30·8 75·6 128·9 ± 62·1 18·1 260·6 40·8 3·11 56·3 -15·5 260·6 107·2 14·6 28·2 79·0 181·6 ±112·6 15·9 229·0 42·4 3·68 58·5 -16·1 229·0 106·0 31·9 32·6 73·4 155·6 ±;80·6h
-~
.-<;::: ~:-;:::: ~ ~..c :9 C)·~ 0-;-+0 -+'> al "' ":ll ~~ e.~ P<·~ <li~ 8~-
--
- -- -- -- - 77 100 84 100 83 100 81 100 83 100 78 100 ---- 81 100 = =- - -·
- -- - - -
-- -
81 100 82 100 85 100 82 100 84 100 81 100 ----
83 100 ----~ " '5b . 0" ~ >=' o~ ·~ al >='<>
-
- - - - - 80 73 78 72 83 73 -- 76 ~ -·- -.. -·- -- - - - --·-- 68 66 68 63 70 68--
67 ~t:::: >-< 0 t"' 0 c;J >-< 0 ~ <1 ~ .q l'j 0 ":! 'tl .p;j 0 >-3 l'j H
z
w1\:) 0 1-'
c
z
...,"'
>i:~ 'rt ·a
::: "
43 ·a H --------- I gm. f)(J 2 !l3 3 98 4 90 i) 96 6 103 1 105 2 90 3 98 4 99 5 109 6 90 13 1 123 14 112 15 11 :; 16 112 171 108 18 112I
13 131 14 1:l0 15 112 16 114 17 111 18 ll8~ ..c to ·a ~
.S
F< gm. 93 (12 05 87 95 lO:l 107 100 107 104 117 98 118 1 ll:~ 104 It:!! 108 114 142 1 130 125 ]•)•) 12:3 124 I ---·c;.: • b1l~ ,;,.0 a-~ > "' ~!$
'L\BLE II (a). Nitro_tJ<'II Metabolis111 lJuta anti till! Calr·ulation of t!tc Hiolu.rrical Value. '""' e e ;....
" 6·1
~..., ~..sz.
"
B~2"l..s
z
~~ -~ ~ ~r.,Metabolic N.
.,
!;c__; :.. ~ ;... h CJ c C,) coe ~~ ~=:N-Low Pe:RIUI>. .e z~
""'"
0"' 0 ~ ""'~~ '""' "' ..c .... c 2 ~
z
>. >,~ :-;::! -~ "' .... p~Enclogenou" N. ; ... """":=, ~ ,...; "
-
P..b"c .... h C) dl p..f=i.a "';:.i~ o.::: ~;j
z
~ >1 ] ~a; 0 ,::: ~
...,
~ ;?; gm.I
gm. mgm. tngm. n1g1n. n1gm. mgm. rngrn. mgm. mgm.l mgm. mgm.l mgm. 1ngm. 9.5 6·2 22·0 3·5iiI
-16·0 16·8 113 6·5 -17·3 2·613-
16·9 18·2 97 G·1 -20·2 3·9:) --12·8 13·2 8() 7 ·1 -26·4 :1·72I
11·9 13·4 96 6·5-
23·0 3·68I
----14·0 14·6 103 6·7 -:l3·1 3·4.5 If! . .j. 18·8 WHOLE ll:T.LOW MAIZE 0·25 I'ER CENT. D-Ln<r:-<F.-DI-HYDRI•CHLORmE l'ERIOll (1·59 PER CENT. N.) 106 95 l03 102 ll3 94 1:?1. ll:l 110 Ill JOt> 113 1:n J:li) lHl 118 117 1·16·0 !l5·4 16·5 3-:;51 21·3 6·1 97·0 16·9 :l-66 16·2 6·6 104·9 16 ·1 3·96 213·1 7·3 116·1 16·9 3·72 27·j 7·4 117·7 22·:! 3·68 27·2 7·1 113·9 17·3 3·45 :l4·5 7·£1 34·8 4·41
I
7·5 37·3 :~·6:{ ()·7 27·~ 4·06 li·!) -I
28-0 4·0fi 7·5 -:l!H! 3·95 7·5 29-~ 3·89 ---- -4·8 !l5·4 39·1 16·8 0·7 96·3 47·4 18·2 10·0 104·9 53·6 13·2 10·3 116·1 44·.5113·4 -5·0 117·7 4\)·4 14·6 7·2 lU·!J 58·9 18·8I
N-Low PERIOD. 18·4115·2 13 ·fi 13·0 :?6·6 24--~ 17·6 15·9 18·4 17·0 14·4 l:l·717-8 1 21·3 74·1
+
::19·8 17·3 30·1 66-:l 32·7 13-(i 40·0 64·9 3-5·2 13·7 30·8 85·3 -54·7 )I). 5 32·9 84·8 l.. 46·1 17·7 41·2 71·7+
36·7 WHOLE YELLOW }fATZE 0·15 PER CENT. TRYP'T'OPHANE PBRIOD (1·51 PER CF::-<'1'. N.) 11·4 171·1I , •.• I
4·11 5:1-::1 18·3 172·1 8·8 132·9 :l~-4 3·63 31·9 11·5 13:l·9 10·2 154·0 25·6 4·06 41·4 15·8 154·0 7·2 108·7 17·6 4·06 2!!·:2 11·6 ]()8. 7 8·1 122 -:3 118 . o 1 3 . 9•> 32·0 14·0 1~2·3 7-!l 119·3 30·0 3·89 :{11·7 10· 7 119·381·5 115·2 :l0·8 ()0-7 111·4 I 58·6 61·9 12·0 15·0 46·9 86·0 1 48·6 78·6 24·2 :l8·8 4!l·8 104·2 I 49·8 53·0 15·9 18·8 34·2 74·5 -:L 38·1 6•).•) 17·0 19·9 42·3 80·0
i :
42·1 i\7 ·2 l:l·7 15·4 41·8 77·.5 + 42·1I I
I -I
£ -=:s ,
__ ;...-+=-""'
~.<>-~oc P..-- ""'~ 83 83 8.5 85 81 85--
84 = 81 83 83 84 85 83--
83 ~h ;lO: :E 43 Q) ;B :Obi> ~0 100 99 100 100 100 100 -- 100 = 100 100 100 100 100 100
--
100 =...,
" 'hil. ..s~ o- ~> 78 69 62 72 72 64 --- 70--
65 65 68 69 65 65--
66 ;;,o.;;~:-- [f) ? ::::: :> ~ ;... ,.... if] :> '4 t:i t:i b:l rJJ ~ q ,.., [f)
1:>.:) 0 1:>.:)
z
;:.:; 19 20 21 22 23 24TAULE II (b). A'dro/}e'fl Metabolism Dat-a and the Calc·ulation of the 1Jiu7o!Jical Value. N-Low PERIOD.
11
--- WHOLE YELLOW MAIZE 0·2 PER CENT. D-LYSINE-DI-HYDROCHLORIDE+
0·15 PER CENT. TRYPTOPHANE PERIOD (1·49 PER CENT. N.) 132 152 142 12·4 184·8 30·0 3·83 47·5 17·5 184·8 55·0 11·5 16·3 38·7 146·1+
99·8 84 100 7!! 123 142 133 10·6 157·9 25·2 3·69 39 ·1 -13·9 157·9 51·5 14·9 19·8 31·7 126·:!+
79·2 84 lOO so 121 141 131 11·4 169·9 30·4 3·94 44·9 14·5 169·9 57·4 19·0 24·9 32·5 137·4 1-82·1 82 100 81 121 142 132 ll·O 163·9 26·8 3·81 41·9 -15·1 163·9 46·6 13·5 17·8 28·8 135·1+
90·5 84 100 82 114 135 125 10·6 157·9 27·6 4·18 44·3 -16·7 157·9 49·4 13·3 16·6 32·8 125·1 1-80·9 83 100 79 108 131 ll5 8·5 126·7 20·0 4·00 34·0 -14·0 126·7 40·0 15·1 17 4 22·6 104·1+
66·1 84 100 82 ---- --
84 100 81 ----===
~ -·1:::
...
0...
0 Q ""' ,-, ;.. t-' ....:.:
t-' ~ ~ 0"'
"d !:0 0..,
t;:j...
'.Z if;Fron1 thP t>tatist i('al auahi;i~ of iltP~P re~lllb it i~ dt~aJ· that I bt•
]l]'()tPin of ,,-hole \YhitP maize i~ ~i~nifi('antl~- ~tqwrior to that of IYholP vellow rnaize. Thi~ difh~rell<'P \\'as r<dh<·r nnexpect .. d, <H1fl can at ]>reseut. only bt· exlllaine<l hy a coll~titutiollal diffPrPllt'P ill th<· protPill nwiPh· of diii'erent strain~ or YarietiP~ of lllai:>:<'. Thi~ point (':til.
bowe~·<·r, tJnl.' l1e ~t>ttlPcll'.' dirpc·t PX]H'l'illlPlltation o11 thi~ a~pn·t.
It i.' hJrlhPr <dso dt>al· that the ~H]lplelll<'llt<ttion 11 ith l.1 ~int· and tryptoph<tllP doP~ not aftpr·t Uw utili:>:<ltion of tht• niimg·pn t·oJdaint•d
111 maJ:>:P. \Yhilr tht· .;illlultaneou,; supplelllt•Jibtiou of ly,;inP and tr,q>tophanP r·ansp,; a I!Htrked im·rpa.;p in thP nit.rng-<'11 11i ili:>::dion of thP protPin~ of .n·llo11 111<11:>:~·.
ThPst• n·~ult~ on lht· ~ti]JjdPlllt'nl<tr.' .. n,·r·t td tht· un1i1Jo <ll'id, o11 till· pro(piu,; of n1ai:>:t' as llll'<hllrPd h,y till• 11itrogt•n uti•li:>::dio11 an• in a•·•·onhllt'l' 11 iih ihP rp,;uii.; oLtaint,d by \[ii<·lwil <111<1 ~llltd.s il!JT.!J ll'ilh till· pained f<·ediii.L(' !t•(•hllique. r't lliil Lt• lloiPd that in thi"
.;(Jlll.\ o11l.1· :t ,;[ig·hi inl'l't'aSt· of :J±:!·(i:; i~ olJtaiJ!l'd h,· tli<' l.l'int•
~upplPllll'llhdion. Thi,; _.;Jnall <liffPreu<·e fall~ 11itl1in the I'XJlPrinH·rdal t•nor. This Dh'<'i'\'ation i.'. tltPl'l'fon·, not i11 a<·•·ord:ntt'l' 11itb ihP fi11ding·~ of \!it('hPll:tlld ~111\Jt.; h\ ltl<'<lll' of ihP pain·<l i'<·Pdillg' it•.;(.
It nm,;i, t:JndoJ'l', hP <t~~lllill't1 tiJ<Ii th<· ~light though in,.;ig·nifi•·ant illl'I'P:t,;P in ni1rog·<'n uiiliz:dion ufiPr the 'l.\·~illt' <tddPndtlltl JJ1<i.\· i11 all prohal,ilit.\' lH·<·onw .sig·uitir·:1nt if tbt· IlllllllH·r of cklPnllinatimJ~ .i~
in<·rp:t~Pd alJ!l lH•HcP ,~Prih· tl1<' indication,; ohtainerl thai h·.;inP 'npplt•I!Jt'lti:dioll on]_,. hring· . .; alwnt a limitt·d illl]ll'lii'PIIIPni i;1 the JJiili:>::ttioll of the maiz<· JIIOtPill'.
( 'tJ);'('L(' 810:\'S.
l. Tht> hiologicnl ,-alues of 11·hole \Yhite nJai:;:,, anrl 1\hole ydlm\
llta!Zt' an• 7ti±l·!ll and 67±fi·D8 at <tppmxi111atel)· S ]lPl' 1'<'111.
1 II otp iII 1 .. 1·e 1.
'2.. The· protPin~ of 11hitc• lll<tlZt" :tlt' ~ignifi('a11tl.1· hPit<·r than that
of .nd I mY nw i:>:P.
:j_ Suppl<,lllent.at.ioJJ 11·ith l.1~illP and t.ryptophanP .;ppara(ely doe~
IIDt ill<'l'l':l~P tlJP llitl'Op_'Pll nii]i:;:atioll of .\·p])tt\1. ll!aizt• (o <lll,l lll<trJ.;:p<J l'X( Pili.
4. Supplt•IlJPiltatiou 11·ith l)sinl' <lnd 1ryptoph<l!JP simn!LtnPouHly marlu·dl_,. in•·rP:J,;p.; iht• niirog· .. 11 ntili:>:ation of iiH• .n·llo"· nJair,e protein.
BOAS FIXSEN, M. A .. .-~.:-;n JACKSOX, H. :\1. ilD:~2). The biologieal values of proteins IV. The hiologif'al Yalues of the protein,; of IY!wat. maizP and mille Bitwhem .• 1 .. Vol. 26. p. nt23.
CO:'\TESCO, D., AND RO\L\:\, G. (l!J:lG). Valuer du mais comnw con,;titnant exclusief de l'nlinwntation tles jPuncs pore8. A.IIIL. !nsf. Nrd. Znotec.
lloumonir. Yol. i5. pp. lO()~Jl:i.
CUCCHER. G .. ANn POPOV. J. D. (Hl:JG).
protein f<~Pds uspd in Bulgaria. Inn.
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