Resultados Presupuesto Total

heigh t of 8 cm. The elution buffer pH -vras 5. 25. Tn e long column for acidic and neu tral am ino acids c ontained r e sin type UR 30 to a h eigh t of 58 cm . Buffer , pH 3 . 25 , ,.ras used a s eluant , b eing replac ed after 90 min by a s econd buffer at pH 4. 30 . T"n e fl ow· rate for all buffer s was 68 ml/hr , an d the flow rat e for

ninhydr i n wa s 34 ml_/hr

.

Cal ibrati on cons tant s for the amino acids wer e ob taine d from cal ibration runs using a standard amino ac i d mixtur e (Pi erc e Ch em i c al Co . , Il l i no i s ,

u. s.A. ) .

_Peaks ob tained from th e che e s e sampl e s wer e identi fied from standard elution tim e s , and quanti tated by th e height-wi dth m ethod o f m easur em ent . Amino _{acids can b e e s t imated thi s way wi th an} accuracy of + 3% for the maj or p eaks (l\'oor e

&

Stein ,

1963 ) .

Determination o f aci

d

in ch e e s e. Th e

leve_{l s} o f _{acid pho sphata s e i n cheeses made id} th _{singl e-s train} star t er s iver e determined using th e assay pro c edur e described b efor e (po 70 ) . Th e campl e consi sted of a bl ended one-fifth dilution of che e s e sampl e , prepar ed as for plate counting, wi th th e addi tion o f m er thiolate to a final conc entration of

0 . 0 3%

to prevent bac terial growth. Sinc e no thing ;.ra s known about sui tabl e inac tiva ting tr eatm ents for th e phosphata se_s o f th e starter s trains , i t wa s not po_{ssible to include a control ch eese} sampl e in whi ch pho sphata s e ac tivi ty had b een inactivated. Henc e , a s a control for th e assay,

2 . 0

ml o f di still ed wat er was sub­ sti tuted for th e ch eese sampl e .

Flavour a ss e s sments. A panel of 6 to 10 experienc

e

d judges assessed th e ch e e s e s for Cheddar flavour and such o ff-flavour s a s

90

b i t t ern e s s , a s tr ingency , frui tine s s and sharpn e s s . The int ensi­

t i e s of th e s e flavour s vrer e scored on a sca.l e of 1 to

5 ,

and th e

desirabi l i ty

o f th e overall ch e e s e fl avour on _a scal e o f 1 to 9 as described previously

(

see Y•

7 9 ) .

R:SSULTS

?'anufa.c and data. Th e manufac turing and

analytic al data for the che e s e s have b een included

(

Tabl es

V and

VI )

sinc e it i s di ffi cul t to assess th e significance of bac t eri­ ological fi ndings unl e s s th ese data are kno:m.

Th e sal t-in-moi s t� e values o f th o first s eri e s o f cheeses

(I)

varied from

3. 5 5%

for ML 1 t o 4 .

25%

for H?. T'nu s th e effect

of 1\aCl

on tee

_curvival o f th e s tar t er organ i sm s

and

pro t eolysi s

i n th e che e s e migh t no t b e stri c tly compe.rabl e b e h·een the

different

che e s e s . A s econd s eri e s o f ch e e s e s

(II)

was made , k e eping th e making of th e ch eeses a s constant as po ssible. The

sal t-in-mo istur e value s of

thi s

s er i e s of cheeses 'ftler e all similar

(

Tab l e

VI )

and c

l

ose to th e average value of

4. 5%

ob tained in c omm erc ial ch eese s .

To compensat e

for the fac t th at the moisture conten t s of the

milk

and curd

differ from that o f th e ch eese after "pr e ssing " , the ac tual counts obtained a s per ml o f milk or p er gram of ch eese curd

have been expr es sed as per gram of curd having a mo i s ture

content equal to _that of _{th e fini shed ch eese.} Th e fac tor used

to adju st the counts -v:as obtained from determination of th e moi sture contents o f the milk , the curd at "draining " , and

Tabl e VI. Routine _analyses o f cheosos a. t 1 4 day s . Cheesema.king seri es Starter strain 'Moi s tur e % Fa t % NaCl % pH

Sal t-in-moi stur e %

--- -· I I I I HP

li'TL1

us 3 zs 3 3 . 8 36 . 6 3₅.6 34 . 0 37 c 5 3 5 . 5 36 . 5 37

.o

1 . 44 1 . 30 _{1 . 34 1 .} 39 4 e 92 4. 9 2 4o 9 5 4. 94 4. 25 3. 5 5 3 . 7 5 4 . 08 II li II II AM1 .A.M2 HP 11L1 35 . 3 34 . 1 _{33. 9} 34 . 3 3 5 . 5 36 . 0 36 . 5 37 . 8 1 .

67

1 .

55

1 .

6 2

_{1 0 6 2} 5. 0 1 4. 98 4. 96 4. 99 4. 7 3 4 . 55

4.78

4 . 7 2 \0 1\)

imr:1 edi a t ely p1" ior to sal ti ng

(Tabl e V) ,

and tnc moi sture

co

n

t

e

nt

s

of th e fin i sh e d ch e e s e s

(Table ·vr ) .

Th e moi s ture c o ntents o f th e milk

u sed for a l l ch e e s e s

was

87% (

i . e. s o l i d s content

1 3%)

at th e time of inocul ati o!l. In thi s v<ay a true i ndi c a t ion of

th e ir.cr 0as e of star t r numb ers c an be obta.i:'led , :ra th er than an

increa s e

d.u e to

_a c o n c e· .tration effec t a s rr:oi s ture i s progres s-

iv ely lost from th e curd.

1·:i th al l s trair:s , _{th e} Daxitmm popul a t i ons wer e a_ttai_r

.

_ed dm·ing _cheesemaking

(

Fig s 1 8 anci. 1 9

)

. Iav1son & ?eagan ( 1 9 57 )

s ir.:ilarly fou!;.cl tha t maxir::um popul ati ons of start er •.;er e a ttained

duri ng making. nOvievor 1 c o n si d erc..bl e _{di fferenc es} 1.; er e found in th e popul a ti o n tr er�ds of t!1e star ter s <iurir;g the ch e e s emaking

pr o c e s s

(

Tabl e

VII ) .

Tl1 e g:c eatest incr ea s e _in c el l nw"TTb er s

o c curr ed du:- i r.s _{t�EJ fir st}

2-�-

t o ₃ h r o f choeser::akir.g to th e s taee after tho •·;hey had been ru.n o "!.'f

( 11Dry").�

lUri ng

th i s

8

In document Memoria de actividades de Red es (página 105-111)