April 18, 2015

Homework Help: Food engineering/biology

Posted by Jennifer on Sunday, May 23, 2010 at 7:22pm.

Can anyone help me out with this problem. For part a i understand i plot microbial numbers against time on semi log paper to determine D value for the two temperatures. But i'm unsure how to do part b.
Alicyclobacillus acidoterrestris is a quite hat resistant microorganism that has been causing problems in the fruit juice industry.Data below shows the thermal inactivation data determined experimentally for A. acidoterrestris spores in orange juice at 85.2 and 91C.

85.2 degrees celcius
Time Spore concentration
(min) in the juice N (cfu/ml)

0 min 1.9* 10^7
20 min 1.6* 10^7
40 min 9.1* 10^6
60 min 7.9* 1^0^6
80 min 4.8* 10^6
120 min 6.2* 10^5
160 min 8.9*10^4
180 min 5.5*10^4

91 degrees celcius
time (min) Spore concentration
in the juice N (cfu/ml)
0 min 1.7*10^7
2 min 8.1*10^6
5 min 4.0*10^6
8 min 2.6*10^6
11 min 1.8*10^6
14 min 8.0*10^5
16 min 5.9*10^5
18 min 2.6*10^5
21 min 2.8*10^5
a. Determine thermal resistance parameters of Alicyclobacillus acidoterrestris in the orange juice.
b. Suggest an appropriate P91C]value for this juice.


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