c. Estimation of shelf life of dried cultures L. rhamnosus R21 by Labuza model 1982
Estimation of shelf life of dried cultures using Labuza model 1982, which utilize the
sorption characteristics isotermik food approaches the critical moisture content. The data needed to determine the shelf life of the product is the initial moisture content Mi, the critical water
content products Mc, the equilibrium moisture content Me, packing permeability kx, extensive packaging A, weight of products to be packaged W, saturated water vapor pressure
at storage conditions Po and the slope of the curve slope of the sorption curve isotermis b. In addition to the water content of the data, other data needed to determine the shelf life is
secondary data obtained from the study of literature. External conditions temperature and RH assumed to be constant during storage, the ratio of water vapor permeability and extensive
packaging kx unchanged and isotermis considered linear sorption on the interval between initial moisture and humidity critical Labuza 1982. Slope isotermis sorption curve is the rate of
increase in the water content of a
w
beginning to reach critical water levels to be predicted Labuza 1982. Slope value can be determined as the ratio between the difference in initial
moisture content and moisture content critical to the difference between the value of initial water activity with the activity of water at the critical moisture content is reached.
The results showed that the initial moisture content Mi dried cultures L. rhamnosus R21 bk is 2.17 or 0.0217 g H
2
Og solids. Value of critical moisture content Mc dried cultures L. rhamnosus R21 in this study is determined by the calculation of the total bacterial culturing dry
L. rhamnosus R21. Critical moisture content dried culture obtained based on the time it takes to maintain the viability of the culture critically dry before experiencing a decrease in the amount of
2.6 x 10
11
log cfug where the water level is at 14.47 bk or 0.1447 g H
2
Og solids Figure 3a. Determination of the critical viability of 2.6 x 10
11
log cfug is determined by the amount of lactic acid bacteria before it has decreased drastically during storage indicating not change the
stability of the bacterial cells because of the increased water content. a
b
Figure 2. Acidification activity of culture of L.rhamnosus R21, a the relationship the number of LAB with acid titration count , b The relationship of the number
of LAB with pH of acidified skim milk
2 4
6 8
10 12
14
0.00 0.05
0.10 0.15
0.20 0.25
0.30 Acid titration count
Co u
n t
o f
L AB
l o
g c
fu g
Acid titration count 2
4 6
8 10
12 14
5.6 5.8
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