Estimation of shelf life of dried cultures L. rhamnosus R21 by Labuza model 1982
a b
Figure 3. a Relations of lactic acid bacteria with the water content during storage for determination of critical moisture content Mc, b sorption curve isotermis dried
cultures L. rhamnosus R21 for the determination of the equilibrium moisture content Me.
Equilibrium moisture content Me is determined by a linear equation of sorption curve isotermis dried culture on the relationship between water content with water activity of dried
cultures were measured using aw meter. Isotermis sorption curve slope values b were determined in the linear region of the curve of the relationship between water content with water
activity Arpah 2001. Slope value of dried cultures L. rhamnosus R21 is 0.2789 from the calculation of 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. Of linear equations in Figure 4b obtained equilibrium
moisture content Me on storage at 75 RH bk 19.75 or 0.1975 g H
2
Og solids, while storage at 80 RH obtained the equilibrium moisture content of 21.11 bk or 0.2111 g H
2
Og solids. Saturated water vapor pressure Po of storage conditions on the shelf life determination is the
saturated vapor pressure at 75 RH and a temperature of 30
o
C in the amount of 31.824 mmHg Labuza et al. 1984.
Packaging used in determining the shelf life of dried cultures are usually aluminum foil packaging, but can also use aluminum foil packaging are plastic coated. The use of plastics for
packaging is quite interesting because of its favorable properties such as easy to set up, has a high adaptability of the product, such as non-corrosive metal containers, as well as easy handling
Syarief et al. 1989. According to Latif 1999 packaging permeability kx for PE poliethylene = 0.169 g H
2
O m
2
.mmHghari; PVC polivinylchloride = 0.544 g H
2
Om
2
.mmHghari, while aluminum foil laminated with plastics PE = 0.013 g H
2
Om
2
.mmHghari Histifarina 2002. Calculation of shelf life of the packaged material assuming weighing 20 g wet weight 19.98 g dry weight, widely used packaging by 11 x 7 cm
2
then the ratio of surface area with heavy packs are packaged culture is at 0.0004 m
2
g .
y = -1.2693x + 29.774 R
2
= 0.8393
2 4
6 8
10 12
14