for dairy industry

2. Progress Seminar

3. INTRODUCTION
Shelf life is the length of time that a product remains saleable without
appreciable deterioration in its quality and acceptability
Factors influence are broadly classified as intrinsic and extrinsic
factors
Intrinsic factors-raw material type & quality, product formulation and
structure
Extrinsic factors-final product encounters as it moves through the food
chain
Interactive - physical, chemical and microbiological deterioration and
loss of acceptability

4. Cheese puri mix
Cheese-puri mix is a dry, convenience product-cheddar cheese,
ghee, maida, SMP and permitted flavourings and preservatives
Composition;

5. Moisture absorption result in nonenzymatic browning, lumping,
caking etc
Being a fat rich product- sensitive to lipid oxidation
Extent of changes dependent on the extent of moisture / oxygen
absorption by the product
Shelf life influenced by the product properties, barrier properties of
the packaging and the storage environment

6. Objectives
Develop mathematical models to predict the shelf
life based on onset of deterioration due to
moisture absorption
Develop mathematical models to predict the shelf
life based on onset of deterioration due to
oxidative rancidity

7. Time required by powder to reach critical moisture content
θs = [ wd / (p* K AP )] Xi∫ Xc [ (d XθS ) / (Rhs – aw )
where;
θs – shelf life time(days)
Wd – dry weight of powder
p* - saturation vapor pressure of water at storage temperature
K - water vapor permeability of packaging material
AP – surface area of packaging material
aw - water activity of powder at storage temperature
XθS – moisture content
Rhs - relative humidity of storage environment
Xi- initial moisture content
Xc- critical moisture content
Critical moisture content - determined separately for two
approaches – cakiness & nonenzymatic browning

8. Moisture sorption study
Equilibrium moisture content (EMC) - Adsorption of moisture by the
cheese puri mix at different RH and temperature
Seven saturated solutions – Different RH and EMC was investigated for
temperatures of 35˚C & 45˚C
ERH values for saturated solutions changes with temperature –
Equations developed Labuza (1984)

9. Effect of temperature on equilibrium moisture content

10. Mathematical Modeling of Isotherm
EMC and ERH data were fitted
GAB
(Rockland 1987)
W - is equilibrium moisture content
Wm - is monolayer moisture content
C & k are constants
Constants of selected model – non-linear regression analysis
Testing of fitness of data and accuracy of prediction-Relative deviation
%E
E=(100/N)Σ (| wcal -wpre|/ w cal)
%E< 10 - for a good fit

11. GAB constants and goodness of fit of data
Model parameters
Model R² %E
C K Wm
(% db)
At 35˚C
GAB
4.0132 1.060 2.24 0.949 7.699
At 45˚C
GAB
0.727426 1.088507 2.69 0.991 8.550

12. sticky point temperature
Reviews- suggests determination of sticky point temperature
- sudden change in torque on shearing
- sample sticking to a glass surface
Sample equilibrated @ different moisture content & temperature
Sample sheared using Brookfield viscometer& torque was monitored
For a given moisture content temp of sample- sudden increase in
torque is taken sticky point temperature

13. Moisture gain v/s cakiness

14. Non ezymatic browning
Browning both subjective &objective methods
subjective - sensory evaluation
Objective
- Enzymatic digestion method (Polombo et al. 1984)
- Images scanned at an interval and imported to
adobe Photoshop lab, histogram analyzed for lightness, a
&b
Change in color
∆E=√(Lo-L*)²+(ao-a*)²+ (bo-b*)²
Lo, ao , bo - zero day & L*, a*, b* -interval

15. Moisture gain v/s Non-enzymatic browning

16. Moisture gain v/s delta E

17. Sensory evaluation data of product kept for shelf life studies
(37˚C& 64% RH)

19. Methods adopted
Sorption study Static moisture gain /loss by/ from the test sample
Sticky point Temperature at which the force necessary to turn
temperature impeller in a material increases suddenly (Lazar et
al.1956)
Non enzymatic Enzymatic digestion method (Polombo et al. 1984)
browning
Oxidative UV absorption of steam distillate at 280nm
rancidity
Peroxide value Standard method prescribed in Kirk &
Ronald(1991)

20. Work to be done
o2 permeability & water vapor permeability of
packaging material
Establishment of critical NEB & corresponding
HMF
Max peroxide value limiting shelf life & rate of
oxygen absorption by powder
shelf life studies (37˚C& 64% RH) under progress