Date post: | 26-May-2015 |
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Health & Medicine |
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Progress Seminar
INTRODUCTIONShelf 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
Cheese-puri mix is a dry, convenience product-cheddar cheese, ghee, maida, SMP and permitted flavourings and preservatives
Composition;
Cheese puri mix
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
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
Objectives
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
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)
Moisture sorption study
Effect of temperature on equilibrium moisture content
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 analysisTesting of fitness of data and accuracy of prediction-Relative deviation
% E
%E< 10 - for a good fit
Mathematical Modeling of Isotherm
E=(100/N)Σ (| wcal -wpre|/ w cal)
GAB constants and goodness of fit of data
Model Model parameters
R² %EC K Wm
(% db)
At 35˚C
GAB 4.0132 1.060 2.24 0.949 7.699At 45˚C
GAB 0.727426 1.088507 2.69 0.991 8.550
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
sticky point temperature
Moisture gain v/s cakiness
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
Non ezymatic browning
Moisture gain v/s Non-enzymatic browning
Moisture gain v/s delta E
Sensory evaluation data of product kept for shelf life studies(37˚C& 64% RH)
Sorption study Static moisture gain /loss by/ from the test sample
Sticky point temperature
Temperature at which the force necessary to turn impeller in a material increases suddenly (Lazar et al.1956)
Non enzymatic browning
Enzymatic digestion method (Polombo et al. 1984)
Oxidative rancidity
UV absorption of steam distillate at 280nm
Peroxide value Standard method prescribed in Kirk & Ronald(1991)
Methods adopted
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
Work to be done