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