The document discusses aseptic processing, which involves sterilizing food products and packaging them into pre-sterile containers, often using ultra high temperature (UHT) methods. It explains the heat transfer process involved, using mathematical models such as the explicit finite difference method, and details microbial inactivation and nutrient degradation during the processing. Additionally, it describes how parameters like heat energy, velocity distribution, and initial microbial population impact the efficacy of the aseptic process.

1. ASEPTIC PROCESS MODELLING
Pragati Singham
Ph.D(FPE)

2. Introduction
 Aseptic processing is the sterilization of the food
product (direct or indirect) and packaging into pre-
sterile containers.
 It may often called UHT (Ultra High Temperature)
processing
Fig. Aseptic process

3.  Three process occurs due to heat treatment
during the process
 Heat transfer
 Microbial inactivation
 Nutrient degradation

4. Heat transfer
 Mathematical model can be used for the heat transfer
 Among the different mathematical models explicit finite
difference method can be used
 Assume there is a liquid food (milk or juices)moving with
laminar flow inside a scraped surface heat exchanger
x = l
δx

5.  The liquid has uniform distribution i.e ρ, Cp, K, A will be
constant
 Heat energy
 According to Fourier law
Where,
q= rate of heat transfer
A= area
K= thermal conductivity
du= change in temperature
dx= change in distance

6. Based on conservation of energy,
change in heat energy(H.E) of the slice=
Input H.E – output H.E = H.E from left end - H.E from
left end
Where,
α = diffusivity (k/ρ C)

7.  Holding
 Cooling

8. Microbial inactivation
The integrated lethality of micro-organisms in the fluid
leaving a hold tube will be different at different positions
Velocity distribution (laminar flow)
………(i)
Considering elemental area of thickness dr within the tube
radius R. No is initial microbial population and N is the
final population, n0 is the organism per unit volume
entering

9. Volumetric flow rate
The residence time of fluid within the area element is L/V,
and the number of survivors, N = No[10−L/(VD).
Let A = (3n + 1)/(n + 1); B = (n + 1) /n; y = r/R in equation (i)
The ratio L/(D) is the lethality, Sv, based on the average
velocity

10. Sv = L/( D)
r = yR
dr = Rdy
The integrated lethality, Si will be log N0/N
On solving
log(N0/N) is the integrated lethality, Si

11. Likewise microbial inactivation
Nutrient degradation is determined
Substituting Sv for log(N0/N)
Nutrient degradation

12. Thank you