R & D on Retort Processing

R & D

Retort processing seems to be a simple processing. But many important critical parameters are involved in this processing.

In order to produce high quality and safe retort food, it is very important to do the proper R & D on the technology to suit the specific application.

The processor should develop the retort processing technology and processing method based on the characteristics of the products, type of packing materials, target shelf life, storage temperature, available utilities and resources etc.

For example, the processing method of a product processing in steam / air retort should be different from that of water immersion retort or water spray retort or rotary retort .

The method of processing a product in a vacuum packed pouches will be different for the same product when processed in standard pouches.

The processing done in cans will be different for the same product when processed in pouches or plastic trays.

The processing method of tomato puree will be different from tomato soup.

The processing done in European countries where the ambient temperature always less than 30 deg C will be different when the same processing is done in Asian countries where the ambient temperature sometimes goes above 40 deg C.

So the technologist should take many factors into the consideration when he develops the processing procedure of the retort food

The aim of the processor should be to optimize the processing, achieve the sterilization effect within shortest time without affecting the required qualities of the food. He should find methods to avoid over exposure of the products to the high temperature and longer duration of time.

He should make sure that the processed products should be equal to or better than its fresh equivalence in all respects including the color, taste, texture, vitamin and nutritional values etc.

Shelf stable food products must be safe, and be in no way hazardous to the health of the consumer. They should be nutritious while tasting good, and last but not least, be reasonably priced.

The Sterilization must be designed to fit those demands. First priority of course, is the product safety, but the retention of high quality is almost equally important.

In order to develop the processing technology, the processor should study the following parameters

1. Fo Value

The Fo value (Lethality Value) indicates the safety of the products.
The sterilization value is calculated to determine the precise heating process to be applied (temperature & time) which is necessary to provide shelf stability to a food product inside a hermetically sealed container. A key factor in this, is the ability of the organisms in the product to withstand the heat.

It is theoretically not possible to attain absolute sterility. But it is possible to sterilize food products for extended storage, to the point where they are safe for human consumption. This degree of sterility is referred to as practical or commercial sterility.

Destruction of all spores of Clostridium Botulinum is the minimum safety requirement.

A process equivalent in sterilizing effect to 12 decimal reductions of the populations of Clostridium Botulinum is sufficient to protect consumer safety. Such a process is called 12D process & it is equivalent to holding the contents of the container at 121.1 C for 2.8 minutes (12D = 12 x 0.23 = 2.8 min)

What is F value?
The F Value is defined as the number of minutes, which it takes to reduce the initial spore count of certain microorganisms to a desired safety level at a defined lethal reference temperature.

What is Fo value?
The symbol Fo is commonly used in the trade to indicate the needed degree of commercial sterility in a thermal processed food product. This Fo value is very specific and based on the reference temperature T = 250 deg F or 121.1 deg C an a z-value as 18 deg F or 10 deg C.

The Fo-value applies always to the least heated spot or zone in the container, the cold spot.

Fo=1 represents the destruction effect during 1 minute at 121.1 deg C and z=10 deg C.
The z-value is an indicator, which shows by how many degrees the temperature has to be raised in order to shorten the heating time by a specific %.

The safe Fo value needs to be estimated in order to define the safety level of the products.

2. Cook Value

 Any application of heat will alter the nutrients and the sensory characteristics of a food product in a number of ways.

 Denaturing and Coagulation of Proteins
 Gelling and Liquifying of Starches and Carbohydrates.
 Decrease/destruction of Vitamins & Other Growth Elements.
 Caramelization of the Sugars
 Browning caused by “Maillard Reactions”.
 Pigment Breakdown and the Denaturing of Spices.

The Right Degree of Cooking (Co value) is defined as the specific stage of cooking, at which any given food is at its best (flavour, texture and appearance wise). This degree is as specific for each food item and it is subject to individual judgment.

So the processor should first estimate the Cook value of each products as the first step in the R & D. Cook Value ( Co value) is the food quality related heating effect that results from 100 deg C for 1 minute with a z value of 33 deg C

Co = 1 means the cooking effect received for a product when it is kept at 100 deg C for 1 minute when the z value is 30 deg C. The processor should find out how much Co value is needed for each products to properly cook during the sterilization.

3. Optimized Temperature and Time

There are safe temperature and time limits for the products ( each ingredients) before it loses its basic qualities. So it is important to estimate the maximum temperature and time duration each product can withstand before it loses its basic qualities.

Fo value could be calculated at any temperature from 100 deg C ( 91.1 deg C to be precise) to 135 deg C. So it is important to find out the suitable holding temperature to protect the quality of food.

The Fo value could be estimated as 4 minutes at 120.0°C (248°F) is equivalent to 10 minutes at 115°C (239°F) which is equivalent to 32.0 minutes at 110.0°C (230°F); or 100.0 minutes at 105°C (221.0°F) or 330 minutes at 100.0°C (212.0°F).

4. Container Protection.

It is important to study the pressure profile of the products and containers during processing, During processing, the pressure will be developed inside the containers due to many reasons. This pressure makes the flexible containers to expand.

Over pressure needs to be applied in order to subside the expansion of the pouches. So it is important to study the pressure profile developed inside the closed containers.

Based on all the above parameters, the processor should define the retort processing profile for that particular product.

The required filling temperature, process time, temperature, holding time, come up time, Fo value, Co value, heat penetration data, cooling time, over pressure profiles etc needs to be estimated and documented while defining the process technology for any specific products.

How to develop the retort processing technology by self ?

Critical parameters to be taken care while developing the technology.

Details about the equipment and machinery used for R & D on retort processing and many more ….