Steam injection

Direct exchangers are based on mixing of heating steam with the liquid food product resulting in very fast heat transfer rate. Steam injection and steam infusion are each used to intimately combine the product with potable steam.

In steam injection, the steam is injected into the fluid food through small hole. A typical example is the production of UHT milk by direct steam injection.

Milk is pre-heated to 75 ° C and then brought into contact with saturated steam, resulting in almost instantaneous heating of the UHT temperature. The milk plus the injected water come in the expansion vacuum vessel, where the added water of the steam injection is removed through condensation in the following condenser.

Control of the pressure in this system is needed for two reasons. First, this is to ensure that the correct amount of water is driven off, and second, that any undesirable volatile odors that may have developed during the injection process are removed.

The advantages of direct steam injection are their quick and accurate temperature control (within less than 1 ° C), the restricted pressure drop under normal flow rates (less than 0.14 bar) and their relatively low noise during operation (less than 80 dB).
Steam injection

Food processing effects on nutritional quality

The basic food preservations methods used by early man are still utilized today.

These and other methods are listed below:
Heat processing: blanching, canning, pasteurization
Drying
Freezing
Fermentation
Milling
Use of microwave ovens
Irradiation
Use of food additives
Nutrient addition
Packaging and storage

An analysis of these processing techniques reveals both favorable and unfavorable effects on nutritional quality.

On positive side, heat processing destroys anti-digestive factors such as trypsin and amylase in cereal grains, peas, and beans, thus improving the bioavailability (digestibility) of the proteins and carbohydrates in the products.

Heat processing also destroys thiaminase, which destroys thiamin in fish, shellfish, brussels sprouts, and red cabbage, and destroys the avidin and other factors in raw eggs white that would otherwise bind biotin and make these nutrients biological unavailable.

Heat processing increases the digestibility of starch and protein by gelatinization and denaturation, respectively and it increases the bioavailability of niacin which is present in many cereals in a bound form.

Heat processing also increases the palatability of food, resulting in increased appeal and nutrient consumption.
Food processing effects on nutritional quality 

Thermal Processing

Thermal Processing
Thermal processing involves heating foods in hermetically sealed containers for a specific time at a specific temperature to eliminate the microbial pathogens that endanger public health and microorganism. And enzymes that deteriorate food during storage.

Credit for the inventions of thermal processing (or canning, as it was originally called) goes to Nicholas Appert, a French confectioner.

The original concept of in container sterilization of foods, however, has come a long way since Appert first introduced “the art of caning” in 1810.

As introduced and developed in the initial stages, the primary focus of caning was safety and shelf stability.

Today, however the consumer demands much more than just safe and shelf-stable food - including, primarily, higher quality food with greater convenience in the end use.

And food processors look for more energy-efficient, cost effective and high speed processing technologies.

High temperature short time (HTST) techniques have primarily evolved to minimize the severity of heat treatment and promote product quality.

Continues aseptic processing and packaging further minimize the heat severity by quick heating and cooling of the food, prior to packaging under aseptic conditions.

This profile, thermostable, microwavable packages have been developed for promoting faster heat transfer rates, which minimizes the heat damage to products quality while adding the convenience of package microwavability.

Rotary and continues cookers for canned foods have been based on product agitation during processing to accelerate the rate of heat transfer in order to promote better quality in processed foods.

Microwave, radio frequency, and ohmic heating techniques have gained attention as alternate and nonconventional rapid heating techniques.

However although different procedure can be employed for thermal processing, it is necessary to design a process that would deliver the required minimum heat treatment to render the food safe.
Thermal Processing