FREEZE DRYING OF MEAT

Batul HussainRoll no. 13FET1008

What is Freeze Drying (Lyophilization)?

•Freeze drying also known as lyophilization is an important process for the preservation and storage of biologicals, pharmaceuticals and foods.

•The basic idea of freeze-drying is to completely remove water from some material, such as food, while leaving the basic structure and composition of the material intact.

•Freeze drying is a process whereby water or other solvent is removed from frozen material by converting the frozen water directly into vapor without the intermediate formation of liquid water.

PRINCIPLE•The main principle involved in freeze drying is a phenomenon called sublimation.

•Sublimation of water can take place at pressures and temperature below triple point.

•The material to be dried is first frozen and then subjected under a high vacuum so that frozen liquid sublimes leaving only solid ,dried components of the original liquid.

FREEZING

PRIMAR

YDRYING

SECONDARY DRYING

STAGES IN FREEZE DRYING PROCESS

FREEZING•The product is frozen below its solidification temperature.

•The freezing temperatures are between −20 °C and −50 °C.

•The freezing is done rapidly. The optimal rate of cooling is 1mm/min.

• The freezing phase is the most critical in the whole freeze-drying process, because the product can be spoiled if improperly done.

Air Freezing : Foods can be frozen in air at temperatures ranging from –18° to – 40 °.

Air Blast Freezing : •Circulation of cold air enables freezing to proceed at a moderately rapid rate. •Products are placed on trays, either loose or in packages and the trays are placed on freezing coils in a low temperature room with cold air blowing over the product

Liquid Immersion Freezing : •A food product is frozen by immersion in or by spraying with a freezant that remains liquid throughout the process. •Freezants: propylene glycol, glycerol, sodium chloride, and mixtures of salt and sugar.

Cryogenic freezing :Liquid nitrogen (LN), liquid “freon” freezant (LFF) is used for food freezing.

FREEZING METHODS

PRIMARY DRYING• The removal of the frozen free moisture by a process of sublimation.

•During the primary drying phase, the pressure is lowered , and enough heat is supplied to the material for the ice to sublime (latent heat of sublimation).

•In this initial drying phase, about 95% of the water in the material is sublimated. This phase may be slow because, if too much heat is added, the material’s structure could be altered.

•The heat is brought mainly by conduction, convection or radiation.

SECONDARY DRYING

•Eliminating the final traces of water which remain due to absorption.

•The temperature is raised higher than in the primary drying phase, and can even be above 0 °C, to break any physico-chemical interactions that have formed between the water molecules and the frozen material.

•At the end of the operation, the final residual water content in the product is extremely low, around 1% to 4%.

•After the freeze-drying process is complete, the vacuum is usually broken with an inert gas, such as nitrogen, before the material is sealed.

Place the material to be preserved onto the shelves.

Machine runs the compressors to lower the temperature in the chamber.

The machine turns on the vacuum pump to force air out of the chamber, lowering the atmospheric pressure below .06 ATM.

The heating units apply a small amount of heat to the shelves, causing the ice to change phase.

This continues for many hours (even days) while the material gradually dries out.

Once the material is dried sufficiently, it's sealed in a moisture-free package

PROCESS

PROPERTIES OF FREEZE DRIED MEAT

•Retains original characteristics of the product, including:colorformsizetastetexturenutrients

•Reconstitutes to original state when placed in water

•Retains original characteristics of the product, including: color, form, size, taste, texture, nutrients.•Reconstitutes to original state when placed in water

•Shelf stable at room temperature - cold storage not required•The weight of the freeze-dried products is reduced by 70 to 90 percent, with no change in volume

•The product is light weight and easy to handle•Shipping costs are reduced because of the light weight and lack of refrigeration

•Low water activity virtually eliminates microbiological concerns•Offers highest quality in a dry product compared to other drying methods

Quality Changes In Freeze Dried Meat• Changes in protein structure and water binding caused by

1. Aggregation or cross linking of undenatured protein.2. Denaturation of protein followed by aggregation.3. Interaction of denatured protein with lipids or

carbohydrates.

• Non-enzymatic browning reactions due to interaction between protein groups and carbonyl compounds fron auto-oxidising lipids.

• Degradation of myoglobin pigment, responsible for the red colour .

• It is also found that degraded heme pigments may catalyse lipid oxidation.

STABILITY OF FREEZE DRIED MEAT•MOISTURE AND OXYGEN are the two most important factors which affect the stability

•The detrimental effects of moisture and oxygen are temperature dependent.

•Packaging used must be impermeable to atmospheric moisture.

•Freeze-dried foods are packed in airtight NITROGEN PACK. This process uses both vacuum oxygen removal and nitrogen flushing.

•Shelf life is from 5 to 8 years and if stored properly can last upto 20 years .

ADVANTAGES

Chemical decomposition is minimized.

Removal of water without excessive heating.

Enhanced product stability in a dry state.

Pharmaceutical and

Biotechnology

Technological Industry

Food Industry

APPLICATIONS