Freeze drying of food

Freeze-drying presents an excellent method for long-term food storage. It involves employing lyophilization, a process that lowers the product's temperature below freezing, followed by the application of a high-pressure vacuum to extract water as vapor. This procedure directly transitions water from its solid state (ice) to vapor, bypassing the liquid phase, while desorbing water from the "dry" layer.

The freeze-drying process consists of three stages:

*Freezing the product, typically done under atmospheric pressure.
*Primary drying, also known as proper freeze-drying, which involves the sublimation of frozen free water. This step is usually carried out under reduced pressure.
*Secondary drying, referred to as desorption drying, which focuses on drying the products to achieve the desired humidity by eliminating the remaining bound water.

Freeze-drying finds extensive application in preserving high-quality food, biological materials, and pharmaceuticals, such as proteins, vaccines, bacteria, and mammal cells. Rapid freezing during the process is crucial to prevent the formation of large ice crystals that could negatively impact the final product's quality. In the primary drying phase, pressure is reduced through the application of a high vacuum, while heat is supplied to facilitate the ice's sublimation.

Freeze-drying stands out as one of the most effective methods for preserving the activity of beneficial plant compounds, like phytochemicals, and nutrients, while maintaining the color, flavor, and structure of the food. Freeze-dried foods exhibit superior quality compared to those dehydrated by alternative techniques. They have a longer shelf life and are lighter in weight than dehydrated counterparts. Furthermore, freeze-dried food retains its color and shape more effectively than dehydrated food, owing to the absence of a liquid phase and the low temperature involved in the process.
Freeze drying of food

Read more...

Food extrusion technology

Food extrusion can be defined as a process of mixing, homogenizing, and shaping low moisture food materials and more recently high moisture food materials are forced through an opening or die with a design specific to the food, and is then cut to a specified size by blades.

Extrusion cooking is a versatile and very efficient technology in food processing. The process is a high-temperature short-time (HTST) process which inactivates enzymes and reduces microbial contamination. Extrusion cooking is mostly preferred, as it has high productivity and significant nutrient retention as compared to conventional cooking.

While food is being forced through the extruder, the food mix is thermomechanical cooked to a high temperature (usually in the range 100°C–180°C), pressure and shear stress that are generated in the screw-barrel assembly.

The laminar flow within the channels on the extrusion screw and extruder die aligns the molecules in the direction of flow to create the crunchy or chewy texture in fabricated food.

Extrusion cooked melts transit from high pressure to low (atmospheric) pressure when they exit the die. The extrudates generally require no further processing except for some minimal drying.

The entire process is continuous and capable of happening in less than a minute. The most common used extruders in the food industry include single-screw and twin-screw systems, with twin-screw systems more widely used because of their flexibility.

Extrusion brings gelatinization of starch, denaturation of proteins, reduces lipid oxidation and anti-nutritional factors. In addition, it is considered a versatile, low cost and very efficient technology in the food processing.
Food extrusion technology

Read more...

Processing systems: Scraped surface heat exchangers

Scraped surface heat exchangers are used for processes likely to result in the substantial deposition of suspended solids on the heat transfer surface. In has been used for many years, and still are used, in aseptic processing systems to heat and cool products.

In principle, a scraped surface heat exchanger is a monotube equipped with a rotating internal scraper. The scraper keeps the heating surface free from any deposits and also promotes turbulence.

Scraped surface heat exchangers can be employed in the continuous, closed processing virtually any pumpable fluid involving cooking, slush freezing, cooling, crystallizing, mixing, plasticizing, gelling, polymerizing heating, aseptic processing, etc.

Use of a scraped surface heat exchanger prevents the accumulation of significant buildup of solid deposits. Unlike tubes that usually operate with water as medium, scrape surface heat exchangers tend to use steam for greater heat transfer efficiency.

Due to the mechanical construction and the moving parts, scraped surface heat exchangers are more expensive than any other heat exchanger use in food processing. They can be justified only for heating/cooling fluid foods that cannot be handled in normal tube or plate heat exchangers.
Processing systems: Scraped surface heat exchangers

Read more...

Biotechnology in food processing

Biotechnology has been broadly defined as the utilization of biologically derived molecules, structures, cells or organisms to carry out a specific process. This is true of many established food processes – for example, cheesemaking and brewing.

The beauty of modern biotechnology lies in the specificity. The biotechnologist can target only one or two protein molecules for change in an organism containing thousands of proteins.

The seemingly minor alterations can have profound effects. The amount of an important flavor, color or enzyme may be increased many fold. It can allow crops to grow under marginal to poor conditions.

With a few exceptions, most short-term results of modern biotechnical applied to food production will be invisible to the consumer’s eye.

However, indirect effects on existing product, such as cost savings and product improvements, will be far reaching.

It is therefore important for the public to be informed of the benefits that the biotechnological revolution can provide.
Biotechnology in food processing

Read more...

Applications of vitamins in processing of food

The technical used for vitamins and their various applications are as below:
Antioxidants 
With increasing awareness concerning the importance of antioxidants in health maintenance, particularly vitamin E, their retention through food processing and storage has been assuming an increasing importance. The antioxidant vitamins C and E frequently are utilized to prevent undesirable color changes and to retard the development of rancid flavor.

Colorants
Riboflavin (vitamin B2: provides a greenish lemon-yellow color) and beta-carotene (pro-vitamin A: provides an orange color) are utilized as natural coloring substances.

Inhibitions of can corrosion
Among functions of ascorbic acid are inhibition of can corrosion in canned soft drinks.

Protection of taste, flavor and clarity 
Other functions of ascorbic acid are protection of flavor and color of wine, prevention of black spot formation in shrimp, stabilization of cured meat color and dough improvement in baked goods.

Other applications of vitamins including:
Prevention of black spot prevention
Prevention of nitrosamine formation 
Flour dough improvement 
Maintenance of color in meat package in controlled atmosphere
Applications of vitamins in processing of food

Read more...

Process of marinating

Marination is a chemical process. Marinating is a conservation process which consists of reducing the water content of fish through the action of salt, and of inhibiting the growth of microorganism through acidification of the medium. Industrial marination processing systems consist of brine injection and tumbling.

The marinade’s acid is the potent substance that chemically softens the connective tissue. It might be derived from lemon juice, wine, or some other ingredient.

Marination by injection is a quick process, achieved by forcing marinade solution into meat by means of one or a number of needle devices.

While tumbling or massaging marination is a method usually carried out in procession plants or retail facilities.

During marinating, the proteins are partially hydrolyzed by tissue enzymes with liberation of peptides and amino acids.

Most of the time, a marinade does not penetrate food much beyond the surface. To be effective, sufficient marinating time is necessary.

Marinating at room temperature is considerably faster than doing it in the refrigerator.
Process of marinating

Read more...

Chemical changes during food processing

Chemical changes that occur during food processing are numerous, and they can be desirable, undesirable of questionable consequence or a combination thereof.

Chemical changes that occur affect its overall quality and may influence both its major and minor components and sensory attributes.

Browning reactions may be caused by enzymatic oxidation of polyphenols and other susceptible compounds if the oxidizing enzymes are not activated.

Advantages that might be attained due to processing of food might relate to reduction in its content of hazardous anti-nutrients such as enzyme inhibitors, cyanogens, glucosinolates, among others as well as control of microbial and enzymatic spoilage.

The major disadvantages of food processing are:
*harm to the sensory properties and nutritive value of some foods, particularly when severe methods of processing are applied to tissues of foods.
*development during some kinds of processing and handling of new chemicals that must be classed as toxicologically undesirable.

The two major chemical changes that occur during the processing and storage of foods, leading to deterioration in sensory quality are lipid oxidation and non-enzymatic browning.

Chemical reactions are also responsible of changes in the color and flavor of foods during processing and storage.

All the changes including chemical, physical, biological, nutritional and sensory, can be measured, so their progress during processing can be followed.

The progress of processing can be measured un many ways, such as chemical analysis, physical measurements, counts of microorganism and color, texture and flavor assessments by sensory panels.
Chemical changes during food processing

Read more...