DESIGN AND FABRICATION OF FREEZE DRYER

ABSTRACT

Water is responsible for changes in the physical, chemical and/or biological characteristics of foods. It is an important component of all biological or living systems. In fresh foods, the percentage of water varies from 60% to more than 90% (Davide and Salvatore, 2012). Water content in foodstuffs during processing, storage and distribution may lead to deterioration of aroma and degradation of nutritional substances because it supports the existence and development of micro-organisms and chemical reactions within the foodstuffs.  Drying or dehydration of foods is the basic food-processing operation used to preserve foods for a long period of time. Although both terms are applied to the removal of water from food, using heat and mass transfer, drying usually refers to natural desiccation such as spreading fruit on racks in the sun; and dehydration designates drying by artificial means such as a blast of hot air.

CHAPTER ONE

INTRODUCTION:

Food is an essential part of everyone’s life. It gives us the energy and nutrients to grow and develop, be healthy and active, to move and work. The body needs a variety of the following 5 nutrients – protein, carbohydrate, fat, vitamins and minerals – from the food we eat to stay healthy and productive. So foods are a complex of all these 5 ingredients.

The world population is increasing and in certain areas of the world there are not enough means for the people to get pure, nutritious and healthy food which fulfils their dietary needs. Availability of Food, its distribution and the economic feasibility is very important. If I talk about my own country Pakistan. Although Pakistan is an Agricultural Country and we are self-sufficient but still we are facing some serious issues in many parts of our country regarding food insecurity, scarcity, unhygienic food, improper storage techniques, post-harvest losses, using old and outdated methods of harvesting and improper preservation of foods. One needs to think of a better solution in order to fulfil the needs of the growing population of the country and eradicate Food Insecurity and assure Food Security in “The Land of Agriculture”.

Food Insecurity has the following two major reasons:

Seasonal Variations:

There are certain times when the food is in abundance and after a few months the same food (fruit, vegetables or grain crops) are scarce. This is due to seasonal variations. Food is a complex of solids, liquids and gases in the form of carbohydrates, fats, proteins and water vapors. So it needs to be preserved keeping in view its complex nature and properties for a longer shelf-life. By preservation techniques one can store food and consume it even in the off-season.

Food Wastage:

The other issue that we are facing today is of Food Wastage. Half of the food that is produced never makes it to our plates. It goes to waste due to improper treatment and post-harvest storage.  We are wasting large volumes of food each year. A significant part of food that we buy from market and the ones we cook and the ones we store all get to waste after a certain short span of time. The unprocessed and perishable commodities like meat and fruits spoil quickly. The cooked food, even when it is refrigerated, it spoils after a few days.

In Pakistan other than major agricultural crops, a large variety of Fruits and Vegetables, meat and poultry products are produced in abundance. A major chunk of these go to waste each year due to one reason or the other. It will be a great saving of the food if this wastage is stopped by using efficient preservation techniques and make the food available in the period of scarcity and reduce the volumes of food that we waste every year.

Need of Preservation, is one aspect and is necessary for assuring Food security. Basic thing is to improve the food preservation techniques. If we look back in the history, the people of every era used different techniques for preserving their foods to consume it at other times. People of colder regions used to store their foods in cool caves. Some used smoking technique (particularly for meat), salting and pickling. Dipping foods in sugar, brine and acidic solutions. Using the energy of Sun and Wind for drying of foods. These are all the methods which are now refined and carried out using high-tech equipment. Techniques like taking the food temperature up (pasteurization, sterilization, UHT) or lowering it (refrigeration and freezing), canning (dipping in brine and sugar solutions), pickling (dipping in acetic acid) and drying, dehydrating (using solar dryers, evaporators and dryers using air) and cooking food using a wide variety of ovens, all are refinements of the methods of preservation used in the past.

Foods (meat, some fruits and vegetables) are frozen to increase the shelf-life and to use them at other times. We can temporarily store our foods and leftovers in refrigerators and freezers, but still, some food commodities perish and deteriorate. And this again adds to the wastage of food. This is because of the moisture present inside the food and the contact of food with oxygen.

When these foods are taken out at the time of their use, and the small ice-crystals in food begin to melt to attain the ambient air conditions, the quality is definitely not the same. It gets soft and the color also degrades. We do not achieve the same quality and freshness as it was on day one. The texture, color, aroma, flavor and all such quality attributes are changed. If we talk about the water activity and microbial growth, it gets inhibited due to freezing. But right after when the product is again taken out of the freezer, the frozen water starts to melt and the microbial activity starts again. This is because the microbes are never killed due to low temperatures, their activity just stops.

So, if anyone who wants to waste less and preserve food for more than a few days or weeks and retain the quality and freshness, needs a better alternate.

FREEZE DRYING- THE NEW TECHNOLOGY:

We are living in a remarkable age, The age of advancement and emerging technologies. The researchers, engineers and technologists are developing new techniques and appliances to tackle all such problems. Amongst these technologies, is the newly developed technology called Freeze Drying or Lyophilization.

Freeze Drying was first developed during World War 2, as a way to keep vaccines for the wounded from spoiling due to uncertain refrigeration while being transported to the war zones. The technology was refined and used during the NASA space program, providing varieties of freeze dried foods for astronauts. This is when the Freeze Drying technology was first used for foods.

Freeze Dried products have a long shelf-life and nutrition preservation. It causes little damage to the nutritional value of the food being preserved compared to methods of high temperatures such as canning or dehydration. It does not shrink or toughen the food and it retains its aroma, flavor, nutritional content, shape and size.

When we compare it with other methods of preservation in terms of food deterioration due to the effect of heat, water and oxygen, Freeze Drying of food and its proper packaging afterwards overcomes all of these factors, to allow long term storage (15 to 25 years).  Neither canning nor dehydration removes all the water from food, but this technique removes almost 100% of the moisture present inside.

After freeze drying, the product has to be stored in an oxygen proof container with an O₂ absorber. This removes all the oxygen through sealing.

Freeze Drying is a new technique and is used all over the world in developed countries in food industries and research labs. This technology is also new in Pakistan but it is still not very common.

It is the removal of ice or other frozen solvents from a material through the process of sublimation and the removal of bound water molecules through the process of desorption.  It is also known as Lyophilization or Cryodessication.

 

Controlled freeze drying keeps the product temperature low enough during the process to avoid changes in the dried product appearance and characteristics. It is an excellent method for preserving a wide variety of heat-sensitive foods.

 

Freeze Drying Process Overview:

Basic principle of Freeze drying is to first freeze the food product below absolute zero temperature and then to suck up all the moisture in the form of ice through sublimation, in the presence of vacuum. Then store it in an oxygen proof container to retain its quality.

For this, following steps and processes are carried out:

• Pretreatment / Formulation
• Loading / Container (Bulk, Flask, Vials)
• Freezing (Thermal Treatment) at atmospheric pressure
• Primary Drying (Sublimation) under vacuum
• Secondary Drying (Desorption) under vacuum
• Removal of Dried Product from Freeze Dryer
• Storing product in Oxygen-proof container afterwards

 

The 3 major parts of a freeze drying recipe include freezing, primary
drying (sublimation), and secondary drying (desorption).

Freezing: The typical objective of freezing is to produce a frozen matrix with sufficient crystal structure to allow the sublimating material to escape. Freezing can range from 1 hour to 24 hours, depending on the application.

 

Primary Drying (Sublimation):

This process drives the unbound moisture out of the product. Sublimation occurs under vacuum. Under vacuum, water only exists in two states: solid or a gas. Heat (in the form of latent heat of sublimation) is provided in the chamber through conduction mechanism, so the ice crystals formed start to sublimate into vapors. This is typically the longest process. At the end of the primary drying cycle, the product will have 3 to 5% moisture content.

Secondary Drying (Desorption):

The secondary drying phase aims to remove unfrozen water molecules, since the ice was removed in the primary drying phase. In this phase, the temperature is raised higher than in the primary drying phase, and can even be above 0 °C. Usually the pressure is also lowered in this stage to encourage desorption (in the range of microbars, or fractions of a pascal). It yields moisture level of 0.5 %.

Components of Freeze Dryer:

The main components of freeze drying equipment are:

• Refrigeration System
• Vacuum System
• Control System
• Product Chamber
• Condenser

There are different types of Freeze Dryers which have been developed. These include Typical Manifold Dryer, Shelf Freeze Dryer, Combination Lab Freeze Dryer, Bench-Top Freeze Dryer, Pilot Freeze Dryer and Production Freeze Dryer.

I am inspired by the Home-Freeze Dryer developed by the American Harvest-Right Company. Harvest-Right is the only home-freeze dryer manufacturer in the world. It helps freeze drying and preserving the nutritious food one cooks at home or anything that one buys from market, for later consumption. One can freeze dry his/her own food at home. This can preserve a variety of foods including meat, fish, chicken, fruits, vegetables and even eggs. It is a new equipment and still not very common at homes in America.

Keeping in view the problems that we are facing in Pakistan regarding food spoilage, improper storage and preservation, which spoils large volumes of food each year at our homes, how about introducing this Home-Freeze Dryer technology in our country? This way people can save their foods, leftovers, fruits and vegetables that they throw away due to spoilage. This can reduce massive food wastage that every house throws away.

Therefore, a plan has been made to design and fabricate a Freeze Dryer, during my master’s degree program, which could be utilized at home level and is suitable for Pakistani conditions.

₦5,000.00 – DOWNLOAD FULL PROJECT DOWNLOAD FULL PROJECT Added to cart

---

---

---

---

Related Project Topics :