Compositional And Physical Changes

CHAPTER ONE

Introduction

As time passes by, the number of population in the world is increasing rapidly and number of mouths to be fed is increasing as well. In some studies, the world population has been predicted to reach 9. 1 billion by 2050 which will require a 70% increase in food production. The production worldwide in regards to agriculture is more and should be sufficient for all individual to survive but every second tons of food and resources are being wasted. With modernization and development worldwide, the storages and the preservations of produce have improved a lot compared to before but still it is excruciating to see huge amount of food getting wasted everyday though there are thousands of people starving and hungry.

Therefore post harvest handling should be given priority so that none of the hard work and sweat of the producer is wasted and none dies from starvation. For it to happen post harvest management is important for both food sustainability and food security. Out of post harvest management techniques, drying and dehydration has been practiced since ancient times and it is still one of the most successful ways of preserving food and dried foods with value addition and fortification are gaining popularities these days. The preservation of food by drying is one of the oldest methods used by man (Loesecke, 2005). Drying is a process by which water is removed from the food, by vaporization or sublimation, thus reducing the water available for degradation reactions of chemical, enzymatic or microbial nature.

The drying rate is influenced by transfer mechanisms, such as vapor pressure of the food and of the drying air, temperature and air velocity, moisture diffusion in the product, thickness and surface exposed for drying (Guińe, 2018). The dried products are not only preserved but the weight is also decreased which makes it easier for transportation during marketing. Many different types of dryers are available in the world such as drum dryers, vacuum shelf dryers, continuous vacuum dryers, spray dryers, rotary dryers, air-lift dryers, continuous fluid-bed dryer, cabinet dryers, tunnel dryer, convection tray dryer and freeze dryer. There are various factors involved in drying in those different types of dryers out of which six of the factors are considered most important. Those six factors are the followings:

1. The design of the dryer- Dehydrator assuring the intimate mixing of rapidly moving air with the material being dried is required for good and rapid drying.
2. Volume of air flow- A high total volume of air flow is most suitable for rapid drying. Sixteen thousand cu ft per minute (cfm) of air will remove on pound of water for every 5°F of temperature drop (Loesecke, 2005).
3. High temperature- Higher the temperature of the incoming air, faster and rapid will be the drying of the material inside the dryer. During the drying of moist products, the materials remain cool due to the rapid evaporation of water so the materials do not get destroyed by high temperature.
4. Proportion of recirculated air- If part of the air exhausted from a tunnel of cabinet dryer is returned and mixed with incoming fresh air and then reheated, the air passing over the product will become moister than without such recirculation (Loesecke, 2005).
5. Rate of input of wet product- Lighter loading in dryers will fasten the drying duration. Thinking that overloading the dryers will increase the product and reduce the time of drying is not true as air has to flow through the maters so if the materials are overloaded and compact, air passage is made difficult which increases the time duration of drying.
6. The nature of the product being dried- If the nature of the material has higher moisture or higher sugar content, that material will take longer time to dry compared to materials with less sugar content or moisture content.

During the process of drying, many physiological and chemical changes take place where structural and physic-chemical modifications affect the final product quality, and the quality aspects involved in dry conversion in relation to the quality of fresh products and apple drying techniques. Currently hot drying air is the most widely used method in post-harvest technology of agricultural products. Using this method, a more uniform, hygienic and attractively colored dried product can be produced rapidly. However, it is an energy consuming operation and low energy efficiency, so the high prices and shortage of fossil fuels. Solar dryers are now increasingly used since they are a better and more energy efficient option (Wankhade, Sapkal and Sapkal, 2012). Therefore this study will be carried out using different types of drying methods on apple fruit and compare the changes with appearance and few compositional changes of the finished product.

Objective of the study

• Comparative analysis of physical and nutritional composition in apple slices dried in sun, tray dryer and freeze dryer.

CHAPTER TWO

Literature review

Apple

The apple is the most ubiquitous of temperate fruits and has been cultivated in Europe and Asia from antiquity, the genetic variability found in the apple has allowed adapted types to be selected for different environments, and selection continues for new types to extend apple culture into both colder and warmer regions ( Janick, Cummins, Brown and Hemmat, 1996).

Definition and plant cultivars

Malusis a genus of family Rosaceae which contains about 30–55 species (Aziz, Anwar, Uddin, Amanat, Ayub and Jadoon, 2013). Under the rosaceae family, Malus domestica is a famous fruit which is commonly known as an apple which grows on the tree Malus pumila. An apple is a round pome fruit with juicy flesh having green, red or yellow skin when ripe. There are both tropical and temperate cultivars of apple depending of different climatic requirements of the world. The different cultivars of apple cultivated in Bhutan are Red delicious, Royal delicious, Red June, Beauty of bath, Red free, Red chief, Red gold, Lobo, Gala, Jonathan, Golden delicious, Mutsu. The major pollinizer cultivars used by the Bhutanese farmers at present include Golden delicious, Jonathan, Red gold and Red June. There are approximately 7500 varieties around the world out of which 1000 is commonly used.

The globally important cultivars are Golden delicious, July red, Granny Smith, Red crimson, Spur golden, Red chief, Liberty, Rome, Gala and Empire ( Tashi, n. d). Nutritional compositionAs one of the most cultivated and consumed fruits in the world, apples are continuously being praised as a “miracle food”. Apples are extremely rich is important antioxidants, flavanoids and dietary fiber. The phytonutrients and antioxidants in apple may help reduce risk of developing cancer, hypertension, diabetes and heart disease. Apples can improve neurological health as a study published in the Journal of Food Science in 2008 suggested that eating apples may have benefit for your neurological health (Nordqvist, 2017). Apples are free of fats and cholesterol so there is no weight gain due to consumption of apple. Quercitin in the skin of the apple protects the brain cells and boron protects the bone. Thanks to some vitamin Bs and vitamin C, skin is benefitted.

Production in Bhutan

Apple is one of the most important cash crops of the Bhutanese people living in temperate areas. Apple was introduced in Bhutan in early sixties (1962) through the guidance of His Majesty the third King late Jigme Dorji Wangchuck. Apple is mostly grown at an altitude range of 2000-2600 masl and is found in Thimphu, Paro, Bumthang and Haa Dzongkhags. The total area under apple cultivation is 3661 acres, Paro being the leading dzongkhag in apple production with a total area of 1796 acres and production of 4,457 MT (Tashi, n. d). Preserving processes of appleApples can be preserved in many forms which will make them available during off seasons. The different types of ways to preserve apples are canning, drying, jelly and jams, frozen apples, apple cider and apple cider vinegar. Canned apples can be a whole apple but chopped apples are preferred due to the surface are it covers. Canned apple slices can be eaten as it is or used to make apple filling. Dehydrated and dried apples can be eaten as snacks and used as additives in baking, cereals and even toppings in puddings and creams. Jelly and jams are always the best sweetDrying methods for apple:

Open sun drying: Drying in the sun is very economical. You only have to spread the produce on a suitable surface and let it dry in the sun (Mnkeni, Soundy and Brutsch, 2008). Few advantages of solar drying are the followings:

• Easy and cheap method of drying.
• Solar drying being one of the oldest drying method does not necessarily require technical expertise.
• Sun drying can be done anywhere until we have a good amount of sun light.
• There is no waste of energy in this method of drying. Few disadvantages of solar drying are:
• The phytochemicals and minerals being volatile in nature, the materials exposed to the direct sun lose those properties.
• Usually the sun drying are done outside, so the drying area can be contaminated as well as no protection against the wind and other animals are provided in many cases.

Tray drying: The materials of the right thickness are uniformly spread on the tray at 50°C for 5 hours. The hot air circulation within the dryer which uses the principle of convection force is applied, drying the materials as the hot air passes through them.

Few advantages of tray drying are:

• It is clean and hygienic in nature due to the enclosed nature of the dryer.
• Less time wastage as the temperature and the time duration for drying are automatically controlled.
• Uniform circulation of hot air through the materials so drying is uniform. Few disadvantages of the tray drying methods are:
• Due to the heat present while drying, some volatile substances from the materials are lost.
• A lot of energy is wasted like electric power and fuel while using tray drying as compared to sun drying.

Freeze drying (lyophilization): It is a process in which the solvent (usually water) is first frozen and then removed by sublimation in a vacuum environment (Vecchio, 2010). The advantages of this methods are:

• The texture of the material remains almost same.
• Freeze dried products are in high demand in this current situation.
• There are minimum nutritional losses in this method.

Some disadvantages of freeze drying are as follows:

• It is very expensive.
• Requires technical expertise.
• It consumes a lot of energy both during freezing of materials in the deep freezer and drying in the freeze dryer. Uses of dried applesAs a hot water infusion: The dried apples can be infused in hot water and consumed. The sweet aroma of the apple and a little tint of sweetness can make a great tea. As well as there will be nutritional benefits in minimum with a soothing after taste.

As dried additives: Dried apples can be used in baking of cakes and cookies as toppings. Exposing to heat may affect on few nutritional compositions but it will still be palatable with good amount of fiber which can aid digestion. It can be consumed as dried fruits along with breakfast cereals and nuts.

Snacks: The dried apples pieces can be chewed on which would be a perfect healthy snacks with loaded nutrition. They can be consumed during off seasons when you miss the taste of fresh apples which are usually available during late summer to autumn. The rightly dried apples will be loaded with good amount of antioxidants, vitamins and they will have soluble dietary fiber.