Chapter 2 Review Of Related Literature Revised 335f4r

CHAPTER 2 REVIEW OF RELATED LITERATURE

2.1 Coconut

The coconut palm, Coco Nucifera L., is a member of the family Arecaceae. The term coconut can refer to the entire coconut palm, the seed, or the fruit, which botanically not a nut but a drupe. The fruit is harvested for its white flesh, husk, and coconut water (Lerner, 2007). It is cultivated for its various benefits, namely nutritional, medicinal advancement against diseases and for the development of industrial products (Mandal, 2011).

The coconut takes between 11 and 12 months to reach full maturity. At five months, the kernel begins to form a thin layer of jelly around the inside of the endocarp or shell. The shell encloses the tender water, a clear sweet liquid (Prades, et al., 2011). Coconut is a fruit in which an outer skin (exocarp) and fibrous husk (mesocarp) surrounds a hard husk (endocarp) with a coconut meat (endosperm) inside (Armstrong, 2008). Coconut fruit is shown in Fig.2.1.

Figure2.1 Coconut Fruit

The production of coconut shows a significant role in the economy of the Philippines. Being the world’s largest producer of coconuts, an average of 2.712 million metric tons of said products were harvested in medium-sized farms in year 2009 up to 2012 as shown in Table 2.1 (FAO, 2011).

Table 2.1 Production of Coconut in year 2009 up to 2012

YEAR 2009 2010 2011 2012

PRODUCITON (Million MT) 2.758 3.030 2.550 2.510

NUT EQUIVALENT (Billion) 15.656 15.540 15.207 15.238

(Source: Philippine Coconut Authority)

2.1.1 Coconut water

Coconut is unique among other fruits because it contains a large quantity of liquid. When it has not yet reach full maturity they are called tender coconut water which can be harvested for drinking. Coconut water in its natural form is recognized as a refreshing drink. Popularity of this drink is increasing due to its good nutritional value, low calorie and free from added ingredients (Paniappan, 2012).

Tender coconuts after removing from the tree can be kept for 15 days without spoilage in ambient conditions (Chandy, 2009).

Once opened the

coconut water becomes off-flavored in taste and turns sour due to intense enzymatic activity. Instead, store it inside the refrigerator if it is not used immediately (USDA, 2009).

Coconut water became a popular drink in the tropics, especially in India, Africa, Caribbean and here in the Philippines. It is presented in the market fresh, canned, and bottled. It has a shelf life of 24 months when placed in bottles (Belargo, 2010).

2.1.1.1 Benefits and Composition

Coconut water contains antioxidants, vitamins and minerals, sugar, proteins, dietary fibre and provides an isotonic electrolyte balance. The biologically pure, coconut water helps to replace fluids, electrolytes and sugars lost from the body during heavy physical activities (Fife, 2008). This natural drink is believed to be useful in preventing and relieving many health problems including dehydration, constipation, digestive disturbances, malnutrition, fatigue, heatstroke, boils, diarrhea, kidney stones, osteoporosis, urinary tract infections, and sterility (Fife, 2008).

Table 2.2 below shows that coconut water is also rich in many essential amino acids including lysine, cystine, phenylalanine, histidine, and tryptophan (Gopikrishna, 2008).

Table 2.2 Composition of tender coconut water

(Source: Journal on Quantitative Analysis of Coconut water)

2.1.1.2 Nutritional Contents

This Table 2.3 shows nutrition value per 100 grams (g) of tender coconut water. It reflects available nutrition facts, vitamins, electrolytes, minerals and its nutrient value and percentage recommended dietary allowances.

Table 2.3 Nutrition Value per 100g of Coconut Water

Principle

Nutrient

Percentage of

Value

RDA

Energy

19 Kcal

1%

Carbohydrates

3.71 g

3%

Protein

0.72 g

1.5%

Total Fat

0.20 g

1%

Dietary Fiber

1.1 g

3%

Vitamins Folates

3 µg

0.75%

Niacin

0.080 mg

0.5%

Pantothenic acid

0.043 mg

<1%

Pyridoxine

0.032 mg

2.5%

Riboflavin

0.057 mg

4%

Thiamin

0.030 mg

2.5%

Vitamin C

2.4 mg

4%

Sodium

105 mg

7%

Potassium

250 mg

5%

Calcium

24 mg

2.4%

Copper

40 mcg

4.5%

Iron

0.29 mg

3.5%

Magnesium

25 mg

6%

Manganese

0.142 mg

%

Zinc

0.10 mg

1%

Electrolytes

Minerals

(Source: USDA National Nutrient data base)

2.2 Membrane Technology

Membrane technology is used in the beverage industry especially in clarification of fruit juice. Membranes range from finely porous structures to nonporous and can remove contaminants such as bacteria and protozoa down to ions (Wang 2013). In last two decades, there has been a significant growth and increase in its application. Membrane technology has full scale global applications in municipal and industrial wastewater,

ultra-pure

water,

speciality

chemicals,

recovery/reuse,

agriculture,

pharmaceutical, power generation, drinking water and beverages (AMTA, 2007).

There are four levels of membrane filtration. These levels are from largest to smallest pore size namely microfiltration, ultrafiltration, nanofiltration, and reverse osmosis. This table also enumerates particular target contaminants from 1 µm to 0.001 µm that are being removed in different filtration level (Dave, 2013).

Table 2.4 Comparison of Membrane Filtration Levels

(Source: Virginia’s Community College)

2.2.1 Microfiltration

Microfiltration (MF) is a type of physical filtration process where a contaminated fluid is ed through a special pore-sized membrane to separate microorganisms and suspended particles from process liquid (Baker, 2012).

Microfiltration can be an alternative to fruit juice preservation and conservation, because it does not involve the use of heat treatment since thermal

processes largely affect the characteristics of fruit juices. The advantages of microfiltration are the use of mild temperature and pressure conditions, which maintain the nutritional quality and the sensorial attributes of the products (Carvalho, 2010).

2.2.1.1 Dead-End Filtration

In dead-end filtration, the feed flow perpendicular to the membrane. The particulates will accumulate and form a cake at the membrane surface. The cake increases in height throughout the filtration period resulting in a decrease in permeate flux (Fumatech, 2010). Therefore the membranes in dead-end operations have to be cleaned at regular intervals either by backwashing or other physical cleaning methods (Lenntech, 2009).

2.2.2 Ceramic Filter Cartridge

In 1846, Henry Doulton has invented the modern form of ceramic that was widely recognized as a premier manufacturer of an effective prevention device for treating infective water. Doulton's original organization for water filters remains in existence, although it has been sold and renamed several times (Berks, 2008). As with most filtration methods, fluid stream is carefully introduced to one side of the filter, which acts to block the age of anything larger than the pore size.

Ceramic filters are inexpensive and effective type of filter that rely on the small pore size of ceramic material to remove dirt, debris, bacteria, protozoa, and microbial cysts but are not effective against viruses since they are small enough to through. The major risks to the success of all forms of ceramic filtration are hairline cracks and cross-contamination (Brown et.al, 2011). In comparison to polymeric membranes, ceramic membranes are slower to foul and can be regenerated using more extreme membrane performance recovery methods, which polymeric membranes are unable to handle due to thermal limitations of polymeric materials (Panglisch, 2009).

2.2.3 Permeate Flux

Permeate flux is usually analyzed by the decline in flux and the decrease of transmission over time resulting to the reversible accumulation of particles on the membrane surface, which eventually progresses to the irreversible cake build-up (Hwang, & Liao, 2011).

Permeate flux may change with filtration time according to the fouling behaviour of the feed solution. High initial permeate flux followed by a rapid flux decrease is characteristic of constant TMP operations. The initial high increase of pressure cause rapid particle deposition which results in a fast build-up of a boundary layer at the membrane surface (Buetehorn et al., 2012). Permeate flux during a microfiltration process of pineapple juice is illustrated in Fig.2.2.

Figure 2.2 Permeate flux during a microfiltration process of pineapple juice

This graph showing filtration of pineapple juice is a typical example of permeate flux during a microfiltration process. There is a decline of the permeate flux attributed to fouling due to pore blocking and cake built up (Yasan et al., 2007). 2.2.4 Membrane Fouling

Membrane fouling is accumulation of non-dissolved material that is either deposited on the pore mouths or walls of the membrane. Fouling leads to an increase in resistance giving less flux for a given vacuum pressure difference. For example, using a metering pump to maintain a fixed permeate flow rate. Understanding the other resistances is important and it is imperative to distinguish a reduction in driving force across the membrane from an increase in resistance because of fouling of the membrane (Field, 2010).

Membrane fouling can be classified as physically reversible or irreversible fouling. Physically reversible fouling can be eliminated totally by physical cleaning or certain pretreatment while physically irreversible fouling can be overcome by chemical cleaning limited to a minimum frequency since repeated chemical cleaning may affect membrane life (Hiroshi et al., 2007).

2.2.5 Transport Phenomena in Membrane Processes

In membrane processing, the external pressure that must be applied for significant permeate flux must be higher than the osmotic pressure of the solution. The basic relationship between applied pressure (by a pump), osmotic pressure, and flow of solvent through a membrane is expressed in of the flux and the driving force and resistances. Eqn1. is for an ideal semipermeable membrane:

Eqn.1

Where J is the flux, A is a membrane permeability coefficient, PT is the transmembrane pressure, and

is the osmotic pressure of the feed solution.

For an ideal membrane and feed solution the Eqn.1 is rewritten given by Eqn.2

Eqn.2

Where A is a membrane permeability coefficient, and

is the viscosity of

permeate. For a particular feed solution at a given temperature, viscosity is

usually included with the A value and can written as in Eqn.3 where

which is rewritten below

is the intrinsic membrane resistance determined using pure

water as the feed.

Eqn.3 In actual operation with a real feed, the membrane resistance may be only a small part of the total resistance.

Eqn.4

If significant membrane fouling occurs because of specific membranesolute interactions, the intrinsic membrane resistance may change based on the Eqn.4. It is ed for by adding another resistance term, RF because of fouling to the model (Cheryan, 1989). 2.2.6 Cleaning Process

The cleaning process is just as important as the actual filtration process. It is fundamental in determining the technical and economic viability of the processes on an industrial scale where efficiency and repeatability are essential (Coutinho, 2009). Membrane cleaning methods can be divided into physical, chemical and physio-chemical. In practice, physical cleaning methods followed by chemical cleaning methods are widely used in membrane applications (Arnal et al., 2011).

In general, acids namely nitric, phosphoric, hydrochloric and sulphuric are often used to remove precipitated salts or scalants, while alkaline cleaning is suitable for organic fouling removal. Other categories of chemical cleaning agents are metal chelating agents, surfactants and enzymes (Mohammadi et al., 2007).

2.2.7 Backwashing

Backwashing is a type of cleaning method that uses reverse mechanism of filtration process wherein the suction pressure is applied on the retentate side. The accumulated cake flushed out from the membrane pores. The pressure on the permeate side of the membrane is higher than the pressure within the membranes, causing the pores to be cleaned. Many techniques have been developed to overcome fouling. Backwashing is typically used to clean membranes, while more persistent foulants are removed by the use of chemical reagents. However, these chemicals sometimes damage the membrane materials reducing the lifetime and efficiency of the membrane and even cause a secondary pollution over cleaned membrane (Arnal, 2011). Fig.2.3 shows the cleaning flow direction in backwashing.

Figure 2.3 Backwash Mechanism