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  • Introduction

    1

    CHAPTER 1

    INTRODUCTION

    India with its varied geographic and agro-climatic climatic conditions has a

    large range of varieties of fruits in its basket and account for around more than 10%

    of world’s fruit production (Indian Horticulture Database, 2011). Different types of

    tropical, subtropical and temperate fruits are produced in the country. Citrus, banana

    and mango are the important tropical fruits largely produced in India. Of these

    Banana (Musa sp.) is the fourth most important food crop in the world after rice,

    wheat and maize with a world production of around 102028.17 thousand MT in 2010

    (FAO, 2012). India is the largest producer of banana in the world with an annual

    production of around 29780.00 thousand MT in 2010 in an area of 830.0 thousand ha

    (FAO, 2012).

    The major banana producing states in India are Tamil Nadu, Maharashtra,

    Gujarat, Andhra Pradesh and Karnataka. Data depicted in Table 1.1 revealed that in

    India the production of banana is rapidly increasing year by year, it has been

    increased from 18887.8 to 29780 thousand MT from 2005-06 to 2010-11.

    Table: 1.1 Area, Production and Productivity of Banana in India

    Year Area (000’ ha) Production (000’

    MT)

    Productivity

    (MT/ha)

    2005-06 569.5 18887.8 33.2

    2006-07 604.0 20998 34.8

    2007-08 658.0 23823 36.2

    2008-09 709.0 26217 37.0

    2009-10 770.3 26469 34.4

    2010-11 830.0 29780 35.9

    Source: Indian Horticulture Database (2011)

    Banana fruits are normally harvested at the mature green stage. A common

    indicator of harvest at this stage is the visual fullness of fruit fingers called 'finger

    angularity'. Some cultivars are harvested at the 'full three-quarters' to 'full' stage of

    maturity. This maturity index is normally coupled with other visual signs including

  • Introduction

    2

    drying up of leaves and dryness of stylar ends. Days after the emergence about 150-

    155 days of flowering of the inflorescence are also used as indicator of harvest.

    Bananas are harvested, transported and stored at the green stage (maturity stage 1)

    until they reach their destination where they will be treated with ethylene for ripening

    and then sold to retail markets. In banana ripening has been divided into seven stages.

    Commercial standard colour charts are available in which 7 stages of ripening were

    reproduced and translated to a numerical scale where Stage 1=all green, 2= green

    with trace of yellow, 3= more green than yellow, 4= more yellow than green, 5=

    yellow with trace of green, 6= full yellow, 7= full yellow with brown spots. In

    banana, post harvest compositional changes following are important since banana is a

    climacteric fruit. Ripening stages of fruit are associated with changes in texture, color

    and flavor leading to the best eating stage. Mostly, banana peel color changes from

    green to yellow while going through the 7 stages of ripening (Stover and Simmonds,

    1987). Texture softens at different rates for each ripening stage partly due to the

    hydrolysis of starch and pectin in banana pulp (Tucker, 1993). The most important

    changes which correspond to the best eating quality for ripening banana are the

    changes in flavor which result from several metabolic reactions. During ripening,

    initiated by ethylene, there is a degradation of pectin structure (Loesecke, 1950).

    However, it is believed that the major cause for softening in ripening banana is

    degradation of starch in the pulp (Tucker, 1993). Starch is hydrolyzed into sugars.

    Starch decreases from 20-23% of fresh pulp in green bananas to 1-2% in fully ripe

    bananas. These changes are concomitant with the increasing sugar content (from 1-

    2% rising to 20%) in the pulp during ripening (Palmer, 1971). Of the total sugars

    present in banana pulp, sucrose (13%), glucose (4%) and fructose (3%) are

    predominant and contribute heavily to the sweet taste of ripe bananas (Seymour,

    1993). Color changes during ripening mainly result from degradation of chlorophyll

    in the peel in the early stages of ripening and the biosynthesis of carotenoids in later

    stages (Seymour, 1993). Tannins are known to interact with salivary proteins and

    glycoproteins, causing fruit to taste astringent, hence the loss of astringency in banana

    pulp during ripening may result from increased polymerization of tannins (Palmer,

    1971). Lipids and total protein content represent only small amounts in banana pulp.

    They do not change substantially during ripening (Goldstein and Wick, 1969).

    Acidity of banana pulp increases during ripening (from pH 5.4 in preclimacteric to pH

  • Introduction

    3

    4.5 in postclimacteric pulp) (Palmer, 1971). There is a report that the astringent taste

    of unripe bananas is probably attributable partly to their oxalic acid content, which

    undergoes significant decarboxylation during ripening (Seymour, 1993).

    Banana when fully ripened is a soft and delicate fruit with a post-harvest shelf

    life of 5-7 days. This makes it prone to injury during transport. Further, release of

    ethylene during bulk storage makes the fruit to ripen faster and the fruits likely to rot

    before reaching its destination. Hence, it has always being considered a ‘problem

    fruit’ with respect to transportation. These reasons contribute to a local market glut,

    resultant price crash and subsequent disinterest among the farming community to

    cultivate it on a large scale. It is hence important to overcome this problem by

    generating an increased demand of this fruit crop. Exploring possibilities of

    converting banana into a cash crop by developing products of commercial interest is

    one way of solving this problem. In developed countries 40-50 % of the annual

    agricultural produce is converted into value added commodities. However, in India it

    is less than 2 % annually. Such a situation further necessitates the development of

    value added products.

    Fruit juices are the most common and demanding products made out of most

    of the fruits. The conversion of fruits into juices was originally developed for utilizing

    the surplus fresh fruits but now processing fruit juices is firmly established in its own

    right as a major industry. Increased awareness in health issue leads to increased in

    consumption of fruit juices. The modern trends in fruit juice technology showed

    increased use of different varieties and species of fruits to produce a wide of finished

    products like juices and their concentrates having good qualities. Varietal characters

    and degree of ripeness of the fruit are important factors affecting quality of juices

    produced. The suitability of a particular variety and degree of ripeness for juice

    extraction is dependent upon a balance of acids and sugars, aroma constituents and

    vitamin content particularly ascorbic acid content.

    Over the last two decades, great advances have been made in the technology

    of fruit juice processing. The advances have been largely towards the improvements

    in the existing conventional processing procedures and equipments as well as

    introducing new techniques to achieve maximum yield of the juice with good quality.

    Mechanical processing, diffusion extraction and enzymatic extraction are the distinct

    methods use for the extraction of fruit juices. Freshly pressed fruit juices contain

  • Introduction

    4

    variable amounts of fine cellular particles with colloidal material, pectic substances,

    gum, protein, tannin and other compounds (Feldmann, 1987). The size of particles

    ranges from 0.001 to 1000 µ. The large particles of about 100 to 500 µ may settle

    down rapidly, other coarse particles may be removed by centrifugation or filtration.

    The types of filters commonly include plate and frame filter press, sheet filter, precoal

    filter and rotary vacuum filter. In addition to the classical methods, ultrafiltration has

    found applications in fruit juices. Colloidal materials in the range of 0.001 to 0.1 µ are

    removed by enzyme treatment (Heatherbell, 1984).

    Due to several advantages of enzymatic extraction method, recently it is used

    widely. Wide varieties of enzymes are in use for different purposes in fruit juice

    industry. Among them pectinases are the most important in the extraction and

    clarification of fruit juices (Kilara, 1982). Pectic substances and pectolytic enzymes

    play a important role in fruit juice processing. The mechanism of enzymatic

    clarification process involves three stages viz. solubilization of insoluble pectins,

    decrease in the viscosity of soluble pectins and finally flocculation of the suspended

    particles (Yamasaki et al., 1964). Most of the commercial pectic enzyme

    preparations used in fruit juice extraction and clarification are of fungal origin

    because of having a low pH optimum and other characteristics suited for fruit juices

    (Rombouts and Pilnik, 1978). These enzyme preparations are marketed either as

    liquid (concentrate) or in powder for

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