Singh et.al.

commonly used in developing countries to detect the

Statistical analysis

fruit maturity (Jha et al. , 2009). Fruit colour is a key

The data were analyzed with SAS software version

attributesȱbecauseȱitȱisȱtheȱfirstȱpropertyȱobservedȱbyȱ

9.3 (SAS Institute Inc., Cary, NC, USA) using one-way

growers and consumers to judge maturity stage and

analysisȱofȱvariance.ȱTheȱdifferencesȱbetweenȱmeansȱ

quality.ȱTheȱvaluesȱofȱcolourȱdifference,ȱchromaticityȱ

wereȱ testedȱ usingȱ theȱ LSDȱ testȱ atȱ 0.05ȱ significanceȱ

differenceȱ(C*)ȱandȱhueȱdifferenceȱshowedȱdifferencesȱ

level. The mean and standard errors of means are

between mature green and yellow fruit as a function

also tabulated. Regression analysis was undertaken

of ripeness stages (Kovacs et al. , 2010. The aim of the

toȱfindȱtheȱrelativeȱcorrelationȱforȱseasonalȱvariationȱ

study was to ascertain relationship between stages

between fruit development and colour.

of fruit development of grapefruit and colorimetric

coordinates L*, a* and b*.

Results and Discussion

Materials and Methods

Fruit diameter

In general, the fruit diameter increased with

Experimental site and peel colour measurements

advancement of season and it was minimum

Fresh fruits of grapefruit cv. Star Ruby were collected

(62.85mm) at 90 DAFS and maximum (90.48mm)

from well managed plants growing at Regional

atȱ240ȱDAFSȱ(Figureȱ1).ȱTheȱfirstȱsharpȱfruitȱgrowthȱ

Station of Punjab Agricultural University at Abohar,

phase was recorded from 90-150 DAFS. Second

Punjab (India). Fruits were harvested manually at

growth phase was recorded from 150-180 DAFS and

monthly intervals from July to December and peel

this phase showed less increase in average diameter

colour was determined at 90, 120, 150, 180, 210 and

asȱcomparedȱtoȱfirstȱgrowthȱphase.ȱTheȱthirdȱgrowthȱ

240 days after fruit set (DAFS). At each sampling

phase was noted from 180-210 DAFS and thereafter,

time, the diameter of fruit was measured with digital

non-significantȱincreaseȱinȱdiameterȱwasȱnoted.ȱTheȱ

vernier’s caliper’s (Mitutoyo, Japan). Similarly, the

increase in fruit diameter might be due to an increase

rind colour was measured by using a Hunter Lab

in cell size because of cell division and cell elongation,

(modelȱ ColorFlex,ȱ Reston,ȱ USA),ȱ withȱ reflectanceȱ which enabled the maximum accumulation of food

mode (RSIN), CIE Lab scale (L*, a* and b*). The

materials. The present result was in conformity with

instrument was calibrated with a standard white

theȱ findingsȱ ofȱ Dalalȱ et al. , (2013) in Kinnow and

ceramic tile and black tile and set up for D65 as

Lamare et al. , (2013) in Sohshang. Seasonal variation

illuminate and a 10° observer angle. Sampling was

of 12.83% was recorded in the fruit diameter during

carriedȱoutȱbyȱloadingȱtheȱquartzȱcuvettesȱwithȱfruitȱ fruit development.

peel sample. The colour was determined using a CIE

L*, a*, b* colour system, where L* indicate luminosity

or lightness (L* = 0 for black and L* = 100 for white),

and the chromatic parameters a* represent the

proportion of redness. On horizontal axis, positive

a* indicate a Hue of red-purple; negative a*, of

bluish-green. On the vertical axis, b* represent the

proportion of yellowness and varies from blue (-) to

yellow (+). The colour purity indicated as chroma C*

is calculated as C* = (a*2 + b*2)1/2 and colour tone

indicated as Hue angle (h°) in a colour wheel of 360°

Figure 1. Fruit diameter of grapefruit at different periods of fruit

(0° = red-purple, 90° = yellow, 180° = bluish-green

development. LSD indicates the least significant difference test

and 270° = blue) is calculated as h° = arctan (b*/a*)

at p<0.05. Values are means ± SE and with a common letter are

described by McGuire (1992).

not significantly different at 5% level.

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