color - share story & experience · 10/20/2010 4 color evaluation objek harus teriluminasi...

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10/20/2010 1 WBS COLOR (WARNA) COLOR Salah satu atribut kualitas yang penting untuk produk pangan Karakteristik fisik yang menentukan daya terima konsumen kerusakan fisik juga dapat ditunjukkan dengan perubahan warna Absorpsi jumlah panjang gelombang tertentu dalam area visible menentukan warna bahan pangan Fenomena yang melibatkan komponen fisik dan fisiologis 400 to 500 nm (blue), 500 to 600 nm (green and yellow), and 600 to 800 nm (red), biasanya diekspresikan dalam istilah hue, value, and chroma pada Munsell color system.

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10/20/2010

1

WBS

COLOR (WARNA)

COLOR Salah satu atribut kualitas yang penting untuk produk

pangan

Karakteristik fisik yang menentukan daya terima konsumen

kerusakan fisik juga dapat ditunjukkan dengan perubahan

warna

Absorpsi jumlah panjang gelombang tertentu dalam area

visible menentukan warna bahan pangan

Fenomena yang melibatkan komponen fisik dan fisiologis

400 to 500 nm (blue), 500 to 600 nm (green and yellow),

and 600 to 800 nm (red), biasanya diekspresikan dalam

istilah hue, value, and chroma pada Munsell color system.

10/20/2010

2

Electromagnetic spectrum

Cahaya didefinisikan sebagai energi radiasi yang dapat

dievaluasi secara visual dalam frekuensi 3.9×1014 Hz sampai

7.9 × 1014 Hz

Visible spectrum and its relation to the

electromagnetic spectrum.

10/20/2010

3

Warna yang dikenal oleh mata manusia berhubungan dengan

radiasi cahaya dalam nilai kisaran berikut

violet-blue (380 < λ < 480 nm)

green (480 < λ < 560 nm)

yellow (560 < λ < 590 nm)

orange (590 < λ < 630 nm)

red (630 < λ < 750 nm)

10/20/2010

4

Color Evaluation

Objek harus teriluminasi

Fenomena fisik (interaksi cahaya dengan objek)

- transmission

- refraction

- absorption

- scattering

- and others.

Wavelengths not absorbed but reflected by or transmitted

through an object are visible to observers.

For example:

- a blue object reflects the blue light spectrum but absorbs

red, orange, yellow, green, and violet.

- if all radiant energy in the visible region is reflected from an

opaque surface, the object appears white.

- if it is almost completely absorbed, the object is black.

10/20/2010

5

Transmission

light goes through the object and essentially does not change

the object is transparent

A colorless object transmits all light with the exception of a

small amount that is reflected.

if none of the light is transmitted the object is black and is

said to be opaque.

Refraction

light goes through two media that have different densities

As example, light travels through medium 1 (such as air) and

then goes through medium 2 (such as water). For any two

media, the refractive index (Ri) is defined as:

Ri depends on light wavelength, and this is clearly observed

when white light goes through a prism

10/20/2010

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Refraction and color

Absorption

light may also be absorbed or lost as visible light when it

interacts with matter

if the object only absorbs only part of the light, it appears

colored

if all light wavelengths are absorbed, the object appears black

if none of the wavelengths is absorbed, the object appears

white.

10/20/2010

7

Scattering

light is scattered when it interacts with matter travels in

many different directions

The deviation of light direction (scattering) is associated with

the interaction between light and the particles in the

diffusion medium.

Scattering is only observed when the particles and the

diffusion medium have different Ri

In the light–material interaction, if part of the light is

scattered and another part transmitted, then the material is

translucent.

On the other hand, if light scattering is so intense that no

light is transmitted, then the object is opaque.

Scattering is very common; the colors of the sky (blue), of

the clouds (white), and most white colors are due to this

phenomenon.

White materials do not show absorption and each light

component is scattered the same amount.

10/20/2010

8

Color Measurement

total carotenoid content vs color for squash

desirable to follow the changes in color of a product during

storage, maturation, processing

often used to determine the ripeness of fruits.

color of potato chips is largely controlled by the reducing

sugar content, storage conditions of the potatoes, and

subsequent processing

color of flour reflects the amount of bran. Freshly milled

flour is yellow because of the presence of xanthophylls

Colour Measurement System

Color is a characteristic of light, which is measurable in

terms of intensity and wavelength

Color of a material becomes visible only when light from a

luminous object or source illuminates strikes the surface

10/20/2010

9

Color order system

Susunan three-dimensional

Lima color order systems yang digunakan untuk pangan:

1. Munsell

2. CIE : The Commission Internationale de l’Eclairage (CIE)

(The International Commission on Illumination)

3. CIE L∗a∗b∗ (CIELAB)

4. Hunter Lab

5. Lovibond.

CIE L∗a∗b∗ (CIELAB) Color Spaces

Lokasi warna pada sistem ini ditentukan dengan koordinat L∗, a∗, danb∗.

L∗ menunjukkan perbedaan antara cerah atau terang (light) (L∗ = 100) dan gelap (dark) (L∗ = 0).

a∗ menunjukkan perbedaan antara hijau (green) (−a∗) dan merah(red )(+a∗)

b∗ menunjukkan perbedaan antara biru (blue) (−b∗) dan kuning(yellow) (+b∗)

Jika L, a, b diketahui maka warna tidak hanya dideskripsikan tapidapat ditunjukkan lokasinya

CIELAB L∗, a∗, and b∗ dikalkulasikan berdasarkan the tristimulus values (Marcus,1998)

10/20/2010

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Hunter Lab Color Space

Berdasarkan L, a, b

L menunjukkan kecerahan 0 (black) hingga 100 (white).

a menunjukkan −a (greenness) to +a (redness)

B menunjukkan −b (blueness) to +b (yellowness).

Hunter scale juga berasal dari nilai X, Y , Z

10/20/2010

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Color Differences (Perbedaan warna)

Total perbedaan warna (E∗) pada CIE L∗a∗b∗ (CIELAB) total color adalah jarak antar warna dalam CIE

∆L∗ adalah perbedaan kecerahan:

L∗sample − L∗standard

∆ a∗ adalah perbedaan merah/hijau:

a∗sample − a∗standard,

∆ b∗ adalah perbedaan kuning/biru :

b∗sample − b∗standard.

10/20/2010

12

Irisan kentang yang digoreng dengan minyak biji bunga

matahari dalam microwave dengan waktu penggorengan yang

berbeda dievaluasi dengan skala CIE.

Sebagai standar digunakan a BaSO4 dengan nilai L∗, a∗, and b∗96.9, 0.0, dan 7.2.

Tentukan E* dan evaluasi hasilnya!

Peningkatan nilai E∗ menunjukkan warna keripik kentang semakin gelap

Solusi:

Nilai L, a, b hasil analisa disajikan dalam tabel berikut hasil

perhitungan ∆E*

10/20/2010

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References

Sahin, S. & Sumnu, S.G. 2006, Physical Properties of Foods, Springer, USA.

MacDougall, D.B (ed). 2002, Colour in food: Improving quality, Woodhead Publishing Limited & CRC Press LLC, Boca Raton.

Delgado-Vargas,F. & Paredes-López, O. 2003, Natural Colorants for Food and Nutraceutical Uses, CRC Press LLC, Boca Raton.

Meilgaard, M., Civille, G. V., & Carr, B.T. 1999, Sensory Evaluation Techniques Third Edition, CRC Press LLC, Boca Raton.

Nielsen, S.Z. (ed). 2003, Food Analysis, third edition, Kluwer Academic/Plenum Publishers, New York.