UDC 664.521 : 543.42 : 621.796 BIBLID: 1450–7188 (2004) 35, 59-64 Original scientific paper
COLOUR CHANGE IN PEPPER (Capsicum annuum) DURING STORAGE
Aleksandra N. Tepić and Biserka L. Vujičić Powders of pepper were stored at ambient temperature, exposed to daylight. The final quality was evaluated by measuring the extractable colour by the American Spice TradeAssociation (ASTA). Also, the possibility of using surface colour measurement, as a supplement to extractable colour measurement was investigated. The use of the chromatic attributes L, a and b, suggested by the Commision Internationale de l'Eclairage (CIE), i.e., of the CIELAB space, made it possible to find the correlation between ASTA and apparent colour of paprika. KEYWORDS: Pepper; colourmeasurement; storage; quality
INTRODUCTION The range of food products that contain pepper or its chemical constituents is really wide. Paprika extracts are also used in pharmaceutical and cosmetic products. Yellow, orange and red colours of pepper originate from the carotenoid pigments formed in the fruit during ripening. Over 30 different carotenoids have been identified in capsicum fruits (1). Someof them are provitamin A carotenoids, essential to human nutrition, and the oxygenated carotenoids that have been studied as anti-cancer agents. Since paprika is used as a colouring agent in food, its market value depends partly on the red colour. Many factors affect pepper colour loss during storage, and the most important is oxidative degradation of carotenoids, caused by exposure to heat, lightor oxygen. Colour of peppers can be evaluated from three different aspects (2): surface (apparent) colour, extractable colour, and carotenoids profiles (3 – 8). Ectractable and surface colour measurements are standard quality evaluations in the spice industry (9 – 16). Surface colour measurements are used to specify colours perceived by the human eye. Verbal descriptions of colours can bedifficult and confusing, because two people may describe the
Aleksandra N. Tepić, BSc., Assist., Dr. Biserka L. Vujičić, Prof., University of Novi Sad, Faculty of Technology, 21000 Novi Sad, Bulevar Cara Lazara 1, Serbia and Montenegro
same colour in very different terms. The perception of colour varies according to the sensitivity of observer, the size of the object being viewed, the lightsource and illumination, the background colour and contrast, and the angle at which the object is viewed. Quantifying colours, or expressing colours numerically, facilitates colour communication and standardization (17). Surface colour varies according to cultivar, growing conditions, dehydration, milling and storage conditions. Extractable colour is a measure of total pigment content. Currentprocedures for measuring extractable colour (total pigments) in dehydrated capsicums and oleoresins were developed and approved by the Association of Official Analytical Chemists (18) and the American Spice Trade Association (ASTA) (9, 19). Extractable colour is measured using a spectrophotometer and is expressed in ASTA units. Generally, the higher the ASTA colour value, the greater the effect on thebrightness or richness of the final product. Paprika with 200 ASTA colour units would give a brighter red to a finished product than an equivalent amount with 100 ASTA colour units (2).
EXPERIMENTAL Samples. Aleva NK cultivars of paprika powder from two different regions (Djala and Stara Pazova) were used. Samples were purchased from the factory "Aleva" Novi Kneževac and stored at ambienttemperature (20°C ± 2) in transparent bottles, exposed to daylight and shaken occasionally. Apparent (surface) colour and extractable colour were measured in paprika powders before storage and then monthly, for 4 months. Apparent (surface) colour measurements. Surface colour was measured using a tristimulus photoelectric colorimeter MOM Color 100. The values L, a, b, λ, a/b and hue angle (h) were...