Visible Spectral Linearisation, Gradient Shift and Normalisation in Quantifying Carambola Acidity

• Published in: Food biophysics 2012-12, Vol.7 (4), p.289-295
• Main Authors: Omar, Ahmad Fairuz, Atan, Hanafi, MatJafri, Mohd Zubir
• Format: Article
• Language: English
• Subjects: Acidity; Analytical Chemistry; Biological and Medical Physics; Biophysics; Chemistry; Chemistry and Materials Science; Color; Food Science; Fruits; Original Article; Reflectance; Sensory perception
• ISSN: 1557-1858; 1557-1866
• DOI: 10.1007/s11483-012-9267-y

Color alteration is one of the major indicators of the maturity and level of ripeness of fruits. A strong relationship also exists between the color and acidity of fruits. Three different spectral analyses have been conducted in the visible region of the measured spectrum to quantify the acidity or pH of B10 carambola. Spectral linearisation, gradient shift, and normalisation analyses within the wavelength range of 550 and 675 nm have been applied on the spectra of intact carambola samples. These two wavelength points are selected because of their best response and strong link to carotenoid and chlorophyll contents in carambola. The spectra are measured through reflectance and interactance measurement techniques. High coefficients of determination (R 2 >0.7) generated for all analyses indicate that a strong relationship exists between the presented color analyses and the acidity of the carambolas. Interactance has a better accuracy and precision in measuring the carambola acidity compared with the reflectance technique.