Simultaneous Measurement of Titratable Acidity and Fermentation Index in Cocoa Beans by Electronic Tongue Together with

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Simultaneous Measurement of Titratable Acidity and Fermentation Index in Cocoa Beans by Electronic Tongue Together with Linear and Non-linear Multivariate Technique Xingyi Huang & Ernest Teye & Joshua D. Owusu-Sekyere & Jemmy Takrama & Livingstone K. Sam-Amoah & Liya Yao & Caleb K. Firempong

Received: 14 January 2014 / Accepted: 7 April 2014 # Springer Science+Business Media New York 2014

Abstract Titratable acidity (TA) and fermentation index (FI) are important quality indicators of cocoa beans. This paper attempted the simultaneous analysis of these indicators by electronic tongue (ET) and two multivariate calibrations. ET was used for data acquisition, while partial least squares (PLSs) and principal component support vector machine regression (PC-SVMR) were used to build the calibration models. Some parameters were optimized simultaneously by leave-one-out cross-validation (LOOCV) in calibrating the model. The performance of the model was tested according to root mean square error of prediction (RMSEP) and correlation coefficient (Rpre) in the prediction set. The results revealed that PC-SVMR model was superior to PLS model in this work. The optimal PC-SVMR model for TA was Rpre = 0.960 and RMSEP=0.0077, while for FI, this was Rpre =0.954 and RMSEP=0.058. This study demonstrated that ET together with SVMR could be used to analyze titratable acidity and X. Huang (*) : E. Teye : L. Yao School of Food and Biological Engineering, Jiangsu University, Xuefu Road 301, Zhenjiang 212013, Jiangsu, People’s Republic of China e-mail: [email protected] X. Huang e-mail: [email protected] E. Teye e-mail: [email protected] E. Teye : J. D. Owusu-Sekyere : L. K. Sam-Amoah School of Agriculture, University of Cape Coast, Cape Coast, Ghana J. Takrama Biochemistry Division, Cocoa Research Institute of Ghana (CRIG), New Tafo, Akim, Ghana C. K. Firempong Kwame Nkrumah University of Science and Technology, Kumasi, Ghana

fermentation index in cocoa beans for quality control purposes. Keywords Cocoa bean . Electronic tongue . PC-SVMR . Titratable acidity . Fermentation index

Introduction Cocoa beans are seeds in a pod from a tropical tree crop known as Theobroma cacao L. Currently, Cote d’Ivory and Ghana (both west African countries) supplies about 65 % of the world’s cocoa beans. The consumption of cocoa beanderived products has increasingly become a popular diet worldwide due to its beneficial health properties, namely, prevention of various diseases such as cancers, hypertension, diabetes, cardiovascular and other related illnesses. Research has also shown that the consumption of cocoa bean has the potential of decreasing the risk of stroke, cardiovascular diseases, platelet aggregation and blood pressure, with improved vascular system (Vlachopoulos et al. 2005; Di Castelnuovo et al. 2012). Cocoa bean products are nutritious foods which contain various phytochemicals such as proteins, minerals, vitamins, carbohydrates and fats and are also a rich source of polyphenols with a higher antioxidant activity than teas and red wines (