Differentiation of gelatine (bovine, porcine and fish) by Maillard reaction using e-tongue and e-nose combined with chemometrics method

Abstract

Food fraud and adulteration are the global issues, currently. One critical issue is about gelatine which comes from a variety of animal sources. Therefore, analytical method for gelatine must be developed. The objectives of this study were to improve the Maillard reaction, which produces flavour compounds in gelatine. A bovine gelatine-xylose model was used for optimisation. Furthermore, this research also aimed to evaluate the ability of E-tongue and E-nose in differentiating gelatine based on its sources and to investigate volatile and non-volatile compounds of gelatine and the Maillard reaction products (MRPs). There were five instruments employed in this research. The first instrument used was Ultra-Violet spectroscopy to determine the browning intensities of gelatine-xylose model's MRPs. The second was E-tongue, which has 16 membrane lipid sensors, and the third was an E-nose with eight metal oxide semiconductors gas sensors. Next, HPLC was used to analysis free amino acids (FAA) as non-volatile chemicals. Lastly, a SPME-GC-MS used to evaluate the volatile organic molecules. This investigation used gelatine standards from bovine, fish, and porcine bought from Sigma Aldrich. MANOVA and ANOVA statistical tests using SPSS software were carried out. Data were also analyzed using a chemometrics that included Principal Component Analysis and Linear Discriminant Analysis. The initial pH, reaction temperature, and heating time had a modest effect on the browning intensity of MRPs and affected the development of brown colour of MRPs. With an initial pH of 10.9, a temperature of 140 °C, and a heating time of 37.28 minutes, the best reaction conditions were established. Additionally, the result showed that E-tongue and E-nose, aided by the Maillard reaction paired with LDA, may be used to differentiate gelatine based on the sources with a percentage of accuracy greater than 95%. Also, the differentiation attained for gelatine samples without Maillard process had an accuracy ranging from 93% to 98%. Eleven amino acids detected for gelatine in various level concentration namely arginine, lysine, isoleucine, leucine, tyrosine, valine, glutamic acid, aspartic acid, threonine, serine, and alanine. Two undetected amino acids in gelatine namely methionine and phenylalanine were detected in the MRPs samples. The diversity of FAA in gelatine and the MRPs induces various E-tongue sensor responses and influences overall sensory qualities. Furthermore, 67 volatile compounds also detected in different concentration level. Among them, furfural, acetic acid, nonanone, dimethyl disulphide, and decanone were considered as the important volatiles in gelatine due to its abundance. In the Maillard reaction products, furfural, 1-(2-furanylmethyl)-1H-pyrrole, 1-(2-furanyl)-ethanone, acetic acid, and 2,2'-bifuran were predominant. Finally, heptanol, octanal, nonanal, nonanone, dimethyl disulphide, and dimethyl trisulphide could be considered as important compounds due to its low odour threshold value. They had a direct impact on the overall flavour of samples assessed using E-nose sensors. All these findings indicate that the proposed extension was successful in meeting the study’s objectives. Keyword: halal authentication, gelatine-xylose, Maillard reaction, E-tongue, E-nose, Principal Component Analysis, Linear Discriminant Analysis.