An on-line detector for efficiently sorting coconut water at four stages of maturity

• Published in: Biosystems engineering 2012, Vol.111 (1), p.49-56
• Main Author: Hahn, Federico
• Format: Article
• Language: English
• Subjects: Agricultural machinery and engineering; Agronomy. Soil science and plant productions; Beverages; Biological and medical sciences; bioreactors; coconuts; Cutting; Detectors; dissolved oxygen; exercise; flavor; Flavours; Fundamental and applied biological sciences. Psychology; Generalities. Biometrics, experimentation. Remote sensing; Hydraulic presses; ingredients; maturity stage; minerals; On-line systems; pulp; rehydration; Sorting; sugars
• ISSN: 1537-5110; 1537-5129
• DOI: 10.1016/j.biosystemseng.2011.10.007

Coconut water is a natural beverage often used for rehydration following exercise because it is rich in sugar and minerals. When making beverages with this ingredient it is important to use water from coconuts at the proper stage of maturity, as the flavour of coconut water changes as coconuts get older. Two experiments were conducted; the first maintaining controlled conditions with a bioreactor and the second quantified dissolved oxygen (DO) and pH at four different stages of maturity. The different stages of maturity of the coconuts were designated very tender, tender, mature and very mature for automatic sorting. Water from three hundred coconuts was sorted by an automatic on-line detector in 1 h. DO measurements settle down in 60 s, so DO ratios between the water measurements 5 s after contacting the water and its saturation value were used. Three models with four rules each were tested using DO ratios, pH values and water volume. DO ratios discriminated very tender coconuts at a success rate of 100%. Very mature brown coconuts with thick, breakable pulp were discriminated at a success rate of 100% as larger water volume differences were encountered. Tender and mature coconuts were differentiated with an accuracy of 92% using pH measurements. The on-line sorter presented an embedded system which controlled the DO and pH acquiring time, opening of the curtain and sorting control valves. Finally, it synchronises the hydraulic press for cutting the next coconut. ► Beverages containing coconut water depend on proper sorting depending on coconut age. ► Water flows through stainless steel tubes measuring DO, pH and water volume. ► On-line detector classified in four stages of maturity with an accuracy over 90%. ► It sorted 300 coconuts in 1 h. ► Very mature brown coconuts can affect beverage quality and should be eliminated.