When I was employed in a juice processing industry, one of our biggest problem was the discoloration of coconut water. Young coconut water concentrates, immediately after processing were fine but were experiencing top discoloration after some time in cold storage. The top were becoming reddish brown. We suspected it was a reaction involving oxygen but wasn’t able to find any suitable solution. The company opted dropping the product line.
Lately, the raw nata de coco I left under the refrigerator got frozen and became pink. I thought it was still related to our previous experience. I guess it is time to find its real cause and solution if possible.
I found only two literature but I think they are enough.
Optimum activities of polyphenoloxydase (PPO) and peroxydase in green coconut water occurred at pH 6.0 and pH 5.5 at temperatures of 25°C and 35°C, respectively. However, various levels of PPO and POD activity are reported in literature. These enzymes are assumed to be responsible for the discoloration (pink, yellow or brown) frequently observed in coconut water. Porexydase activity was also observed in coconut water samples stored at -20°C.
Coconut water uses, composition and properties: a review. By: Alexia Prades, Manuel thDornier, Nafissatou Diop, Jean-Pierre Pain.
The pink discoloration in coconut water is a result of the initial enzymatic reaction of the polyphenol oxdydate (PPO) on the phenolic substrates which are naturally present in the product. Enzyme activity is further enhanced by metal contamination such as copper and exposure to high temperature during processing and storage. Younger coconuts are more prone to discoloration than matures.
Control of pink discoloration in coconut water. By: B. Garcia, D.B. Masa, M.J. Rodriguez and R. Rolle
The last set of authors belong to Philippine Coconut Authority. I suggest contacting the agency if you want to know more about control of coconut water discoloration.