Characteristic properties of crude pineapple waste extract for bromelain purification by membrane processing

Bromelain enzyme can be extracted from pineapple fruit including its waste parts. It is a valuable ingredient for various markets especially in the food and pharmaceutical areas. This enzyme can be extracted by membrane-based technology, but there is a lack of understanding of the properties of the crude pineapple extracts to link to functional membrane properties for efficient purification operation. This study focused on establishing characteristic properties of the crude pineapple waste mixture (CWM) extract, constituting of 57 % peel, 28 % crown and 15 % core, as a source of the enzyme and relevant to membr'ane processing. Rheological properties at different temperatures and pH levels were also determined in order to propose appropriate processing conditions for a practical and an efficient membrane operation. The CWM extract contained appreciable specific enzyme activity of 394.9 CDU/mg protein that would need to be purified at least 2–4 fold to achieve a required market standard. Existence of polysaccharides, particularly pectin, in the extract would be expected to cause fouling issues in membrane process, thus pre-treatment may be required to remove this compound from the mixture. The protein molecular weight of the CWM extract ranged between 11.7 and 26.9 kDa. The selection of membrane molecular weight cut-off (MWCO) should be above or below this range to isolate the enzyme. The evaluation on rheological properties of the CWM extract showed that it demonstrated lower viscosity at higher temperature and at neutral pH. Therefore, selection on temperature of 20–25 °C and pH 7 throughout the membrane purification operation has been recommended.