| Popis: |
Rejection of enzymes and elimination of yeast cells from honeys, using various mol. wt. cut off (MWCO) membranes, were examined in the clarification procedure. Use of membrane technology to produce a honey which is free from microorganisms and suspended matter, but which contains a significant level of enzymes, was also evaluated. Forest/Rock bee honey (Apis dorsata) was strained through a muslin and used in the experiments. Honey samples were analysed for diastase activity, sugars, yeast counts and hydroxymethylfurfural (HMF) value. Permeates from membranes with MWCO of 25-100 (x 103) exhibited no diastase activity; permeate flux rates were 0.9-1.15 kg m-2 h-1. Membrane processing completely removed yeasts. A microfiltration membrane of pore size 100 nm eliminated microorganisms whilst retaining nutritional factors; an ultrafiltration membrane of 20 000 MWCO fractionated this microfiltered honey into 2 fractions, i.e. an enzyme-rich honey (enzymes enriched 2.2x) and a regular ultrafiltered honey. Because honey is viscous, it required dilution before membrane processing, so subsequent vacuum concn was evaluated; as processing temp. increased, HMF value and loss of enzymes increased; it is thus suggested that this process should be conducted at as low a temp. as possible. |
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