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Enzymatic determination of L-malic acid in honey






Food Chemistry 62(4): 503-508, Aug

Enzymatic determination of L-malic acid in honey

L-Malic acid determination has been carried out in honey using a direct enzymatic method. The sample solution was prepared from 2.5g honey in 100 ml Milli-Q water. The enzymatic determination was measured spectrophotometrically at 340 nm, using glutamate-oxaloacetate transaminase and L-malate dehydrogenase. The direct method combines precision (CV was 3.5%, at worst), good recovery (100 +- 3.5 %), zero interference, simplicity, and low cost (cost was reduced by 50% using a microtest). This direct enzymatic method was applied to 20 floral honeys of Galicia (northwestern Spain) and the results ranged between 94 and 596 mg kg-1 (mean 246 mg kg-1) of L-malic acid, which is in keeping with value ranges obtained by other authors. Different clarifications (as polyvinyl-polypyrrolidone (PVPP), Carrez, Carrez with NaOH, Carrez with KOH, Carrez together with PVPP and activated charcoal) and a pair of controls have also been used but the precision and the recovery of direct enzymatic method of L-malic acid in honey did not improve. To study the interaction of beta-lactoglobulin (BLG) with flavour compounds a fast screening methodology was developed. BLG (variant AB, pure A and pure B) was immobilized onto a silica support, filled into a column and combined with a HPLC-system. A total of 24 different flavour compounds were injected and their retention times determined at different pHs and protein concentrations. The binding constant for each compound was calculated from the retention times and the protein concentration of the column. This simple system allows the rapid screening of many flavour compounds under a variety of external conditions like pH, salt content and flavour concentration. This procedure also permits the study of competitive effects with several flavour compounds in the solution.

Accession: 003127003

DOI: 10.1016/s0308-8146(97)00166-0

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Related references

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