Changes in properties of palm sugar syrup produced by an open pan and a vacuum evaporator during storage

Headnote

Article history

Received: 18April 2013

Received in revised form: 13 May 2013

Accepted: 18 May 2013

Keywords

Boras sits flabellifer Linn.

Syrup

Storage

Nonenzymatic browning

Quality

Abstract

The aim of this study was to monitor the changes in the properties of palm sugar syrup produced by an open pan and a vacuum evaporator at 70°C and 80°C during storage under 4°C and room temperature (30°C) for 12 months at monthly intervals. During storage. Maillard reaction took place in samples stored under 4°C lower than those stored under 30°C. This was shown by lower a* values, intennediate browning products (IBP), browning intensity (BI) and HMF content, and higher L* values, fructose, glucose and free amino group contents during storage for 12 months. HMF, a possible mutagen formed by nonenzymatic browning during the heating and storage of sugar based products, seems of particular interest and concern. Only the sample produced by an open pan and stored under 30°C contained HMF content (50.58 mg/kg) higher than the permitted maximum limit (40 mg/kg as recoimnended by the Codex Alimentarious). However, other samples still contained HMF in agreement with this standard. In addition, the microbiological quality and total soluble solids of all samples complied with Thai legislation standards for palm sugar syrup during 12 months of storage.

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Introduction

Palmyra palm trees are widely grown in Africa, South Asia, South America, Australia and in other tropical countries (Morton, 1988). In Southern Thailand, these trees are widely grown and very popular in Petchaburi and Songkhla provinces. They are planted on the dykes of rice fields for shading the rice and tapping the palm sap for cooking. The unique flavour of palm sugar syrup has made it popular as an ingredient in confectionery and baking products. In addition, emphasis on the consumption of natural foods has resulted in the use of palm sugar concentrate as an alternative sweetener. Palm sugar syrup is obtained by heating fresh palm sap obtained from the Palmyra palm tree (Borassus flabellifer Linn.) until it is concentrated. This syrup is popular among Thai consumers; however it has not yet been produced for industrial purposes.

Traditionally, palm sugar syrup is produced by evaporating the palm sap in an open pan, and heated, using a wood...