Temperature dependence of acid and calcium-induced low-methoxyl pectin gel extracted from Cyclea barbata Miers

• Published in: Food hydrocolloids Vol. 81; pp. 300 - 311
• Main Authors: Yuliarti, Oni, Mardyiah Binte Othman, Radyiatul
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-08-2018
• Subjects: Cold-set gelation; Green jelly leaf; Low-methoxyl pectin; Molecular weight; Neutral sugars; Green jelly leaf; Cold-set gelation; Low-methoxyl pectin; Neutral sugars; Molecular weight
• ISSN: 0268-005X; 1873-7137
• DOI: 10.1016/j.foodhyd.2018.03.004

The gel formation behaviour of green jelly leaf (GJL) pectins isolated by using water extraction method with extraction temperatures of 45, 65, 85 and 95 °C was investigated. The isolated pectins were also analysed for the yield, physicochemical and functional properties. The yield, molecular weight (Mw) and galacturonic acid content varied from ∼10 to 13% w/w, 3 × 105 to 12 × 105 g/mol and ∼75–86% w/w, respectively. Gelation of GJL pectins was a cold-setting gel and could be induced by acid and/or divalent ions; however, the latter gelation method showed a lesser temperature dependence than acid-induced gel. The addition of NaCl had enhanced the gel structure due to electrostatic screening effect. The mechanical spectra response showed that GJL pectin was typically gel-like with G′ greater than G″ and strongly influenced by pH and calcium concentration. The variation in pectin gel structures was also attributed to difference in pectin physicochemical properties particularly the degree of esterification (DE). Furthermore, lower DE pectins with higher charge values exhibited a stronger gel like properties with less variation on mechanical spectrum compared to higher DE pectins. These findings showed considerable potential of GJL pectin as a thickener and gelling agent and could be useful for development of low-sugar and high calcium content food with different textures.
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•Extraction temperatures had affected the green jelly leaf pectin physicochemical properties.•Gelation was a cold-setting gel and could be induced by acid, divalent ions and combination of both.•Variation in DE had led to variation in gel strength and gel-sol transition.•Ion-mediated gelation showed a lesser temperature dependence than acid-induced gel.•The addition of NaCl enhanced the gel structure due to electrostatic screening effect.