Evaluation of some important physicochemical properties of starch free grewia gum

Elijah I. Nep, I.m. Sims, Gordon Morris, Vassilis Kontogiorgos, Alan Smith

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated.The gum was extracted by maceration of the inner bark in deionised water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated.The GG extract had total carbohydrate content of ~60% out of which 11.8% was starch, and a protein content of 2.3%. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH. © 2015 Elsevier Ltd.
Original languageEnglish
Pages (from-to)134-140
Number of pages7
JournalFood Hydrocolloids
Volume53
Early online date20 Feb 2015
DOIs
Publication statusPublished - Feb 2016

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Grewia
Starch
physicochemical properties
starch
extracts
Gingiva
Glucuronic Acid
galacturonic acid
glucuronic acid
bark
Polysaccharides
Carbohydrates
Sugars
Acids
Digestion
polysaccharides
digestion
Proteins
sugars
sampling

Cite this

Nep, Elijah I. ; Sims, I.m. ; Morris, Gordon ; Kontogiorgos, Vassilis ; Smith, Alan. / Evaluation of some important physicochemical properties of starch free grewia gum. In: Food Hydrocolloids. 2016 ; Vol. 53. pp. 134-140.
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Evaluation of some important physicochemical properties of starch free grewia gum. / Nep, Elijah I.; Sims, I.m.; Morris, Gordon; Kontogiorgos, Vassilis; Smith, Alan.

In: Food Hydrocolloids, Vol. 53, 02.2016, p. 134-140.

Research output: Contribution to journalArticle

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T1 - Evaluation of some important physicochemical properties of starch free grewia gum

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AU - Sims, I.m.

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AU - Kontogiorgos, Vassilis

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N2 - Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated.The gum was extracted by maceration of the inner bark in deionised water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated.The GG extract had total carbohydrate content of ~60% out of which 11.8% was starch, and a protein content of 2.3%. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH. © 2015 Elsevier Ltd.

AB - Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated.The gum was extracted by maceration of the inner bark in deionised water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated.The GG extract had total carbohydrate content of ~60% out of which 11.8% was starch, and a protein content of 2.3%. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH. © 2015 Elsevier Ltd.

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