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Title: STRUCTURES AND FUNCTIONAL PROPERTIES OF APPLE (MALUS DOMESTICA BORKH) FRUIT STARCH

Author
item Stevenson, David
item DOMOTO, PAUL - IOWA STATE UNIVERSITY
item JANE, JAY-LIN - IOWA STATE UNIVERSITY

Submitted to: Carbohydrate Polymers
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/6/2005
Publication Date: 3/3/2006
Citation: Stevenson, D.G., Domoto, P.A., Jane, J. 2006. Structures and functional properties of apple (malus domestica borkh) fruit starch. Carbohydrate Polymers. 63:432-441.

Interpretive Summary: Starch of immature fruit was studied from six apple cultivars (Gala, Golden Delicious, Granny Smith, Jerseymac, Jonagold, and Royal Gala). Apple starch had 26-29% amylose (straight chain molecules), and the branched amylopectin molecules had the longest branch chain-lengths reported for any starch. The long branch-chains resulted in the rare phenomenon of very low paste breakdown when starch in water was stirred while heated and subsequently cooled. Apple starch had some unique properties that add to the understanding of structure/function relationships of starch, that will assist the starch industry in producing starches with novel applications.

Technical Abstract: Structures and functional properties of fruit starch of six apple cultivars (Gala, Golden Delicious, Granny Smith, Jerseymac, Jonagold, and Royal Gala) were investigated. Apple starches exhibit CA-type X-ray diffraction patterns, and granule diameters ranged from 2 to 12 micrometer. Immature apple fruit had 44-53% starch (dry basis). The apparent amylose content was high (40-48%), but the average branch chain-length of amylopectin was long (DP 27.9 to 29.6), resulting in the absolute amylose content of 26-29%. The weight-average molecular weight of amylopectin ranged from 4.6 to 11.1 x 108. The proportion of long-branch chains of amylopectin (DP greater than or equal to 37), determined by anion-exchange chromatography with a post-column amyloglucosidase reactor and a pulsed amperometric detector, ranged from 29.7 to 32.4%. The onset gelatinization temperature of the starch ranged from 64-66 deg C, and the delta-H of starch gelatinization was 16-18 J/g. The percentage retrogradation of the gelatinized starch, after being stored for 7 days at 4 deg C, ranged from 42-47%. Most distinctive characteristic of apple starch was that three cultivars had extremely low breakdown (less than 4 RVU) and high setback (greater than 100 RVU) at 8% (w/w) starch concentration. Peak and final viscosities ranged from 99-148 and 144-224 RVU, respectively. Pasting temperature was around 70 deg C.