Cereal Chem. 80(1):91-98Flours of two soft wheat cultivars were fractionated into native, prime, tailing, A-, and B-type starch fractions. Starch fractions of each cultivar were characterized with respect to A/B-type granule ratio, amylose content, phosphorus level (lysophospholipid), and pasting properties to investigate factors related to wheat starch pasting behavior. While both cultivars exhibited similar starch characteristics, a range of A-type (5.7-97.9%, db) and B-type granule (2.1-94.3%, db) contents were observed across the five starch fractions. Though starch fractions displayed only subtle mean differences (<1%) in total amylose, they exhibited a range of mean phosphorus (446-540 mg/g), apparent amylose (18.7-23%), and lipid-complexed amylose (2.8-7.5%) values, which were significantly correlated with their respective A-and B-type granule contents. A-type (compared with B-type) granules exhibited lower levels of phosphorus, lipid-complexed amylose, and apparent amylose, though variability for the latter was primarily attributed to starch lipid content. While starch phosphorus and lipid-complexed amylose contents exhibited negative correlation with fraction pasting attributes, they did not adequately account for starch fraction pasting behavior, which was best explained by the A/B-type granule ratio. Fraction A-type granule content was positively correlated with starch pasting attributes, which might suggest that granule size itself could contribute to wheat starch pasting behavior.

Starch A-and B-type granules were isolated from soft wheat (Triticum aestivu?n L.) genotypes representing the four granule bound starch synthase I (GBSSI) classes, and characterized according to composition and properties. While total (TAM) and apparent (AAM) amylose contents of both granule fractions decreased as starch waxy character increased, the A-type granules possessed higher TAM and AAM contents than B-type granules for a given genotype. From wild-type to waxy, a general transition was observed from B-to A-type starch granule fractions with higher levels of lipid-complexed amylose (LAM) and phospholipid. Within a genotype, A-type (relative to B-type) granules possessed higher gelatini

Cereal Chem. 80(5):544-549Wheat has great potential to make inroads into starch markets with the advent of partial waxy and waxy starches of diverse composition and properties. The majority of isolated starch utilized in food applications is chemically modified to improve starch properties according to the intended use. Therefore, it is critical to understand factors that affect wheat starch reactivity. This work investigated the relative reactivities of normal, partial waxy, and waxy wheat starches and their respective Aand B-type starch granule fractions. Native starch isolated from four closely related soft wheat lines (normal, partial waxy, and full waxy) was modified through 1) substitution (propylene oxide analog) and 2) cross-linking (phosphorus oxychloride) reactions to generate both types of modified starch products for each wheat line. Characterization of the unmodified starch fractions confirmed compositional differences among the cultivars and their respective granule types. In cross-linking reactions, B-type granules were slightly more reacted than A-type granules for all cultivars, while the waxy starch generally exhibited higher reactivity compared with normal and partial waxy starches. For the substituted starches, no differences in reactivity were observed among the cultivars or between the two granule types.

Cereal Chem. 83(5):544-550Eight soft spring wheat (Triticum aestivum L.) genotypes representing the four granule bound starch synthase I (GBSSI) classes were evaluated with respect to flour/starch characteristics and pasting behaviors. Native starch was isolated from genotype straight-grade flours (94.8-98.1% of starch recovered) to approximate the starch populations of the parent flours. As anticipated, amylose characteristics varied among the genotypes according to GBSSI class and accounted for the primary compositional difference between genotypes. Total (TAM), apparent (AAM), and lipid-complexed (LAM) amylose contents ranged from 1.0-25.5 g, 0.7-20.4 g, and 0.3-5.6 g/100 g of native starch, respectively, and grad-ually decreased with the progressive loss of active Wx alleles. In addition, genotype flour total starch (FTS) and A-type starch granule contents, which ranged from 81.7-87.6 g/100 g of flour (db) and 61.6-76.8 g/100 g of native starch (db), respectively, generally decreased with an increase in waxy character in parallel with amylose characteristics, as likely secondary effects of Wx gene dosage. Though amylose characteristics predominantly accounted for the majority of genotype flour pasting properties, FTS content and ratios of A-to B-type granules also exhibited significant influence. Thus, loss of one or more Wx genes appeared to induce measurable secondary effects on starch characteristics and properties.

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