Physicochemical properties of twenty‐one Caribbean sweet potato cultivars
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Summary The physical, chemical and physicochemical properties of twenty‐one Caribbean sweet potato cultivars were investigated. Hunter L a b colour parameters were measured, chroma, colour intensity and hue angle were calculated. Proximate composition, vitamin C, amylose, reducing and non‐reducing sugars contents were determined using standard methods. Pasting properties were determined using Rapid Visco Analyser. Tuber size (length, r = 0.72, n = 21, P < 0.0015; width, r = 0.85, n = 21, P < 0.0002) was highly correlated with weight of the tubers. External colours of the tubers ( L = 28.7–63.1, a = +5.9 to +18.0, b = +3 to +19.3) were lower than the flesh colours ( L = 60.8–84.0, a = −2.4 to +27.8, b = +9.9 to +28.5). Proximate composition is typical of sweet potato cultivars but significant differences exist among cultivars. Total sugar, amylose and amylopectin contents ranged from 1.8 to 4.7%, 15.3–31.2% and 68.8–84.7%, respectively. Cooking profiles of the sweet potato flours showed similar trend. Pasting temperature, peak time, swelling power and solubility ranged from 78.3 to 93.0 °C, 3.3–4.8 min, 5.6–23.5 and 11.7–45.7%, respectively.Keywords:
Proximate
Flesh
Mangifera
The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.
Granule (geology)
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The molecular structure and the expression levels of starch biosynthesis-related genes of three types of high-amylose maize (HAM) genotypes and one normal maize (NM) genotype at 5–35 days after pollination (DAP) were studied. Size exclusion chromatography (SEC) analysis showed that the molecular size of amylopectin molecules in NM increased from 5 to 35 DAP and the amylose content in HAM genotypes increased from 15 to 35 DAP. Correlation analysis for both NM and HAMs combined showed that SBEIIb and ISAII were negatively correlated with the contents of amylose and long amylopectin chains (DP > 30) and positively correlated with the content of short amylopectin chains (DP ≤ 31) and the molecular size of amylopectin molecules. Correlation analysis for only the HAMs showed that amylose content was negatively correlated with SBEI and SSIIa. In both correlation analyses, SSIIa showed a negative correlation with the average chain lengths of amylose chains.
Positive correlation
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Three wheat varieties(Ningmai 9,Sumai 6 and Chongqing bread wheat)were used in 1999～2000 to analyze dynamics of starch components and ratio of amylose contents to amylopectin contents of wheat grain.The fastest accumulation for amylose in three wheat varieties appeared during 17～27 d after anthesis,but for amylopectin,was at mid-stage of grain filling.The dynamics of ratio of amylose contents to amylopectin contents shapedS-it descended at early stage of grain filling,then ascended at mid-stage,and decreased at late stage.There were significantly positive correlations in amylose contents,amylopectin contents and ratio of amylose contents to amylopectin contents between 1999 and 2000.The differences of amylose contents,amylopectin contents and ratio of amylose contents to amylopectin contents were significant among sampling times.Among varieties the differences of amylose contents,ratio of amylose contents to amylopectin contents were not significant(P0.05),but the difference of amylopectin contents was significant(P0.01).
Anthesis
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During cotton leaf development, starch accumulation was characterized by an initial rise to a maximum at the second to the fourth leaf from the apex. Then, starch content progressively decreased with leaf age. Starch accumulation was inversely related to the ratio of amylopectin to amylose. Differences between leaves in this ratio resulted from variations in both amylose and amylopectin levels. Fluctuations in amylose levels were more extreme than those of amylopectin.During the diurnal cycle, amylopectin was accumulated more than amylose in both young and old leaves during the day. During the night, amylopectin was degraded more than amylose in young leaves and vice versa in older leaves. The rate of change of the amylopectin to amylose ratio during the day was consistently higher than that during the night.
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The independent localisation of amylose and amylopectin in a range of dry and hydrated native starch granules with varying amylose content (0—70 %) has been indirectly visualised using enzyme-gold cytochemical markers. Increasing amylose content was clearly demonstrated to result in distinct changes in granule architecture. In the absence of amylose (waxy maize starch) a framework of closely packed concentric layers of amylopectin exists in the granules. Low amylose content (potato starch) results in alternating layers of densely packed amylopectin and amylose molecules. High amylose content (amylomaize starch) granules were shown to possess an amylopectin centre surrounded by an amylose periphery encapsulated by an amylopectin surface. Elongated granules without the amylopectin centre were also observed in high amylose starches suggesting a relationship between amylopectin, amylose and granule shape. A model of starch granule architecture is proposed where increased compartmentalisation of amylose and amylopectin is observed in granules containing increasing levels of amylose.
Granule (geology)
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Characterization
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Branching (polymer chemistry)
Degree of polymerization
Glycogen branching enzyme
Starch synthase
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Nine wheat cultivars with similar total starch content and different amylose and amylopectin content in mature stage were classified into three groups: low amylose, medium amylose and high amylose. The dynamic changes in ratio of amylose to amylopectin, and the activity changes of four enzymes in relation to starch biosynthesis and their relationships to the amylose and amylopectin accumulated during grain filling period were examined. The results showed that the ratio of amylose and amylopectin of wheat cultivars from group of high amylose was significantly higher than those of the other groups in the 28 d and 35 d after anthesis, and that the different ratio of amylose to amylopectin of variant wheat cultivars was caused by different amylose and amylopectin accumulation rate during middle and late stages of grain filling. Wheat cultivars, from group of low amylose, also with low granule bounded starch synthetase (GBSS) activity during filling stage and with low adenosine diphosphate glucose pyrophosphorylase (ADPGPPase) and uridinediphosphate glucose pyrophosphorylase (UDPGPPase) activity during middle stage and late stage of filling, produced less amylose in grains. High soluble starch synthetase (SSS) activity enhanced accumulation of amylose and amylopectin in the early stage of filling, but it would accelerate amylopectin accumulation and decelerate amylose accumulation in the late stage of filling.
Starch synthase
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Abstract Results are presented for a series of light‐scattering experiments on the stability of the starch components, amylose and amylopectin, in 0.33 M KCl. Potato, regular maize amylose, and the amylose from two amylomaize starches have been studied. The findings are generally in agreement with previous studies in this area, but in the case of amylopectin, contrary to the findings of Čeh and Vene , no retrogradation has been observed.
Retrogradation (starch)
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