Genotypic Differences And Regulation Effects On Starch Physicochemical Properties Of Waxy Maize

Using the waxy maize varieties or lines that released in recent years in China as materials, the genotypic differences for starch physicochemical properties were studied and the regulation effects of cultivation measures such as fertilizer treatments, sowing and harvesting date on it were clarified. Further, the effects of kernel components and process condition on it were analyzed. The mains results of the study were as follows.Physicochemical properties (Swelling power, solubility, water binding capacity, gelatinization, retrogradation and pasting characteristics) for waxy maize starch were significantly different among 54 waxy maize varieties or lines come from Chinese waxy maize regional test. The variation ranges for swelling power, solubility, water binding capacity, enthalpy of gelatinization, peak temperature, gelatinization range, percentage of retrogradation, peak viscosity, breakdown and pasting temperature were 2.9~25.3 g/g,34.7~66.7%,97.4~194.5%,45.9~57.0 J/g,7.7~12.0℃,32.8~78.8%,87.7~169.9 RVU,37.5~83.8 RVU,71.8~75.8℃and 69.8~73.9℃, respectively. The variation for peak temperature and pasting temperature was little, whereas the variation for the other characteristics was large (variation coefficient>5.9%). Theλmax for waxy maize starch were mainly between 532.2 nm and 540.3 nm, except for Xinshinuoyu01, Danhuangnuo02 and Shanbainuo12, which were 580.5 nm, 557.9 nm and 551.1 nm, respectively, indicating theλmax of starch was mainly presented by amylopectin. The variation range for blue value and iodine binding capacity were 01274~0.7789 and 0.56~1.05, respectively. The three characteristics were negatively correlated to the percentage of retrogradation, peak viscosity and breakdown, and positively correlated to setback. By analysis the microelements content in starch, no significantly correlations were observed between Ca, K, Na, Cu, Fe content and the physicochemical characteristics, whereas significantly correlations were observed between other microelements content (P, S, Mn, Zn and B) and some physicochemical characteristics. Though the waxy maize starch was composed by 100% amylopectin, the variations of long/short chain ratio and microelements content caused the starch physicochemical properties were different among genotypes, which could afford references for its utilization.Significant regulation of fertilizer treatment on starch pasting, thermal and crystalline properties were observed. The fertilizer treatments didn't change the diffraction pattern and the starch exhibited typical A-type diffraction pattern. Peak time, pasting temperature, transition temperature (onset, peak and conclusion temperature), and peak height index and gelatinization range were little affected by fertilizer treatments. Compared with the treatment of only N applied in basic fertilizer, adding P or (and) K fertilizers decreased the peak viscosity, breakdown, the percentage of retrogradation and enthalpy of retrogradation, but increased crystallinity. With larger amount of N topdressing at jointing stage, peak viscosity increased gradually, breakdown, the percentage of retrogradation and enthalpy of retrogradation showed no significant differences in treatments of topdressing N 150 and 300 kg ha-1 and higher than 0 kg ha-1 treatments. The physicochemical characteristics of waxy maize starch were improved to be the better (higher crystallinity, enthalpy of gelatinization, peak viscosity, breakdown and lower percentage of retrogradation) when the top dressing was N 150 kg ha-1 at jointing stage on the basis of N 75 kg ha-1 +P2O5 65 kg ha-1+K2O 70 kg ha-1 as the basic fertilizer.Starch cryatalline structure and pasting properties were affected by growth seasons. All starch samples showed a typical A-type diffraction pattern, indicating the growing season has no effect on it. However, the growing season significantly influenced the starch crystalline and pasting properties. Starch obtained from autumn season, compared with that from spring season, showed higher degrees on crystallinity, peak intensities (2θ=15°, 17°, 18°, 20°, and 23°), peak viscosity, trough viscosity, final viscosity, and breakdown. The setback of starch of waxy corn in autumn season was significantly lower than that in spring season, although they both in low values. The crystallinity, peak intensities, and pasting characteristics were significantly different among the eight waxy corn cultivars. The crystallinity was positively correlated with the peak viscosity (r = 0.72, P < 0.01), breakdown (r = 0.85, P < 0.01), trough viscosity (r = 0.52, P < 0.05), pasting temperature (r = 0.55, P < 0.05), whereas, it was negatively correlated to setback (r = ?0.49, P < 0.05). The differences of pasting properties between growing seasons were mainly caused by the differences of crystallinity and peak intensities of starch in waxy corn. Harvesting dates were observed affect the yield and starch pasting properties of waxy maize.The grain yield increased gradually when the harvesting date was postponed and the increasing rate was highest at 35-40 days after pollination (DAP), which reached 5.2 % per day, and the increasing rate was slow after 40 DAP. The starch content rose first and fell later and it reached a peak at 35-40 DAP. Pasting temperature was stable among different harvesting dates. Peak viscosity, trough viscosity, breakdown, final viscosity and peak time rose first and fell later with the postponed harvesting date, these five pasting characteristics reached a peak at 40 DAP, and setback was the lowest at this time. The effects of harvesting date on peak time and pasting temperature were lower, while those were larger on peak viscosity, trough viscosity, breakdown, final viscosity and setback. Considering the changing trend of grain yield, starch content and RVA characteristics, 40 DAP might be the optimum harvesting time as the grain yield was relative high, the starch content was the highest and the RVA characteristics was ideal at this time in this experiment.The physicochemical properties of starch were affected by protein and lipid content. The starch granules presented polygonal and irregular shapes. Protein removal and lipid removal didn't change the diffraction pattern of waxy maize and all samples presented typical A-type diffraction pattern. Protein removal and lipid removal decreased the crystallinity, and the effect of lipid removal on starch was higher than protein removal on flour. The starch showed lower swelling power, higher solubility and light transmittance than flour. Defatting decreased the swelling power and solubility, whereas the light transmittance was increased. The enthalpy of gelatinization was increased after protein removal and it was decreased after lipid removal. After stored at 4°C for 7 days, the gelatinized samples exhibited lower transition temperature and enthalpy of retrogradation. The percentage of retrogradation was highest for flour and lowest for starch. RVA studies found that protein removal increased the peak viscosity, trough viscosity, final viscosity and breakdown viscosity. Simultaneity, setback viscosity, peak time and pasting temperature were decreased. Lipid removal decreased the RVA characteristics except for breakdown viscosity. The information generated in this study on the physicochemical properties of the flour, starch and defatted starch of waxy maize could provide guidance on possible uses of it.The process conditions on RVA characteristics of waxy and normal corn starches were studied, and the RVA characteristic differences between waxy corn starch and normal corn starch in different reaction programs and starch concentrations were clarified using waxy corn variety (Yunuo No. 7) and normal corn variety (Nongda 108) as material. The RVA characteristics were changed under different reaction programs, the starch presented higher peak viscosity, breakdown viscosity and pasting temperature, lower peak time in the procedure with higher heating-cooling rate and longer 95℃keeping time. Compared with normal corn starch, waxy corn starch exhibited higher peak viscosity and breakdown, lower trough viscosity, final viscosity, setback, peak time and pasting temperature. The RVA characteristics were affected by starch concentration. With the increment of starch concentration, peak viscosity, trough viscosity, breakdown, final viscosity and setback gradually increased, peak time decreased slightly. Starch couldn't paste when the concentration was very low and the pasting temperature was decreased when the concentration increased. The peak viscosity of waxy corn starch was higher than normal corn starch when the concentration was low, and it was reverse when the concentration was higher (11%).