4. Conclusions
Physicochemical properties of starches of three golden kiwifruit varieties (Gold3, Gold9 and Hort16A) were characterized with normal maize and potato starches as control. The total starch content in outer pericarp of kiwifruit was higher than that of the core tissue. The shapes of outer pericarp and core starches were rather similar and were partially spherical with flattened sides, and former had larger granule size (∼9.6 μm) than the latter by ∼1.5 μm. All the kiwifruit starch has B type polymorph, and the core starches had somewhat lower degree of crystallinity by ∼1%. Core starches had higher amylose content and enzyme susceptibility and lower gelatinization parameters than outer pericarp starch. Swelling and water solubilisation, and rheological properties of outer pericarp starches were analyzed and compared with those of maize and potato starches. The ΔH of gelatinization of kiwifruit starches were higher than common starches. The yield stresses of outer pericarp starch pastes were higher than potato and maize starch pastes. Dynamic rheological properties of outer pericarp starches of kiwifruit were more similar to those of potato starch than maize starch. The relatively small differences in the properties and composition between Gold3, Gold9 and Hort16A suggest that starch may not be a key factor affecting the shelf life of storage for different varieties of kiwifruit. The results of this study will be of great importance to better understand the role of starch in the quality of kiwifruit products as well as potential development of this starch for applications.
Conflicts of interest
The authors declare no conflicts of interest.
Acknowledgements
Dr. Gustavo Hernandez kindly helped us with kiwifruit collection. Technical assistance from Mr. Guantian Li and Ms. Ling Zhang is gratefully acknowledged. Associate Professor Yacine Hemar kindly provided us with the access to the facility for rheology and particle size distribution analysis. Punchbowl Kiwifruit Services kindly donated the kiwifruit.