Abstract: Crude whole navel orange pulp was subjected to ball milling treatment to develop whole fruit products with reduced particle size and improved rheological properties. The whole fruit paste of Gannan navel orange was ball milled for different durations (0, 30, 60, 90, 120, 150, and 180 min). Changes in its particle size and rheological properties were examined. The results showed that ball milling could effectively reduce the particle size of the whole fruit pulp. The average particle diameter decreased from 110.00 to 56.53 μm after ball milling for 180 min, by 49% overall. The whole fruit pulp became more and more delicate and uniform without aggregation with the increase of milling time. The shear strength increased with the increase of shear rate, while the apparent viscosity decreased. Shear thinning occurred in the fruit pulp, which was a typical pseudoplastic fluid with good viscoelasticity. Compared with the unmilled pulp, the whole pulp ball milled for 60 min showed the highest viscosity and the most stable gel-like state and was suitable for the processing of jam products with higher viscosity, whereas the pulp system ball milled for 30 min exhibited the lowest viscosity but the best fluidity and was suitable for the processing of juices with better fluidity. This study provide a rationale for the processing of whole citrus fruit products.

Key words: ball milling, whole pulp of Gannan navel orange, particle size, rheological properties