Blend matters: Impact of blending rice cultivars on milling yield and physicochemical attributes

Background and Objectives

Blending (commingling or mixing) different rice cultivars before milling is a common practice aimed at saving time and effort in managing rough rice. Alternatively, blending is done to achieve the desired quality for the final product. It can lead to processing inefficiencies and inconsistent product functionality, ultimately impacting the economic value of rice. Despite its prevalence in farm or industrial settings, the extent to which this blending practice affects milling yield and the physical and chemical attributes of rice grown in Arkansas remains insufficiently studied. This study aimed to fill this gap by investigating the impact of blending different hybrid long-grain cultivars (RT 7521 FP, RT 7321 FP, XP 753), pureline long-grain cultivars (CLL 16, Ozark), and medium-grain cultivars (Titan, RT 3202) on rice milling yield and physicochemical attributes. Blending before and after postharvest drying was studied. Five types of blends were made among the long-grain cultivars with varying percentages, and one blend was made among medium-grain cultivars. Specifically, the study compared individual cultivars and the length-to-width ratio (L/W), thickness, chalk distribution, milling yield, color, pasting, and cooking properties of the resulting blends.

Findings

The analysis revealed significant effects of rice blending on the L/W and thickness of the composite lot. While some cultivars benefited from blending, others experienced a reduction of values in the composite lot. For example, blending RT 7321 FP with other hybrids decreased the composite lot's overall L/W by 0.13, whereas blending RT 7521 FP increased it. Differences were also observed in chalk percentage, with RT 7521 FP and RT 7321 FP showing the highest percentages. However, blending these cultivars with others reduced the composite lot's overall chalk percentage. Regarding milling yield, pre-drying blending yielded better results compared to post-drying blending. Individual cultivars, such as RT 7321 FP and XP753, exhibited head rice yields of 47.27% and 58.60%, respectively, while blending hybrid cultivars resulted in an overall head rice yield of around 52%. Among the pasting properties, in hybrid cultivars, when blended among themselves and with pureline cultivars, the viscosities decreased significantly when compared to its individual cultivars. Variations were also observed in the cooking duration, with RT 7521 FP having a duration of 26 min. However, when blended with other cultivars, the cooking duration ranged between 21 and 22 min. Significant differences were observed in the textural properties of hardness, gumminess, and resilience. These findings offer valuable insights for rice farmers and processors, guiding optimizing blending practices to enhance the overall milling yield and quality of rice.

Conclusions

It was found that blending can both positively and negatively impact various quality parameters. Cultivars with high L/W ratio and lower chalk % were compromised when mixed with less L/W ratio and higher chalk %. Pureline cultivars, when blended, performed better in terms of head rice yield pasting properties, and mixing hybrid and pureline cultivars reduced the hardness and gumminess among the textural properties.

Significance of Study

The trends observed through this research offer essential information in the decision-making process of when to blend rice, what cultivars to blend, and the expected implications of blending on milling yields and physicochemical attributes.