Efficient Husking of cereals to improve Bran Purity, value and utilisation

Lead Participant: Koolmill Systems Limited

Abstract

Koolmill and the National Centre of Excellence for Food Engineering (NCEFE) collaborated to develop an improved rice milling system and valorise the by-products of rice milling (102755/105862). Specifically, these projects target SME millers in Rural communities: the objective is to create and retain added value in rural communities transforming smallholder growers/SME Millers, from low value commodity producers, to market leading added value food processors.

Traditional rice milling comprises two processes: husking and bran removal. Husking is achieved by passing the paddy (raw rice) between two rotating rubber rolls being pushed together under pressure. Think old-style mangle for squeezing water from washing: that's a 'modern' husker. Bran is 'milled' from the brown rice in multiple processes (typically up to 5) producing finished white rice.

The two processes are fundamentally different. Husking is a 'one-shot' operation to remove the fibrous husk and bran removal is a gradual process through multiple contacts within the milling chambers of abrasive or frictional machines.

Traditional huskers are a pain for millers, requiring regular maintenance and repair. Husking rolls have a relatively short life at around 24 hours. Setting huskers is a compromise between husking efficiency and broken brown rice. Higher closing pressures increase the husking efficiency but result in higher levels of broken rice. Reducing closing pressures reduces broken rice but with poor husking efficiency.

102755/105862 improved bran milling performance, increasing the power saving from 80% to over 90% and milling chamber capacity from 60 to 150kg/hr/chamber. Milling from brown to white, the bran removed is pure, very fine and will generate significant new revenue streams for rice millers. This value is dependent on the purity of the bran.

Koolmill has previously demonstrated the capability of coated abrasives to be an effective husking medium. The loss in capacity from paddy to white compared to brown to white milling was only 4%, with a relatively high husking efficiency, over 80% power savings and reducing white broken rice from 30% to less than 5%.

The downside of this increased bran milling performance is a reduction in husking efficiency, and the combination of husk and bran discharged together reducing the purity and potential value of the bran. With over 75 million tonnes of rice bran produced the opportunity is to take bran from a low-value waste, used for oil extraction and animal feed, to a valuable and nutritional beneficial human food ingredient.

There are many nutrition bioactives stored naturally within cereal brans including a range of biotechnology approaches for improving fibre, phytosterols, polyphenols, phenolic acids, antioxidants. These can be enhanced or made more bio-available through secondary processing.

Realising that value is dependent on fine clean bran driving the need for a separate husker. The industry is ready for new more efficient husking option and this would confirm Koolmill and NCEFE as global thought leaders in cereal milling, offering a unique ultra-low power paddy to white milling solution set to transform a global market projected to purchase $4 billion of rice milling equipment over the next 5-years.

Lead Participant

Project Cost

Grant Offer

Koolmill Systems Limited, Birmingham £94,348 £ 94,348

Publications

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