Production of Novel Rice Flour Fractions

Transcription

1 Production of Novel Rice Flour Fractions A report for the Rural Industries Research and Development Corporation by Michael Southan February 2006 RIRDC Publication No W05/196 RIRDC Project No BRE-3A

2 2006 Rural Industries Research and Development Corporation. All rights reserved. ISBN X ISSN Production of Novel Rice Flour Fractions Publication No. W05/196 Project No. BRE-3A The information contained in this publication is intended for general use to assist public knowledge and discussion and to help improve the development of sustainable industries. The information should not be relied upon for the purpose of a particular matter. Specialist and/or appropriate legal advice should be obtained before any action or decision is taken on the basis of any material in this document. The Commonwealth of Australia, Rural Industries Research and Development Corporation, the authors or contributors do not assume liability of any kind whatsoever resulting from any person's use or reliance upon the content of this document. This publication is copyright. However, RIRDC encourages wide dissemination of its research, providing the Corporation is clearly acknowledged. For any other enquiries concerning reproduction, contact the Publications Manager on phone Researcher Contact Details Michael Southan BRI Australia Ltd. PO Box 7 North Ryde NSW Phone: Fax: [email protected] In submitting this report, the researcher has agreed to RIRDC publishing this material in its edited form. RIRDC Contact Details Rural Industries Research and Development Corporation Level 2, Pharmacy Guild House 15 National Circuit BARTON ACT 2600 PO Box 4776 KINGSTON ACT 2604 Phone: Fax: [email protected]. Website: Published in February 2006 ii

3 Foreword Rice, as either whole grain or broken grain is ground into flour to be used as an ingredient in a wide range of food products. In the past, rice flour milling has been seen as a way to add value to broken grain which is otherwise much less valuable than whole grain. The wheat industry segregates specific varieties to capture the benefits of unique functional properties associated with individual varieties in flour. The rice industry has not investigated whether specific rice varieties also impart different functional properties to rice flour. This publication describes the production and properties of rice flours which are not only unique to individual varieties but also to specific stages of the flour milling process. This project was funded from industry revenue which is matched by funds provided by the Australian Government. This report, an addition to RIRDC s diverse range of over 1500 research publications, forms part of our Rice R&D program, which aims to improve the profitability and sustainability of the Australian rice industry. Most of our publications are available for viewing, downloading or purchasing online through our website: downloads at purchases at Peter O Brien Managing Director Rural Industries Research and Development Corporation iii

4 Acknowledgments Mr. Phil Williams of SunRice assisted with the selection of rice varieties for this project and organised the segregation and delivery of rice samples to BRI Australia, Sydney. SunRice provided oil and moisture analysis of rice flour samples. Dr. Melissa Fitzgerald of NSW Agriculture, Yanco measured starch and cooking properties of flour samples. The assistance of both Phil and Melissa was invaluable and gratefully appreciated. iv

5 Contents Foreword... iii Acknowledgments... iv Executive Summary... vi 1. Introduction Rice Milling Rice Varieties and Characteristics Rice Flour Objectives Methodology Pilot Milling Samples Particle Size Analysis Chemical Analysis Results Flour Milling Performance Particle Size Distribution Starch Damage Protein Content Oil and Moisture Content Flour Paste Viscosity Implications Recommendations v

6 Executive Summary Rice flour is milled from either broken or whole grain and is used in breakfast cereals, rice crackers, extruded snack foods, beverages, confectionery, pet foods, small goods, baby food, as flavour carriers, coatings and batters, noodles, as bulking agents, as gelling or thickening agents and in breads and biscuits. Commercial rice flour produced in Australia is differentiated by range of particle size and physical grain type. However, large variations in flour performance could exist if the variety mix in the long grain and medium grain classes significantly changes. The physico-chemical properties of rice flour produced from individual varieties has not been investigated. Substantial new market opportunities for the rice industry could be exploited by understanding the performance of individual rice varieties in the flour milling process and marketing rice flour more specifically by matching the functional properties of the rice flour to the requirements of existing and new rice food products. The objectives of this project were to: investigate the flour and flour milling properties of individual rice varieties produce new types of fine rice flour, and assess the physical and functional properties of these flours. Amaroo, Doongara, Illabong and Langi were milled on the BRI Australia Pilot Mill to flour with a particle size of less than 100 µm. Doongara produced the greatest amount of flour with an average flour yield of 80.9% compared with Illabong at 55.8%, Amaroo at 53.3% and Langi at 47.1% flour yield. The physical and functional properties of the flour streams were different. 1 st break flour of Doongara was coarser than the flour from Amaroo, Illabong and Langi but for the reduction flours Doongara flour was finer than Amaroo, Illabong and Langi. Amaroo had the highest level of starch damage across most of the flour streams and Illabong the lowest. 1 st break roll flours for all varieties across both seasons had the highest protein contents. Doongara and Amaroo 1 st break roll flours had the highest oil levels. Flour paste viscosities for cooked flours for 1 st break flours from Amaroo and Doongara were lower than for the last reduction roll (F) flours. These differences in viscosity were not due to differences in protein content of the flours. Doongara flours were higher in amylose content than Amaroo flours and the amylose content and cooked flour textures for both varieties increased with increasing number of grinding passages. The break roll flours which are only a small proportion of the total flour produced in the milling process have substantially different functional properties from the reduction flours. All these properties make the break flours very attractive as high value rice flours with potentially improved nutritional and functional properties for specific food applications. These new flour types will potentially increase the value of the rice industry by expanding the rice value adding chain. Currently, rice flour production is approximately 40,000 tonnes per year. If sales or value of rice flour could be doubled, just by supplying new types of flour for new products the added value could be equivalent to $30 million. vi

7 1. Introduction 1.1 Rice Milling The complete rice grain harvested from the field is referred to as paddy rice. The first process in rice milling is to mechanically remove the outer protective shell (or hull) of the paddy to reveal the wholegrain or brown rice grain. Hulls are high in silica and not suitable for human food manufacture but whole are used for animal bedding, stockfeed, fruit juice extraction and as a component in potting mixes. When ground into a finer material, hulls are also used for pet litter and incinerated to make industrial ashes. Wholegrain brown rice is either sold as brown rice or further processed to milled or polished white rice. The polishing process in rice milling removes the outer bran layers of brown rice using an abrasion or polishing process. White and brown rice are cooked and consumed whole or used to manufacture breakfast cereals, creamed desserts, savoury rices and salads. When partially cooked or parboiled, rice is used as an ingredient in dehydrated and canned foods and in convenient frozen/microwavable meals. Rice bran that is stabilised to prevent rancidity is sold either as a granulated, flaked, powdered or shredded food in supermarkets or as an ingredient for food products such as high fibre breads, crispbreads and extruded breakfast cereals or blended with bran form other grains or fruit juices. Rice bran is not only high in fibre but contains protein, vitamins and minerals as well as functional compounds such as γ-oryzanol which has antioxidant and cholesterol lowering activities in humans. In the unprocessed or non-stabilised form, rice bran is used generally in stockfeed. The processing of paddy rice to white rice also results in broken grain from the polishing process. The amount of broken grain depends on several factors such as the set up of the rice polishing machines, the variety of rice and the growing environment. Smaller particle size is more suitable to some food manufacturing processes such as extrusion. The large pieces of broken rice grains are used in the production of breakfast cereals, confectionery (puffed rice) and stockfeed. Small pieces of broken rice are used to extract starch as an ingredient for food manufacture or are used in pet foods and stockfeed. Both whole and broken rice grains are also ground into rice flour. Rice flour is used by people who are coeliacs or have an allergy to wheat or dairy based foods. Fine rice flour is used in the manufacture of baby food, baked products, bulking agents and flavour carriers because of its neutral colour, taste and aroma. Coarse rice flour is used as a cereal binder for small goods because it has a high water holding capacity and to make snack foods. 1.2 Rice Varieties and Characteristics Japonica rice which is better adapted to temperate climates is the main rice type grown in Australia. The varieties, their description and class are shown in Table 1. 1

8 Table 1. Varieties of rice grown in Australia Variety Class Description Koshihikari Millin Opus Amaroo Jarrah Paragon Langi Short Grain Japanese Style Medium Grain Long Grain Australian Style Soft short grain rice for Japanese cuisine Soft cooking rice Adaptable Long grain rice suited to savoury cuisine Doongara Illabong Long Grain Firmer Cooking Medium Grain Arborio Long grain which is not sticky after cooking; suited to savoury foods Soft cooking chalky rice used for risotto and paella; the rice absorbs the flavour of the dish Kyeema Long Grain Fragrant Jasmine Style Long fragrant grain suited to Thai style cuisine Adapted from SunRice Types of Rice. Varieties in bold were used in this project. The short grain varieties, Koshihikari, Opus and Millin have a soft, sticky texture and glossy appearance when cooked. Medium grain varieties such as Amaroo, Jarrah and Paragon are used for breakfast cereals and desserts; they are moister and stick together more after cooking than the long grain varieties. Brown rice is available from medium grain paddy rice. The long grain varieties (Langi and Doongara) are more firm and free flowing than the short and medium grain varieties when cooked, particularly the variety Doongara which is a higher amylose rice. Long grain rice is used in frozen meals and convenient prepared home meal products. Brown, organic white and organic brown and parboiled rice are available from long grain varieties. Parboiled rice is soaked, cooked by steaming and dried before being milled. The resulting product has a golden colour resulting from nutrients in the bran leaching into the grain during steaming. 1.3 Rice Flour Rice flours are produced across a broad range of particle size specifications and are classed as grits, coarse medium grain flour, coarse long grain flour, medium flour and fine flour. All these flours can be used in breakfast cereals, rice crackers, extruded snack foods, beverages, confectionery, pet foods, small goods, baby food, as flavour carriers, coatings and batters, noodles, as bulking agents, as gelling or thickening agents and in breads and biscuits. Commercial rice flour produced in Australia is differentiated by particle size distribution specification and medium grain or long grain. However, large variations in flour performance might exist if the variety mix in the long grain and medium grain classes significantly changes. The physico-chemical properties of rice flour produced from individual varieties has not been investigated. There may be substantial new market opportunities for the rice industry by understanding the performance of individual rice variety flours and marketing rice flour more specifically for existing and new food products. 2

9 2. Objectives The objectives of this project were to: investigate the flour and flour milling properties of individual rice varieties produce a novel fine flour by dry milling rather than wet milling, and add value to the rice industry through the production of new types of rice flour for trialling in current rice flour food products and the development of new rice flour based products. 3. Methodology 3.1 Pilot Milling The BRI Australia Pilot Mill was configured to mill rice broken and whole grains using 3 break rolls (1 st bk, 2 nd bk and 3 rd bk), 1 sizings roll (SZ) and 7 reduction rolls (A, B, C, D, E, F and B2). The 3 break rolls replicated the SunRice long grain flour mill which also has 3 break rolls but the reduction system of the BRI Australia Pilot Mill was significantly longer than the SunRice flour mill which has only 2 reduction rolls. The use of extra reduction rolls for further grinding in the Pilot Mill enabled a finer flour to be produced (less than 100 µm) than the finest commercial flour. Pin mills were used before Break Middlings (BM) plan sifter section and after A, B, C and D reduction rolls while drum detachers were used after B2, E and F reduction rolls. The rate of rice broken grain or whole grain feeding to 1 st break roll was between 370 and 500 kg/hr depending on the variety and its resistance to grinding. The plan sifter was configured to sieve out flour that was less than 100 µm. Unground sample that over-tailed the sifter section of the last reduction roll (F) was collected. Stock samples were collected under the plan sifter during the milling of each variety, weighed and assessed for particle size distribution and chemical properties. Ringing (caking of flour on the roll) was observed on the reduction rolls set to apply high grinding pressures. 3.2 Samples Three tonnes of the following rice varieties from the 2001 harvest were milled to flour: Amaroo Doongara Illabong Three tonnes of the following rice varieties from the 2002 harvest were milled to flour: Amaroo Doongara Illabong Langi 3

10 Amaroo was chosen as the variety representative of medium grain rice. Doongara was chosen to represent a high amylose rice. Illabong was selected for the arborio style while Langi was selected as a long grain rice. 3.3 Particle Size Analysis Flour stocks sampled under the plan sifter, under the break and reduction rolls and under the cyclones were analysed for particle size distribution using a Fritsch analysette 3PRO vibratory sieve shaker. Sample (50 grams) was placed in the top (greatest aperture) Endecott sieve of the stack. A sieving aid ball was added to each sieve and the sieve stack shaken for 2 minutes with 2 mm amplitude. The sieves used in each stack to measure the particle size distribution for stocks samples from the plan sifter, the break and reduction rolls and under the cyclones are summarised in Table 2. Table 2. Endecott sieve sizes used to measure particle size distribution of stock samples. Sieve Size (µm) Sample source Plan Sifter Under Cyclones Under Rolls Chemical Analysis Starch damage, protein content and flour colour were measured at BRI Australia using in-house NATA accredited methods BRI S7 (AACC starch damage method), BRI P7 (Kjeldahl protein, N x 5.95) and BRI C4, respectively. Oil and moisture content was measured by SunRice according to their in-house method and Rapid Visco Analysis and starch characterisation of samples was carried out by NSW Agriculture, Yanco according to their in-house methods. 4

11 4. Results 4.1 Flour Milling Performance The stock quantity analyses and flour yields are summarised in the following tables and graphs. Table 3. Flour Stream Analysis for AMAROO 2001 Harvest Rate of Rice Feed to 1 st Break Roll = 475 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D E F SZ TOTAL FLOUR YIELD Table 4. Flour Stream Analysis for DOONGARA 2001 Harvest Rate of Rice Feed to 1 st Break Roll = 455 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D F SZ TOTAL FLOUR YIELD

12 Table 5. Flour Stream Analysis for ILLABONG 2001 Harvest Rate of Rice Feed to 1 st Break Roll = 486 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D E F SZ TOTAL FLOUR YIELD Table 6. Flour Stream Analysis for AMAROO 2002 Harvest Rate of Rice Feed to 1 st Break Roll = 380 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D E F SZ TOTAL FLOUR YIELD

13 Table 7. Flour Stream Analysis for DOONGARA 2002 Harvest Rate of Rice Feed to 1 st Break Roll = 386 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D F SZ TOTAL FLOUR YIELD Table 8. Flour Stream Analysis for ILLABONG 2002 Harvest Rate of Rice Feed to 1 st Break Roll = 375 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D F SZ TOTAL FLOUR YIELD

14 Table 9. Flour Stream Analysis for LANGI 2002 Harvest Rate of Rice Feed to 1 st Break Roll = 375 kg/h Flour < 100 µm Flour Weight Time Rate Flour Yield Stream kg min kg/h % 1st bk nd bk rd bk A B B BM C D F SZ TOTAL FLOUR YIELD Figure 1. Flour Yield for Amaroo, Doongara, Illabong and Langi Rice Varieties from the 2001 and 2002 Harvests Yield of Flour (<100 um) for Amaroo, Doongara, Illabong and Langi Rice Varieties Flour Extraction (%) Amaroo Doongara Illabong Langi 8

15 Tables 3, 4 and 5 summarise the flour stock quantities collected from the milling of Amaroo, Doongara and Illabong varieties from the 2001 harvest. Tables 6, 7, 8 and 9 contain the milling data from Amaroo, Doongara, Illabong and Langi varieties from the 2002 harvest. Mill set up and samples collected were slightly different for some varieties. Doongara from both 2001 and 2002 harvests was not milled with E reduction roll in the system because E roll had a very low rate of feed from B2 and D reduction rolls and Doongara produced a high yield of fine flour. This flow was also used for Illabong and Langi from the 2002 harvest. Alternatively, the milling flow for Amaroo from both the 2001 and 2002 harvests included E reduction roll because Amaroo resisted grinding to a flour particle size less than 100 µm. Illabong was milled with E reduction roll in the flow for the 2001 harvest sample and without for the 2002 harvest sample. There was very little difference in flour yield between the two systems indicating that the variety of rice had a greater effect on flour yield than the length of the milling system. A build up of stock on the reduction rolls was noticed when using high grinding pressures. Doongara produced the greatest amount of flour for both harvest samples with an average flour yield of 80.9%. Illabong was second producing an average of 55.8% and Amaroo produced an average of 53.3% flour. Only 1 sample of Langi was milled which yielded 47.1% flour. Figure 2. Flour Yields from Break and Reduction Rolls for 2001 Harvest Samples Stock Quantities for 2001 Amaroo, Doongara and Illabong Varieties Flour Yield (%) Doongarra 2001 Illabong 2001 Amaroo st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Flour Stream Figure 2 shows that Doongara produced significantly more flour on the reduction rolls A, B, C and especially D compared with Illabong and Amaroo from the 2001 harvest samples. This mirrored the 9

16 low proportion of flour produced by 1 st break, 2 nd break and 3 rd break rolls and break middlings. Amaroo was the most resistant to grinding especially on A reduction roll. Figure 3. Flour Yields from Break and Reduction Rolls for 2002 Harvest Samples Stock Quantities for 2002 Amaroo, Doongara, Illabong and Langi Varieties Flour Yield (%) Doongarra 2002 Illabong 2002 Amaroo 2002 Langi st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Flour Stream Figure 3 shows that the 2002 harvest samples had similar flour yields for most of the streams except A, C and D reduction rolls where Doongara yielded significantly more flour than the other varieties. For both 2001 and 2002 harvests Doongara had at least double the flour yield produced on D reduction roll compared with the other varieties. Illabong produced the most break roll (1 st break, 2 nd break and 3 rd break rolls combined) flour over both harvests compared with the other varieties. This is likely to be a result of Illabong having a chalky centre which would disrupt early in the milling process to produce flour. 4.2 Particle Size Distribution All the flour streams collected from the quantity analysis were sieved to determine the size distribution within the flours from each roll. The following tables summarise the size distribution within each flour stream for each milling trial. Stock samples were also taken from under the rolls before sieving and for Doongara from the 2001 harvest samples were taken from under the cyclones i.e. after the rolls but before the plan sifter. 10

17 Table 10. Sieve Analysis of 2001 DOONGARA Stocks Sampled from Under the Rolls Sieve Size (µm) Stock >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B B C D F Table 11. Sieve Analysis of 2001 ILLABONG Stocks Sampled from Under the Rolls Sieve Size (µm) Stock >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B B C D E F Table 12. Sieve Analysis of 2001 AMAROO Stocks Sampled from Under the Rolls Sieve Size (µm) Stock >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B B C D E F

18 Tables 10, 11 and 12 are the particle size distributions for 2001 harvest Doongara, Illabong and Amaroo stocks collected under the rolls, respectively. The particle size distribution for stocks taken under 1 st break and D reduction rolls are shown in Figure 4 as Doongara produced similar flour yields to Illabong and Amaroo on 1 st break roll and produced much more flour on D reduction roll. Figure 4 shows that Illabong and Amaroo had a similar particle size distribution for 1 st break and D reduction roll stocks whereas Doongara had coarser particles in the 1 st break roll stock and finer material in the D reduction roll stock. Doongara appears to initially fracture into large pieces on 1 st break roll but then break down into finer particles after grinding on the reduction rolls. Figure 4. Particle Size Distribution from 1 st Break and D Reduction Roll Stocks for 2001 Harvest Samples Particle Size Distribution for 1st Break and D Roll Stocks Doongara 1st Illabong 1st Amaroo 1st Doongara D Illabong D Amaroo D % by Weight >1400 >1000 >710 >500 >106 <106 Particle Size (um) As Doongara fractured differently from Illabong and Amaroo and produced much more flour on the head reduction rolls, stocks of Doongara were collected under the cyclones after passing through the pin mills. Table 13 contains the particle size distribution for the stocks collected under the A, B, B2, C, D, BM and F cyclones. The data summarised in Figure 5 shows that the size distribution of the samples collected from under the cyclones becomes narrower and more concentrated around 100 µm from A stock through to F stock. Consecutive grinding on the reduction rolls reduces the proportion of coarse material and the proportion of fine flour is also reduced because it is sieved out of the milling system. 12

19 Table 13. Sieve Analysis of 2001 DOONGARA Stocks Sampled from Under the Cyclones Flour Sieve Size (µm) Stream >300 >212 >150 >106 >90 <90 (%) A B B C D BM F Figure 5. Particle Size Distribution from Samples Collected Under the Cyclones for 2001 Harvest Doongara Particle Size Distribution for Doongara Cyclone Stocks A B B2 C D BM F % by Weight >300 >212 >150 >106 >90 <90 Particle Size (um) 13

20 Table 14. Sieve Analysis of 2001 DOONGARA Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B B C D F Table 15. Sieve Analysis of 2001 ILLABONG Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B B C D E F Table 16. Sieve Analysis of 2001 AMAROO Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B B C D E F

21 Tables 14, 15 and 16 show the particle size distribution of the flours collected from each flour stream for under the plan sifter for 2001 harvest Doongara, Illabong and Amaroo, respectively. Figure 6 shows the particle size distribution for the 1 st break and D reduction flours for the three varieties. A similar trend was observed for the particle size distribution of the flours as for roll stocks of 1 st break and D reduction rolls. Doongara had coarser flour than Illabong and Amaroo for 1 st break flour and more fine flour than Illabong and Amaroo for D reduction roll. Figure 6. Particle Size Distribution from 1 st Break and D Reduction Roll Flours for 2001 Harvest Samples Particle Size Distribution for 1st Break and D Roll Flours Doongara 1st Illabong 1st Amaroo 1st Doongara D Illabong D Amaroo D % by Weight >106 >90 >63 >53 <53 Particle Size (um) Table 17. Sieve Analysis of 2002 ILLABONG Stocks Sampled from Under the Rolls Sieve Size (µm) Stocks >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B C D F

22 Table 18. Sieve Analysis of 2002 AMAROO Stocks Sampled from Under the Rolls Sieve Size (µm) Stocks >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B B C D E F Table 19. Sieve Analysis of 2002 LANGI Stocks Sampled from Under the Rolls Sieve Size (µm) Stocks >1400 >1000 >710 >500 >106 <106 (%) 1st bk nd bk rd bk SZ A B B C D F Particle size distribution for Illabong, Amaroo and Langi stocks under the rolls from the 2002 harvest (Tables 17, 18 and 19) showed similar trends to the 2001 samples. Langi 1 st break stock was coarser than Illabong and Amaroo. However, Amaroo stock from under D reduction roll was finer than Illabong and Amaroo (Figure 7). Likewise, the particle size distribution for the flour streams collected from under the sifter showed similar trends for Amaroo, Illabong and Langi from the 2002 harvest as Doongara, Illabong and Amaroo from the 2001 harvest (Tables 20, 21 and 22). For the 2002 samples Amaroo had the coarsest 1 st break roll stocks (Figure 8) and was second coarsest after Doongara for the 2001 samples. For the 2002 samples Langi s D roll stock was slightly finer than Illabong which was second finest after Doongara from the 2001 harvest. These data indicate that Doongara produced the widest particle size range of the four varieties milled to flour. 16

23 Figure 7. Particle Size Distribution from 1 st Break and D Reduction Roll Stocks for 2002 Harvest Samples Particle Size Distribution for 1st Break and D Roll Stocks Illabong 1st Amaroo 1st Illabong D Amaroo D Langi 1st Langi D % by Weight >1400 >1000 >710 >500 >106 <106 Particle Size (um) Table 20. Sieve Analysis of 2002 Illabong Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B C D F All

24 Table 21. Sieve Analysis of 2002 Amaroo Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B B C D E F All Table 22. Sieve Analysis of 2002 Langi Flour Sampled from Under the Sifter Flour Sieve Size (µm) Stream >106 >90 >63 >53 <53 (%) 1st bk nd bk rd bk BM SZ A B B C D F All

25 Figure 8. Particle Size Distribution from 1 st Break and D Reduction Roll Flours for 2002 Harvest Samples Particle Size Distribution for 1st Break and D Roll Flours Illabong 1st Amaroo 1st Illabong D Amaroo D Langi 1st Langi D % by Weight >106 >90 >63 >53 <53 Particle Size (um) 4.3 Starch Damage Rice contains starch granules which can be cracked or broken during the flour milling process. In wheat flour starch damage is important for increasing the amount of water that flour can absorb before becoming too sticky to handle. This may also be important for some rice food products which may produce higher yields with higher levels of starch damage and therefore higher levels of water absorption e.g. Rice noodles and rice breads whereas rice crackers which are a dry product would require low water absorption. Figures 9 and 10 show the levels of starch damage for the flour streams from Doongara, Illabong and Amaroo from the 2001 harvest and Doongara, Illabong, Amaroo and Langi for the 2002 harvest. Generally, Amaroo produced the highest level of starch damage across most of the flour streams (Figures 9 and 10). The 1 st break and Break Middlings flours had the lowest levels of starch damage. This would be expected because these flours have had the least amount of grinding. The B2 flours were generally the highest in starch damage and interestingly, the F reduction roll flours which had been exposed to the most grinding had low levels of starch damage. This may be because most of the flour that would be extracted in the mill had already been removed and the remaining material was very resistant to grinding. Illabong appeared to have the least amount of starch damage which is most likely because Illabong is an Arborio type which has a soft chalky centre. 19

26 Figure 9. Starch Damage for Flour Streams from 2001 Harvest Samples Starch Damage for 2001 Amaroo, Doongara and Illabong Varieties Starch Damage (%) Doongarra 2001 Illabong 2001 Amaroo st bk 2nd bk 3rd bk BM SZ A B C D B2 E F F o'tails Flour Stream Figure 10. Starch Damage for Flour Streams from 2002 Harvest Samples Starch Damage for 2002 Amaroo, Doongara, Illabong and Langi Varieties Starch Damage (%) Doongara 2002 Amaroo 2002 Illabong 2002 Langi st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Str. Run Flour Stream 20

27 4.4 Protein Content The protein content of the flour streams was measured for all millings (Figures 11 and 12). Doongara, Amaroo and Langi for both seasons showed higher protein levels for 1 st break roll flours and lower protein contents for 3 rd break flours. The reduction flours gradually increased in protein content with further consecutive grindings. The high protein levels of the 1 st break flours may be from residual protein from the aleurone layer still adhering to the outside of the grain after polishing. The gradual increase in protein content of the reduction roll flours might reflect that the harder material which required more grinding to be released as flour is held together by protein which bonds the material making it harder. Figure 11. Protein Content for Flour Streams from 2001 Harvest Samples Protein Content for 2001 Amaroo, Doongara and Illabong Varieties Protein Content (%) Doongarra 2001 Illabong 2001 Amaroo st bk 2nd bk 3rd bk BM SZ A B C D B2 E F F o'tails Flour Stream 21

28 Figure 12. Protein Content for Flour Streams from 2002 Harvest Samples Protein Content for 2002 Amaroo, Doongara, Illabong and Langi Varieties Protein Content (%) Doongara 2002 Illabong 2002 Amaroo 2002 Langi st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Str. Run Flour Stream 4.5 Oil and Moisture Content The flour streams from the 2002 Amaroo, Doongara, Illabong and Langi samples were analysed for oil content (Figure 13). The oil measured is residual from the bran which was removed during the polishing process. Doongara and Amaroo had the highest oil levels in the 1 st and 2 nd break roll flours. Illabong showed the least variation in flour oil content. It is not clear why Doongara and Amaroo had the highest levels of oil in the break flours because the polishing appeared to be efficient for all samples with no obvious brown rice in the samples. The difference in oil content between the varieties may simply result from a dilution effect because Doongara and Amaroo produced the least amount of flour on 1 st and 2 nd break rolls and therefore the relative amount of oil in these flours would be higher. There were no obvious trends for roll stocks (Figure 14). Moisture contents for all flour streams were very similar ranging between 10.9 and 11.7% (Figure 15). Generally, the moisture content rose from 1 st break to 3 rd break flours and slowly decreased with consecutive reduction roll flour streams i.e. A to F flours. However all these differences were minor. However, the moisture content for the roll stocks (Figure 16) increased from 1 st break roll to 3 rd break roll for all varieties suggesting that the drying times for the larger particle size stocks was not sufficient for all moisture to be removed. 22

29 Figure 13. Oil Content for Flour Streams from 2002 Harvest Samples Oil Content for 2002 Amaroo, Doongara, Illabong and Langi Flours 3.5 Oil Content (%) Doongara 2002 Amaroo 2002 Illabong 2002 Langi st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Str. Run Flour Stream Figure 14. Oil Content for Roll Stocks from 2002 Harvest Samples Oil Content for 2002 Amaroo, Doongara, Illabong and Langi Roll Stocks Oil Content (%) Doongara 2002 Amaroo 2002 Illabong 2002 Langi st bk 2nd bk 3rd bk SZ A B C D B2 E F Roll Stock 23

30 Figure 15. Moisture Content for Flour Streams from 2002 Harvest Samples Moisture Content for 2002 Amaroo, Doongara, Illabong and Langi Flours 12.0 Moisture Content (%) Doongara 2002 Amaroo 2002 Illabong 2002 Langi st bk 2nd bk 3rd bk BM SZ A B C D B2 E F Str. Run Flour Stream Figure 16. Moisture Content for Roll Stocks from 2002 Harvest Samples Moisture Content for 2002 Amaroo, Doongara, Illabong and Langi Roll Stocks 12.0 Moisture Content (%) Doongara 2002 Amaroo 2002 Illabong 2002 Langi st bk 2nd bk 3rd bk SZ A B C D B2 E F Roll Stock 24

31 4.6 Flour Paste Viscosity Rapid Visco Analysis of 1 st break, 2 nd break, 3 rd break, B and F flours for Doongara and Amylose were carried out to determine if the functional properties of the flours were different. Figure 17 shows that the peak and final viscosities for 1 st break flour was lower than for F roll flour and that the viscosity increased with the amount of grinding required to release flour for Amaroo. A similar trend was observed for Doongara (Figure 18). The starch functionality was reassessed after removal of proteins from the flours to determine if the differences in viscosity were due to protein which was higher in the break roll flours. However the same trends were observed after protein removal (Data not shown). The flour streams produced by the break rolls were relatively high in oil content and further work is required to determine if the same trends for viscosity are seen after defatting the flour samples. Amylose content for the same flour samples and the cooked rice flour texture is shown in Table 23. As expected, the Doongara flours were higher in amylose content than the Amaroo flours. For both Amaroo and Doongara the amylose content of the flour streams increased with increased grinding i.e. 1 st break roll was lowest and F reduction roll was highest. The texture of the cooked flours followed a similar pattern. Figure 17. Starch Paste Viscosity Curves for Amaroo Flours from the 2002 Harvest Amaroo Viscosity (cp) BK 2BK 3BK B F Time (min) 25

32 Figure 18. Starch Paste Viscosity Curves for Doongara Flours from the 2002 Harvest Viscosity (cp) BK 2BK 3BK B F Doongara Time (min) Table 23. Amylose Content and Cooked Rice Flour Texture for Amaroo and Doongara Flours from the 2002 Harvest Amylose (%) Texture (N) Flour Streams Doongara Amylose Doongara Amylose 1 st Break nd break rd break B F

33 5. Implications Clear functional differences and processing properties have been identified for individual rice varieties and flour streams. Doongara produced the greatest yield of fine rice flour using dry flour milling and a minimum of grinding roll passages. SunRice have recently commissioned two new flour mills. The long grain mill is set up with 3 break rolls and 2 reduction rolls while the medium grain mill has 2 break rolls and 2 reduction rolls. The finest flour currently produced by these mills is on the medium grain mill which produces a flour with 5% by weight retained on a 212 µm sieve, 35-55% retained on a 150 µm sieve and 40-60% passing through a 150 µm sieve. The 2 mills could be configured to have 3 break rolls, 1 sizings roll and 4 reduction rolls. With this configuration and from the work presented in this project the SunRice mill should be able to achieve yields of around 75-80% for flour less than 100 µm in size. Work with SunRice has highlighted that there have been difficulties in producing even the finest flour on their product list. The reasons for this were related to efficiencies in sieve cleaning which was improved with minor modifications to the sieve cleaning aids which were designed to handle wheat flour but not rice flour. We would be confident that with the improvements in place SunRice can produce flour less than 100 µm with minimum modifications. Doongara appears to be the most appropriate variety to mill to fine flour not only because it produces high yields but because it has a lower glycaemic index than other varieties, has a higher amylose content which confers greater firmness for cooked rice products and would best suit the milling systems in place at SunRice. The product range of rice flours can be extended by producing rice flours with specific functional properties by collecting individual flour streams. This is demonstrated by the break flours for Doongara and Amaroo having about 5% less amylose and therefore softer cooked textures. Break flours for Doongara and Amaroo were also higher in oil and protein content and the particle size distribution was coarser than the reduction flours which may reduce the glycaemic index for these flours. All these properties make the break flours very attractive as high value rice flours with potentially improved nutritional and functional properties for specific food applications. The benefit of this work would be increased sales of rice and rice flour through the availability and use of a wider range of specific flour types. These new flour types will potentially increase the value of the rice industry by expanding the rice value adding chain. Currently, rice flour production is approximately 40,000 tonnes per year. If sales of rice flour could be doubled, just by supplying new types of flour for new products the added value could be equivalent to $30 million. 27

34 6. Recommendations The following recommendations resulting from the outcomes of this project are as follows: 1. Doongara or another high amylose variety be segregated at harvest for rice flour production 2. SunRice trial the production of fine rice flour utilising the type of mill flow used in this project 3. Specific functional flours be produced by collecting break flours separately 4. Break flours are tested for suitability over a range of end products both by SunRice and by other users of rice flour 5. Other varieties are tested for their flour milling performance and potential for high value, functionality specific properties such as waxy and par boiled rice. 28