[[en/index|English]] · [[zh/index|中文]] · [[en/phytolith_植硅体/rice-husk-phytolith|EN]] · [[zh/phytolith_植硅体/rice-husk-phytolith|中文]] # Rice husk phytolith http://archaeobotanist.blogspot.com/2018/01/rice-husk-phytoliths-and-morphological.html > The husks of rice are full of silica and often all the cells of silicified. The rows of cells on the rice husk include trapezoidal 梯形 phytoliths the upper corners of which often form into peaks, as in the image below. These are diagnostic of the genus Oryza 稻米, although a few similar forms may occur more rarely in other grasses. These are often the most frequent form of rice phytolith. Because these derive from husk, disposed of after dehusking, they are an indicator of dehusking waste and useful in crop-processing studies. ![[rice_phytolith_double_peak.jpg]] > Variation in husk phytoliths exists but its significance in terms of domestication, varietal changes, cultivation ecology remains unclear and deserved further study. ![[double_peak_measurements.png]] Dr. Martin Hodson (expert on wheat phytoliths) had a complaint: > "I know this will sound dim, but what exactly is a `double-peaked phytolith`? It looks like it might be a cell wall type analogous to the `papillae` that we find in the husks of wheat. In other words, what is the anatomical origin of these phytoliths? I have been wandering around the literature for ages an nobody seems to say!" ## Rice plants also have aridity issue? Tian: Rice is grown in paddy field 水田。 Why does it need a lot of phytoliths to fight aridity? GU Yansheng: Rice is only intermittently irrigated. There have to to periods of 'no water at all' --- for the rice plant to 'breathe'. So for periods, the soil is dry and the rice plant needs a way to hold water. ## Why isn't rice consumption linked to esophageal cancer? Tian: It could be: - the morphology of the rice husk phytolith --- which does not have a `peeling` effect on the epithelium - the process of the rice harvesting and dehulling --- which does not allow phytolith to contaminate 'white rice' grains ************** ## From paddy rice to brown rice to white rice (稻谷-糙米-大米) http://nyj.jingzhou.gov.cn/ywbk/kjfw/202112/t20211221_671312.shtml > After dehusking, paddy rice becomes brown rice; only after the seed coat of the brown rice is milled off do we get the white rice we eat daily. If white rice is compared to a boiled egg, the seed coat is the eggshell, and processing is like peeling the shell — the cleaner the shell is removed, the higher the milling precision; the more shell residue remains, the lower the precision. http://www.jxxf.gov.cn/xfxxxgk/c100927/202108/1953125d29404777857e6bbcea5102d8.shtml > In rice processing, the process of removing the husk from paddy rice is called "dehusking" (砻谷, lóng gǔ); the process of removing the bran layers from brown rice is called "milling" (碾米, niǎn mǐ). https://zh.wikipedia.org/zh-hans/%E7%B1%B3%E7%B3%A0 > After threshing and dehusking, paddy rice yields brown rice, which is the complete rice fruit. The rice we usually eat refers to processed polished rice, which is the endosperm portion of the rice seed. The part discarded in the transition from brown rice to polished rice is rice bran (米糠). https://patents.google.com/patent/CN202569822U/zh > Dehusking and milling are two important basic processes in rice processing. Dehusking generally removes the husk from paddy rice by mechanical extrusion and rubbing, yielding brown rice and rice husks; the husks are generally separated from the brown rice by winnowing, with light materials such as husks discharged with the air (husk removal), leaving brown rice. > Milling generally removes the outer skin of brown rice by grinding or extrusion and abrasion, yielding white rice and bran (bran powder); the bran can be separated from the white rice by winnowing, with the bran discharged with the airflow (bran removal), leaving white rice. https://zhuanlan.zhihu.com/p/86633040 > When processing rice with modern equipment, the paddy rice is first dried to remove moisture and screened to remove impurities. The paddy rice then enters the rice huller; this step mainly removes the husk. The paddy rice passes between two rubber rollers rotating in opposite directions, and the husk is crushed and detached under the pressure of the rollers. > The rice separated from the husk at this point is still brown rice. It then enters the polisher, where the brown rice is rolled and polished on large grinding wheels to remove the yellowish bran layer on the surface, becoming shiny white rice. After screening to remove broken rice, the uniform, qualified rice can be packaged and sold. https://japan-agritrading.com/zh/blogs/japan-agri-trading-blog/rice-milling-machine-and-rice-huller ![[unhulledRice_BrownRice_WhiteRice.jpg]] ## Basic knowledge of rice (稻米基本知识) http://www.pjrice.com/index.php?ac=article&at=list&tid=123 ``` Rice belongs to the family Poaceae (Gramineae), subfamily Oryzoideae, genus Oryza Linnaeus; it is an annual herb widely distributed in tropical and subtropical regions. Two botanical species of rice are important cereal crops for human nutrition: one is Asian cultivated rice (Oryza sativa), widely grown around the world, and the other is African rice (Oryza glaberrima), grown in West Africa. These are the only two cultivated rice species in the genus Oryza; in addition, there are more than 20 wild rice species. Asian cultivated rice (also called common cultivated rice) originated from common wild rice (Oryza rufipogon). Rice is characterized by wide adaptability, high yield per unit area, good nutrition, and multiple uses, and is distributed throughout the world's rice-growing regions. African cultivated rice (also called glaberrima rice) originated from long-stamen wild rice (Oryza longistaminata) and is now cultivated only to a small extent in West Africa. Although rice originated in hot, humid tropical regions, through long-term evolution and differentiation, cold-tolerant, early-maturing varieties can now be grown in cold areas such as Mohe County, Heilongjiang Province, China, at latitude 53°29′N, and on plateaus at 3000 m elevation in Nepal and Bhutan; rice's adaptability is unmatched by other crops. According to water supply conditions, rice is divided into: deepwater rice (grown in deep water), irrigated rice (dependent on irrigation), and upland rice (dryland rice). According to ecogeographic differentiation, it is divided into indica (籼稻) and japonica (粳稻); according to temperature and photoperiod response, into early, late, and mid-season rice; according to grain starch properties, into non-waxy (glutinous) and waxy rice. Globally, irrigated rice dominates: irrigated rice accounts for about 1/2 of the total harvested area of world rice and 3/4 of total production, mostly distributed in humid, subhumid, and humid tropical ecological zones of the subtropics and tropics. Upland rice accounts for 13% of the world's rice area but only 4% of total production. Rainfed rice (completely dependent on rainfall) accounts for about 34% of the world's rice area. Deepwater rice covers about 11 million hectares, with very low yields, averaging only 1.5 tons per hectare. Grain structure of paddy rice The external structure of the paddy grain consists mainly of two parts: the husk (颖, glume) and the caryopsis (brown rice). From outside to inside, the grain has the husk (glume), the bran layer (the general term for pericarp, seed coat, and aleurone layer), the embryo, and the endosperm. After the husk is removed by the huller, brown rice is obtained. Brown rice is a caryopsis; after further milling to remove the outer skin layer, the bran (including pericarp, seed coat, germ, aleurone layer, and a small part of endosperm) is removed, and the remaining endosperm is the edible rice. 1. The husk (颖) The husk includes four parts: the inner glume, outer glume, sterile glumes, and the husk tip (which may extend into an awn). The two margins of the inner and outer glumes hook together to wrap the brown rice, forming a completely sealed husk. For japonica rice, the husk accounts for about 18% of grain weight; for indica rice, about 20%. At the base of the outer side of the inner and outer glumes there is one sterile glume each, which supports the grain and protects the inner and outer glumes. Both inner and outer glumes have longitudinal veins: the outer glume has five, the inner glume three. The tip of the outer glume bears an awn; the inner glume generally has no awn. Generally, most japonica rice has awns, while most indica rice is awnless; even when awns exist, they are mostly short. Awned paddy has a lower bulk density, poorer flowability, and the cooked rice has less expansion but greater stickiness. 2. The caryopsis (brown rice) Brown rice is called the caryopsis. It consists of the pericarp, seed coat, embryo, and endosperm. The pericarp and seed coat are the outermost layers of the caryopsis; some brown rice seed coats contain pigments and thus show colors such as yellow, purple, and black. The embryo is located on the ventral side of the brown rice, comprising four parts: plumule, radicle, mesocotyl (embryo axis), and scutellum. The endosperm, inside the seed coat, is the largest part of the grain, including the aleurone layer and starchy cells. In brown rice, the pericarp and seed coat account for about 2%, the aleurone layer 5%–6%, the embryo 2.5%–3.5%, and the endosperm 88%–93%. ``` ************** ## Rice and millet processing - Harvey, E. L., & Fuller, D. Q. (2005). Investigating crop processing using phytolith analysis: the example of rice and millets. Journal of Archaeological Science, 32(5), 739–752. ![[rice_processing.jpg]] Caption: Fig. 3. Schematic representation of the major processing stages for rice showing the products and waste produced by each process. Phytoliths are in white and macro-remains in black. For example, first winnowing produces grains with spikelets and therefore husk phytoliths, and the waste contains rice leaves and stem (fan-shaped bulliforms and scooped rice bilobes) and various weeds associated with rice cultivation such as grasses (bilobes shown, also saddles, long cells), sedges, and phragmites (keystone bulliform). After dehusking the waste of winnowing includes husks as well as large weeds, which also may be removed by hand picking. ![[millet_processing.jpg]] Caption: Fig. 5. Schematic representation of the major processing stages for millets showing the products and waste produced by each process. Phytoliths are in white and macro-remains in black. **Figures 2 and 4** in the paper are also useful. Too bad there is not one for wheat in this paper. I'll keep searching ... *************** ## Trichomes on rice husks Rice husks also have a lot of trichomes --- they should also be siliceous. But how siliceous? We have seen different intensities of Si in trichomes of different wheat landraces ... --- based on the hairiness of the glumes ... So, we might need to pay attention to not just shapes/morphology, but also composition, hardness, and durability etc. May need to collect and analyze rice husk specimens together --- early rather than late ...