This week I thought that I would review a couple of papers on Hiroshima rice. I came across these papers on the analysis of Hattan rice which is grown only in Hiroshima. This piqued my interest because this rice, while only grown in Hiroshima, is sold to 32 Prefectures in 2003 and 24 Prefectures in 2006. I had never heard of this rice (not that this means anything) until I came across the papers so I kept reading to learn more. As it turns out Hattan varieties are well suited for futsu shu (standard table sake) because of the shinpaku (starchy white center in sake rice) but are not as well suited for Daiginjo because of the fragile nature of that shinpaku.
Masahiko Tamaki is the first author on each of the papers I will discuss today. Rie Kiharra and Takao Tsuchiya are also authors on all three papers. There are several other authors but they vary paper to paper. The three papers are:
- Varietal Difference of Polishing Characteristics and Suitability for Sake Brewing in “Hattan-Type Varieties” of Rice Suitable for Brewing Original Hiroshima Sake
- Properties of Starch and Protein of “Hattan-Type Varieties” of Rice Suitable for Brewing Original Hiroshima Sake
- Varietal Differences in Endosperm Structure Related to High-degree Polishing Properties of “Hattan Varieties” of Rice Suitable for Brewing Original Hiroshima Sake
Hattan type rice goes back to at least 1875 when private growers were breeding rice based on Hattanso. Not long after this in 1907 the Hiroshima Prefecture Agriculture Experiment Station began working on producing better strains of Hattan-type rice. The primary goal for the improved strain was to produce rice with a more prominent shinpaku, better disease resistance, lodging resistance and higher yield. Initially, in 1921 this led to the development of Hattan No. 10. It had a low yield, was susceptible to lodging and rice blast and had a long culm, none of which are advantages. Despite these disadvantages it was used for breeding material. In 1962, this continued work produced Hattan No. 35 from Hattan No. 10 by introducing rice blast resistance. Later in 1965 Hattan No. 40 was bred. Much later, or much more recently, in 1984 two new varieties were bred from Hattan No. 35 by improving its yield; Hattan-nishiki No. 1 bread for hilly areas and Hattan-nishiki No.2 bred for altitudes above 400m. These last two both have the same high yield and lodging resistance as does table rice (non-glutinous rice).
The breeding program has succeeded in producing rice with larger grain size, higher percentage shinpaku and a higher percentage of the grains having this characteristic shinpaku. It also resulted in rice characteristics that are advantageous of sake brewing; better absorption of water and higher digestibility (that is the koji enzymes can convert more of their starch to sugar and protein to amino acids). These characteristics have made Hattan No. 35, Hattan-nishiki No. 1 and No. 2 well suited for sake brewing.
However, both Hattan-nishiki No. 1 and No. 2 are easily broken during polishing while Hattan No. 35 has a smaller harder shinpaku that is not easily broken. The level of breakage for No. 1 and No. 2 make them unsuitable for ginjo and daiginjo brewing, so only Hattan No. 35 is used for this. But Hattan No. 35 is by no means ideal because its cultivation characteristics are lacking.
It seems that one characteristic of the shinpaku between those that are fragile and those that are less so, is a “lined-white-core” or, in the terminology I have been using, a “lined-shinpaku.” I am not sure what a lined-shinpaku is, I will have to watch for more on this. Yamada-nishiki also seems to have just such a shinpaku, a lined-shinpaku that is.
The analysis in these papers show that the starch and protein composition of the various Hattan varieties are virtually the same so the composition does not account for the fragility. Maybe the endosperm structure can account for the fragility? The final paper looks at just this question. It concludes, yes, the structure seems to be the main cause. Hattan-nishiki No. 1 and No. 2 both have large shinpaku but also large number of interstices (gaps in the structure) while Hattan No. 35 has fewer gaps. In addition Hattan No. 35 has a lined-shinpaku while Hattan-nishiki No. 1 and 2 do not.
Comparing the Hattan-type rice with Yamada-nishiki the authors find that Yamada-nashiki has the same lined-shinpaku as Hattan No. 35 but with even fewer gaps. All of this (lined-shinpaku with low number of gaps) leads to less fragility for Yamada-nishiki than Hattan No. 35.
So, while a large shinpaku is important for sake brewing it is not enough by itself to make a rice type suitable for daiginjo.
P.S. Furukawa, S. is referenced in the 2ed paper