Final harvest details show the wheat quality problem

Press, 13 July 1984, Page 25

Final harvest details show the wheat quality problem

Nearly one-third of the total wheat crop submitted for testing during 1984 was rejected for milling. The final wheat quality bulletin for the year from the Wheat Research Institute, Christchurch, shows that lines representing 95,856 tonnes of production scored less than 12 on the M.D.D. bake score test and were therefore rejected for milling as undergrade. The rejected tonnage represents 32.2 per cent of th 297,592 tonnes in the total number of lines submitted for testing, compared with 26.5 per cent rejected of the 309,461 tonnes tested in 1983.

A further quarter of the total harvest in 1984 intended for milling was graded category B, com-

pared with 20 per cent in 1983.

Over all, 125,708 tonnes were graded category A (164,635 tonnes in 1983) or 42.2 per cent (53.2) of the crop; 76,028 tonnes category B (62,801 tonnes) and 95,856 tonnes rejected. The amount of Rongotea wheat grown doubled from 1983 to 1984 and this cultivar was badly hit by a reduction in quality due to the wet growing and harvesting season throughout Canterbury. In 1984 Rongotea was nearly half of all wheat

grown, compared with 24 per cent in 1983 and in North Canterbury and the Christchurch districts it contributed to half of the rejected wheat. Although this might be statistically predictable it is not a good performance from the most widely grown cultivar and one which is expected to perform well in Canterbury. Its share of rejected wheat grew from only 3.2 per cent the previous year to 24.9 per cent. Rongotea managed to get 55.7 per cent of the variety’s total tonnage into category A, 28.1 per cent category B

and 16.2 per cent rejected. Oroua showed 66.8 per cent category A and 16.6 per cent in each of category B and rejected. It represented about 14 per cent of total wheat tested, down slightly from 19 per cent the year before.

Rongotea had an average baking score this year of 14.8 although this variety had an average score by district as low as 13.8 around Christchurch and 13.1 around Dunedin. Its national average of 14.8 was a mirror image of its 1983 (and more normal) average

of 18.4. Oroua had a national average of 16.6 this year compared with 18.9 in 1983. The national baking score average over all varieties dropped 1.7 points to 13.3, a statistic which was highlighted by a W.R.I. scientist, Dr Howard Dengate, in his summary of the figures in the final quality bulletin.

“The drop reflects the cool damp summer, which allowed starch deposition to continue in the grain after protein deposition had slowed,” he said.

“This drop in quality, in

part compensated by increased yields, had the effect of increasing the proportion of the crop falling into category B, particularly in the areas from North Canterbury to Timaru. “In those areas the average bake score dropped by over four points. “The other notable feature of this harvet was the extremely high proportion of the crop rejected in the Invercargill district, amounting to 77 per cent of the total crop,” Dr Dengate said.

“In the Invercargill district only 12 per cent of the crop was considered to be category A and 35 per cent of the crop was sprouted S 3 or worse.”

Tonnages from the Invercargill and Dunedin districts also dropped considerably this year, probably below 40 per cent of the 1983 tonnages. Sprouting was a widespread problem this year. In all 6 per cent of the crop (17,558 tonnes) was sprouted S 3 or worse. The bulletin also explained the difference between the sprout index as measured by the W.R.I. and the falling number test as being used by the Wheat Board and others. Dr Dengate said there was no useful relationship between the index and a falling number result although the latter test may be useful for day-to-day quality control on a mill or bakery because it is quick to do. He said the kernel weights increased by 10 per cent on average this year and the national yield average was 4.7 tonnes per ha, compared with 4.3 tonnes per ha in 1982 and 4.4 tonnes in 1983.