Harvest conditions: Effects on wheat quality and routes to addressing issues of agronomic, processing and financial

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For the 2013 crop of UK wheat, the weather during planting was poor hence, farmers sowed more spring wheat, but because the weather improved, the final crop quality was average.

For the 2013 crop of UK wheat, the weather during planting was poor hence, farmers sowed more spring wheat, but because the weather improved, the final crop quality was average.

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  • 1. Digital Re-print - May | June 2014 Harvest conditions: Effects on wheat quality and routes to addressing issues of agronomic, processing and financial www.gfmt.co.uk Grain & Feed MillingTechnology is published six times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies, the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published. ©Copyright 2014 Perendale Publishers Ltd.All rights reserved.No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1466-3872
  • 2. F or the 2013 crop of UK wheat, the weather during planting was poor hence, farmers sowed more spring wheat, but because the weather improved, the final crop quality was average. The aim of the miller is to maintain the production of flour that performs consist- ently in processing. Hence, the miller tests wheat quality to maintain the quality of the raw materials entering the mill. Quality means different things for dif- ferent products and therefore a number of factors are important when assessing wheat quality. Some quality issues will render wheat unsuitable for human or even animal con- sumption. Wet wheat is unsuitable for safe storage and can lead to fungal-based spoilage or premature germination. Wheat contaminated by the addition of foreign material, ergot or chemicals leads to food safety risks. Partially germinated grains, those of low density, of unsuitable varieties or low protein content may be unsuitable for processing. The role of the grower Growers play a key role in producing high quality wheat. They begin influencing wheat quality by selecting appropriate varieties for the soil type and climate. The planting season defines the varieties sown. During the lifecycle of the plant, the farmer monitors plant health. They use this information to treat the crop with nutrients such as nitrogen and sulphur and chemicals such as herbicides and pesticides to encour- age healthy plant growth. The weather influences plant growth and the opportunities to plant seeds and apply treatments can limit the farmer’s control of wheat quality. After harvest, the safe storage of wheat before trade to the miller is essen- tial. For further information see, The Home Grown Cereals Authority (HGCA) “Grain Storage Guide for Cereals and Oilseeds,” which applies food safety approaches to the storage of cereals (www.hgca.com). The variety of wheat largely defines the quality of subsequent products, for example, flour. The genetics of a variety endows resistance to disease and premature germination whilst also defining grain shape, specific weight, resistance to variations in harvest conditions and the ability to store protein efficiently. To support the farmers in selecting appropriate varieties in the UK, the National Association of British and Irish Millers (nabim) publish a categorisation of wheat varieties, summarised in Table 1, based on at least three years of trial data. The trials consider the suitability of the wheat for bread and biscuit processing. The role of the miller The miller is responsible for supplying consistent flour of the quality required by the baker and therefore demands control over wheat quality. A contract of trade defines the quality measurements and sets acceptable limits. These tests include rapid tests by mill intake laboratories that enable the efficient unloading of wheat. However, where quality raises concerns, further testing may be required. The miller uses rapid tests, summarised in Table 2, to measure the quality of traded wheat at the mill. These include a visual inspection to determine the suitability of the wheat for milling and may result in rejection: Damaged grains could indicate infesta- Table 1: Categorisation of wheat varieties, published by nabim to communicate their preference for UK wheat varieties demonstrated as suitable for processing (Source: nabim Wheat Guide 2013 www. nabim.org.uk) Group 1 These varieties perform consistently in milling and baking. Group 2 These varieties exhibit bread- making potential, but not of the consistent high performance of those in Group 1. Some speciality varieties may be included. Group 3 These varieties are suitable for biscuit, cake and other soft- milling, low protein applications. Group 4 These varieties do not meet the processing quality criteria described for Groups 1-3. Harvest conditions: Effects on wheat quality and routes to addressing issues of agronomic, processing and financial by Mervin Poole, Analytical Service, Cereals and Ingredients Processing Department, Campden BRI, UK 46 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF
  • 3. tions by insects or mites. Enzymes produced by insects to digest wheat proteins render the protein unsuitable for some baking applications Odours, taints, shrivelled, pink or green grains may suggest contamination by mould or chemicals, which indicates a risk of poi- sonous mycotoxins or dangerous chemicals entering the food chain Ergot is a fungus from the genus Claviceps. The fruiting bodies are dark coloured fun- gal spores known as sclerotia that contain poisonous alkaloids. They have a creamy white centre of similar size and density to a wheat grain and are therefore difficult to separate from wheat. The risk to human and animal health excludes wheat from the food chain if it contains these poisonous sclerotia. Furthermore, the EU Commission Regulations (Numbers 1234/2007 and 1272/2009) have set maximum levels per- mitted under EU regulations of 500mg/kg of sclerotia in wheat Dark coloured grains can indicate heat- damage due to drying the wheat at high temperatures. Heat above approximately 40˚C damages the proteins in wheat making them less capable of producing a functional gluten network Skilled intake technicians may recognise varieties by visual examination. A passport scheme supports the traceability of wheat and states its variety. As a significant propor- tion of quality is fixed by variety, this is a key indicator of quality and further testing may be required if the sample does appear as expected Moisture, protein and other factors Independent to the visual inspection, the miller measures moisture because wheat cannot be stored safely above 14.5 percent moisture on a mass basis. Drying grain is expensive and grain is traded based on weight. Therefore, the miller does not wish to pay for either the cost of drying or the extra weight of the water included with the grain. The miller measures protein content because specific products need appropriate flour protein for their manufacture. The acceptable threshold for bread wheat is 13.0 percent. Below 13.0 percent wheat protein, the derived flour is incapable of maintaining the consistent bread loaf-volumes expected by consumers. Premature germination of wheat due to variety, moisture and heat in either the field or following storage causes the production of an enzyme, which breaks down stored starch to sugar. The miller measures the quantity of this enzyme by the Hagberg Falling Number test. Low Falling Number values indicate excess enzyme. The threshold for bread wheat is a minimum of 250s. Below this level, the enzyme releases too much sugar, which feeds the yeast causing uncontrolled holes or Table 2: Tests used to assess wheat quality in a mill intake laboratory Test Considerations and impact Limits Sensory evaluation Infestation, odours, taints, heat-damage and variety all suggest safety and quality failures Protein content poor bread volume and texture >13% on a dry matter basis Moisture content Unsafe for storage, costly to dry, <14.5% Specific weight (Hectolitre weight or bushel weight) Low density equates to lower flour yields during milling and below 76kg/hl indicates grain quality problems >76kg/hl α-Amylase content (Hagberg’s falling number) Too much sugar released from the starch during baking. Dark, sticky breadcrumb with large holes. >250s May - June 2014 | 47GRAIN&FEED MILLING TECHNOLOGY F
  • 4. darkening of the breadcrumb structure. Both of these contribute to undesir- able bread, which does not meet consumer expectations. Excess enzyme can also lead to stickiness of the dough and crumb causing dough processing and bread slicing failures. The miller measures the density of the wheat. Known as the Hectolitre or Bushel Weight tests, the results help identify shrunk- en grain due to disease, drought or damage from insect infestations. The acceptable threshold for bread wheat is 76kg/hl. Higher levels are associated with higher flour yields from the wheat because plump grains have lower surface bran to endosperm ratios. The conclusions of these tests will influ- ence the suitability of the wheat for process- ing into flour and its sale to a baker. The results will conclude the trade agreements for the wheat and define the payment the farmer receives for their crop. Farmers are dependent on weather throughout the lifecycle of the plant to produce good quality wheat. Late summer, autumn and winter of 2012 were very wet and prevented the sowing and establishment of wheat in the UK because the land was too wet to work. In response, the farmers selected more spring wheat varieties and sowed these in the spring of 2013. Opportunities for good plant husbandry during the life cycle of the plant improved following a cold spring. The warm and dry summer increased plant growth rates. The farmers harvested the crops under dry conditions. After harvest, they stored the wheat under controlled conditions to maintain quality. The summer and harvest conditions in 2013 helped the crop to recover from expectations of a disastrous harvest. The final quality assessments suggest the quality of the harvest was average. Based on HGCA estimates, the total UK wheat yield decreased from 15.2mt in 2011, to 13.3mt in 2012 and 11.9mt in 2013 (www.hgca.com). Nabim classify Group 1 and Group 2 vari- eties as potentially suitable for bread making. The basic intake requirements used to assess quality include; a specific weight of greater than 76kg/hl, a protein content of greater than 13.0 percent and Falling Number values greater than 250s. The proportions of samples meeting these criteria when surveyed after the 2011, 2012 and 2013 harvests are summarised in Table 3. We made a comparison of the 2013 and 2011 crops. We did not compare the 2012 crop because it was abnormal and the quality was not a reflection of average crop performance in the UK. Of the nabim Group 1 and 2 varieties harvested in 2013 more samples met the intake requirements for falling number than 2011 but fewer met the requirements for protein or specific weight. The farmers concentrate on producing good quality wheat throughout the lifecycle of the plant. For the millers, the commercial incentives to use locally available wheat out- weigh the cost of importing wheat. However, the negative effect of any food safety scare outweighs any commercial incentive to use the most readily available crop. The 2013 harvest in the UK Dry conditions prevailed during the 2013 UK harvest. The dry conditions helped avoid prema- ture germination and enabled safe storage of the crop. The Falling Number values of >250s in more than 90 percent of bread- making samples meant that excess sugars in baking were unlikely to be common. The bakers can easily compensate for low levels of enzyme in the bakery and therefore the low level of enzyme is unlikely to cause concern. Low specific weight in 2013 appears to be due to a proportion of small or shrivelled grains. It is of concern because it is predomi- nantly evident in the survey of Group 1 varieties. The root cause of such shrivelled grains is important because drought, pre- mature harvesting or disease can define the risk of using these samples in the food chain. Small grains due to drought or premature harvesting will result in a low flour yield and potential bran contamination without care- ful and costly mill adjustment. Small grains due to disease are associated with higher mycotoxin risks associated with mycotoxin producing fungi such as the Fusarium species. Mycotoxin contaminated samples are excluded from the food chain when safe lim- its are exceeded. However, specialist equip- ment is available that can separate samples based on their density to recover the plump grains. This expensive process will recover a proportion of plump grains from the sample. Grain sorters, which rely on image tech- nology, remove individual grains contami- nated by Fusarium. However, not all Fusarium species pro- duce mycotoxins. Hence, the removal of all Fusarium contaminated grains by grain sort- ers is both wasteful and expensive. With only 28 percent of Group 2 wheat meeting the grain intake specifications in 2013, low protein is a potential problem. The main impacts of low protein bread wheat are low and inconsistent loaf volumes. The baker can add gluten to improve the loaf volume. However, this is expensive because glu- ten is manufactured from wheat. A remaining option is to import wheat of the appropriate quality. This incurs higher transport costs. However, this option may be associated with lower risks and process- ing costs, causing it to be a realistic option. In conclusion, the harvest conditions have lead to a small, average quality UK crop in 2013. Although the crop was better than anticipated, the penetration of the quality is unlikely to compensate for the shortage. Hence, imports of wheat to meet the demand for consistent products are likely to continue. About the author: Mervin Poole manages the analytical service of the Cereals and Ingredients Processing department at Campden BRI. The service supports innovation and training at Campden BRI by provid- ing testing to the cereals, ingredients and animal feed industries. Campden BRI is the UK’s larg- est independent membership-based organisation carrying out research and development for the food and drinks industry worldwide. It is committed to providing industry with the research, technical and advisory services needed to ensure product safety and quality, process efficiency and product and pro- cess innovation. Contact Mervin on: mervin.poole@ campdenBbri.co.uk or telephone: +44 1386 842287 Table 3: Proportions of wheat samples surveyed from the 2011-13 UK bread making crops that met the mill intake criteria limits for specific weight, protein content and Falling Number (source data from: www.hgca.com) % of samples tested that met intake requirement of: Group 1 Group 2 2011 2012 2013 2011 2012 2013 Specific weight (>76kg/hl) 91 10 25 86 8 73 Protein (>13%) 50 50 50 37 60 28 Falling number (>250s) 86 56 93 84 38 90 "The miller is responsible for supplying consistent flour of the quality required by the baker and therefore demands control over wheat quality. A contract of trade defines the quality measurements and sets acceptable limits" 48 | May - June 2014 GRAIN&FEED MILLING TECHNOLOGYF
  • 5. www.gfmt.co.uk LINKS • See the full issue • Visit the GFMT website • Contact the GFMT Team • Subscribe to GFMT A subscription magazine for the global flour & feed milling industries - first published in 1891 INCORPORATING PORTS, DISTRIBUTION AND FORMULATION In this issue: • Role of extruders in Halal food production • Fortification Fortification in rice and flour • IAOM 118th Annual Conference & Expo May-June2014 • GM soybeans The on-farm facts • Harvest conditions: wheat quality and addressing issues • The Mills Archive GFMT becomes a patron first published in 1891 This digital Re-print is part of the May | June 2014 edition of Grain & Feed Milling Technology magazine. Content from the magazine is available to view free-of-charge, both as a full online magazine on our website, and as an archive of individual features on the docstoc website. Please click here to view our other publications on www.docstoc.com. To purchase a paper copy of the magazine, or to subscribe to the paper edi- tion please contact our Circulation and Subscriptions Manager on the link adove. INFORMATION FOR ADVERTISERS - CLICK HERE Article reprints All Grain & Feed Milling Tecchnology feature articles can be re-printed as a 4 or 8 page booklets (these have been used as point of sale materials, promotional materials for shows and exhibitions etc). If you are interested in getting this article re-printed please contact the GFMT team for more informa- tion on - Tel: +44 1242 267707 - Email: jamest@gfmt.co.uk or visit www.gfmt.co.uk/reprints