The Satake Centre for Grain Process Engineering (SCGPE) at the University of Manchester Institute of Science and Technology (UMIST) in the U.K. has its primary focus on education, training and research in grain process engineering.
Significantly, SCGPE is based in the Chemical Engineering Department at UMIST. "Chemical engineers have contributed to the design, operation and management of the vast majority of non-food process industries for well over 100 years but, until recently, have had little involvement in food-related industries," Professor Colin Webb, Head of the Department of Chemical Engineering, told World Grain.
With its emphasis on process engineering research, the center provides a unique perspective for grain processors both in food and non-food sectors of the industry. Research includes primary processing of cereals, such as flour milling. Secondary processing encompasses breadmaking, biscuit manufacture, brewing and breakfast cereal manufacture.
Current projects are investigating the creation and dynamic evolution of cereal-based food foams, wheat starch extraction and small scale brewing. It is also exploring novel uses of cereals for food and non-food applications, in particular the application of fermentation technology for the development of processing strategies to improve the economic competitiveness of grain-based alternatives for non-food products.
TRANSFORMING ART INTO SCIENCE
Most cereal processing starts with a milling stage, where the interaction of the physico-chemical properties of the kernel with the design of the milling equipment determines process efficiency and product functionality and it is this primary processing area that provides the major thrust for research activities in the SCGPE.
"Primary processing research provides the basis for the Centre’s ambitious plans to transform the traditional art of flour milling into a modern scientific process," Webb said. This can only be achieved through a complete fundamental understanding of the process. Current research is aimed at providing a full mathematical description of the particle breakage associated with milling, using the Centre’s pilot mills and the Satake STR100 Test Roller Mill.
The feed to any roller mill will have a distribution of a number of different properties, particularly size. Likewise, the output from the roller mill will have a distribution of the same properties. Taking size as an example, the distributions of input sizes and output sizes can be defined in mathematical terms as probability density functions.
The input size distribution is given by the term p1 (D), which simply represents the probability of any individual particle being of size D, where size D is in the range of smallest to largest particle. Similarly the output can be defined by p2 (x), representing the probability of any individual particle in the output being of size x. Although not necessarily a simple one, there must be a relationship between p2 (x) and p1 (D), which is attributable to the action of the rollers on the particles as they pass through the mill. This relationship can be described by the following equation:
Where (x, D) represents a breakage function (the probability of an output particle of size x having been produced as a result of breakage of an input particle of size D).
Work within the Centre has enabled the simplification of this equation by assuming that each particle will mill independently of all others. High-speed video images of wheat grains passing through the Satake STR-100 Test Mill have confirmed the validity of this assumption as have predictions based on the use of the breakage equation.
Research in this area continues and it is now possible to construct breakage equations and predict milling performance over a very wide range from a very small set of experimental data. Webb believes this will be a powerful tool for millers to use in deciding mill settings for different grists and also for quality control purposes.
The ultimate aim is to be able to predict the performance of every roller milling operation throughout the flourmill based on simple-to-obtain data.
RECYCLING FOR EFFICIENCY
A further area of research that staff and students in the Centre are pursuing has the goal of reducing the number of steps in a typical flour milling process. For chemical engineers, it is unusual to see a process flow diagram without ‘recycling’ being used. The flour milling process, however, is almost entirely void of recycle streams where separate fractions from each operation go ahead as new streams to the next operation. While this is essential in many parts of the process, there are opportunities for combining some streams and also, in some cases, for recycling particles that have been insufficiently broken to go back to the same roller mill. A significant reduction in the number of operations is possible and research carried out in the Centre has been tested in full-scale mills to verify the potential usefulness of such an approach. Preliminary results indicate that increased extraction rates and energy savings can both be achieved without compromising product quality.
Sifting is the other major unit of operation within flour milling. Discrete Element Modelling (DEM) studies are ongoing to develop mathematical models and practical design procedures for sifting operations.
DEBRANNING FOR PROFIT
A newer development in milling technology is debranning, with consequences for mill design and operation, milling efficiency, flour functionality and baked product quality. Several debranning studies are currently under way.
Two of these projects at the Centre are combining debranning and fermentation technology to develop novel products from cereals. The first of these is applying wheat debranning technology to oats as a tool for facilitating the extraction of anti-oxidants, then using fermentation to enhance the value of the residual starchy material.
In a similar wheat-based project, the potential for producing biodegradable plastics economically from wheat is being demonstrated, with debranning again applied at the front end of the process to improve economics and control. Bran also has consequences for healthy diets and for bread structure and quality, and the interaction between bran components and bread aeration is another focus of current research.
Webb defines grain process engineering as "the application of process engineering principles to the production of food and non-food products of cereal grains." He believes this new discipline provides the opportunity to acquire the fundamental understanding necessary for the development of efficient, flexible, controllable processes for the 21st century.
Grain buyers and marketers are demanding premium quality grain and processed grain products to meet increasingly stringent requirements of their domestic and overseas customers. To better manage quality across a supply chain, sophisticated real-time monitoring technologies are required. They must be universal, relatively inexpensive, easy to use and reliable, with minimal sample preparation.
On the other side of the world from UMIST, in Australia, the CSIRO Stored Grain Research Laboratory is working closely with other research organizations to develop new grain and end-product quality assessment techniques based on Near Infrared Spectroscopy (NIRS), digital imaging, and the detection of volatile compounds using aroma sensing techniques.
NIRS technology is currently being used by bulk handling companies and large private grain storage and handling operators to measure protein, oil and water content of different grain types. However, NIRS is capable of delivering rapid measurement of a much wider range of quality parameters of importance to the grain supply chain. For example, it may prove valuable to closely monitor changes in the quality of grain during storage, and to identify malting barley and feed grain quality.
Digital imaging provides a rapid method to measure the size, shape, texture and color of grains. Its applications at receival and storage sites may include varietal identification, detection of mold contamination and grain defects such as black point and pre-harvest spouting, detection of weed seeds and admixture by other grains.
SNIFFING OUT MOLD
Aroma sensing is an area of science of considerable interest to food technologists. Commonly referred to as the "electronic nose," this technology is designed to simulate the human nose. Volatile compounds are channeled into the device in a carrier gas stream that passes over a series of chemical sensors. The sensors contain an extensive library of known odors, and identify test compounds, that are the same. The identification of mold contamination on foodstuff is an area where aroma sensing may have important applications.
The combined use of these new and developing technologies will provide many sectors of the grain industry, including commercial grain storers and handlers, food processors and marketers, with the tools to detect quality changes, varietal differences, odors in poorly stored grain and detection of chemical residues.
METHYL BROMIDE ALTERNATIVES
CSIRO is urgently seeking alternatives to methyl bromide, pending its phase-out for most uses in developed countries in January 2005 under the terms of the Montreal Protocol. The Laboratory has developed or evaluated a number of new and alternative compounds that show potential as fumigants for grain and other durable commodities.
The importance of phosphine cannot be over-stated, and the laboratory’s research is focused on maintaining its efficacy and use. The commercialization of new application methods that have important advantages over existing ones, is an important aspect of CSIRO’s research. In this regard, a new aluminum phosphide formulation and generator developed by the Laboratory in conjunction with United Phosphorus Limited in India is close to commercial release.
CSIRO also has the patent on two promising compounds, carbonyl sulfide and ethanedinitrile, and has re-evaluated the use of ethyl formate, a very old and almost forgotten fumigant.
Carbonyl sulfide is not as fast acting as methyl bromide against insects, but it is faster than phosphine. It naturally occurs in food and it breaks down rapidly. Commercial use of carbonyl sulfide is still several years away, but the Laboratory has an agreement with a manufacturer to produce commercial carbonyl sulfide under the trade name Cosmic. Carbonyl sulfide has been shown to be highly efficacious against insect pests on bulk grain, hay and dry timber products.
Ethyl formate is currently registered and used in Australia for dried fruit under the trade name Erinol. Ethyl formate is present in high concentrations naturally in many fresh fruits and vegetables.
The fumigant has shown remarkably fast action against stored product insects and may have potential use in unsealed and partially sealed stores.
Ethyl formate is an old fumigant that had been evaluated in Australia for grain protection back in the mid-1940s. The interest in ethyl formate as a grain fumigant waned following the introduction of methyl bromide and phosphine in the 1950s. Events have turned full circle and the CSIRO SGRL has rejuvenated interest in ethyl formate as a potential fumigant for the protection of farm stored grains. Future studies will focus on the development of ethyl formate formulations and safe application techniques for fumigation during inloading, in-situ and at outturn of grain in farm and commercial situations.
The reliance on phosphine to control insects in poorly sealed farm silos or bulk bins has resulted in widespread low level resistance, dangerous practices, and grain being delivered to central storage containing live insects and intact formulation that continues to produce phosphine.
Unlike phosphine, ethyl formate kills insects rapidly and its residues break down to naturally occurring products, formic acid and ethanol.
Trials using ethyl formate have been undertaken on wheat, sorghum and navy beans that were stored in unsealed farm bins. These trials have shown ethyl formate kills insects within hours, unlike phosphine, which takes days and requires a well-sealed store. Ethyl formate was however less potent at low temperatures (less than 15°C, 50°F), which is similar to phosphine. At low temperatures liquid ethyl formate does not readily vaporize, and distribution of the fumigant in grain is slower and less uniform.
The challenges are that ethyl formate is potentially flammable when the liquid formulation is used at high concentrations, and is rapidly absorbed by grain and broken down to inert compounds. The fumigant therefore needs to be applied to grain at high dosage rates and in a quick release form.
A cylinderized formulation of ethyl formate combined with carbon dioxide, Vapormate, developed by BOC Limited, may resolve these problems. Laboratory studies are being undertaken by SGRL to assess the efficacy against stored product insects, and absorption and distribution behavior when applied at different flow rates to bulk grain. The addition of carbon dioxide has been shown to enhance insect toxicity and reduce the potential flammability risk. Further studies are planned for both the liquid and cylinderized formulations.