WO2001009590A1

WO2001009590A1 - Method of, and instrument for, analysing cereal grains

Info

Publication number: WO2001009590A1
Application number: PCT/GB2000/002862
Authority: WO
Inventors: Gyanchand Sachin Chandra; Stephen Geoffrey Garland; Graham John Gasson; Robert Edwin Muller
Original assignee: Brewing Research International
Priority date: 1999-07-31
Filing date: 2000-07-28
Publication date: 2001-02-08
Also published as: AU6298100A; GB9917958D0; EP1125110A1

Abstract

An instrument for analysing cereal grains includes a sample holder (10) for holding a cereal grain, a light source (28) for illuminating a cereal grains in the sample holder, and a detector (32) for detecting and measuring the intensity of light emanating from the grain. A cereal grain (34) in the sample holder (10) is illuminated with light from the light source (28), and transflected light emanating from the grain is detected with the light detector (32). The intensity of the detected light is measured, and the grain is categorised according to the intensity of the detected light.

Description

METHOD OF, AND INSTRUMENT FOR, ANALYSING CEREAL GRAINS

The present invention relates to a method of, and an instrument for, analysing cereal grains. In particular, but not exclusively, it relates to such a method and instrument for use in monitoring the internal structure of malted barley endosperm, in connection with a brewing operation.

The principle ingredient in most beers is barley malt. Barley itself is not used because it contains cell wall and other materials (composed of starch, betaglucans and pentosans) which interfere with the brewing process and give rise to poor quality beers. Furthermore, barley contains neither the enzymes nor the flavour active materials required for effective processing and high quality beers.

Barley may be divided into three components:

1. an embryo, which will grow into the next barley plant,

2. the aleurone cells which synthesise enzymes,

3. an reserve of proteins and starch called the endosperm, and 4. a protective husk.

The grain is converted into malt during the malting process. In order to achieve this the raw barley is steeped in water several times and then allowed to germinate. After several days of germination the enzymes required for further processing have been formed, and the small starch granules and cell walls have been digested and removed. The malt is then kilned to dry it and to develop many of the roasted caramel flavours associated with beer.

A critical part of the malting process is the conversion of the grain endosperm from a hard, tightly packed reserve of protein and starch into a friable, easily digested material. This process is termed modification. It depends on two factors:

• activity of the embryo and the aleurone generating the appropriate enzymes to achieve modification, and

• an endosperm structure that will permit the passage of water and hence enzymes to the site of activity i.e. the cell walls and small starch granules.

If either of these fails then the grain will not modify properly and the malt quality will not be such to allow subsequent trouble-free processing. Malt modification can be monitored using these changes. A well-modified malt will have a degraded cell wall structure and very few small starch granules. Depending on the malting regime employed, grains can be either under-modified or over-modified. Slightly under- modified malt is needed for lager beer production.

There are several simple methods of assessing embryo activity including plate germination tests (so called geπninative energy, gerπώiative capacity and dormancy tests, which are described in Recommended Methods of the Institute of Brewing, published by the Institute of Brewing, Clarges Street, London.)

In addition, there is a plethora of enzyme based analyses that indicate the activity of a germinating embryo.

As shown in Figure 1, the barley endosperm consists of a matrix of protein, starch and cell wall materials. The starch is included as large granules 1 and small granules 2 that are embedded in the protein material. This is surrounded by a cell wall structure including a protein middle lamella 3, an outer wall 4 containing Pentosan and β-Glucan, and an inner wall 5 containing β-Glucan. These three components may be put together in a variety of different ways with different proportions of each contributing to the overall structure.

Figure 2(a) compares electron micrographs of two typical but very different endosperm structures. The first picture (M) shows a mealy endosperm in which the entire structure is loosely packed. There is preponderance of large starch granules, very few small starch granules, only a small amount of cell wall material and the protein matrix is not a major feature. The second picture (S) shows a steely type endosperm in which there is considerably more cell wall material, many more small starch granules and the protein matrix holding these together is far more prorninent.

Also shown in figure 2(b) are light micrographs of grain sections showing the visible appearance of steely and mealy endospe rms. The mealy endosperm (M) appears white and matt resembling the crumb structure of a load of bread. The steely endosperm (S) is grey brown and has a glassy/plastic appearance. The third light micrograph, designated M/S, shows a case where part of the endosperm is mealy and part is steely. In fact this last case is probably the most common situation and it is only rarely the case that a grain is entirely one type or another.

Because the steely endosperm is more tightly packed than the mealy type, it is more difficult to hydrate and the enzymes responsible for the modification process pass through more slowly. For precisely these reasons the steely endosperm, or fractions that are steely, modify more slowly. That is not to say that steely endosperms cannot be modified, only that they modify at a different rate to the mealy type. What is important is that the maltsters are aware of the material that they are dealing with, so that they can adjust their process accordingly. Thus a device that monitors the meali/steeliness of a grain would be of considerable use to them.

There are very few instruments that will determine this parameter. Traditionally, the maltster has relied on the Farinator. This is a device that cuts a sample of grain, in a transverse manner, to reveal a plane of the endosperm. This is examined visually and a judgement is made. The device has several drawbacks. It is only qualitative and does not provide any quantitative information. The final judgement generally lies with the experience of the operator. The Farinator cuts across only one plane and, as shown in Figures 3(a) and 3(b), this may well give rise to misleading information. If the plane of the cut is in fact through a non-representative part of the grain, then the wrong conclusion may be drawn. For example, the grain shown in Fig. 3a has a large mealy area 6, but the cross-section resembles that of a steely grain, whereas the grain shown in Fig. 3 a has a relatively small mealy area 7, but the cross-section appears to be that of a very mealy grain. Bearing in mind earlier comments that few grains are entirely of one type, this is an important consideration. This test is also destructive.

Other instruments to measure grain/endosperm quality include the Instron® and the milling energy system.

The Instron® is a type of penetrometer used mainly in the wheat industry. It relies on the penetration of a probe into the grain and wheats are then classified as hard or soft. Although quantitative information is gained the test is destructive. Milling energy is based on the retardation of a spirining mill wheel when it is used to grind a sample of grain. Only bulk samples can be analysed. In this case the test is again destructive. (Swanston, J.S. and Taylor, K. The milling energy of malted barley and its relationship with hot water extract and alpha-amylase activity. Journal of the Institute of Brewing, May/June 1988, 94(3), 143-146.)

A simple robust and quantitative method, which can identify the appropriate quality of endosperm structure, is currently unavailable to maltsters.

It is an object of the present invention to provide a method of, and an apparatus for analysing cereal grains that mitigates at least some of the aforesaid disadvantages.

According to the present invention there is provided a method of analysing cereal grains, wherein a cereal grain is iUuminated with light from a light source, light emanating from the grain is detected with a light detector and the intensity of the detected light is measured, and the grain is categorised according to the intensity of the detected light.

The method allows the character of the grain to be analysed quantitatively and non- destructively. The method allows the whole grain to be analysed and is quick, accurate and simple, and lends itself to automation.

Advantageously, transflected light emanating from the grain is detected and the intensity of the transflected light is measured. This provides an accurate indication of the mealiness/steeliness of the grain.

The light detector is preferably substantially aligned with the light source, although it may alternatively be arranged to detect transflected light emerging from the grain at an acute angle to the incident beam.

Advantageously, light intensity measurements are made for a plurality of grains and the results of those measurements are collected and processed to provide a bulk grain analysis. The light intensity measurements for the plurality of grains may be made consecutively, preferably by mounting the grains individually in the compartments of a multiple- compartment sample holder and moving each of those compartments in turn into a testing device for analysis. The individual grains may for example be mounted in a carousel-type sample holder.

Advantageously, the grains are illuminated with a light beam having a diameter of less than 2mm, and preferably approximately 1mm. The light source may be a laser, which may have a wavelength in the range 600-700nm.

Advantageously, the aperture of the light detector is greater than the diameter of the light beam incident on the grains, allowing it to detect light scattered by the grain at an acute angle to the incident beam.. The diameter of the light detector may for example be in the range 2mm to 20mm, and is preferably approximately 5mm.

Advantageously, whole grains are analysed. Alternatively, dehusked grains may be analysed.

The method may be used in monitoring the internal structure of grains and preferably the grain endosperm, for example barley endosperm and preferably malted barley endosperm. The method may be used in connection with a brewing operation.

According to another aspect of the invention there is provided an instrument for analysing cereal grains, the instrument including a sample holder for holding a cereal grain, a light source for iliurninating a cereal grain in the sample holder, and a detector for detecting and measuring the intensity of light emanating from the grain.

Advantageously, light detector is arranged to detect transflected light emanating from the grain. Preferably, the light detector is substantially aligned with the light source.

The instrument may include a data processing device, for example a computer, for categorising the grain according to the intensity of the detected light. The data processing device may be arranged to collect and process light intensity measurements for a plurality of grains, and to provide a bulk grain analysis based on those measurements.

Advantageously, the sample holder has multiple compartments, each for receiving an individual grain, and drive means for moving each of those compartments in turn into a testing device for analysing the grains. This may, for example, be a carousel-type sample holder. Advantageously, the light source generates a light beam having a diameter of less than 2mm, and preferably approximately 1mm. The light source may be a laser, which may have a wavelength in the range 600-700nm.

The aperture of the light detector may be greater than the diameter of the light beam incident on the grains. The aperture may for example be in the range 2mm to 20mm, and is preferably approximately 5mm.

The invention further provides an instrument according to the preceding paragraphs for use in monitoring the internal structure of grains, particularly grain endosperm, more particularly barley endosperm, and even more particularly malted barley endosperm. The instrument may be intended particularly for use in connection with a brewing operation.

An embodiment of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows the cell wall structure of barley endosperm;

Figure 2(a) shows two scanning electron micrographs of endosperm structures, and figure 2(b) shows light micrographs for three endosperm structures;

Figures 3(a) and 3(b) illustrate a prior art method of analysing grains by cutting a grain with a Farinator;

Figure 4 shows the appearance of dehusked barley grains on a light box;

Figures 5(a) and 5(b) illustrate the transmission of light through different types of barley grain;

Figure 6 is a partially sectional side view of a device according to an embodiment of the present invention;

Figures 7(a) and 7(b) show a sample holder in plan and sectional side view, and figures 7(c) and 7(d) show a sample well in the sample holder at an enlarged scale, and

Figures 8(a) and 8(b) show a grain being analysed in the device. We have observed that if a sample of barley grain is de-husked and examined on a light box, two types of grain are clearly visible: this is shown in Figure 4. One type of grain 8 is opaque and appears dark, the other 9 is translucent and appears to be much lighter. By analysing the different grains, we have found that the dark grains 8 are those with a mealy character and the lighter grains 9 are those with a steely character.

Without wishing to be bound by theory, Figs. 5(a) and 5(b) illustrate why we believe this may be. The mealy endosperm shown in Fig. 5(a) contains much free space between the starch granules 1 , and scatters light effectively. Little light passes through the grain, which therefore appears dark. The steely grain shown in Fig. 5(b), which contains a considerable protein matrix, acts as a lens and the light is scattered much less but is also partially focussed to the viewer. Transflected light therefore emerges from the grain and it appears light.

Based on these observations, we have designed an instrument for analysing grains, an embodiment of which is shown in Figs. 6 to 8. The instrument includes a sample holder 10 made from a disk of black Delrin™ material having a diameter of 180mm and a thickness of 6mm. One hundred sample holding wells 12 are provided around the periphery of the disk. Each well 12 consists of an oval depression formed in the upper surface of the disk, having a length of 9mm, a width of 4mm ad a depth of 4mm. This shape matches that of a typical barley grain, which can therefore sit securely in the well. A hole 14 having a diameter of 2.5mm extends downwards from the centre of each well through to the underside of the disk.

The disk 10 has a central aperture 15 that fits over a rotatable spindle 16 having a removable knob 17 for retaining the disk in place. The spindle 16 is driven by a stepper motor 18 via a drive belt 20 and two pulleys 20,22.

An optical measuring device 24 is mounted adjacent one side of the disk 10 and includes a horizontal slot 26 having a height of about 8mm into which the edge of the disk 10 extends. A light source 28, for example a small solid state laser producing a substantially parallel beam of radiation with a diameter of about 1 mm, a wavelength of approximately 670nm and a power of about 3mW, is mounted in the lower face of the slot and is aimed upwards. A short vertical passageway 30 is provided in the upper face of the slot opposite the light source 28 and in this is mounted a light sensor 32, for example a photodiode, having an effective aperture of about 5mm. The arrangement is such that when the disk 10 is in place, light from the laser 28 passes through the hole 14 in one of the sample holding wells 12 and is detected by the sensor 32. The stepper motor 18 is arranged to advance each of the sample wells 12 in turn into alignment with the light source 28.

In use, the sample holder disk 10 is loaded by placing a grain of barley 34 in each of the sample holding wells 12, so that they lie securely within the wells. The barley grains may be whole or alternatively they may have had their husks removed. The grains may be inserted by hand, which allows the operator to reject any over- or under-sized grains that would not sit properly within the wells. In addition, a preliminary sieving step may be employed to pre-select grains of the correct size. The disk 10 is placed on the spindle 16 and locked in place with the knob 17.

The principles of operation are shown in Figs. 8a and 8b. A barley grain 34 having an endosperm 36, a husk 38 and an embryo 40 is located in a well 12 on the sample holding disk 10. The disk is locked in position on the spindle 16 with the edge of the disk within the slot 26 in the optical measuring device 24 and the well 12 holding the grain 34 aligned with the light source 28. Light from the laser 28 shines through the hole 14 in the underside of the well 12 onto the grain 34 located in that well. The light is transflected within the endosperm 36 of the grain, and some of that light emerges from the upper surface of the grain and is collected by the light sensor 32. The output of the light sensor is amplified and measured, providing data relating to the amount of transflected light sensed for that grain, this data is collected by a data logger and stored for analysis by a computer (not shown).

It should be noted that the beam of light from the light source 28 is very narrow (diameter about 1mm) and is directed precisely at the centre of the grain 34, whereas the light sensor 32 is much larger (diameter about 5mm), so that is detects transflected light emerging from substantially the whole of the grain, allowing the starch content of the whole grain to be monitored. This avoids inaccurate readings with grains of the types shown in Figs. 3(a) and 3(b) in which the starch distribution within the grain is non-uniform.

As mentioned above, the amount of light detected by the sensor 32 depends on the mealiness/steeliness of the grain, the amount of light being higher for grains with a steely character and lower for grains with a mealy character. The data for the hundred grains in the sample holder is collected and analysed, giving an indication of the bulk mealiness/steeliness of the grain batch.

Some examples of typical data sets for different grain samples are provided below in charts 1 to 4. Chart 1 shows the results for a test carried out on a sample of Fanfare barley, chart 2 shows the results for a sample of Epic barley, chart 3 represents a sample of Chariot barley and charts 4 and 5 represent the results for samples of Chariot and Epic malt.

Chart la represents the light transflectance measurements (LTM) for each of the ninety seven individual grains in the sample. It can be seen that the photosensor output values vary from less than 1 OOmV to nearly 1 OOOmV. In chart lb, these results have been collected into six groups, representing LTM values in the ranges <100mV, 100-199mV, 200-299mV, 300- 399mV, 400-499mV, and >500mV. The results are presented in tabular and bar chart format. Mealy grains have been found empirically to be those with an LTM value below 200mV, which in this sample represents 18% of the grains. This is typical for a grain having a mixture of mealy and steely grains.

Comparing chart 1 with the other charts, it can be seen that the Epic barley (chart 2) is relatively steely, having only 1% mealy grains, whereas the Chariot barley (chart 3) is relatively mealy, having 84% mealy grains. The malt have a higher proportion of mealy grains, the Chariot malt having 95% and the Epic malt having 20% mealy grains.

It can be seen therefore that the instrument provides useful information about the proportions of mealy and steely grains in a sample. A spreadsheet program in a computer can be used to arrange the results in a graphical format such as that shown in the charts.

To summarise, some important features of the device include:

• The difference in endosperm structure can be monitored by the passage of light intensity of the grains on the light source. • A light detector can be used for quantitative results.

Since the light can be arranged to pass through the whole grain, quantitative information about the whole grain can be obtained.

• When a light of appropriate intensity is used, e.g. a laser light, the grain does not have to be de-husked and thus the whole grain can be examined. • The system is non-destructive and the grain can be used for other purposes.

• In a preferred design, individual grains can be examined.

• Individual analysis of many (e.g. 100) single grains can be used to obtain information regarding the homogeneity of the bulk sample.

A principle aim of the device is to obtain information about the homogeneity of the grain bulk. This is achieved by monitoring each grain separately and reporting the individual result as well as an average score.

Various modifications of the instrument and the method are of course possible, some examples of which are described below.

As the transflected light is scattered over a range of angles, it is not essential for the light source and the sensor to be directly aligned. The light sensor may therefore be mounted at an acute angle to the incident light beam.

Directly transmitted light and/or the reflected light may also be detected and measured to assist in the analysis. For this purpose, the instrument may have additional light sensors, for example with a transmitted light sensor mounted directly in line with the light source, a reflected light sensor mounted at an obtuse angle to the incident beam, and a transflected light sensor mounted at an acute angle to the incident beam.

While a laser is the preferred light source, owing to its intensity and narrow beam, other suitable light sources may also be used. Further, while the preferred wavelength is in the range 600-700nm, other wavelengths may also be suitable, including wavelengths beyond the visible spectrum.

Instead of analysing the grains consecutively, a plurality of grains may alternatively be analysed simultaneously, for example by analysing an image of a back-lighted sample of grains. BRI rapid LTM measurement

Sample Name: Fanfare Date: 10/07/00 Sample number: control Hour: 9:46 AM

Stage: Barley

Filter 1: 995 Filter 2: 101 Filter 3:

Chart la

Percentage of mealy grains: 18%

LTM values in ascending order

Chart lb BRI rapid LTM measurement

Sample Name. Epic Date: 06/07/00

Sample number- control Hour: 9:55 AM

Stage: Barley

Filter 1: 994 F Filter 2: 180 Filter 3:

Chart 2a

Percentage of mealy grains. 1 %

LTM values in ascending order

Chart 2b BRI rapid LTM measurement

Sample Name: Chariot Date: 10/07/00 Sample number: control Hour: 9:34 AM

Stage: Barley

Filter 1 : 1003 Filter 2: 169 Filter 3:

Chart 3a

Percentage of mealy grains: 84%

LTM values in ascending order

Chart 3b BRI rapid LTM measurement

Sample Name: Chariot Date: 06/07/00

Sample number: control Hour: 10:09 AM

Stage: Malt

Filter 1 : 994 Filter 2 107 Filter 3:

Chart 4a

Percentage of mealy grains 95%

LTM values in ascending order

Chart 4b BRI rapid LTM measurement

Sample Name: Epic Date: 06/07/00

Sample number: control Hour: 10:17 AM

Stage: Malt

Filter 1 : 994 F Filter 2: 183 Filter 3:

Chart 5a

Percentage of mealy grains: 20%

LTM values in ascending order

Chart 5b

Claims

1. A method of analysing cereal grains, wherein a cereal grain (34) is illuminated with light from a light source (28), light emanating from the grain is detected with a light detector (32) and the intensity of the detected light is measured, and the grain is categorised according to the intensity of the detected light.

2. A method according to claim 1 , wherein transflected light emanating from the grain is detected and the intensity of the transflected light is measured.

3. A method according to claim 1 or claim 2, wherein the light detector (32) is substantially aligned with the light source (28).

4. A method according to any one of the preceding claims, wherein light intensity measurements are made for a plurality of grains (34) and the results of those measurements are collected and processed to provide a bulk grain analysis.

5. A method according to claim 4, wherein the light intensity measurements for the plurality of grains are made consecutively.

6. A method according to claim 5, wherein the light intensity measurements for the plurality of grains are made by mounting the grains (34) individually in compartments (12) of a multiple-compartment sample holder ( 10) and moving each of those compartments in turn into a testing device (24) for analysis.

7. A method according to claim 6, wherein the individual grains (34) are mounted in a carousel-type sample holder (10).

8. A method according to any one of the preceding claims, wherein the grains are illuminated with a light beam having a diameter of less than 2mm, and preferably approximately 1mm.

9. A method according to any one of the preceding claims, wherein the light source is a laser.

10. A method according to any one of the preceding claims, wherein the light has a wavelength in the range 620-690nm.

11. A method according to any one of the preceding claims, wherein the aperture of the light detector (32) is greater than the diameter of the light beam incident on the grains (34).

12. A method according to any one of the preceding claims, wherein the diameter of the light detector (32) is in the range 2mm to 20mm, and is preferably approximately 5mm.

13. A method according to any one of the preceding claims, wherein whole grains are analysed.

14. A method according to any one of the preceding claims, for use in monitoring the internal structure of grains.

15. A method according to any one of the preceding claims, for use in monitoring the internal structure of grain endosperm.

16. A method according to any one of the preceding claims, for use in monitoring the internal structure of barley endosperm.

17. A method according to any one of the preceding claims, for use in monitoring the internal structure of malted barley endosperm.

18. A method according to any one of the preceding claims, for use in connection with a brewing operation.

19. An instrument for analysing cereal grains, the instrument including a sample holder (10) for holding a cereal grain, a light source (28) for illuminating a cereal grain in the sample holder, and a detector (32) for detecting and measuring the intensity of light emanating from the grain.

20. An instrument according to claim 19, wherein light detector (32) is arranged to detect transflected light emanating from the grain.

21. An instrument according to claim 19 or claim 20, wherein the light detector (32) is substantially aligned with the light source.

22. An instrument according to any one of claims 19 to 21 , including a data processing device for categorising the grain according to the intensity of the detected light.

23. An instrument according to claim 19, wherein the data processing device is arranged to collect and process light intensity measurements for a plurality of grains, and to provide a bulk grain analysis based on those measurements.

24. An instrument according to any one of claims 19 to 23, wherein the sample holder (10) has multiple compartments (12), each for receiving an individual grain, and drive means (18) for moving each of those compartments in turn into a testing device (24) for analysis of the grains.

25. An instrument according to claim 24, including a carousel-type sample holder (10).

26. An instrument according to any one of claims 19 to 25, wherein the light source (28) generates a light beam having a diameter of less than 2mm, and preferably approximately 1mm.

27. An instrument according to any one of claims 19 to 26, wherein the light source (28) is a laser.

28. An instrument according to any one of claims 19 to 27, wherein the light has a wavelength in the range 620-690nm.

29. An instrument according to any one of claims 19 to 28, wherein the aperture of the light detector (32) is greater than the diameter of the light beam incident on the grains.

30. An instrument according to any one of claims 19 to 29, wherein the diameter of the light detector (32) is in the range 2mm to 20mm, and is preferably approximately 5mm.

31. An instrument according to any one of claims 19 to 30, for use in monitoring the internal structure of grains.

32. An instrument according to claim 31 , for use in monitoring the internal structure of grain endosperm.

33. An instrument according to claim 32, for use in monitoring the internal structure of barley endosperm.

34. An instrument according to claim 33, for use in monitoring the internal structure of malted barley endosperm.

35. An instrument according to claim 34, for use in connection with a brewing operation.