GB2098725A

GB2098725A - Measurement of food material properties

Info

Publication number: GB2098725A
Application number: GB8111841A
Authority: GB
Original assignee: United Biscuits Ltd; United Biscuits UK Ltd
Current assignee: United Biscuits Ltd; United Biscuits UK Ltd
Priority date: 1981-04-14
Filing date: 1981-04-14
Publication date: 1982-11-24

Abstract

A method and apparatus for on- line measurement of food material parameters provides for comparison of radiated and reflected visible or near infrared radiation and the derivation from the measured wavelengths of a measure of the or each food parameter. Biscuits travel on a conveyor (2) under a test head (5) comprising LED's or other radiation sources (8) and focussing lenses (10) which direct radiation at different specific wavelengths each associated with a selected parameter on the biscuits (4), a part of each projected radiation passing via beam splitters (9) to a first detector (11) which produces outputs representative of the radiated radiations. A focussing means (14) and second detector (12) receives the diffusely reflected radiations and produces sequential outputs representative of them. Sequential comparison of the associated incident and reflected radiations enables each food parameter to be monitored in turn. The reflected radiation at two wavelengths is compared for each parameter. <IMAGE>

Description

SPECIFICATION Measurement of food material properties The invention relates to the measurement of the properties of food materials by means of radiation reflected therefrom.

In the monitoring and control of food maufacturing processes there is a need for measurement of properties or parameters such as colour and moisture content of food materials, as they are being processed. Continuous or very frequent on-line measurements of such parameters allows any divergence from pre-established values to be quickly detected and corrected by adjustment of the material mix or of manufacturing conditions such as temperature and humidity. However, on-line measurements must be made under adverse circumstances which discourages the use of the more sensitivetechni- ques available.

The invention accordingly provides a method of and apparatus for on-line measurement of at least one parameter of a food material, in which a comparison is made of modulated infrared radiation directed onto and reflected from the material at at least two wavelengths to derive a measure of the parameter.

By projecting the radiation in modulated form, for example, in repeated short frequency modulated pulses, the measurement can be rendered effectively independent of ambient radiation, and by use of solid state radiation sources in the form of light emitting diodes (LEDs), or lasers, each providing radiation at a stable predetermined wavelength, the parts of the apparatus in proximity to the material can be rendered simple and robust. The wavelengths selected for each parameter to be measured are such as to afford a significant and reliable measure of the parameter, and are located in the visible wavelength range (for colour measurement) and preferably otherwise in the near infrared range, of about 0.4 lim to 2.5 lim.

For the measurement of, say, four parameters, for example, colour, moisture content, fat content and sugar content, eight LEDs can be grouped together, and the radiation they supply reflected from the food material to be received by single detector. The detector output can be associated with the respective L.E.D. sources by energizing the latter in successive pulses of oscillation at a predetermined frequency, of, say, a few hundred kHz, and sampling the output during the duration of each pulse through a band pass filter, or by modulating the sources, continuously energized, at different frequencies and applying the detector output to appropriate bandpass filters to obtain separate outputs due to each source.The food material, can be an undivided mass, such a dough, cream or chocolate, or an unfinished, partially finished orfinished divided product, for example, uncooked, or partly or completely cooked biscuts.

The invention makes it possible to provide for the sensitive and reliable measurement of desired parameters, with nearly total, immunity from the effects of ambient illumination, at a wide variety of factory locations for example over conveyors or storage vessels.

The invention is further described below, by way of example, with reference to the accompanying drawing, in which the single figure is a side view of an illustrative apparatus embodying the invention, shown schematically with circuitry in block diagram form.

The illustrated apparatus is shown located above a conveyor 2 on which biscuits 4 are being carried, at a processing stage at which certain properties of the biscuits are to be measured. The apparatus comprises a test head 5 comprising a housing 6 containing four sources 8 of radiation of different wavelength, each source being conveniently constituted by a solid state device, a light emitting diode (LED) capable of providing an output of which the intensity is quite closely concentrated around a single wavelength selected in accordance with the parameter to be measured. Although four of the sources 8 are shown, any plural number can be provided depending on the number of parameters to be dealt with by the apparatus. The sources 8 can be arranged in any convenient pattern, the row of sources shown being merely illustrative.

The radiation from each source 8 goes through a beam splitter 9 and then through a focussing lens 10 in the wall of the housing 6 by which the radiation is closely focussed onto the biscuits 4 as they are carried past the test head 5. Within the housing 6 is a first radiation detector 11 positioned to receive radiation from the beam splitters 9.

Radiation reflected from the biscuits is collected, by focussing means 14 in the wall of the housing 6, from a fairly large area around the common point at which radiation from all the sources 8 impinges, and the focussed radiation directed to a second detector 12 in the housing 6. The second detector 12 thus reliably receives radiation from the sources 8 in spite of irregularities of the surface of the biscuits and minor variations in thickness. The test head 5 is arranged so that the second detector 12 receives only diffuse reflection, receipt of specular reflection being prevented.

To avoid the adverse effects of the ambient illumination inevitably present in on-line situations such as that illustrated, the souces 8 are not continuously energised, but are arranged to provide radiation successively, in pulses of oscillation at a predetermined frequency. This is achieved by supplying an energising voltage from an oscillation source 15 to each of the sources 8 through a respective one of four gates 16, the gates being enabled in turn by signals from a sequencing device 18.

The outputs of the detectors 11,12 are sampled and held by respective devices 19,20 which act as input devices to an interface unit 21. The interface unit 21 also receives an input from the sequencing device 18 to enable the detector outputs to be sampled at times appropriate to the periods during which the sources 8 are energized and to enable the sampled outputs to be associated with the respective energized source.

The sampled detector outputs are supplied by the interface unit 21 to a microprocessor 22 in which the attenuation of the radiation due to reflection from a biscuit 4 is measured by comparison of the two outputs. The sources 8 are selected to emit radiation of wavelengths appropriate to the various parameters of the biscuits which are to be measured and the microprocessor 22 includes a memory device in which is stored information by which the reflectance at each wavelength is calulated, and appropriate compensation made for such factors as atmospheric dust and ambient temperature effects and also for measurement made in gaps between the biscuits.

The microprocessor 22 provides outputs on lines 24,25 to recording display and control equipment, as may be required.

The illustrated apparatus can be modified in various ways within the scope of the invention, for example, as to the number of pairs of radiation sources. The sources can be energized continuously and modulated at different frequencies, the detector outputs being separated by bandpass filters, so that measuements are made continuously and treated in parallel, and continuous microprocessor outputs provided.

CLAIMS (Filed 14April 1982) 1. A method of on-line measurement of at least one parameter of a food material, in which a comparison is made of modulated infrared radiation directed on to and reflected from the material at least at two wavelengths, in order to derive a measure of the or each parameter.

2. A method according to claim 1, in which the radiation is projected on to the food material in repeated short-frequency modulated pulses.

3. A method according to claim 1 or 2, in which a solid-state radiation source is used.

4. A method according to any preceding claim, in which the projected radiation is selected from the visible wavelength range and the near infrared range.

5. A method according to any preceding claim, in which a single detector is associated with a plurality of radiation sources each arranged to monitor a selected food parameter.

6. A method according to claim 5, in which the respective radiation sources are energized successively and the output of the detector is sampled via a band-pass filter in order to provide a measure of each respective parameter.

7. A method according to claim 5, in which the respective radiation sources are energized continuously while undergoing modulation at specific different frequencies and the detector output is applied to separate band-pass filters each associated with a respective parameter.

8. A method according to claim 1, substantially as described with reference to the accompanying drawings.

9. An apparatus for effecting on-line measurement of at least one parameter of a food material, which comprises at least one source of modulated infrared radiation positioned so as to project the radiation on to a region receiving or traversed by the food material, the radiation being at least at two wavelengths, a detector located so as to receive radiation reflected from the food material and means for comparing the radiated and reflected radiations so as to permit derivation of a measure of the or each parameter.

10. An apparatus according to claim 9, in which the or each radiation source is a solid-state device.

11. An apparatus according to claim 10, in which the or each radiation source is a light-emitting diode or a laser arranged to emit radiation at or around a selected wavelength selected in accordance with the associated food material parameter.

12. An apparatus according to claim 10, in which the or each radiation source is associated with a beam splitter and a focussing lens arranged to focus the projected radiation on the region and a first radiation detector is positioned as as to receive radiation from the or each beam splitter.

13. An apparatus according to claim 12, in which a focussing means is provided so as to receive radiation reflected from the food-receiving or traversed region and is arranged to direct such reflected radiation to a second radiation detector.

14. An apparatus according to claim 13, in which comparator means for measuring the wavelengths of the projected and reflected radiations are provided and are arranged to receive outputs derived from the first and second detectors.

15. An apparatus according to claim 9, substantially as described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. interface unit 21 to a microprocessor 22 in which the attenuation of the radiation due to reflection from a biscuit 4 is measured by comparison of the two outputs. The sources 8 are selected to emit radiation of wavelengths appropriate to the various parameters of the biscuits which are to be measured and the microprocessor 22 includes a memory device in which is stored information by which the reflectance at each wavelength is calulated, and appropriate compensation made for such factors as atmospheric dust and ambient temperature effects and also for measurement made in gaps between the biscuits. The microprocessor 22 provides outputs on lines 24,25 to recording display and control equipment, as may be required. The illustrated apparatus can be modified in various ways within the scope of the invention, for example, as to the number of pairs of radiation sources. The sources can be energized continuously and modulated at different frequencies, the detector outputs being separated by bandpass filters, so that measuements are made continuously and treated in parallel, and continuous microprocessor outputs provided. CLAIMS (Filed 14April 1982)

1. A method of on-line measurement of at least one parameter of a food material, in which a comparison is made of modulated infrared radiation directed on to and reflected from the material at least at two wavelengths, in order to derive a measure of the or each parameter.