Journal of Food Engineering 70 (2005) 165–170
www.elsevier.com/locate/jfoodeng
Cutting forces in foods: experimental measurements
Tim Brown *, Stephen J. James, Graham L. Purnell
FRPERC, University of Bristol, Churchill Building, Langford, North Somerset BS40 5DU, UK
Received 26 May 2004; accepted 20 September 2004
Abstract
Investigations into parameters affecting cutting forces in foods were undertaken to identify basic trends such as the relationship
of cutting forces to cutting speeds and food temperatures. A simple plain blade was used to cut three typical foodstuffs (cheese,
bacon and beef) at three feed speeds and three temperatures. After each cut the blade was passed through the product a second time
to measure forces indicative of friction on the sides of the blade.
Cutting forces for cheese decreased with increasing temperature and increased with cutting speed. The relatively homogeneous
nature of the samples resulted in consistent and repeatable measurements. For bacon, variable salt content gave rise to different ice
contents and thus hardnesses in samples at the same ÔfrozenÕ temperatures. Layers of fat and muscle boundaries also produced
marked deviations from the average forces. Force results were therefore scattered but increased with decreasing temperature.
The effect of cutting speed was not consistent for all forces, but higher speeds generally produced higher forces. For beef, there
was a marked difference between frozen and unfrozen samples but little difference between samples at different unfrozen temperatures. In unfrozen samples, cutting speed had little effect on forces, whereas faster cutting speeds produced higher forces in frozen
samples. The proportion of total cutting forces made up by friction was found to be consistent over all temperatures and speeds for
cheese and bacon, but markedly higher in the frozen beef samples compared to the unfrozen samples.
2004 Elsevier Ltd. All rights reserved.
Keywords: Cutting force; Friction; Cutting speed; Temperature; Food
1. Introduction
The design and operation of food cutting equipment
and associated processes such as tempering to achieve
suitable physical properties have traditionally been
based on adaptations of systems used for processing
materials such as metal or wood (Brown, James, Purnell,
& Swain, 2000). Developments have been empirical and
in an environment of commercial competitiveness, the
sharing and publication of knowledge and fundamental
science has been limited. In the meat industry, cutting is
*
Corresponding author. Tel.: +44 117 928 9239; fax: +44 117 928
9314.
E-mail address: tim.brown@bris.ac.uk (T. Brown).
0260-8774/$ - see front matter 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jfoodeng.2004.09.022
known to have a direct effect on profitability. Cevger,
Sariozkan, & Guler (2003) showed that cutting broilers
into joints could increase the profits of a poultry plant
by up to 15.6% and there was an improvement of almost
2% when manual cutting was replaced by a machine
operation.
Literature searches for information on cutting forces,
which could be used for design or optimisation, have revealed few published data. As stated by McGorry,
Dowd, & Dempsey (2003), even for hand cutting operations ÔThe force exposure associated with meat cutting
operations and the effect of knife sharpness on performance and productivity have not been well documentedÕ. The same authors developed specialised
hardware which allowed them to measure peak cutting
moments of up to 17.2 Nm in manual lamb shoulder
boning.
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T. Brown et al. / Journal of Food Engineering 70 (2005) 165–170
To develop optimal cutting and slicing systems, data
are required on cutting forces for different food types
and how they vary with such factors as cutting temperature, speed, type of cutting device e.g. blade profile and
edge angle. King (1999) measured the forces, and hence
fracture energies, required to cut frozen meat. A knife
oscillating in a slicing action was used to cut horse M.
semimembranosus and M. longissimus dorsi over a range
of temperatures ( 1.5 C to 30 C) and vibration frequencies (0–1000 Hz). The blade required less force to
cut when slicing than when not slicing; the decrease in
force was proportional to the velocity of the slicing motion. These data can be applied to cutting and dicing
operations with frozen meat. However, many meat
cutting operations take place at temperatures above
the initial freezing point of 1.5 C.
Cheese, bacon and beef are three common foods that
are cut and sliced at many times from production to
consumption. This paper details the construction of a
simple apparatus for cutting force measurement and
presents cutting force data for cheese, bacon and beef.
The temperatures investigated cover most of the range
of interest for industrial processing.
Fig. 1. Schematic of product, holders, blade and cut path.
2. Materials and methods
chamber, positioned and immediately cut to minimise
any temperature gain. The centre temperatures of three
samples in each test group (food–temperature–speed
combination) were measured before and after cutting
and friction force measurement using a handheld temperature probe (T2006, Digitron) to check that no
appreciable sample warming had occurred.
2.1. Food products
2.3. Equipment
Three products were selected for the measurements:
• cheese (mature cheddar sourced from a single local
manufacturer),
• beef (cut from lean muscles from topside primals
sourced from an on-site abattoir),
• bacon (cut from back joints sourced from a single
commercial supplier).
2.2. Sample preparation and fixturing
Samples of each product were band-sawed or manually cut to fit into rectangular section plastic holders of
inside dimensions 110 mm long · 50 mm wide · 48 mm
high. The holders fitted tightly into a slightly larger,
rectangular supporting socket mounted on a support fixture. Narrow slots in the sides of the socket and holder
allowed the passage of the blade for the trials (Fig. 1).
This method of fixturing provided both restraint for
the samples and ensured that they had repeatable
dimensions to an accuracy of approximately ±1 mm.
Once cut to size and placed in holders, all the samples
were wrapped to avoid moisture loss and conditioned to
their required cutting temperatures in a refrigerated
chamber adjacent to the experimental cutting rig.
For each cutting trial, a sample was removed from the
The cutting tool (Stanley heavy duty trimming blade
type 1992) was held in a non-retractable knife handle,
modified slightly to allow rigid attachment to an instrumented support plate. The support plate was mounted
on a horizontal traverse platform driven by a ballscrew
rotated at controlled speeds by an electric motor
(M42004-01A-200, AEG). This allowed fixed and
repeatable speeds of cutting. For each parameter combination, a new blade was chosen at random from a single
batch of blades to minimise blunting from repeated
cutting.
The relative positions of the product holders and the
blade were set to give a constant cut depth of 16 mm vertically into the sample, i.e. not through the full thickness
of the sample. This resulted in a cut area of 16 mm deep
by 50 mm long = 800 mm2. Cutter position was recorded
using the output from a draw-wire sensor (WDS-1000P60-CR-P, Micro Epsilon).
The edge of the blade was orientated at 45 to the
feed direction (Fig. 1) to minimise any build-up of force
before the blade entered the sample, and give a more
Ôsteady-stateÕ cutting force through the sample. This resulted in horizontal and vertical force components,
which were measured through the instrumented support
plate using a configuration of four strain gauges. The
strain gauge signals were conditioned (2120A, 2110B,
Measurements Group Inc.) and recorded at a frequency
T. Brown et al. / Journal of Food Engineering 70 (2005) 165–170
of approximately 100 Hz using PC-based logging software developed in-house for the trials.
2.5. Data measured and its interpretation
For all parameter combinations, six replicate cuts
were made. After each cut, the sample was removed
and the blade returned to its start position. The sample
was then replaced for a second traverse of the blade to
measure forces attributable to friction between the side
of the blade and the sample.
The recorded force data during the cutting and the
friction traverses were plotted and analysed for maximum and average horizontal and vertical forces for
the duration of the Ôsteady-stateÕ cutting, i.e. when the
blade was fully inserted to its intended depth (16 mm).
The horizontal and vertical force data were then processed to give the ÔtotalÕ resultant forces (the square root
of the sum of squares for horizontal and vertical forces).
The data were statistically analysed using Analysis of
Variance to test for the significance of parameter effects
at the 5% probability level (P < 0.05).
3. Results
3.1. Raw data profiles
The force profiles of a typical set of replicate measurements (horizontal cutting forces in cheese in this
case) are shown in Fig. 2. The forces ramped up as the
blade entered the product (with its cutting edge at 45
to the edge of the sample), levelled out during fully
developed cutting where the cut depth was constant,
and finally ramped down as the blade left the sample.
Friction forces generally exhibited profiles which
were very similar in shape to those for cutting forces
but lower in magnitude.
In the example shown there was good repeatability,
due to the fairly homogeneous nature of cheese. For
the less homogeneous meat tissues in bacon and beef,
Cutting Force (N)
Three cutting speeds typifying the relatively low
speeds found in manual and slow machine cutting were
used for each set of trials (30 mm s 1, 100 mm s 1 and
250 mm s 1).
Product temperatures of 5 C, +5 C and +15 C
were selected for cheese and beef. For bacon, cutting
at higher temperatures proved difficult due to deformation of the samples, so lower temperatures at which
more ice was present in the meat were used ( 15 C,
10 C and 5 C). These are closer to the ÔtemperedÕ
conditions used for bacon slicing (Brown, Gigiel, Swain,
& James, 2003; James & James, 2002).
30
20
10
0
510
530
550
570
590
-10
Position (mm)
Fig. 2. Horizontal cutting forces for cheese at 15 C and 30 mm s 1.
30
Cutting Force (N)
2.4. Experimental conditions
167
20
10
0
510
530
550
570
590
-10
Position (mm)
Fig. 3. Horizontal cutting forces for beef at 5 C and 30 mm s 1.
greater variability and irregularity was found, as shown
in Fig. 3.
3.2. Maximum and average forces
The mean and standard deviation values of forces
from the replicate cutting traverses at each parameter
combination are shown for the three products in Tables
1–3, together with derived resultant forces (the square
root of the sum of squares of horizontal and vertical).
As the proportion of the total cutting forces made up
by friction was found to be relatively constant for each
product, friction forces are expressed as averaged percentages of the total cutting forces to avoid excessive
data presentation.
The statistical analysis confirmed that for all three of
the products, the effect of sample temperature on horizontal, vertical and resultant forces was significant.
Cheese and bacon exhibited the expected trend that
lower temperatures produced higher cutting forces.
The temperatures used for beef included one below the
initial freezing point, and this produced far higher forces
than those above the initial freezing point.
However, the effect of cutting speed was more variable. For cheese, its effect was significant for all forces.
Forces increased with cutting speed as would be expected. For beef and bacon, only its effect on the maximum and average horizontal forces, and the average
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T. Brown et al. / Journal of Food Engineering 70 (2005) 165–170
Table 1
Cutting forces measured in cheese
Temp. (C)
Speed (mm/s)
Horizontal force (N)
Maximum
5
5
15
30
100
250
30
100
250
30
100
250
Vertical force (N)
Average
Maximum
Resultant force (N)
Average
Maximum
Average
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
39.8
55.3
61.2
26.7
34.8
43.2
15.7
22.3
26.8
4.4
5.0
4.5
6.3
2.6
4.8
1.2
2.9
4.5
30.9
45.6
54.6
21.4
29.8
36.6
12.6
18.3
23.9
5.7
2.6
2.5
5.6
2.7
3.8
1.0
2.6
2.3
9.5
9.5
11.2
5.3
5.8
7.3
3.8
4.0
5.2
1.6
1.0
2.5
1.8
1.2
2.3
0.8
0.9
2.4
6.5
6.5
9.1
2.6
3.7
5.0
1.5
1.3
2.2
1.4
1.2
2.5
1.7
1.1
2.4
0.6
1.2
1.0
41.0
56.2
62.2
27.2
35.3
43.8
16.1
22.7
27.4
4.1
4.8
4.8
6.3
2.5
4.9
1.2
2.9
4.7
31.6
46.0
55.4
21.6
30.0
37.0
12.7
18.3
24.0
5.6
2.4
2.7
5.7
2.7
3.9
1.0
2.6
2.3
Table 2
Cutting forces measured in beef
Temp. (C)
5
5
15
Speed (mm/s)
30
100
250
30
100
250
30
100
250
Horizontal force (N)
Vertical force (N)
Resultant force (N)
Maximum
Average
Maximum
Average
Maximum
Average
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
121.8
156.3
170.3
21.7
15.8
19.8
21.2
17.8
15.0
10.8
13.3
31.5
5.1
9.2
4.1
6.4
6.2
4.3
111.8
148.1
155.7
14.3
11.5
14.1
13.8
13.1
12.6
9.7
14.9
27.9
3.3
6.2
1.1
3.2
4.1
2.2
61.3
83.5
77.3
19.5
13.7
13.3
18.5
17.3
15.7
13.8
40.8
13.1
5.0
7.8
3.3
7.2
9.5
9.9
53.8
64.5
56.8
11.1
8.0
9.9
11.5
10.6
11.5
13.7
39.1
18.2
2.7
3.7
2.0
3.0
3.9
6.6
137.1
179.6
187.5
29.2
21.0
24.0
28.2
24.9
22.4
9.0
28.6
30.9
6.9
12.0
5.0
9.4
10.9
9.0
124.8
164.3
167.0
18.1
14.0
17.2
18.0
16.9
17.5
8.7
25.4
24.2
4.2
7.1
1.9
4.2
5.5
5.4
Table 3
Cutting forces measured in bacon
Temp. (C)
15
10
5
Speed (mm/s)
30
100
250
30
100
250
30
100
250
Horizontal force (N)
Vertical force (N)
Resultant force (N)
Maximum
Average
Maximum
Average
Maximum
Average
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
77.0
82.3
88.7
30.7
34.5
52.2
20.3
12.5
16.5
13.8
8.1
19.7
7.1
11.7
12.3
8.5
5.4
4.1
62.3
64.2
74.4
22.4
27.7
43.7
12.4
8.8
13.1
9.2
5.0
17.6
4.8
11.8
10.8
3.3
4.6
4.8
50.0
50.3
44.2
22.2
29.0
38.7
14.8
10.8
14.2
12.2
20.2
13.3
4.4
13.6
13.8
6.6
1.2
1.6
39.4
37.0
37.2
16.6
22.9
31.8
9.7
9.1
11.5
12.1
16.8
11.9
3.2
10.2
9.8
4.3
0.9
2.7
92.8
97.2
99.6
38.0
45.2
65.4
25.3
16.8
21.9
9.8
16.4
20.7
7.6
17.5
16.4
10.3
4.5
3.6
74.6
75.1
83.8
27.9
36.0
54.3
16.0
12.9
17.6
7.1
9.4
18.2
5.4
15.2
13.2
4.6
3.9
4.7
resultant forces was significant. For the beef samples below the initial freezing point, the effect of cutting speed
was more marked than for those above the freezing
point, with the latter being similar in magnitude and
inconsistent in order.
There were also some significant interactions between
the effects of temperature and speed for cheese and beef
(for maximum and average horizontal and resultant cutting forces), but not for bacon.
To illustrate some of the trends in the data, the values
for the maximum resultant forces for the three products
are presented in Figs. 4–6, which include both cutting
and friction results.
Friction forces averaged 46% of the total cutting
forces for cheese, with this proportion being relatively
constant across all temperatures and speeds. For bacon,
the average was 43%. There was a marked difference between friction forces in the frozen and unfrozen beef
T. Brown et al. / Journal of Food Engineering 70 (2005) 165–170
Fig. 4. Maximum and average resultant cutting forces (total and friction) in cheese.
Fig. 5. Maximum and average resultant cutting forces (total and friction) in beef.
Fig. 6. Maximum and average resultant cutting forces (total and friction) in bacon.
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T. Brown et al. / Journal of Food Engineering 70 (2005) 165–170
samples, with the frozen values averaging 28% and the
unfrozen only 23%, both considerably lower than the
other products.
4. Discussion
In general, the data for the three products followed
expected trends. Decreasing temperature produced
higher cutting and friction forces. In the case of cheese,
the relationship between forces at the different temperatures was substantially linear. Where freezing was introduced for one set of samples of beef, significantly higher
forces resulted. Freezing to some degree was present in
all of the bacon samples, and this was reflected by another linear relationship.
Increased cutting speeds generally resulted in higher
forces, except in the case of the unfrozen beef samples
where forces remained similar. However, an attempt at
repetition with bacon at temperatures in the chilled
range resulted in bunching up of the material rather
than cutting, with subsequent failure of the blades.
The relatively homogeneous nature of cheese resulted
in steady, repeatable force plateaus during cutting. The
variable physical and chemical composition of the beef
and bacon samples produced less steady and more variable forces. Although care was taken to cut the samples
from lean areas of original material, the samples contained different amounts of fat and occasional muscle
boundaries and connective tissue. Cutting through such
boundaries resulted in pronounced maximum forces. In
the case of bacon, additional variability most probably
resulted from differences in salt and moisture content
introduced during the curing process. Such differences
give rise to varying amounts of ice at any given Ôsemi-frozenÕ temperature, and consequently variable hardness.
Further sources of variability other than those inherent in the products may have impacted on the results.
The method of product fixturing imposed more control
than is usually present in commercial cutting operations,
but nevertheless still allowed some movement and in the
case of some chilled samples, bunching up of material.
Blunting of the blades was not evident in the cheese
and bacon trials, but could have played a part in producing some of the variability in the beef trials, particularly where large forces were produced in cutting frozen
samples.
The method used to indicate the proportion of force
due to friction produced consistent results over all temperatures and speeds for cheese and bacon. For beef
however, friction forces in the frozen samples were proportionately higher than those in the chilled samples.
This could be attributed to the greater rigidity of the
material exerting a stronger ÔclampingÕ effect on the
blade.
For the faster cutting speeds, the relatively slow logging rate meant that the numbers of data points captured during traverse of the fairly short cut path were
limited. To better characterise cutting force profiles with
peaks and troughs such as those found for beef and bacon, these trials re-affirmed the need for rapid data capture and ideally larger samples to allow greater length of
cut path. The use of systems capable of measuring and
recording at frequencies up to 1000 Hz has subsequently
been adopted.
5. Conclusions
The cutting trials generally confirmed expected
trends, such as increased forces resulting from higher
speeds and lower temperatures. They also revealed
sources of variability due to inherent product characteristics and movement and distortion of samples.
Although some reduction in blade sharpness most probably occurred during cutting of the six replicates in each
sample set, its effects were not readily apparent as a progressive increase in forces.
The introduction of much more rapid data capture,
improved product fixturing and use of larger samples
for future trials will help to minimise or better capture
the effects of such sources.
Acknowledgement
The authors would like to thank DEFRA for supporting this work under the Advanced Food Manufacturing LINK scheme.
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