PaddyCheck: An Instrument for Rice Quality Determination

instruments
Article
PaddyCheck—An Instrument for Rice
Quality Determination
Jeanette Purhagen1 ID, Raivo Loosme1, Nils Wihlborg1, Jenny Fjällström2,*, Peter Åberg2,
Henrik Andrén1, Gunnel Wihlborg1, Torbjörn Mikaelsson2, Martin Lagerholm2 ID
and Frans Lindwall2
1 Perten Instruments AB, Garnisonsgatan 7A, SE-254 66 Helsingborg, Sweden;
[e-mail] (J.P.); [e-mail] (R.L.); [e-mail] (N.W.);
[e-mail] (H.A.); [e-mail] (G.W.)2 Perten Instruments AB, P.O. Box 9006, SE-129-09 Hägersten, Sweden; [e-mail] (P.A.);
[e-mail] (T.M.); [e-mail] (M.L.); [e-mail] (F.L.)
* Correspondence: [e-mail]; Tel.: [phone]
Received: 26 April 2018; Accepted: 2 July 2018; Published: 3 July 2018
Abstract:Severalof the rice quality parameters are nowadays determined manually or partly
manually, which leads to subjective results. In order to analyse the rice quality and avoid most of the
manual handling, the PaddyCheck instrument was mainly developed to measure the paddy/rough
rice kernels.However,the design and technique of the instrument are also suitable for brown
rice kernels.The PaddyCheck instrument measures the physical properties of the rice kernels as
well as texture properties and translucency.Initial calibrations have been developed to correlate
these properties with the Head Rice Yield and Chalkiness, which are two of the most common and
important quality parameters for rice.
Keywords: paddy rice; HRY; rice quality
1. Introduction
Rice is the 3rd most produced grain in the world [1]. The three largest producers are China
with 28% of the total rice production, India with 22% and Indonesia with 10% [2]. From the global
rice production, 80% is used for food, while 3.5% is used for feed [2]. Therefore, it is of immense
interest to have good quality control methods for the rice.The quality of rice is determined by the
physical, physicochemical and the functional properties. These properties include the variety, kernel
size and size homogeneity, aroma, panicles properties, shape type, head rice yield (HRY), chalkiness
and cooking properties (gelatinization, retrogradation, stickiness etc.).Several of these properties
require manual evaluations, which can affect the objectivity and will differ between different evaluators
worldwide [3,4].
Since some of these properties, such as HRY, can be directly related to the value that the crop will
have for the miller, a quick and objective quality control determination is needed that can be performed
directly on paddy kernels in more facilities and closer to the farmers.Nowadays, samples are sent
away to different reference labs to be test-milled, which can result in the farmer waiting 4–5 days to
obtain the results.The ISO 6646:2011 standard method used for the HRY determination procedure
consists of several subjective, manual and time-consuming steps, including preparations, de-husking
and milling, before the HRY can be calculated [5].
Severalfactors affect the HRY measurement.Cracking and fissures can appear before and
during harvest, during storage and during the drying process, which results in kernel breakage [6,7].
Instruments 2018, 2, 11; doi:10.3390/instruments2030011 www.mdpi.com/journal/instruments

Instruments 2018, 2, 11 2 of 10
Furthermore,the degree of milling,handling procedures,harvest moisture and moisture content,
immature kernels, diseases, chalkiness and mixture of slender type influences the HRY [8–14].
The quality parameter chalkiness, which is also called white belly, is a measurement of the opacity
of the endosperm, which can reduce the hardness of the kernels [15,16]. Chalkiness can occupy >50%
of the kernel area and can be caused by both varietal and environmental factors, such as the packing
degree and morphology of the starch granules, high temperature, insufficient nutrition supply and the
durability of the ripening [17–20]. Traditionally, chalkiness was measured manually, although the use
of image analysis methods has been very convenient and are now commonly used [21,22].
The aim of and motivation behind the development of the first PaddyCheck instrument was to
develop a portable instrument that can measure physical properties, crack resistance and translucency
of paddy rice samples in a fast, objective and easy way. The measurement of the physical properties
would provide information about the length and shape (i.e., the ratio between the length and the
width), which is an important characteristic for determining quality [4]. Lu and Siebenmorgen [23]
found a good correlation between the HRY and compression force,which shows that the texture
measurement can be used in the determination of the HRY.The crack resistance uses the texture
measurement to determine the break resistance with a force up to 17 N of each kernel in the sample.
Chalky kernels have higher opacity than non-chalky kernels and by measuring the translucency of the
kernels, the chalkiness of the kernels might be determined. Fang et al. [24] showed that multiple rice
quality parameters, such as size, HRY and chalkiness, could be determined by using image analysis
on the milled rice. However, since the degree of milling affects the HRY [8], it would be preferable to
measure the paddy rice directly.Thus, an instrument that combines texture measurements, colour,
size and shape as well as translucency of the kernels with limited manual handling and preparations
of the samples would have a great potential for measuring the quality of rice kernels.Today rice is
typically analysed as brown rice or milled rice with scanner type of instruments. The PaddyCheck is
the first instrument to analyse the paddy rice and to determine the main quality parameters for the
paddy rice trade.
2. Materials and Methods
The PaddyCheck instrument (Figure 1) is designed to be used for both paddy/rough rice
kernels and brown rice kernels.Kernels of both Indica and Japonica rice have been used during
the development, while the size dimensions of the paddy and brown rice used during the development
are shown in Table 1.The operator pours the kernels manually into the instrument and there are a
range of discs with different cavity sizes for different sorts of rice.
Instruments 2018, 3, x FOR PEER REVIEW 2 of 10
The quality parameter chalkiness, which is also called white belly, is a measurement of the opacity
of the endosperm, which can reduce the hardness of the kernels [15,16]. Chalkiness can occupy >50% of
the kernel area and can be caused by both varietal and environmental factors, such as the packing
degree and morphology of the starch granules, high temperature, insufficient nutrition supply and the
durability of the ripening [17–20]. Traditionally, chalkiness was measured manually, although the
use of image analysis methods has been very convenient and are now commonly used [21,22].
The aim of and motivation behind the development of the first PaddyCheck instrument was to
develop a portable instrument that can measure physical properties, crack resistance and
translucency of paddy rice samples in a fast, objective and easy way. The measurement of the physical
properties would provide information about the length and shape (i.e., the ratio between the length
and the width), which is an important characteristic for determining quality [4]. Lu and
Siebenmorgen [23] found a good correlation between the HRY and compression force, which shows
that the texture measurement can be used in the determination of the HRY. The crack resistance uses
the texture measurement to determine the break resistance with a force up to 17 N of each kernel in
the sample. Chalky kernels have higher opacity than non-chalky kernels and by measuring the
translucency of the kernels, the chalkiness of the kernels might be determined. Fang et al. [24] showed
that multiple rice quality parameters, such as size, HRY and chalkiness, could be determined by using
image analysis on the milled rice. However, since the degree of milling affects the HRY [8], it would
be preferable to measure the paddy rice directly. Thus, an instrument that combines texture
measurements, colour, size and shape as well as translucency of the kernels with limited manual
handling and preparations of the samples would have a great potential for measuring the quality of
rice kernels. Today rice is typically analysed as brown rice or milled rice with scanner type of
instruments. The PaddyCheck is the first instrument to analyse the paddy rice and to determine the
main quality parameters for the paddy rice trade.
2. Materials and Methods
The PaddyCheck instrument (Figure 1) is designed to be used for both paddy/rough rice kernels
and brown rice kernels. Kernels of both Indica and Japonica rice have been used during the
development, while the size dimensions of the paddy and brown rice used during the development
are shown in Table 1. The operator pours the kernels manually into the instrument and there are a
range of discs with different cavity sizes for different sorts of rice.
Figure 1. The PaddyCheck Instrument.
Figure 1. The PaddyCheck Instrument.

Instruments 2018, 2, 11 3 of 10
Table 1. Size dimensions of paddy and brown rice used.
Length Width Thickness
Paddy/Rough 6–11 mm 1–3.4 mm 1–3.4 mm
Brown 5–9 mm 1–3.3 mm 1–3.3 mm
2.1. Mechanics
The PaddyCheck instrument is designed to be a standalone instrument. It has a built-in chargeable
battery and is equipped with a touchscreen, on which the test profiles are selected.The calibration
values and results are displayed in Figure 2. In addition, the instrument also has USB-ports to be used
for saving and processing raw data; and for connecting barcode readers or keyboards.
Instruments 2018, 3, x FOR PEER REVIEW 3 of 10
Table 1. Size dimensions of paddy and brown rice used.
Length Width Thickness
Paddy/Rough 6–11 mm 1–3.4 mm 1–3.4 mm
Brown 5–9 mm 1–3.3 mm 1–3.3 mm
2.1. Mechanics
The PaddyCheck instrument is designed to be a standalone instrument. It has a built-in chargeable
battery and is equipped with a touchscreen, on which the test profiles are selected. The calibration values
and results are displayed in Figure 2. In addition, the instrument also has USB-ports to be used for saving
and processing raw data; and for connecting barcode readers or keyboards.
(a) (b) (c)
Figure 2. Touchscreen with selectable menus and displays. (a) Settings to define before analysis; (b)
Settings to calibrate the load cell; (c) The results.
2.2. Singulation
The instrument measures each kernel of the sample separately. The kernels are separated and
transported by a disc containing cavities to fit single rice kernels (Figure 3). Each disc has a specific
cavity size and the selection of disc can be optimized for the kernel size, which thus enhances the
analysis of the kernels. By choosing a suitable disc for the sample, the camera functions will be
improved as fewer kernels become stuck in the cavities and double kernels can be avoid. Four metal
scrapes are used to brush the singulation disc to get the kernel into the cavity in a correct position. If
the kernel sticks out from the cavity, the scrapes either swipes the kernel into the cavity or the kernel
will be removed by the scrapes and end up with the rest of the kernels to be measured. After the
measurements of a kernel are obtained, a small ejector pushes the used kernel out of the cavity, so it
ends up in the collecting tray (Figure 4).
Figure 3. Singulation disc with cavity size of 11 × 3.5 mm.
Figure 2.Touchscreen with selectable menus and displays.(a) Settings to define before analysis;
(b) Settings to calibrate the load cell; (c) The results.
2.2. Singulation
The instrument measures each kernel of the sample separately.The kernels are separated and
transported by a disc containing cavities to fit single rice kernels (Figure 3). Each disc has a specific
cavity size and the selection of disc can be optimized for the kernel size, which thus enhances the
analysis of the kernels.By choosing a suitable disc for the sample,the camera functions will be
improved as fewer kernels become stuck in the cavities and double kernels can be avoid. Four metal
scrapes are used to brush the singulation disc to get the kernel into the cavity in a correct position.
If the kernel sticks out from the cavity, the scrapes either swipes the kernel into the cavity or the kernel
will be removed by the scrapes and end up with the rest of the kernels to be measured.After the
measurements of a kernel are obtained, a small ejector pushes the used kernel out of the cavity, so it
ends up in the collecting tray (Figure 4).
Instruments 2018, 3, x FOR PEER REVIEW 3 of 10
Table 1. Size dimensions of paddy and brown rice used.
Length Width Thickness
Paddy/Rough 6–11 mm 1–3.4 mm 1–3.4 mm
Brown 5–9 mm 1–3.3 mm 1–3.3 mm
2.1. Mechanics
The PaddyCheck instrument is designed to be a standalone instrument. It has a built-in chargeable
battery and is equipped with a touchscreen, on which the test profiles are selected. The calibration values
and results are displayed in Figure 2. In addition, the instrument also has USB-ports to be used for saving
and processing raw data; and for connecting barcode readers or keyboards.
(a) (b) (c)
Figure 2. Touchscreen with selectable menus and displays. (a) Settings to define before analysis; (b)
Settings to calibrate the load cell; (c) The results.
2.2. Singulation
The instrument measures each kernel of the sample separately. The kernels are separated and
transported by a disc containing cavities to fit single rice kernels (Figure 3). Each disc has a specific
cavity size and the selection of disc can be optimized for the kernel size, which thus enhances the
analysis of the kernels. By choosing a suitable disc for the sample, the camera functions will be
improved as fewer kernels become stuck in the cavities and double kernels can be avoid. Four metal
scrapes are used to brush the singulation disc to get the kernel into the cavity in a correct position. If
the kernel sticks out from the cavity, the scrapes either swipes the kernel into the cavity or the kernel
will be removed by the scrapes and end up with the rest of the kernels to be measured. After the
measurements of a kernel are obtained, a small ejector pushes the used kernel out of the cavity, so it
ends up in the collecting tray (Figure 4).
Figure 3. Singulation disc with cavity size of 11 × 3.5 mm. Figure 3. Singulation disc with cavity size of 11×3.5 mm.