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. 2020 Aug 20;58(6):2089–2097. doi: 10.1007/s13197-020-04718-6

Application of pulverization and thermal treatment to pigmented broken rice: insight into flour physical, functional and product forming properties

I Sapna 1, A Jayadeep 1,✉
PMCID: PMC8076387  PMID: 33967307

Abstract

The utilization of rice for food purposes involves pulverization and thermal processing which may affect its quality characteristics. Hence pigmented broken rice was processed in plate mill and hammer mill followed by thermal treatment by toasting to study the physical, and functional characteristics and their effect on rice noodle quality. Results showed that plate milled rice flour showed high concentration of particles with size below 148 µm particle (44%), increased redness (21%), bulk density (17%), sedimentation value (75%), damaged starch (72%), peak viscosity (17%), and caused microstructural changes compared to the hammer mill. The toasting of plate milled red and black rice flour caused an insignificant influence on particle size, color, and bulk density. However, it increased the sedimentation value to 134% and 94% and damaged starch by 44% and 19% in red and black rice flour respectively. Further, a reduction in peak viscosity (22%) in red, and increase (16%) in black, along with microstructural changes were also observed. The rice noodle prepared using plate milled, and toasted red rice flour was sensorily acceptable and exhibited excellent textural properties. The study showed that plate milling and thermal treatment significantly affect the quality characteristics of pigmented rice flour and end-product quality.

Electronic supplementary material

The online version of this article (10.1007/s13197-020-04718-6) contains supplementary material, which is available to authorized users.

Keywords: Black rice, Red rice, Broken rice, Plate mill, Thermal processing, Rice noodles

Introduction

Rice (Oryza sativa L.) is consumed by more than three billion people, with an annual production of approximately 680 million tons worldwide (Bodie et al. 2019). Rice varieties are available in different colors from white to purple. The utilization of rice for food purposes involves milling for de-husking the paddy and polishing to remove the bran. Broken rice is a by-product of rice milling, and depending on the milling techniques as high as 25% of rice broken is generated and has low economic value. There is a steady increase in the demand for rice flour, as it is gluten-free and hypoallergenic. Food industries prefer using rice flour over other flours in baby food, puddings and other food products. Hence utilizing broken rice for flour preparation become more economically justifiable (Bodie et al. 2019).

In recent times, pigmented rice varieties such as red, black, and purple rice, are receiving the attention of health-conscious consumers due to their nutritional and health beneficial properties. Pigmented rice varieties contain vitamins, minerals, fiber and bioactive components such as phenolics, oryzanol and vitamin E possessing various health beneficial properties such as antioxidant, anti-inflammatory, anti-atherosclerotic, anti-carcinogenic, anti-allergic and hypoglycaemic activities (Dinesh Babu et al. 2009; Deng et al. 2013). These cultivars are prone to higher breakage during milling compare to white variety with a total broken of 20–25% only. Broken rice generation during husk removal result in unpolished broken (8–15%) and further polishing lead to polished broken (10–15%). As the market for healthy foods has increased, the demand for brown rice has been growing due to its nutritional and health beneficial properties. Thus, value addition to the generated pigmented broken rice can result in the development of health foods. Different milling methods like a hammer, plate, pin, roller, burr milling, etc., are used in the preparation of rice flour. Further, traditional food preparation involves thermal processing of flour. Previous studies have shown the effect of milling and thermal treatment on the physicochemical and functional properties of rice (Nishita and Bean 1982; Tran et al. 2011; Ponnappan et al. 2017; Bruna et al. 2014, Pandey et al. 2016). However, information on the processing of pigmented broken rice is meagre. Hence the objective of this study is to investigate the effect of milling and thermal processing on physical, functional and product forming properties of broken unpolished(brown) rice from red and black rice varieties.

Materials and methods

Raw material

For studying the effect of processing on two different rice varieties, Paddy of Jyothi red rice (non-waxy), Burma black rice (waxy) was purchased from Agricultural Produce Marketing Corporation and local vender respectively in Mysore. Ready to use white rice flour used for preparing traditional foods was purchased from a supermarket in Mysore district, Karnataka, India.

Sample preparation

De-husking of paddy was done using centrifugal disc sheller (Kisan Krishi Yantra Udyog, Kanpur), followed by head and broken rice separation in a paddy separator. Pigmented broken rice, thus generated was used in sample preparation. For studying the effect of milling, broken red rice was milled using a hammer (Natraj atta maker 2011) and plate-mill (Madras standard plate mill) with three passes in each mill. Further thermal effect was studied by toasting plate-milled red and black rice flour at 90 °C to 100 °C for 30 min in an Uruli roaster (pilot Smith (India) Pvt. Ltd, Kerala, India, Model No. CD-10). Commercially available white rice flour used for the preparation of rice noodle was obtained from a local market. Flours were analyzed for physical, functional and product forming qualities.

Physical parameters

Flour color was measured by the color measuring system based on CIE L*,a*,b* scales (Konica Minolta Spectrophotometer CM5, Japan). L* is a measure of the brightness from black (0) to white (100). The alphabet a* describes red–green color with positive a* is redness, and negative a* is greenness. Alphabet b* represents the yellow-blue color with positive b* is yellowness and negative b* is blueness (Good 2002).

Particle size distribution was measured using Microtrac particle size and shape analyzer (Microtrac blue wave S3500, USA, 2013) with tri-laser diffraction.

The moisture content of the flour was analyzed by the oven drying method with a slight modification in temperature, which is at 130 °C for 2 h (Horwitz 2000).

The bulk density was measured according to the method described by Okaka and Potter (1977). A 10 g of rice flour was filled in a 25 ml graduated cylinder, and tapped 20 times. The bulk density was calculated as the weight per unit volume of the sample. Absolute density was measured by adding 1 g sample in a graduated cylinder containing 10 ml of petroleum ether, change in volume was noted, and absolute density calculated as weight per unit volume.

Functional properties

The sedimentation value of the flour determined by the method described by Bhattacharya and Ali (1976). 1 g of sample added to a 25 ml measuring cylinder noted the volume and adding 10 ml of distilled water. The cylinder tightly covered and mixed by inversion. The suspension was inverted again for 2 min and allowed to stand for 4 h at 25 °C. The occupied volume of the sample was noted and calculated the percentage change in volume. The sedimentation value of the flour is studied to know the water absorption capacity.

Visco amylographic characteristics of the flour were determined using Brabender micro Visco-amylograph (Model-803202, Germany, 2009). Ten percentage slurry of flour in water was initially heated to 30 °C. Heating was continued up to 95 °C and held for 5 min; the temperature was decreased to 50 °C and held for 1 min. The mixture continuously stirred for a total run time of 19.6 min. The viscosity was measured in Brabender units (BU). Parameters recorded are gelatinization temperature (GT), peak viscosity (PV), hot paste viscosity (HPV), cold paste viscosity (CPV), final viscosity (FV), breakdown viscosity (BD) and setback viscosity (SB).

Starch damage was determined according to the approved method (AACC International 2010) (Gibson et al. 1993) with a starch damage assay kit (Megazyme International Ireland, Bray, Ireland).

Microscopic structure of rice flours

The microstructure of the flour was studied using an electronic scanning microscope (SEM) (LEO435VP, Cambridge, UK). The flour was sprinkled on scotch tape fixed on metal stubs and gold-coated (about 100°A) in a KSE 24 M high vacuum evaporator. The gold-coated samples were scanned at the selected portions depicting distinct morphological features of the flour particles. Particles were photographed at different magnifications.

Product forming quality of pigmented broken rice flours

In order to assess the product forming quality, fresh rice noodles were made. A similar type of food is used in India as string hopper, vermicelli, etc. Fresh rice noodles were prepared by adding rice flour samples to boiling water and mixed with a ladle to form the dough (flour and water in 1:1.5 ratios). The mixture was held for 10 min for even distribution of the gelatinized starch. The dough was then placed in an extruder fitted with a die of 0.5 mm diameter pore size and extruded to get strands. These strands were steam-cooked for 5 min in a pressure cooker containing water required for a steam generation without whistle and stored in a casserole for 15 min before sensory analysis. Cooked product assessed for product qualities such as sensory attributes and textural profile.

Sensory analysis of rice noodle

Five trained panelists evaluated the prepared rice noodle. The sensory characteristics evaluated were color, string texture, mushy texture, smooth texture, stickiness to hand, string strength (breakage on pulling), stickiness, coarseness, chewiness, bran taste, unpleasant aftertaste and overall quality by quantitative descriptive analysis (QDA) method. The single cooked product served to each panelist on a glass plate. Panelists were asked to mark on a scale of 0–15 cm to indicate the intensity of each attribute listed on the scoreboard, where 1 represents the least preferred and 15 the most preferred. The acceptable scale is 7 and above.

Textural profile analysis (TPA) of rice noodles

The TPA of rice noodles was analyzed using a load cell of 30 kg and a 75 mm compression probe in texture analyzer (TA.HD Plus, Stable Microsystems, England, UK). A full piece of rice noodles was kept on a heavy-duty platform. The test and post-test speed set to 2 mm/s, with the probe compression by 50% and jaw compressing the bite-size of food two times. Based on the force, parameters like hardness, adhesiveness, springiness, cohesiveness, chewiness and resilience were calculated.

Statistical analysis

The values in the tables are mean ± SD (standard deviation) of three independent determinations. Data were analyzed using SPSS software (IBM SPSS statistics version 25). Two-way ANOVA was used to find out the difference among samples with significance level at p ≤ 0.05.

Results and discussion

Physical and functional properties of flour samples

Color values

Color value data (Table 1) indicate that there was no significant difference in the lightness of hammer and plate-milled red rice untoasted flour; however, toasting caused a decrease in the brightness. Hammer-milled red untoasted flour showed a 21% reduction in the redness value when compared to plate-milled red untoasted flour. However, an increase of 8% in the redness value was observed in the plate-milled red toasted flour when compared to untoasted flour. The red color of the grain is contributed by the pigments present in the bran and the increase in the redness value of plate-milled flour could be due to the complete pulverization of endosperm and bran causing exposure of bran particle surface. On the other hand, plate-milled untoasted flour showed higher yellowness value when compared to hammer-milled untoasted flour and further toasting increased the yellowness value by 5%. Similar trend was observed in the case of black rice flour. There was no significant difference in lightness and redness value of plate-milled untoasted and toasted black rice flour. However, the yellowness value was increased by 10% in toasted black rice flour. The increase in yellowness could be due to caramelization (Hofmann 1998) and Millard’s reaction (Rufian-Henares et al. 2009) of sugars and amino acids that happened during heat treatment. Color analysis of the commercial flour showed higher lightness value.

Table 1.

Effect of pulverization and toasting on the physical property of flours

Rice flour Moisture (%) Colour value Bulk density (g/L) Absolute density (g/ml)
L a b
Red rice hammer milled flour (untoasted) 12.3 ± 0.12a 75.3 ± 0.03a 5.2 ± 0.01a 10.9 ± 0.01a 540 ± 5.4a 1.67 ± 0.20a
Red rice plate milled flour (untoasted) 10.5 ± 0.06b 74.5 ± 0.13a 6.3 ± 0.05b 11.6 ± 0.05b 625 ± 5.8b 2.22 ± 0.25b
Red rice plate milled flour (toasted) 6.5 ± 0.25c 72.0 ± 0.07b 6.8 ± 0.02c 12.2 ± 0.03c 689 ± 5.7c 1.67 ± 0.18c
Commercial flour 8.2 ± 0.22d 90.0 ± 0.09d − 0.9 ± 0.01d 6.8 ± 0.02d 555 ± 5.1d 1.54 ± 0.12d
Black rice plate milled flour (untoasted) 13.0 ± 0.01a 67.4 ± 0.08a 3.13 ± 0.02a 4.9 ± 0.03a 555 ± 18.0a 1.48 ± 0.32a
Black rice plate milled flour (toasted) 5.7 ± 0.15b 65.4 ± 0.13a 3.02 ± 0.01a 5.4 ± 0.03b 572 ± 23.0a 1.40 ± 0.10a
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L, lightness; a, redness; b, yellowness. Values are mean ± SD. Effect of milling and toasting of each variety compared separately. Commercial flour compared with red plate milled flour toasted (Different alphabets indicate significant difference at p < 0.05 of respective comparisons)

Moisture content

Moisture content analysis (Table 1), showed that plate-milled red rice untoasted flour showed a 15% reduction in moisture content compared to hammer-milled red untoasted flour. The difference in the moisture content of differently milled flour could be due to an increase in temperature during milling. It is reported that the hammer-mill produces up to 75 °C temperature (Nishita and Bean 1982), whereas the plate-mill produces up to 95 °C depending on the clearance between the plates and severity of grinding (Haridas Rao et al. 1989). Further, toasting caused a reduction of 38% and 56% in the moisture content of both red and black plate-milled toasted flour respectively. The reduction could be due to the prolonged contact of the flour with roaster leading to the moisture evaporation from the flour. The commercial flour showed a moisture content of 8.2%, as low moisture level is maintained in the packed flour for storage purpose and to increase the shelf life.

Bulk density and absolute density

The density analysis (Table 1) showed that plate milled red untoasted flour exhibited a 16% higher bulk density and 33% higher absolute density when compared to hammer milled red untoasted flour. Further, toasting increased the bulk density of plate-milled red toasted flour by 10% and caused no significant change in the bulk and absolute density of the black rice flour. The change in densities could be due to the space formed by the starchy endosperm and loss of integrity in starch–starch and starch-protein matrix (Chandrasekhar and Chattopadhyay 1990). Commercial flour showed similar bulk density like back rice flour. Between red and black rice flour, black rice exhibited a lower density value. The lower density of the flour could be due to the heterogeneity of the particle size and shape as the coarser particles occupy more volume than the finer particle. Further, with the increase in moisture content, a decrease in densities was observed which could be due to the increase in mass owing to moisture gain in the sample was lower than accompanying the volumetric expansion of the bulk (Pradhan et al. 2008).

Particle size distribution

The particle size (Table 2) showed that plate-milled red untoasted flour had a smaller mean particle size (78.7 µm) and produced a higher percentage of < 148 µm particles, which is 44% higher when compared to hammer-milled flour. This is because the hammer-mill works on the comminuting principle and the plate mill works on the abrasion principle (Katti et al. 2008), which is the reason for bringing down the particle size of fiber-rich bran material, in whole rice. On the other hand, toasting had no significant effect on the mean particle size and < 148 µm particles in both red and black flour. Among both rice varieties, plate-milled black rice flour showed larger mean particle size (105.1 µm) and 23% lesser < 148 µm particles, which may be due to the structural change in the endosperm of the black rice. Commercial flour had a mean particle size and < 148 µm particles close to plate-milled red toasted flour. The results clearly show that plate-mill produces flour with a high number of finer particles and according to previous reports flours having finer particles (< 150 µm) improve the end product sensory qualities and likeability and decreases the stickiness, surface roughness compared to coarse particles.

Table 2.

Effect of pulverization and toasting on the particle size distribution of flours

Rice flour Mean particle size (µm) 352(µm) (%) 248 (µm) (%) 176 (µm) (%) 148 (µm) (%) <148 (µm) (%)
Red rice hammer milled flour (untoasted) 119.7 ± 3.0a 3.0 13.0 20.0 7.0 57.1
Red rice plate milled flour (untoasted) 78.7 ± 2.8b 0.5 2.1 8.2 8.1 82.1
Red rice plate milled flour (toasted) 74.8 ± 2.4b 0.4 1.3 7.3 7.9 83.5
Commercial flour 70.71 ± 2.1b 0.3 1.7 6.1 7.9 87.5
Black rice plate milled flour (untoasted) 105.1 ± 3.5a 4.2 8.2 6.9 6.6 63.1
Black rice plate milled flour (toasted) 110.2 ± 3.3a 1.0 6.6 11.9 10.4 66.5
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Values are mean ± SD. Effect of milling and toasting of each variety compared separately. Commercial flour compared with red plate milled flour toasted (Different alphabets indicate significant difference at p < 0.05 of respective comparisons)

The microstructure of the flours

SEM study of the rice flour showed that hammer-milled red untoasted flour had large, cuboidal shaped particles with intact starch structure. On the other hand, plate-milled red untoasted flour had finer particles with flat surfaces without having the distinction of starch particles. The variation could be due to the degradation of the starch structure caused by the severity of grinding. In the case of black rice untoasted flour, both finer and coarser particles having flat surfaces were present with completely pulverized bran. Further toasting resulted in the finer particles with swollen starch grain in both red and black rice flour. The swelling of particles on toasting could be due to the disorganization and expansion of the cavities found in the starch particles (Mariotti et al. 2006). The larger mean particle size of black rice flour observed in particle size analysis is correlating with the SEM observation which shows the partially pulverized bran particles. Commercial flour also showed the puffed nature of starch, indicating the toasting of the flour (Fig. 1).

Fig. 1.

Fig. 1

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Microstructure of the flours: a Hammer milled red rice untoasted flour; b plate milled red rice untoasted flour; c plate milled red rice toasted flour; d commercial flour; e plate milled black rice untoasted flour; f plate milled black rice toasted flour; magnification × 4000

Sedimentation value

The sedimentation value analysis (Table 3) showed that plate-milled red untoasted flour showed a significant increase in the sedimentation value when compared to hammer-milled red untoasted flour. This variation could be due to the presence of a higher percentage of the finer particle in plate-milled flour, which increases water uptake (de la Hera et al. 2013). Further, toasting also caused the highest percentage change in sedimentation value in both red (133.3%) and black (94.4%) rice flour. The increase may be because the raise in toasting temperature and time (Akubor et al. 2000) causes the porosity in endosperm and consequently increases the water uptake by the endosperm (Mariotti et al. 2006). In addition to this, the presence of higher damaged starch also helps in rapid hydration in the flours (Hasjima et al. 2013), which is in agreement with the observation made in this study. Among red and black rice flour, red rice flour showed the highest percentage change in sedimentation value as red rice contains a high amount of amylose. Amylose is amorphous and absorbs more water than crystalline amylopectin (Lawal et al. 2004), which is high in black rice. Commercial flour had 58.3% of sedimentation value.

Table 3.

Effect of pulverization and toasting on the functional property of flours

Rice flours Sedimentation value (% change in volume) Starch damage (%)
Red rice hammer milled flour (untoasted) 50.0 ± 2.90a 4.7 ± 0.26a
Red rice plate milled flour (untoasted) 87.5 ± 0.10b 8.1 ± 0.69b
Red rice plate milled flour (toasted) 134 ± 8.95c 11.7 ± 0.22c
Commercial flour 58.3 ± 2.80d 8.2 ± 0.78d
Black rice plate milled flour (untoasted) 66.7 ± 0.10a 13.4 ± 0.64a
Black rice plate milled flour (toasted) 94.4 ± 7.9b 15.9 ± 0.90b
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Values are mean ± SD. Effect of milling and toasting of each variety compared separately. Commercial flour compared with red plate milled flour toasted (Different alphabets indicate significant difference at p < 0.05 of respective comparisons)

Damaged starch

Damaged starch analysis (Table 3) showed that plate-milled red untoasted flour had 72% higher damaged starch when compared to hammer-milled red untoasted flour. The difference in damage maybe because during the plate-milling cell wall gets ruptured due to simultaneous attrition and shearing between the plates causing more damage. Whereas, in the hammer-mill, only endosperms get fragmented (Katti et al. 2008). On the other hand, toasting caused an increase in starch damage by 44% in red and 19% in black rice flour as during toasting, starch granules get gelatinized and burst due to a high temperature, causing starch damaged (Mariotti et al. 2006). Among red and black rice flour, black rice flour had greater starch damage due to the presence of a significant amount of amylopectin, which gets destroyed faster by the application of heat (Correa et al. 2013). In the case of commercial flour, 8.8% starch damage observed.

Pasting properties

The pasting property analysis (Table 4 and Supplementary Figure 1) showed that milling and toasting caused no significant difference in the gelatinization temperature (GT) of both red and black rice flour. However, among both the flour, black rice flour showed lesser GT, which could be due to the difference in amylose content as GT increases with an increase in amylose content (Correa et al. 2013). The commercial flour showed GT almost similar to that of plate-milled red untoasted flour.

Table 4.

Effect of pulverization and toasting on the viscosity profile of flours

Rice flours Viscosity parameters
GT (°C) PV (BU) HPV (BU) CPV (BU) FV (BU) BD (BU) SB (BU)
Red rice hammer milled flour (untoasted) 74 ± 6.68a 181 ± 16.41a 139 ± 12.63a 327 ± 29.67a 339 ± 30.75a 42 ± 3.79a 188 ± 17.04a
Red rice plate milled flour (untoasted) 76 ± 3.40a 211 ± 9.51b 155 ± 6.97b 367 ± 16.49a 380 ± 17.09b 56 ± 2.54b 211 ± 9.51b
Red rice plate milled flour (toasted) 74 ± 0.40a 172 ± 4.00c 146.5 ± 0.50c 290 ± 8.00b 301 ± 8.00c 25.5 ± 4.50c 144 ± 8.50c
Commercial flour 76 ± 6.94a 587 ± 53.30d 515 ± 46.72d 1083 ± 98.30c 1099 ± 99.74d 73 ± 6.58d 568 ± 51.59d
Black rice plate milled flour (untoasted) 59 ± 3.10a 371 ± 38.00a 204 ± 8.00a 277 ± 5.00a 284 ± 5.50a 167 ± 30.00a 73 ± 13.00a
Black rice plate milled flour (toasted) 61 ± 0.84a 431 ± 38.31b 254 ± 20.98b 354 ± 28.54b 361 ± 28.73b 177 ± 17.62a 101 ± 7.57b
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GT, Gelatinization temperature; PV, peak viscosity; HPV, hot paste viscosity; CPV, cold paste viscosity; FV, final viscosity; BD, breakdown; SB; setback; BU, Brabender unit. Values are mean ± SD. Effect of milling and toasting of each variety compared separately. Commercial flour compared with red plate milled flour toasted (Different alphabets indicate significant difference at p < 0.05 of respective comparisons)

Plate-milled red untoasted flour showed a 17% increase in the peak viscosity (PV) compared to hammer-milled red untoasted flour. The increase in the PV could be due to the presence of a higher number of fine particles. Fine particles have higher hydration properties, and a reduction in particle size exposes a greater surface area for the binding of water molecules (Baek and Lee 2014) and takes less time to reach peak viscosity.

On the other hand, plate-milled red toasted flour showed 18% lower PV than plate-milled red untoasted flour. The decrease in PV could be due to the partial gelatinization of starch granules during toasting and increased damaged starch content (Sharma et al. 2011; León et al. 2006) as damaged starch granules quickly swell in the presence of heat with rapid hydration and produce less peak viscosity (Mariotti et al. 2006).

In the case of black rice, the toasted flour showed 16% higher PV than untoasted flour. The difference in PV could be due to the additional heat treatment given to flour during toasting. Since, in the presence of lower amylose content in black rice, the crystalline amylopectin needs high energy for gelatinization (Krueger et al. 1987). Among the two rice varieties, black rice flour showed higher peak viscosity than red rice flour as amylopectin granules swell rapidly to a greater extent than an amylose molecule (Correa et al. 2013).

Plate-milled red untoasted flour showed higher pasting profile values such as an increase of 12% in HPV, CPV, FV, and SB as well as 33% BD compared to hammer-milled untoasted flour. This could be due to a high number of fine particles, which causes increased granule swelling. The lower pasting profile values of hammer-milled untoasted flour could be due to the significant number of larger particles since larger particles reduce the hydration rate and require higher time to develop viscosity during heating (Hasjima et al. 2013).

On the other hand, plate-milled toasted flour showed a lower pasting profile of 6% HPV, 27% CPV, 26% FV, 120% BD, and 47% SB compared to plate-milled untoasted flour. As the heat treatment causes pre-gelatinization of starch granules (Bruna et al. 2014), severe disruption of the starch structure (Chen et al. 2003) and the formation of damaged starch contributes to the reduction in viscosity parameters (Dhital et al. 2010, 2011). Further, the decrease in PV, HPV, and CPV was presumably due to attrition-induced damage of granules. Broken fragments and fractured granules have lower viscosity parameters than intact granules (Stevenson et al. 2007).

Viscosity profiles were reversed in black rice flour as toasted flour showed higher viscosity values than untoasted flour. Black rice toasted flour showed an increase of 25% HPV, 28% CPV, 27% FV, 6% BD, and 38% high SB than untoasted flour. As explained, amylopectin granules break down during toasting due to heat treatment, enhancing the gelatinization capacity of the toasted flour, resulting in high viscosity profile values.

Among both the flours, plate-milled red untoasted flour showed lower PV, HPV, BD, and higher SB than black untoasted flour, which indicates that granules in red rice flour disrupt efficiently. Lower BD indicates that granules are less susceptible to heat at 95 °C. Red rice untoasted flour also showed higher FV and SB than black rice untoasted flour due to the rapid aggregation of the leached amylose during the cooling of starch paste (Cleary and Brennan 2006). Commercial rice flour showed higher viscosity profiles than red and black rice; this could be due to the absence of bran.

Sensory characteristics of rice noodles prepared from different flours

Rice noodle was prepared using processed flour samples, and the sensory analysis was carried out. The sensory scores showed that rice noodles prepared using a hammer and plate-milled red untoasted flour had the least quality characters. Similarly, rice noodles prepared using plate-milled black toasted flour also scored least on sensory characteristics as the strands were sticking to each other and the plate (due to high amylopectin content) which made it difficult for sensory evaluation and showed not suitable for the preparation of product like rice noodle. On the other hand, rice noodle prepared using plate-milled red toasted flour scored high on sensory qualities such as visual qualities [color (9), lack of mushiness (3) and smooth texture (12)]; moderate stickiness to hand (4.5) and right string strength (10.5). Mouthful parameters [low stickiness (6.75), coarseness (3), chewiness (6), bran taste (5.25), Unpleasant aftertaste (3)] and best overall quality (12.75) (Supplementary Figure 2). In comparison with rice noodles prepared using commercial flour, plate-milled red toasted flour products were approximately the same in all the quality characteristics. It scored less in parameters like color, stickiness to mouth, chewiness and bran taste due to the presence of bran which increases chewing of the product and gives a characteristic bran flavor. Overall product the prepared using plate-milled red toasted flour showed good sensory qualities and matched with the commercially available flour product.

Textural profile analysis of cooked rice noodle

Textural properties of the product studied were hardness the maximum force required for the compression of the product. Adhesiveness: the total force needed to pull the compression plunger away from the product. Cohesiveness: the rate at which the material disintegrates under mechanical action. Springiness: height recovered by the product between the end of the first bite and the beginning of the second bite. Gumminess: hardness x cohesiveness and chewiness: gumminess x springiness. Product hardness and adhesiveness are the two most critical textural properties considered by the consumer.

In comparison to the product prepared using commercial flour, red rice, noodle prepared using plate-milled red toasted flour showed 23% higher hardness (Table 5). Adhesiveness or stickiness was lower in red rice, noodle as bran reduces the stickiness of the product (Doss et al. 2019). The springiness, which is an excellent attribute of the rice noodle, was on par with commercial rice product, and both the products had almost similar gumminess, cohesiveness and chewiness.

Table 5.

Textural profile analysis of rice noodle

Textural parameters Commercial flour product Plate-milled red toasted flour product
Hardness (g) 621 ± 75.62a 763 ± 101.29b
Adhesiveness (gs) − 3.82 ± 1.73a − 1.00 ± 0.32b
Cohesiveness 0.63 ± 0.07a 0.54 ± 0.06a
Springiness 0.72 ± 0.14a 0.73 ± 0.09a
Gumminess 391.08 ± 76.49a 419.91 ± 103.70a
Chewiness (g mm) 286.61 ± 102a 314.11 ± 114.25b
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Values are mean ± SD. Commercial flour product compared with red rice toasted flour product (Different alphabets indicate significant difference at p < 0.05 of respective comparisons)

Conclusion

Milling method and toasting affect the quality characteristics of the pigmented rice flour, and its effect was investigated in red and black. Pigmented broken rice. Plate-milling decreases the moisture content, increases finer particle, redness value, bulk density, sedimentation value, damaged starch content, peak viscosity, and causes changes in the microstructure of starch. On the other hand, the toasting of the flour does not affect the particle size, color, and bulk density but reduces the moisture content. Further, toasting increases the sedimentation value, damaged starch, and has no effect on gelatinization temperature, but reduces the peak viscosity in red and increases in black rice flour, and causes puffiness in the starch structure. Product quality evaluation of rice noodles prepared by using plate milled toasted red rice flour has the best sensory and textural qualities equivalent to the traditional product.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (DOCX 200 kb) (200.8KB, docx)

Acknowledgements

Project funded by Govt. of India XII plan project AGROPATHY (BSC0105).

Footnotes

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Contributor Information

I. Sapna, Email: sapna_vasudream@yahoo.com

A. Jayadeep, Email: jayadeep@cftri.res.in

References

  1. Akubor PI, Isolokwu PC, Ugbane O, Onimawo IA. Proximate composition and functional properties of African breadfruit kernel and flour blends. Food Res Int. 2000;33:707–712. doi: 10.1016/S0963-9969(00)00116-2. [DOI] [Google Scholar]
  2. Baek JJ, Lee S. Functional characterization of brown rice flour in an extruded noodle system. J Korean Soc Appl Biol Chem. 2014;57(4):435–440. doi: 10.1007/s13765-014-4102-4. [DOI] [Google Scholar]
  3. Bhattacharya KL, Ali SZ. A sedimentation test for pregelatinized rice products. Lebensm Wiss Technol. 1976;9:36–37. [Google Scholar]
  4. Bodie AR, Micciche AC, Atungulu GG, Rothrock MJ, Jr, Ricke SC. Current trends of rice milling byproducts for agricultural applications and alternative food production systems. Front Sustain Food Syst. 2019;3:47. doi: 10.3389/fsufs.2019.00047. [DOI] [Google Scholar]
  5. Bruna A, Ricardo TP, Josiane B, Rafael AS, Moacir CE, Elessandra RZ, Alvaro RGD. The effects of heat–moisture treatment of rice grains before parboiling on viscosity profile and physicochemical properties. Int J Food Sci Technol. 2014;49:1939–1945. doi: 10.1111/ijfs.12580. [DOI] [Google Scholar]
  6. Chandrasekhar PR, Chattopadhyay PK. Studies on micro structural changes of parboiled and puffed rice. J Food Process Preserv. 1990;14:27–37. doi: 10.1111/j.1745-4549.1990.tb00123. [DOI] [Google Scholar]
  7. Chen J, Lii C, Lu S. Physicochemical and morphological analyses on damaged rice starches. J Food Drug Anal. 2003;11(4):283–289. [Google Scholar]
  8. Cleary L, Brennan C. The influence of a (1 → 3) (1 → 4)-β-D-glucan rich fraction from barley on the physicochemical properties and in vitro reducing sugars release of durum wheat pasta. Int J Food Sci Technol. 2006;41:910–918. doi: 10.1111/j.1365-2621.2005.01141. [DOI] [Google Scholar]
  9. Correa MJ, Ferrero C, Puppo C, Brites C. Rheological properties of riceelocust bean gum gels from different rice varieties. Food Hydrocoll. 2013 doi: 10.1016/j.foodhyd.2012.11.022. [DOI] [Google Scholar]
  10. de la Hera E, Gomez M, Rosell CM. Particle size distribution of rice flour affecting the starch enzymatic hydrolysis and hydration properties. Carbohydr Polym. 2013 doi: 10.1016/j.carbpol.2013.06.002. [DOI] [PubMed] [Google Scholar]
  11. Deng G-F, Xu X-R, Zhang Y, Li D, Gan R-Y, Li H-B. Phenolic compounds and bioactivities of pigmented rice. Crit Rev Food Sci Nutr. 2013;53:296–306. doi: 10.1080/10408398.2010.529624. [DOI] [PubMed] [Google Scholar]
  12. Dhital S, Shrestha AK, Gidley MJ. Effect of cryo-milling on starches: functionality and digestibility. Food Hydrocoll. 2010;24(2–3):152–163. doi: 10.1016/j.foodhyd.2009.08.013. [DOI] [Google Scholar]
  13. Dhital S, Shrestha AK, Flanagan BM, Hasjim J, Gidley MJ. Cryo-milling of starch granules lead to differential effects on molecular size and conformation. Carbohydr Polym. 2011;84(3):1133–1140. doi: 10.1016/j.carbpol.2011.01.002. [DOI] [Google Scholar]
  14. Dinesh Babu P, Subhasree RS, Bhakyaraj R, Vidhyalakshmi R. Brown rice-beyond the color reviving a lost health food—a review. Am Eurasian J Agron. 2009;2(2):67–72. [Google Scholar]
  15. Doss PPP, Chevallier S, Pare A, Le-Bail A. Effect of supplementation of wheat bran on dough aeration and final bread volume. J Food Eng. 2019;225:28–35. doi: 10.1016/j.jfoodeng.2019.01.014. [DOI] [Google Scholar]
  16. Gibson TS, Kaldor CJ, Mc Cleary BV. Collaborative evaluation of an enzymatic starch damage assay kit and comparison with other methods. Cereal Chem. 1993;70:47–51. [Google Scholar]
  17. Good H. Measurement of color in cereal products. Cereal Foods World. 2002;4:5–6. [Google Scholar]
  18. Haridas Rao P, Leelavathi K, Shupralekar SR. Effect of damage starch on the chapati-making quality of whole wheat flour. Cereal Chem. 1989;66(4):329–333. [Google Scholar]
  19. Hasjima J, Li AE, Dhita S. Milling of rice grains: effects of starch/flour structures on gelatinization and pasting properties. Carbohydr Polym. 2013;92:682–690. doi: 10.1016/j.carbpol.2012.09.023. [DOI] [PubMed] [Google Scholar]
  20. Hofmann T. Studies on the relationship between molecular weight and the color potency of fractions obtained by thermal treatment of glucose amino acid and glucose/protein solutions by using ultracentrifugation and colour dilution technique. J Agric Food Chem. 1998;46:3891–3895. doi: 10.1021/jf980397. [DOI] [Google Scholar]
  21. Horwitz W. Official method of analysis of AOAC International. 17. Maryland: AOAC International; 2000. [Google Scholar]
  22. Katti SV, Kumar S, Malleshi NG. Studies on the effect of milling finger millet in different pulverisers on physico-chemical properties of the flour. J Food Sci Technol. 2008;45(5):398. [Google Scholar]
  23. Krueger BR, Knutson CA, Inglett GE, Walker CE. A differential scanning calorimetry study on the effect of annealing on gelatinization behaviour of corn starch. J Food Sci. 1987;52:715–718. doi: 10.1111/j.1365-2621.1987.tb06709.x. [DOI] [Google Scholar]
  24. Lawal OS, Adebowale KO, Oderinde RA. Functional properties of amylopectin and amylose fractions isolated from bambarra groundnut (Voandzeia subterranean) starch. Afr J Biotechnol. 2004;3(8):399–404. doi: 10.5897/AJB2004.000-2082. [DOI] [Google Scholar]
  25. León AE, Barrera GN, Pérez GT, Ribotta PD, Rosell CM. Effect of damaged starch levels on flour-thermal behaviour and bread staling. Eur Food Res Technol. 2006;224:187–192. doi: 10.1007/s00217-006-0297. [DOI] [Google Scholar]
  26. Mariotti M, Alamprese C, Pagani MA, Lucisano M. Effect of puffing on the ultrastructure and physical characteristics of cereal grains and flours. J Cereal Sci. 2006;43(1):47–56. doi: 10.1016/j.jcs.2005.06.007. [DOI] [Google Scholar]
  27. Nishita KD, Bean MM. Grinding methods: their impact on rice flour properties. Cereal Chem. 1982;59(1):46–49. [Google Scholar]
  28. Okaka JC, Potter NN. Functional and storage properties of cowpea-wheat flour blends in bread making. J Food Sci. 1977;42:828–833. doi: 10.1111/j.1365-2621.1977.tb12614. [DOI] [Google Scholar]
  29. Pandey S, Asha MR, Jayadep A. Changes in physical, cooking, textural properties and crystallinity upon iron fortification of red rice (Jyothi) J Food Sci Technol. 2016;53(2):1014–1024. doi: 10.1007/s13197-015-2130-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Ponnappan S, Thangavel A, Sahu O. Milling and physical characteristics of pigmented rice varieties. Int J Food Chem. 2017;1(1):24–29. doi: 10.11648/j.ijfc.20170101.15. [DOI] [Google Scholar]
  31. Pradhan RC, Naik SN, Bhatnagar N, Swain SK. Moisture-dependent physical properties of Karanja (Pongamiapinnata) kernel. Ind Crops Prod. 2008;28:155–161. doi: 10.1016/j.indcrop.2008.02.006. [DOI] [Google Scholar]
  32. Rufian-Henares JA, Delgado-Andrade C, Morales FJ. Assessing the Maillard reaction development during the toasting process of common flours employed by the cereal products industry. Food Chem. 2009;114:93–99. doi: 10.1016/j.foodchem.2008.09.021. [DOI] [Google Scholar]
  33. Sharma P, Gujral HS, Rosell CM. Effects of roasting on barley β-glucan, thermal, textural and pasting properties. J Cereal Sci. 2011;53(1):25–30. doi: 10.1016/j.jcs.2010.08.005. [DOI] [Google Scholar]
  34. Stevenson DG, Jane JL, Inglett GE. Structure and physicochemical properties of starches from sieve fractions of oat flour compared with whole and pin-milled flour. Cereal Chem. 2007;84(6):533–539. doi: 10.1094/CCHEM-84-6-0533. [DOI] [Google Scholar]
  35. Tran TTB, Shelat KJ, Tang D, Li E, Gilbert RG, Hasjim J. Milling of rice grains. The degradation on three structural levels of starch in rice flour can be independently controlled during grinding. J Agric Food Chem. 2011;59(8):3964–3973. doi: 10.1021/jf105021r. [DOI] [PubMed] [Google Scholar]

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