Effects of whey protein concentrate, feed moisture and temperature on the physicochemical characteristics of a rice-based extruded flour

Accepted Manuscript Effects of whey protein concentrate, feed moisture and temperature on the physicochemical characteristics of a rice-based extruded flour Carla da Silva Teba, Erika Madeira Moreira da Silva, Davy William Hidalgo Chávez, Carlos Wanderlei Piler de Carvalho, José Luis Ramírez Ascheri PII: DOI: Reference:

S0308-8146(17)30163-2 http://dx.doi.org/10.1016/j.foodchem.2017.01.145 FOCH 20537

To appear in:

Food Chemistry

Received Date: Revised Date: Accepted Date:

16 September 2016 30 January 2017 31 January 2017

Please cite this article as: Teba, C.d.S., da Silva, E.M.M., Chávez, D.W.H., de Carvalho, C.W.P., Ascheri, J.L.R., Effects of whey protein concentrate, feed moisture and temperature on the physicochemical characteristics of a ricebased extruded flour, Food Chemistry (2017), doi: http://dx.doi.org/10.1016/j.foodchem.2017.01.145

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Title page

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Effects of whey protein concentrate, feed moisture and temperature on the

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physicochemical characteristics of a rice-based extruded flour

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Carla da Silva Teba1, Erika Madeira Moreira da Silva2**, Davy William Hidalgo

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Chávez1, Carlos Wanderlei Piler de Carvalho3, José Luis Ramírez Ascheri3

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(1) UFRRJ, Federal Rural University of Rio de Janeiro, Post-Graduation Program in

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Food Science and Technology. Rodovia BR 465 Km 7, Seropédica – RJ, Brazil. CEP:

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23890-000, . Email address: [email protected] ; [email protected]

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(2) UFES, Federal University of Espirito Santo, Post-Graduation Program in Nutrition

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and Health (PPGNS), Center of Health Sciences. Avenida Marechal Campos, 1468,

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Maruípe,

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[email protected]

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(3) Embrapa Food Technology. Avenida das Américas nº 29.501, Guaratiba, Rio de

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Janeiro –RJ, Brazil. CEP: 23020-470. Email address: [email protected];

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[email protected]

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**Corresponding author

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Email address: [email protected] (E.M.M. Silva)

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Tel.: +55 27 3335-7001 / +55 27 99853-6476

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Vitória-ES,

Brazil.

CEP:

29040-090.

Email

address:

1

Effects of whey protein concentrate, feed moisture and temperature on the physicochemical characteristics of a rice-based extruded flour

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Running title: Extrusion parameters on whey protein and rice flour blends

4

Abstract

5

The influence of whey protein concentrate (WPC), feed moisture and temperature on

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the physicochemical properties of rice-based extrudates has been investigated. WPC

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(0.64 to 7.36 g/100 g rice) was extruded under 5 moisture (16.64 to 23.36 g/100 g) and

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5 temperature (106.36 to 173.64 ºC) established by a 3² central composite rotational

9

design. Physicochemical properties [color, porosimetry, crystallinity, water solubility

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and absorption, pasting properties, reconstitution test, proximate composition, amino

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acids, minerals and electrophoresis] were determined. WPC and feed moisture increased

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redness, yellowness and decreased luminosity. Feed moisture and temperature increased

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density and total volume pore. WPC and moisture increased crystallinity, but only WPC

14

increased solubility and decrease the retrogradation tendency. Increasing temperature

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increased the viscosity of the extrudates. The addition of WPC improved the nutritional

16

composition of the extrudates, especially proteins. It is suggested that the extrusion

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process positively affected the retention of most of the polypeptides chains.

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Keywords: whey protein concentrate; rice; extrusion; chemical composition; gel

19

electrophoresis; x-ray diffraction.

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1. Introduction

21

Extrusion technology, in recent times, has become one of the major processes

22

for producing varieties of food. During this process, the raw materials undergo many

23

chemical and structural transformations, such as starch gelatinization, protein

24

denaturation, complex formation between amylose and lipids, and degradation reactions

25

of vitamins and pigments (Dushkova, Menkov, & Toshkov, 2011). The extruder 1

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functions as a complex and complete processing unit, that is capable to convert more

27

than one kind of raw material into one fully cooked food product. Extruders may be

28

more cost-effective to operate than traditional cooking systems because they perform

29

multiple unit operations (e.g., mixing, blending, cooking, forming) in one single

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machine, which increases productivity and reduces production costs. Also, the process

31

allows precise control over the cooking parameters and process optimization (Berrios,

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Ascheri, & Losso, 2013).

33

The nutrient density of extruded foods has been low, once these products are

34

predominantly made from rice or corn flour, with high levels of carbohydrates. Thus,

35

whey protein concentrate as a valuable source of proteins and minerals is one of the

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highest-quality components for possible extrudate enrichment (Brnčić, Bosiljkov,

37

Ukrainczyk, Tripalo, Brnčić, Karlović, Karlović, Ježek, & Topić, 2011). This protein

38

source has high biological quality resulting from its essential amino acid contents,

39

especially leucine (11.8 %) and lysine (9.5 %), and is a good source of valine (4.7 %),

40

threonine (4.6 %), methionine (3.1 %) and phenylalanine (3.0 %) (Etzel, 2004).

41

Dissanayake, Liyanaarachchi, and Vasiljevic (2012) have documented that whey

42

proteins containing a higher percentage of denatured proteins produced emulsions with

43

greater viscosity and stability. Thus, the whey has not been only used for improving the

44

nutritional value, but also the rheological and functional aspects (Afizah, & Rizvi,

45

2014).

46

In the extrusion processing, besides the protein concentration, moisture content,

47

and the mechanical parameters of the extruder significantly affect the physical and

48

sensory qualities of extrudates (Day, & Swanson, 2013).

49

In the Abd El-Ghany, El-Asser, Nagy, and Abd El-Maksoud (2013) study, the

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incorporation of 10% of whey protein concentrate in substitution of a starchy mixture

2

51

(with rice and corn) improved the nutritional value of the extruded products, where it

52

increased protein content and protein digestibility.

53

Extrudates with good quality were produced with up to 25% of whey protein

54

concentrate in substitution for rice, corn or potato flours (Onwulata, Smith, Konstance,

55

& Holsinger, 2001). However, Fernandes, Madeira, Carvalho, and Pereira (2016)

56

demonstrated that although it is feasible to obtain extruded product with good expansion

57

from the substitution of corn grits for up to 17% of whey protein concentrate, the best

58

acceptance was observed for products made with 5% of this protein.

59

The objective of this study was to evaluate the effects of the addition of whey

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protein concentrate (WPC), feed moisture and temperature on the physicochemical

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characteristics of a rice-based extruded flour.

62 63

2. Material and methods

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2.1 Material and blend preparation

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The polished white rice (Oryza sativa L.) was purchased in local shops (Rio de

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Janeiro, Brazil). Rice grains were ground in Laboratory Mill 3600 disk mill (Perten

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Instruments, model 3600, Kungens Kurva, Sweden), obtaining white rice flour. The

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WPC powder was donated by the company Alibra® Ingredients Ltda (Campinas, São

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Paulo, Brazil).

70

The WPC and rice flour were manually mixed in proportions established by the

71

experimental design (Table 1). WPC was mixed with polished rice in proportions of

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0.64 to 7.36 g/100 g. Flour moisture content was determined to establish the amount of

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added water necessary to adjust the moisture content of the blend to the required levels

74

of 16.64 to 23.36 g/100 g. The moisture of the blend was then equilibrated overnight

3

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under refrigerated conditions to guarantee homogeneity and dispersion of the water

76

throughout the dough before extrusion.

77

2.2 Extrusion processing

78

The extrusion process was performed in a single-screw extruder Brabender

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20DN DSE coupled to a module 330 Food Torque Rheometer (Duisburg, Germany). A

80

feed rate of 2.0 kg/h and screw speed of 140 rpm were held constant throughout the

81

process at a pressure of 9-11 MPa. The screw configuration was L/D 1:2 (compression

82

ratio) and included a circular die 3 mm in diameter, with temperature regulation

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performed by a corresponding Brabender® Circulatory System. The extrusion trials

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were started after the equilibrium temperatures of the feed zone (zone 1 – 60ºC) and

85

transition (zone 2 – 80ºC) zone were reached, and these temperatures remained constant

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throughout the process. In the third zone, temperature variations were applied according

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to the experimental design (Table 1). The extrudates were dried (Fabbe-Primar, São

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Paulo, SP, Brazil) in a forced-air drier at 60°C for 4 h until they reached 4-7 g/100 g

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moisture. The final dried samples were milled in a disc mill with 0.8 mm sieve size. The

90

extruded flours were maintained under refrigeration (5-8ºC) until further analysis.

91

2.3 Instrumental color

92

The instrumental color analysis of the polished rice and WPC flours, as well as

93

the extruded flours, was performed by transmittance using a Hunterlab Colorquest

94

colorimeter, model XE (Reston, Virginia, USA). A CIELAB and CIELCh scale were

95

used to measure the Hunter color parameters (L*, a* and b*).

96

2.4 Porosimetry

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The evaluation of the absolute density and total pore volume of raw materials

98

and extruded flour was performed using a pycnometer helium gas (Micromeritics®,

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Accu PYC II model – 1340, Norcross, GA, U.S.A.). Helium was used for all the

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100

analyses, totaling, for each sample, 10 purges at a constant temperature of 24-26°C with

101

an equilibration rate of 0.005 psig.min-1 and a peak in each purge up to 19 psig. The

102

accuracy adopted for the experimental results was 0.01%.

103

2.5 Crystallinity index of extruded mixed flours

104

The modification of the physical structure of the starch was determined

105

following the method of X-ray diffraction (D2 Phaser, Bruker, Alemanha) proposed by

106

Hayakawa, Tanaka, Nakamura, Endo, and Hoshino (1997). The interlayer spacing (d)

107

was calculated by the Bragg equation:

sen Ɵ =

108

ƛ

109

Where: ƛ correponds to the wavelength used (ƛ = 1.5406 Å) and Ɵ is the angle where

110

the peak is detected on the diffractogram.

111

2.6 Water solubility and water absorption indexes

112

The determination of the water solubility (WSI) and water absorption (WAI)

113

indexes of the samples was performed according to the basic principles of the method

114

described by Anderson, Conway, Pfeifer, and Griffin Jr. (1969).

115

2.7 Pasting properties

116

The pasting properties of the extruded samples were analyzed using a Rapid

117

Visco Analyzer (RVA Super-4 model, Newport Scientific Pvt. Ltd, Australia). The

118

viscosity profiles were recorded using sample suspensions consisting of 3.0 g (14 g of

119

water/100 g) of a sample milled with a Perten mill model and 25 mL of water. The

120

sample was held at 25ºC for 2 min, heated to 95ºC (held for 3 min) and cooled to 25ºC,

121

and the test was completed within 20 min. The heating and cooling phases were

122

performed with a temperature gradient of 6 ºC/min. The values of the initial viscosity,

123

maximum viscosity, final viscosity and setback (retrogradation tendency) were

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124

expressed in Pascal-seconds (Pa·s). For the RVA, samples with particle sizes between

125

125 and 250 mm were used.

126

2.8 Reconstitution test

127

The determination of the reconstitution time or dissolution of pre-gelatinized

128

mixed flours for selecting the best formulations to prepare rapid dissolution products

129

was performed according to the methodology described by Omobuwajo, Busari, and

130

Osemwegie (2000) with modifications. To perform this technique, 10 grams of each

131

sample was dissolved in 50 mL of distilled water contained in a 250 mL beaker at room

132

temperature and stirred continuously with the aid of a glass rod. The time required to

133

disintegrate and completely solubilize the samples was monitored by a timer and

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regarded as the reconstitution time. After 30 minutes of rest, the samples were observed

135

again to verify possible transformation, such as phase separation and possible lump

136

formation.

137

2.9 Proximate composition

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The raw materials and the extruded flours were analyzed for moisture, nitrogen

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(using a conversion factor of 5.95 for polished rice and 6.38 for WPC and extruded

140

flours – FAO, 2003), ash, and lipids according to the Association of Official Analytical

141

Chemists (AOAC, 2005). The total carbohydrate content of the samples was calculated

142

by: 100 - (moisture + ash + protein + lipids). The energy value was determined in kJ

143

according to the formula – Atwater factor system: energy = (% protein x 17) + (%

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carbohydrate x 17) + (% lipids x 37).

145

2.10 Minerals

146

The mineral composition was examined to determine the content of calcium,

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copper, iron, phosphorus, magnesium, manganese, potassium, sodium and zinc in raw

148

material and the extruded flours, according to the methodology proposed by the AOAC

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149

(2005; method 990.08, item 9.2.39). Quantification of minerals was performed in

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plasma emission spectrometer ICP Spectroflama Flame (Kleve, Germany) using atomic

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emission spectrometry after complete digestion of the sample in nitric and perchloric

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acids (method 975.03, item 2.3.05).

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2.11 Amino acids

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The amino acid profiles of the raw materials and the extruded flours were

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determined in duplicate according to the AOAC (2005; method 994.12). The

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quantification was performed using a high performance liquid chromatograph (HPLC)

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(Alliance Waters 2695 - Massachusetts, USA) with fluorescence detection (Alliance

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Waters 2475 - Massachusetts, USA). The essential amino acid score (EAAS) was

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calculated considering the amino acid content, using the FAO/WHO (1985) standard as

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a reference for children between 2 and 5 years old, 10 to 12 years old, and adults,

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according to Pires, Oliveira, Rosa, and Costa (2006).

162

2.12 Electrophoresis

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Electrophoresis of proteins in a polyacrylamide gel in the presence of sodium

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dodecyl sulfate (SDS / PAGE) was conducted according to the method proposed by

165

Laemmli (1970), using 1 mm spacers, a packing gel (3.5%) and a separating gel (12%).

166

The molecular weight standard used was Unstained Natural Standards Broad-Range

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(Bio Rad) with molecular weights ranging from 6,400 to 200,000 gmol-1.

168

2.13 Regression modeling and statistical analysis

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A 3² central composite design was used to study the effects of interactions of

170

whey protein concentrate (0.64 to 7.36 g/100 g of polished rice), feed moisture content

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(16.64 to 23.36 g/100 g) and temperature in the third zone (106.36 to 173.64 ºC) on the

172

color, porosimetry, water solubility index and pasting properties of the extrudates.

173

Overall, 20 experimental runs were conducted, each with eight factorial points studied

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at three levels (-1, 0, +1); six-star corner points (two for each variable), using α = 1.68

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as rotability; and six central points to meet the statistical design requirements. Actual

176

levels for suitable extrusion cooking were selected according to preliminary studies and

177

data from previous literature. The second order polynomial equation fitted with coded

178

variables was as follows:

179

Y = β0 + β 1X1 + β 2X2 + β 3X3 + β 11X1² + β 22X2 ² + β 33X3 ² + β 12X1X2 + β13X1X3 +

180

β 23X2X3 + ξ

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Y is the experimental response; β0 is the coefficient for intercept; β1, β2, and β3 are

182

linear coefficients; β11, β22, and β33 are quadratic coefficients; β12, β13, and β23 are the

183

interactive coefficients; X1, X2, and X3 are independent variables (X1

184

concentrate, X2 = moisture, X3 = temperature); and ξ is the experimental error. The

185

effect of each term and its statistical significance for the response variables were

186

analyzed using the standardized Pareto chart (Montgomery, 2012). The chemical

187

analysis results were subjected to one-way analysis of variance (ANOVA) followed by

188

the Tukey test. Statistical significance was considered at 5% probability for all analyses

189

and was performed using the software Stati stica version 10.0 (Statsoft Inc., Tulsa, OK,

190

USA).

191

3. Results and discussion

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3.1 Color

=

whey protein

193

The increase in temperature had a greater impact on the lightness of the extruded

194

flour, increasing these values. On the other hand, the increase in WPC and feed

195

moisture content affected negatively, with the capacity to reduce the lightness values

196

(Fig. 1A). It is important to note that the color of the extruded products may vary

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according to the combination of the stablished parameters such as, feed moisture,

198

temperature and specially the chemical components of each raw material and its

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199

proportion on the mixture. Stojceska, Ainsworth, Plunkett, and Ibanoglu (2009)

200

observed that the increase in the feed moisture (up to 17 g/100g) decreased the lightness

201

in some ready-to-eat snacks made from food by-products. The increase in WPC content

202

also decreased the lightness of a corn and rice based extruded (Brnčić et al., 2011; El-

203

Ghany, El-Asser, Nagy, & El-Maksoudm, 2013). About the effect of the processing

204

temperature, Sacchetti, Pinnavaia, Guidolin, and Dalla Rosa (2004) found that the

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extrusion temperature appeared to have little effect on the product’s lightness and a*

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values in a rice based snack with low values of substitution.

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It is known that the main reason for changes in colour is the outcome of the

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Maillard reactions, which are divided in a three-step process: in the initial stage, there is

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a reaction between reducing sugar and amines, which results in colourless products;

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intermediary stage follows, which results in colourless or slightly yellow coloured

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products. Intensive-coloured products are the outcome of the final stage of the process

212

(Ames, 1998).

213

Note that, the increase of the combination of WPC and feed moisture increased

214

the redness (a*) and yelowness (b*) of the extruded blend (Fig. 1B-1C). A previous

215

study by Jamin, and Flores (1998) also suggested that a higher yelowness value is an

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indication of higher protein content. On the other hand, the temperature, when evaluated

217

isolated, had the tendency to decrease the redness (Fig. 1B). When combined with the

218

increase of feed moisture and the WPC content the temperature elevation can reduced

219

the yelowness of the products.

220

3.2 Porosimetry

221

The absolute density is defined as the mass of powder per unit of absolute

222

volume. The total pore volume can be calculated as the difference between the bulk

223

volume and true volume. Likewise, if open pore volume and closed pore volume are

9

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determined, their sum is total pore volume (Webb, 2001). The increase in feed moisture

225

(up to 23 g/100 g) and the temperature (up to 173ºC) were able to increase the values of

226

density (Fig. 1D). Despite the increase in those parameters increased the total pore

227

volume, it is worth to highlight that the interaction between moisture and temperature

228

was able to reduce the total pore volume of the extruded samples (Fig. 1E). The

229

excessive increase in moisture can cause minor expansion of extruded samples by

230

reducing the shear rate induced within the barrel, obtaining products with a lower

231

volume and higher weight. In a study by Ali, Chinnaswamy, and Hanna (1996),

232

increasing the temperature and extruder screw speed was able to increase the total pore

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volume in extruded corn. There was no effect of the addition of WPC on density and

234

porosity of the extrudates (Fig. 1D-1E), unlike Yadav, Anand, and Singh (2014) who

235

found a reduction in density by adding up to 7.5 g/ 100 g of the WPC to a blend with a

236

starchy material (extrusion conditions: - feed moisture: 14g/100g; - screw speed: 350

237

rpm; temperature in the 3rd zone: 130ºC; to produce expanded snacks). In this case,

238

despite the WPC amount was similar to the quoted study, it is important to consider the

239

interaction between the other established parameters (feed moisture, temperature and

240

screw speed) as well as the purpose of final product (expanded snacks or rapid

241

dissolution extruded flours). In this case, is probably that the established amount of

242

WPC was not sufficient to cause a significative changing in the porosimetry of the

243

extrudate flour. So, the shear rate during the operation (given by feed moisture,

244

temperature oscilations and the screw speed) was capable to change de porosimetry,

245

causing a significative conversion degree of the material during the extrusion process.

246

3.3 Crystallinity index (CI) of extruded mixed flours

247

The crystallinity of the granules may vary between 15-45% and can be

248

characterized into three main patterns by X-ray diffraction, types A, B and C.

10

249

Subsequent analysis of the XRD patterns (figures not shown) revealed that the samples

250

had a profile similar to crystal type "A". The default type A is denser and has less space

251

for water molecules, usually being found in cereal starches (Lobo, & Silva, 2003).

252

The combination of rising WPC (to 0.64 up to 7.36 g/100g) and feed moisture

253

(16.64 up to 23.36 g/100g) variables were able to increase the CI in extruded samples

254

(from 20.18% to 29%) (Fig. 1F). The increase in the WPC content may cause a

255

reduction in the total starch content. Also, high moisture content may facilitates the

256

material flow inside the extruder barrel, decreasing the shear rate and residence time,

257

which would perhaps decrease the degree of starch gelatinization.

258

The CI of extruded samples ranged from 20.18% to 29%, while the CI of rice

259

was 31.88% (Table 1). It was also observed that, compared with to white rice, a

260

decrease (9 to 37%) in the crystalline structure in the samples subjected to the extrusion

261

process was noted (Table 1). The main peaks were displayed at d= 11.48 (7.7°), d= 6.71

262

(13.18°) and d= 4.44 (19.98°) in 2Ɵ for mixed flours. Polished white rice flour

263

presented three diffraction peaks [d= 5.87 (15.2°), d= 5.18 (17.3°) and d= 3.83 (23.2°)]

264

in 2Ɵ. Cooking extrusion can destroy the organized crystal structure of the starch. Such

265

destruction may be complete or partial, depending on the extrusion variables, such as

266

moisture content and shear rate, and also the ratio of amylose/amylopectin of the starch

267

in use. It is clear that the starch granules can resist the "breaking" of their typical

268

structure during extrusion at high moisture and low-grade shear conditions; however,

269

increasing the severity of the heat treatment causes the granules to lose their organized

270

structures.

271

3.4 Water absorption and water solubility indexes

272

The increased content of WPC was the only variable able to increase the

273

solubility values of the samples (Fig. 2A). This was also observed by Yadav et al.

11

274

(2014) using up to 7.5 g/100 g WPC. Perhaps, the increase of WSI values is probably

275

because the WPC is soluble and presents as higher soluble solids. The increase of raw

276

material rich in proteins was also able to raise the solubility values of the extruded

277

samples (Sumago, Gulati, Weier, Clarke, & Rose, 2016). Moreover, both the moisture

278

and temperature increase were able to reduce the solubility of the extruded samples

279

(Fig. 2A). The significant increase in feed moisture has the ability to reduce the

280

gelatinization of the starchy material during extrusion. Thus, the starch granules that

281

were not fully gelatinized are not destroyed and, thus, there is no formation of smaller

282

molecular compounds which would favor the solubility increase.

283

Although the proteins of vegetables, including cereals and legumes have

284

hydrophilic sites, the denaturation process that occurs during extrusion may trigger the

285

same loss of hydration capacity, favoring solubility (Silva, Ascheri, Ascheri, & Teba,

286

2013).

287

The variables in the extrusion process were not able to significantly modify the

288

water absorption values, as previously indicated by Yadav et al. (2014). Thus, the

289

Pareto chart was not generated. Examining the non-extruded rice flour, it was observed

290

that the extrusion process was able to increase both solubility and absorption of the

291

samples (Table 1).

292

3.5 Pasting properties

293

All variables used in the extrusion process were capable of altering the viscosity

294

profile of the extruded samples (Fig. 2B-2E). In general, the content of WPC had great

295

influence on viscosity, decreasing it. Onwulata, Tunick, and Thomas-Gahring (2014)

296

showed that the presence of WPC in extruded blends reduced the viscosity of all

297

samples. The initial viscosity, referring to the sample viscosity values when subjected to

298

the initial cycle of investigation (at 25ºC) was positively influenced by temperature

12

299

applied during the extrusion processing (Fig. 2B). When comparing raw samples of

300

white rice to extruded samples subjected to heat treatment (Table 1), there was a

301

significant increase in the inicial viscosity at 25°C (and the other viscosity values) as

302

indicated by changes in starch granules following gelatinization caused by heat during

303

cooking. The increase in the extrusion temperature was also able to cause an increase in

304

the maximum and final viscosities (Fig. 2C-2D). This means that perhaps, the applied

305

temperature in the process was able to keep a proportion of starch granules capable of

306

increasing the viscosity when subjected to heating at 95°C in the viscometer (maximum

307

viscosity). Finally, these starch granules, when cooled, had undergone agglomeration of

308

amylose chains leading to retrogradation, thus increasing the final viscosity.

309

The increase in WPC content (in substitution to rice flour) reduces the total

310

amount of starch in the sample, favoring the decrease of the maximum, final and

311

setback viscosities in all samples. When associated with the processing moisture, the

312

WPC also tended to reduce the final viscosity and setback viscosity (Fig. 2D-2E).

313

Heating causes the swelling of starch granules resulting in starch gels, increasing the

314

maximum viscosity at 95ºC. Starch gels have been defined as composites consisting of

315

swollen granules filling an interpenetrating polymer network, and the major polymer in

316

the network is amylose. So, the decrease in final viscosity may also indicates the

317

destruction of this gel structure (Singh, Nakaura, Inouchi, & Nishinari, 2008).

318

Additionally, amylose and lipids assist in maintaining granule integrity during heating;

319

thus stronger disintegration of the swollen starch granules in the presence of low

320

amylose may also have resulted in lower setback values (Singh et al., 2008).

321

3.6 Reconstitution test and selection of the best assays

322

The dissolution time of the extruded mixed flours ranged from 27 s (test 12) to

323

50 s (tests 7 and 9) (Table 1), which can be considered a good time for fast-dissolving

13

324

products. Note also that the WPC content had a positive quadratic influence on the

325

reconstitution time (Fig. 2F). Thus, evaluating results derived from the reconstitution

326

test as well as tests with higher WPC content, it appears that the samples with the best

327

features for this test were: T5 (46 s), T8 (47 s), T10 (48 s) and T16 (43 s). These

328

samples showed better overall appearance after reconstitution and 30 minutes after

329

resting; there was no formation of lumps, and gels were uniform and creamy. These

330

flours in general also showed good paste viscosity characteristics and water absorption.

331

It is noteworthy that there was no phase separation in any of the developed flours.

332

3.7 Proximate composition

333

The best assays and raw materials were analyzed for their proximate

334

composition. The extruded samples with higher levels of WPC showed higher protein

335

content (Table 2). Furthermore, the increase of WPC resulted in extruded samples with

336

higher lipids and ash and a lower total carbohydrate content. The final moisture of the

337

extruded samples was higher in treatments with higher levels of WPC and feed

338

moisture, but still ideal for the preservation (shelf stable) of the extruded products

339

(approximately 5 g/100g) (Berrios, 2011). The raw samples of rice and WPC had a

340

composition similar to several studies, including Coutinho, Batista, Caliari, and Junior

341

(2013) and Leksrisompong, Miracle, and Drake (2010) who found for rice flour (10.45

342

g moisture/100g, 6.52 g proteins/100g, 0.96 g lipids/100g, 0.22 g ash/100g) and for

343

twenty samples of whey protein (3.37 to 6.76 g moisture/100g, 66.4 to 88.3 g

344

proteins/100g, 0.00 to 7.08 g lipids/100g and 1.94 to 9.09 g ash/100g).

345

3.8 Minerals

346

WPC has a higher content of minerals analyzed when compared to polished

347

white rice flour, except for iron (Table 2). Dairy products in general are not sources of

14

348

this mineral, specially because of the food processing (Santillán-Urquiza, Ruiz-

349

Espinosa, Angulo-Molina, Vélez Ruiz, & Méndez-Rojas, 2017).

350

The extruded mixed flours containing higher WPC levels had higher levels of

351

sodium, magnesium, phosphorus, potassium and calcium. Morr, and Foegeding (1990)

352

demonstrated that WPCs obtained from different commercial sources had considerably

353

mineral contents, including calcium, sodium and phosphorous. No changes were

354

observed in the manganese, copper and zinc content, even with the addition of WPC.

355

Iron content oscillated between the extrusion treatments. This can be attributed to a

356

possible contamination of the samples within the extruder during processing. As

357

evidenced in the present study, Casper, Wendorff, and Thomas (1999) also observed

358

that potassium represented the largest component of WPC - bovine cheese whey (620

359

mg/100g); calcium (510 mg/100g), sodium (570 mg/100g), phosphorous (320

360

mg/100g), and magnesium (70 mg/100g) represented other major minerals in WPC.For

361

these authors minor ash components included copper, zinc, and iron.

362

3.9 Amino acids

363

Due to its characteristics, WPC had higher levels of most of the analyzed amino

364

acids (except methionine and glycine), relative to white rice (Table 3). Among the

365

extruded mixtures, no significant variations in relation to the levels of most amino acids

366

were observed. Because it is a heat treatment, extrusion processing can reduce the

367

retention of amino acids. But, considering the amino acid content of the raw material, as

368

well as the amino acid content of the extruded samples, an increase in amino acid

369

contents after the extrusion process was observed. The retention rates are generally

370

dependent on feed moisture, temperature, and other extrusion parameters. Loss of amino

371

acids can be partially explained by the Maillard reaction during the extrusion process,

372

which is a major concern in developing a quality product with a high nutritional value.

15

373

Also, free amino acids are much more sensitive to damage during extrusion cooking

374

than those in proteins (Singh, Gamlath, & Wakeling, 2007). In this previous study, no

375

significant changes were found in the retention of essential amino acids, except lysine,

376

in the extrudates made from milk protein (at 10 and 30 g/100 g levels; 110 and 125ºC,

377

19 and 23.5 g/100 g feed moisture). Retention of other essential amino acids varied

378

from 80 to 100% in most situations. Extrudates processed at low-feed moisture and high

379

temperature showed the greatest loss in essential amino acids. Additionally, in this

380

study, the milk protein level did not significantly affect the amount of lysine retained in

381

the extruded products.

382

Regarding the essential amino acid score in the extruded samples, it was

383

observed that the amino acids lysine and leucine were limited considering the age range

384

between 2 and 5 years old. Only lysine was limited for children between 10 and 12

385

years old and only for the extruded sample with a lower content of WPC (T5). The other

386

amino acids were not limited, even for adults.

387 388

3.10 Electrophoresis

389

It was observed that the extruded samples maintained an electrophoretic profile

390

similar to each other (Fig. 3). The results indicated that all fractions present in rice were

391

identified in extruded mixed flours. The main markers observed in the rice flour were

392

referred to the molecular weights of 21.66 kDa and 34.15 kDa, representing β-glutelin

393

and α-glutelin, respectively (Silveira, Santos, Didonet, Didonet, & Brondani, 2010). The

394

WPC showed a strong band highlighted with a molecular weight of approximately 17.6

395

kDa, suggesting that theis marking refers to the β-lactoglobulin fraction (Edwards,

396

Creamer, & Jameson, 2008). Also, the samples containing higher WPC contents

397

presented similar marking to the same level (most notably in T10 and T16). The same

16

398

was not evidenced in T9 treatment, presenting the lesser proportion of whey protein

399

(0.64 g/ 100 g WPC).

400

Polypeptide markers at approximately 62.3 kDa identified in the sample of WPC

401

were discreetly evidenced in the extruded samples. It is possible that this molecular

402

weight corresponds to bovine whey albumin (Edwards et al., 2008). Pehaps the

403

treatment by extrusion (considering the variations in temperature and moisture) was

404

able to maintain intact polypeptide chains, with most reductions being most observed in

405

proteins from WPC for all treatments, regardless of temperature and moisture variation.

406

Also, other markers were identified in WPC at 41.55 kDa (not identified

407

fraction) and approximately 75 kDa (lactoferrin fraction – Etzel, 2004), which were not

408

evidenced in the extruded samples.

409

4. Conclusions

410

The addition of WPC (up to 7.36 g/100 g) positively influenced the quality of

411

the final extruded sample, with regard to the increased solubility of the mixed flours and

412

reduced tendency for retrogradation, which are ideal conditions for rapid dissolution

413

products. In this context, the thermoplastic extrusion stands out as being a high

414

temperature short time processing, allowing the combination and suitability of different

415

processing parameters, for the production of extruded flours for use in baby foods and

416

other uses. Furthermore, the addition of WPC contributed positively to increased protein

417

quality and content, as well as some minerals. The increased temperature (up to 173ºC)

418

positively contributed to the increased viscosity of samples; however, increasing the

419

feed moisture (up to 23 g/100 g) also favors the reduction of solubility and increased

420

density, suggesting a lower degree of cooking of the extruded samples. Note also that

421

the operating conditions applied during processing by extrusion were able to maintain

422

intact polypeptide chains, with losses only observed in proteins derived from WPC.

17

423

The production of extruded flours from the by-products of rice and whey protein

424

can be a great alternative to producing processed food and may be of commercial

425

interest due to the characteristics of this mixture.

426

5. Conflict of interest

427

The authors attest that there were no interests that competed with objective

428

interpretation and presentation of the results.

429

6. Acknowledgments

430

The authors gratefully acknowledge Federal Rural University of Rio de Janeiro,

431

Coordination for the Improvement of Higher Education Personnel (CAPES) for the

432

scholarship, as well as Embrapa Food Technology and Alibra Ingredients for the

433

donation of whey protein.

434

7. References

435

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436

concentrate texturized at acidic pH: Effect of extrusion temperature. LWT - Food

437

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438 439 440 441

Ali, Y., Hanna, M.A., & Chinnaswamy, R. (1996). Expansion characteristics of extruded corn grits. LWT - Food Science and Technology, 29 (8), 702-707. Ames, J. M. (1998). Applications of the Maillard reaction in the food industry. Food Chemistry, 62(4), 431–439.

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Anderson, R.A., Conway, H.F., Pfeifer, V.F., & Griffin Jr., L. (1969). Gelatinization of

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corn grits by roll- and extrusion-cooking. Cereal Science Today, 14 (1), 4-11.

444

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Maskan, M., & Altan, A. Advances in Food Extrusion Technology. Contemporary

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Coutinho, L.S., Batista, J.E.R., Caliari, M., & Soares Júnior, M.S. (2013). Optimization

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soybean. Food Science and Technology, 33(4), 705-712.

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465

Dissanayake, M., Liyanaarachchi, S., & Vasiljevic, T. (2012). Functional properties of

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whey proteins microparticulated at low pH. Journal of Dairy Science, 95, 1667-

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proteins. Pages 163-203. In: Thompson, A., Boland, M., & Singh, H. Milk

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proteins: from expression to food. New York: Elsevier, 2008. 535 p.

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El-Ghany, I.H.A., El-Asser, M.A., Nagy, K.S., & El-Maksoudm, A.A.A. (2013). Effect

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of milk proteins on physical and chemical characteristics of crispy puff snacks.

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Etzel, M.R. (2004). The emerging role of dairy proteins and bioactive peptides in

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nutrition and health. Manufacture and use of dairy protein fractions. The Journal

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479

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for proteins in foods. Technical series, 77. Rome: FAO Publications, 87p.

482

Fernandes, A.F., Madeira, R.A.V., Carvalho, C.W.P., & Pereira, J. (2016). Physical and

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sensory characteristics of pellets elaborated with different levels of corn grits and

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whey

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Fuente, M.A., Singh, H., & Hemar, Y.L. (2002). Recent advances in the characterisation

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characteristics of hexaploid wheat (Triticum aestivum L.): properties of starch

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gelatinization and retrogradation. Cereal Chemistry, 74 (5), 576-580.

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Jamin, F.F., & Flores, R.A. (1998). Effect of additional separation and grinding on the

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chemical and physical properties of selected corn dry-milled streams. Cereal

494

Chemistry, 75, 166–170.

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495 496

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Leksrisompong, P.P, Miracle, R.E., & Drake, M. (2010). Characterization of flavor of

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whey protein hydrolysates. Journal of Agricultural and Food Chemistry, 58,

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6318–6327.

500 501 502 503

Lobo, A.R., & Silva, G.M.L. (2003). Resistant starch and its physicochemical properties. Brazilian Journal of Nutrition, 16 (2), 219-226. Montgomery, D. C. (2012). Design and analysis of experiments. (8th ed.). New York: Wiley, (Chapter 6).

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Morr, C. V., & Foegeding, E. A. (1990). Composition and functionality of commercial

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whey and milk protein concentrates and isolates: a status report. Food

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Onwulata, C.I., Smith, P.W., Konstance, R.P., & Holsinger, V.H. (2001). Incorporation

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of whey products in extruded corn, potato or rice snacks. Food Research

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Onwulata, C.I., Tunick, M.H., & Thomas-Gahring, A.E. (2014). Pasting and extrusion

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Pires, C.V., Oliveira, M.G.A., Rosa, J.C., & Costa, N.M.B. (2006). Nutritional quality

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Sacchetti, G., Pinnavaia, G.G., Guidolin, E., & Dalla Rosa, M. (2004). Effects of

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water absorption of pre-cooked flours made with maize and carioca type beans

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531

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extrusion cooking using different water feed rates on the quality of ready-to-eat

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snacks made from food by-products. Food Chemistry, 114, 226-232.

538

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542 543

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546

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547

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548

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549 550 551

Figure 1 - Estimates of linear (L) and quadratic (Q) effects of the whey protein

552

concentrate, feed moisture, and temperature on the rice-based extruded flour. A:

553

lightness, B: red-green color, C: yellow-blue color, D: density, E: total volume pore, F:

554

crystallinity index, 1L by 2L, 1L by 3L, and 2L by 3L: interaction between the

555

independent variables (1L: whey protein concentrate, 2L: feed moisture, and 3L:

556

temperature). The line indicates the 95% confidence level, and factors with standardized

557

effect values to the right of the line are statistically significant. The respective

558

polynomial equations with the coefficients of regression of the significant variables are

559

expressed below the graphics.

560 561

Figure 2 - Estimates of linear (L) and quadratic (Q) effects of the whey protein

562

concentrate, feed moisture, and temperature on the rice-based extruded flour. A:

563

lightness, B: red-green color, C: yellow-blue color, D: density, E: total volume pore, F:

564

crystallinity index, 1L by 2L, 1L by 3L, and 2L by 3L: interaction between the

565

independent variables (1L: whey protein concentrate, 2L: feed moisture, and 3L:

566

temperature). The line indicates the 95% confidence level, and factors with standardized

567

effect values to the right of the line are statistically significant. The respective

23

568

polynomial equations with the coefficients of regression of the significant variables are

569

expressed below the graphics.

570 571

Figure 3 – Gel electrophoresis (SDS/PAGE) of whey protein concentrate, rice flour, and

572

extruded flours. T3 (2 g/100 g WPC - 22 g/100 g feed moisture - 120°C); T5 (2 g/100 g

573

WPC - 18 g/100 g feed moisture - 160°C); T8 (6 g/100 g WPC - 22 g/100 g feed

574

moisture - 160°C); T10 (7.36 g/100 g WPC - 20 g/100 g feed moisture - 140°C); T16 (4

575

g/100 g WPC- 20 g/100 g feed moisture - 140°C).

576 577 578

24

579 580

Table 1. Experimental design with real values for whey protein concentrate (X1), feed

581

moisture (X2), and temperature (X3), as well as the results obtained in the experiments

582

examining the rice-based extruded flours**

Runs

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

X1 X2

X3

L*

a*

83. 0.1 30 4 6. 18. 83. 120 0.1 0 0 30 4 2. 22. 84. 120 0.4 0 0 87 2 6. 22. 81. 0.5 120 0 0 28 8 2. 18. 87. 160 0.5 0 0 36 0 6. 18. 86. 160 0.4 0 0 48 1 2. 22. 86. 160 0.3 0 0 01 8 6. 22. 84. 160 0.2 0 0 77 0 0. 20. 84. 140 0.5 64 0 90 4 7. 20. 81. 140 0.2 36 0 01 1 4. 16. 85. 140 0.3 0 64 44 4 4. 23. 81. 0.4 140 0 36 57 2 4. 20. 106. 83. 0.2 0 0 36 29 0 4. 20. 173. 85. 0.4 0 0 64 90 0 4. 20. 84. 140 0.3 0 0 95 1 4. 20. 85. 140 0.1 0 0 06 9 2. 0

18. 120 0

b*

W W ρabs TP CI AI IV PV FV SB SI RT (g/c (cm3 (% (g (Pa (Pa (Pa (Pa (% (s) 3 m) ) ) gel. .s) .s) .s) .s) ) -1 g )

8.2 1.38 6 96

0.28 03

29. 8.4 7.9 1.0 02 6 3 26

0.5 29

0.8 32

0.5 43

46

10. 1.37 44 32

0.27 18

21. 10. 7.6 0.7 68 96 6 63

0.5 56

0.6 87

0.4 64

47

8.6 1.49 5 30

0.33 02

21. 6.6 8.2 0.8 21 4 3 79

0.6 46

1.1 65

0.7 86

49

13. 1.48 72 32

0.32 58

21. 7.3 7.6 0.8 99 5 9 78

0.5 89

0.5 15

0.3 53

48

8.3 1.44 8 62

0.30 85

23. 7.5 7.6 1.0 55 7 4 02

0.5 69

0.8 10

0.5 09

46

10. 1.45 08 91

0.31 46

22. 8.7 7.4 0.9 64 8 0 86

0.5 23

0.6 63

0.4 34

47

7.9 1.47 7 78

0.32 33

23. 5.4 8.5 1.0 34 8 7 36

0.7 51

1.2 06

0.8 22

50

10. 1.50 46 67

0.33 63

22. 6.5 8.0 1.0 30 0 1 94

0.6 66

0.6 77

0.4 36

47

8.1 1.45 3 69

0.31 36

23. 7.5 7.9 0.9 03 7 1 94

0.6 90

1.1 39

0.7 50

50

10. 1.42 20 52

0.29 84

23. 9.3 7.4 0.6 58 8 7 95

0.4 22

0.6 44

0.3 93

48

9.2 1.40 9 11

0.28 63

22. 9.5 7.5 0.8 06 4 7 94

0.4 71

0.7 40

0.4 80

32. 90

11. 1.49 98 27

0.33 01

26. 8.2 7.9 1.1 88 4 8 81

0.7 24

0.5 86

0.4 20

27. 44

10. 1.39 17 74

0.28 44

24. 9.6 7.3 0.7 71 9 3 75

0.5 07

0.7 48

0.4 78

40

9.2 1.47 3 64

0.32 27

26. 7.6 7.6 0.9 42 1 2 71

0.6 63

0.9 30

0.5 74

38

9.1 1.47 2 42

0.32 17

22. 10. 7.8 0.9 43 53 2 68

0.6 82

0.8 01

0.5 28

45

9.3 1.44 7 45

0.30 77

22. 9.8 7.6 0.8 24 0 0 28

0.6 18

0.8 63

0.5 81

43. 06

25

17

4. 0

20. 140 0

18

4. 0

20. 140 0

19

4. 0

20. 140 0

20

4. 0

20. 140 0

Standard deviation central points

-

-

-

86. 0.5 91 0 84. 0.5 66 2 83. 0.3 81 6 84. 0.1 51 9

9.2 1.48 0 04

0.32 45

20. 8.0 7.4 0.9 56 4 8 68

0.6 03

0.8 64

0.6 09

36. 76

9.1 1.46 0 17

0.31 59

20. 9.2 7.5 0.9 60 2 9 88

0.6 89

0.9 24

0.6 19

40. 28

9.4 1.44 3 61

0.30 85

22. 8.8 7.0 0.8 06 0 5 60

0.6 87

0.8 53

0.5 63

36. 62

9.8 1.42 0 99

0.30 07

20. 9.3 7.0 0.8 18 1 6 13

0.6 58

0.7 99

0.5 20

40. 28

1.1 0.1 0.2 0.02 6 6 7

0.01

0.9 0.6 0.2 0.0 5 6 8 8

0.0 4

0.0 4

0.0 4

2.7 2

583

85. 6.9 1.48 0.32 31. 0.7 2.4 0.0 1.2 6.8 5.6 0.2 58 6 18 515 88 6 2 14 17 79 62 5 Whey 89. 0.0 14. 1.30 0.23 -- --protein 53 2 01 32 26 - **: Data are expressed as the mean of three replications. L*: lightness, a*: red-green color, b*: yellow-

584

blue color, ρabs: absolute density, TP: total pore, CI: crystallinity index, WSI: water solubility index,

585

WAI: water absorption index, IV: initial viscosity, PV: peak viscosity, FV: final viscosity, SB: setback,

586

RT: reconstitution time.

Rice flour

--

--

--

26

Table 2. Proximate composition and mineral content of rice flour, whey protein concentrate, and extruded flours

Composition

RF

WPC

T5

T8

T10

T16

CV (%)

Proximate composition (g/100 g) Moisture

9.89

6.97

4.82 ± 0.03 c

6.10 ± 0.05a

5.82 ± 0.04 a

5.48 ± 0.08b

9.93

Proteins

6.84

88.09

8.74 ± 0.00 c

13.82 ± 0.14a

13.62 ± 0.05a

11.26 ± 0.05b

20.09

Lipids

0.75

1.89

0.32 ± 0.00 b

0.38 ± 0.01 ab

0.45 ± 0.02 a

0.37 ± 0.01b

14.08

Ash

0.48

2.95

0.40 ± 0.01 c

0.56 ± 0.02a

0.51 ± 0.00ab

0.47 ± 0.01b

13.93

81.65

0.10

85.36 ± 0.06 a 78.82 ± 0.30b

79.30 ± 0.17b

82.08 ± 0.21b

3.70

1502.34

1547.11

1586.90

1572.05

1576.07

Total carbohydrates Energetic value (kJ)

1564.73

Minerals (mg/100 g) Sodium

5.44

180.80

5.99±0.30 c

14.88±0.05 a

14.55±0.10a

9.71±0.92b

34.98

Magnesium

25.05

63.80

20.96±0.16c

26.20±0.02 a

22.57±0.02bc

23.29±1.06b

8.90

Phosphorous

81.40

239.40

98.94±0.63b

113.35±0.99a

106.45±0.24 ab 104.60±4.35ab

5.44

Potassium

55.55

543.45

84.33±0.19c

118.20±1.04a

112.76±0.53 a

96.34±3.51b

13.99

Calcium

5.77

412.25

11.89±0.13c

33.66±0.29 a

33.21±0.91a

21.26±1.53b

38.82

Manganese

1.12

ND

1.75±0.01 a

1.75±0.01a

1.74±0.01 a

1.74±0.11a

3.90

Iron

0.55

0.41

0.38±0.01 b

1.75±0.11b

1.92±0.00 a

1.84±0.15a

85.80

Copper

0.66

ND

0.33±0.00 a

0.33±0.00a

0.31±0.00 a

0.33±0.02a

3.26

Zinc

1.57

ND

1.46±0.00 a

1.49±0.01a

1.38±0.01 a

1.41±0.11a

4.35

- **: Data are expressed as the mean ± standard deviation of three replications for proximate and two replications for minerals. ND: not determined. RF: Rice flour. WPC: Whey protein concentrate. Runs: T5 (2 g/100 g WPC - 18 g/100 g feed moisture - 160°C); T8 (6 g/100 g WPC - 22 g/100 g feed moisture 160°C); T10 (7.36 g/100 g WPC - 20 g/100 g feed moisture - 140°C); T16 (4 g/100 g WPC- 20 g/100 g feed moisture - 140°C). Means with different letters in the same line are significantly different according to Tukey’s test (p<0.05). CV: Coefficient of variation.

27

1

Table 3. Amino acid content of rice flour, whey protein concentrate, and extruded flours mg/g protein Amino CV Rice acids (%) WPC T5 T8 T10 T16 flour Aspartate

34.36

94.07 93.25±7.28a

Serine

29.24

49.72 50.34±1.62a

Glutamate

115.50

104.20±3.0 97.65±16.6 91.92±1.88 7a 52.10±0.00 a

1a 49.56±5.71 a

a

8.96

47.96±0.00 a

5.50

159.8 175.63±12. 185.24±5.1 173.27±28. 169.18±3.1 4

14 a

Glycine

18.27

15.74 36.04±0.81a

Histidine

12.43

15.93 22.31±0.81a

Arginine

14.62

27.77 73.80±2.43a

Threonine

19.01

70.27 44.05±0.81b

2a 30.75±1.53 b

22.07±1.53 a

57.53±0.51 b

04a 30.10±1.04 b

20.19±2.60 a

56.17±5.71 b

4a 32.86±0.00 ab

21.31±0.00 a

7.59

7.99

6.86

65.72±1.26 12.5 ab

4

56.08±0.51 53.96±5.71 a 47.51±0.63 11.1 a

48.84±1.53

b

5

45.74±0.63

Alanine

41.67

44.65 48.63±2.43a

Proline

46.05

54.79 50.34±3.24a

Tyrosine

19.74

32.04 35.47±0.00a

Valine

25.58

52.94 51.49±3.24a 54.63±0.51 51.40±7.27 a 51.51±0.00 6.41

a

55.35±0.51 a

32.20±1.53 ab

45.89±6.75 a

ab

52.50±6.75 a

30.10±1.04 b

a

49.73±0.00 a

31.97±1.26 ab

6.75

7.09

6.88

28

a

Methionin 11.62

7.61 39.47±4.05a

e Lysine

13.89

82.64 40.62±2.43a

Isoleucine

16.81

59.64 84.67±4.85a

Leucine

67.98

106.5 6

49.20±0.00a

50.65±2.05 a

48.84±0.51 a

a

48.09±8.83 a

46.26±6.23 a

42.18±0.63 13.4 a

8

43.07±0.63 a

9.38

94.43±0.51 90.31±11.4 85.26±0.00 a

45.22±1.53 a

2

a

43.69±2.60 a

a

7.15

45.74±0.63 a

5.33

Sulfurous (Methioni

175.63±0.8 185.24±0.3 173.27±0.5 169.18±3.0 25.87

ne +

22.12

9a

6a

2a

8a

7.82

Cysteine) 2

- **: Data are expressed as the mean ± standard deviation of two replications. WPC: Whey protein

3

concentrate. Runs: T5 (2 g/100 g WPC - 18 g/100 g feed moisture - 160°C); T8 (6 g/100 g WPC - 22

4

g/100 g feed moisture - 160°C); T10 (7,36 g/100 g WPC - 20 g/100 g feed moisture - 140°C); T16 (4

5

g/100 g WPC- 20 g/100 g feed moisture - 140°C). Means with different letters in the same line are

6

significantly different according to Tukey’s test (p<0,05). CV: Coefficient of variation.

7 8 9 10 11 12 13 14

29

15 16 17 18

1) Whey protein concentrate (WPC) was added to rice-based extruded flour.

19

2) The extrusion conditions were manipulated to produce rapid dissolution flours.

20

3) The addition of WPC improved the nutritional and rheological characteristics of the

21

flours.

22

4) The extrusion conditions allowed for the protein quality to be maintained in the final

23

product.

24

30