Physicochemical properties of sorghum and technological aptitude for popping. Nutritional changes after popping

LWT - Food Science and Technology 71 (2016) 316e322

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Physicochemical properties of sorghum and technological aptitude for popping. Nutritional changes after popping E.E. Llopart a, b, S.R. Drago a, b, * a b

Instituto de Tecnología de Alimentos, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829, Santa Fe, Argentina CONICET, Godoy Cruz 2290, Buenos Aires, C1425FQB, Argentina

a r t i c l e i n f o

a b s t r a c t

Article history: Received 26 August 2015 Received in revised form 23 February 2016 Accepted 7 April 2016 Available online 9 April 2016

The aims were to characterize 28 hybrids of red (RS) and white (WS) sorghum by physicochemical analysis, relate them with their technological aptitude for popping, and asses nutritional changes after popping in selected samples. Through principal component analysis it was observed that the higher the grain hardness, the higher apparent volume of popped product was, and performance was higher for WS. An indicator of the ability of sorghum hybrids to pop was developed. Comparing precooked samples with their native flours, no significant difference for protein and fat content was observed, but ash, dietary fiber, and minerals were reduced by popping. Protein digestibility increased but available lysine decreased (WS:1.3 and RS:1.2 times). Phytic acid, polyphenols and antioxidant capacity were reduced (WS: 1.3 and RS: 1.5; WS: 1.3 and RS: 1.8; WS: 1.3 and RS: 1.7 times, respectively), but whole flour precooked by popping can be considered an important source of antioxidants. Popped sorghum is an interesting alternative as food itself, or as ingredient for making other foods such as cereal bars. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Whole grain Sorghum Popping Antioxidants

1. Introduction Dietary recommendations of the World Strategy for populations (CODEX, 2006) recommend the consumption of whole grains (WG). The beneficial effects of WG on health is due to fiber, micronutrients and phytochemicals present in the outer layer of the grain €nen, & Poutanen, 2011) as well as and germ (Raninen, Lappi, Mykka WG are an important source of antioxidants (Miller, Rigelhof, Marquart, Prakash, & Kanter, 2000). Epidemiological studies suggest that consumption of WG, including sorghum, reduces mortality from cardiovascular disease, which is probably related to its antioxidant properties (Awika & Rooney, 2004). Incorporating WG into the diet is low by the lack of habits,

Abbreviations: AV, apparent volume; AP, aptitude for popping; BD, bulk density; BPC, bound polyphenol content; d.b., dry basis; DCa%, calcium bio-accessibility; DFe %, iron bio-accessibility; DZn%, zinc bio accessibility; F%, percentage of flotation; F, fine fraction; FPC, free polyphenol content; MR, milling ratio; PA, phytic acid; AC, antioxidant capacity; PCA, principal component analysis; PP, popping performance; T, thick fraction; TPC, total polyphenol content; TW, test weight; WG, whole grains; WS, white sorghum; RS, red sorghum. * Corresponding author. Instituto de Tecnología de Alimentos, Facultad de Ingeniería Química, Universidad Nacional del Litoral, Santiago del Estero 2829, Santa Fe, Argentina. E-mail address: sdrago@fiq.unl.edu.ar (S.R. Drago). http://dx.doi.org/10.1016/j.lwt.2016.04.006 0023-6438/© 2016 Elsevier Ltd. All rights reserved.

problems due to higher cooking times and limited amounts of processed foods based on them, due to technological difficulties of incorporating WG in foods (Drago et al., 2010). One possibility is to expand the grains by popping, which is a traditional, simple, inexpensive and rapid method (Gonz alez, Torres, De Greef, Tosi & Re, 2002). During popping, grains are exposed to high temperature for short time, which leads to explosion of the grain with the consequent transformation of cereal, changes in nutritional profile and lifetime of the product, and inactivation of undesirable microorganisms and certain antinutrients (Nath, Chattopadhyay, & Majumdar, 2007). In addition, this process develops flavors and therefore, improves acceptability (Sreerama, Sasikala, & Pratape, 2008). The optimum conditions for popping depend on the method used and the characteristics of the grains such as the proportion of horny endosperm and pericarp resistance. It is also know, that some properties of the grains can predict or explain the behavior in different processes such as hectoliter weight, percentage of flotation, density and milling ratio (De Dios, Puig, & Robutti, 1992) thus it is important to define the parameters that distinguish sorghum hybrids suitable for popping. The aims of the study were to characterize 28 hybrids of sorghum by physicochemical analysis, assess their technological aptitude for popping, determine the relationship among them and

E.E. Llopart, S.R. Drago / LWT - Food Science and Technology 71 (2016) 316e322

evaluate some nutritional changes after popping in selected samples. 2. Material and methods 2.1. Raw material 28 sorghum hybrids: 14 white (WS) and 14 red (RS) were evaluated. The Research Program Pannar Sorghum Seed Company RSL donated some of them and others were from commercial sources. 2.2. Methods 2.2.1. Proximate composition Moisture, ether extract, protein and ash were determined according the AACC methods (AACC, 2000). 2.2.2. Minerals Mineral content was measured by atomic absorption spectroscopy using an Atomic Absorption Spectrophotometer (Analyst 300 Perkin Elmer) after dry ashing. To determine Ca content, lanthanum chloride was used at a final concentration of 0.5% in order to minimize the effect of phosphates. 2.2.3. Total polyphenols (TPC) Free (FPC) and bound (BPC) phenolic compounds were extracted according to Qiu, Liu, and Beta (2010). Then, phenolic compound content was determined by the Folin-Ciocalteau method (Singleton, Orthofer, & Lamuela-Raventos, 1999) using gallic acid as standard. 2.2.4. Physical properties 2.2.4.1. Test weight (TW). A 0.25 L Hectoliter Weight Schlopper type scale was used. The results were expressed in kg/hL according to Maxson, Fryar, Rooney, and Krishnaprasad (1971).

317

popped grain weight (dry basis) (d.b.) (g). 2.2.5.2. Popping performance (PP). It was calculated on a dry basis as: (%) ¼ popped grain weight (d.b.) (g)/initial weight (d.b.) (g). 2.2.5.3. Ability for popping (AP). An indicator of the ability of sorghum hybrids to pop was developed, which integrates the information provided by TW, AV and PP as follow:

AP ¼ TW  AV  PP = 10000 Where, TW: test weight (kg/hL), AV: apparent volume (cm3/g grains exploited), PP: popping performance. 2.2.6. Nutritional assessments Selected hybrids (PEX 40730 W and PAN 8918) flours and precooked popped flours were milled with a Ciclotec mill (UD Corp Boulder ColoradoeUSA) using a 1 mm sieve and were analyzed regarding to: 2.2.6.1. Proximate composition. It mentioned before.

was

determined

as

was

2.2.6.2. Available lysine. The method of Carpenter modified by Booth (1971) was used. 2.2.6.3. Protein digestibility. The in vitro method according to Rudloff and Lonerdal (1992) was used. 2.2.6.4. Mineral bio-accessibility. The method of dialyzability according to Drago, Binaghi, and Valencia (2005) was used to estimate iron, zinc and calcium bio-accessibility (DFe%, DZn% and DCa %, respectively). 2.2.6.5. Total polyphenols mentioned before.

(TPC). It was determined as was

TW ½kg=hL ¼ W ðg=0:25 LÞ  100 L = 1 hL 1 kg = 1000 g

2.2.6.6. Phytic acid content (PA). AOAC (1995) method was used.

Where W is the weight in g of 0.25 L.

2.2.6.7. Antioxidant capacity (AC). It was determined by the method of inhibition of the radical cation ABTSþ according to Cian, Luggren, and Drago (2011).

2.2.4.2. Milling ratio (MR). 50 g sample were ground and sieved. The remaining material in the 1 mm sieve was considered the thick fraction (T) and the material that passed through the 0.5 mm sieve was the fine fraction (F). The milling ratio was calculated as: T/F (De Dios, Puig & Robutti, 1992). 2.2.4.3. Percentage of flotation (F%). It is the percentage of grains that float in carbon tetrachloride (CL4C) (Hallgren & Murthy, 1983). 2.2.4.4. Bulk density (BD). It was determined by volume displacement in a graduated cylinder and calculated as: BD (g/cm3) ¼ seed weight/(final volume - initial volume) (Chandrashekar & Kirleis, 1988; De Dios, Puig & Robutti, 1992). 2.2.5. Popping process Adapted fluidized bed VP Model Dryer equipment (Bench Scale Equipment Co., Inc., Dayton, Ohio) was used. Based on previous studies with sorghum hybrids, the following conditions were defined for popping: 250  C temperature for 1 min, 14% and 18% moisture content. The following parameters were evaluated on popped samples: 2.2.5.1. Apparent volume (AV). Apparent Volume of popped sorghum was calculated as: AV (cm3/g) ¼ popped grain volume (cm3)/

2.2.7. Statistical analysis All determinations were performed in duplicate. Normality test (Chi-Square, ShapiroeWilks, Z for skewness and Curtosis Z) were performed for analysis the data. When p-value was higher than 0.05, in two or more of the test, the distribution was considered normal and the mean and standard deviation (SD) were reported. ANOVA was used to determine significant differences among samples. For not normal population, KruskaleWallis test was performed and the median and interquartile range (IR) were reported. Multiple regression was applied to correlate AP with physicochemical results. Statistical software (Statgraphics plus 3.0) was used to perform normality test (Chi-Square, ShapiroeWilks, Z for skewness and Curtosis Z), analysis of variance, multiple regression and principal component analysis (PCA). 3. Results and discussion 3.1. Physicochemical characteristics of sorghum hybrids The results of chemical composition and mineral content of sorghum hybrids are presented in Tables 1 and 2, respectively. All of them were normally distributed, except TPC, FPC, and BPC. The

318

E.E. Llopart, S.R. Drago / LWT - Food Science and Technology 71 (2016) 316e322

Table 1 Proximate composition, phytic acid (PA), free phenolic compounds (FPC) and bound phenolic compounds (BPC) of white (WS) and red (RS) sorghum hybrids.* Hybrids

PEX 40730 W PAN 8706 W PEX 9261 W PAN 8648 PAN 8648 W A9941W WS01 S9C474C TOB48W A9947W Jowar Short ACA544 WS02 Jowar Food WS Average*# PEX 9273 10SAR 0025 10SAR 0010 PEX 42353 PEX 42334 PEX 40676 PAN 8918 PEX 9247 PEX 42345 PEX 1282 PEX 41027 PEX 41011 PEX 9269 PAN 8816 RS Average*#

Protein

Ether extract

Ash

PA

FPC

BPC

(g/100 g)

(g/100 g)

(g/100 g)

(mg/100 g)

(GA mg/100 g)

(GA mg/100 g)

11.9 11.1 9.9 11.4 11.1 10.7 9.8 10.4 9.8 10.7 8.5 9.1 9.5 10.9 10.3 10.7 10.1 11.8 11.0 9.9 11.2 10.7 9.9 11.5 11.2 11.4 9.1 11.1 11.0 10.8

± 0.0 ± 0.0 ± 0.1 ± 0.1 ± 0.0 ± 0.1 ± 0.1 ± 0.1 ± 0.1 ± 0.0 ± 0.0 ± 0.1 ± 0.1 ± 0.1 ± 0.9* ± 0.0 ± 0.0 ± 0.0 ± 0.3 ± 0.1 ± 0.0 ± 0.0 ± 0.1 ± 0.0 ± 0.1 ± 0.1 ± 0.4 ± 0.1 ± 0.1 ± 0.8*

3.1 3.1 3.3 3.0 3.0 3.0 3.1 2.9 2.7 3.4 2.8 3.0 3.1 2.8 3.0 3.0 2.8 3.0 3.0 2.9 3.1 3.0 2.9 3.2 2.9 3.2 3.0 3.0 3.0 3.0

± 0.1 ± 0.1 ± 0.0 ± 0.1 ± 0.1 ± 0.1 ± 0.1 ± 0.1 ± 0.0 ± 0.1 ± 0.0 ± 0.1 ± 0.1 ± 0.0 ± 0.2* ± 0.1 ± 0.0 ± 0.1 ± 0.0 ± 0.0 ± 0.1 ± 0.1 ± 0.1 ± 0.0 ± 0.1 ± 0.1 ± 0.0 ± 0.0 ± 0.1 ± 0.1*

1.7 1.8 1.5 1.6 1.5 1.3 1.5 1.2 1.2 1.3 1.2 1.2 1.5 1.2 1.4 1.8 1.5 1.2 1.1 1.5 1.6 1.6 1.5 1.4 1.5 1.5 2.0 1.5 1.7 1.5

± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.1 ± 0.2* ± 0.1 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.1 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.0 ± 0.1 ± 0.0 ± 0.1 ± 0.2*

928.1 918.1 869.1 877.0 850.9 881.9 960.2 1017.4 739.7 953.9 1008.4 829.1 843.3 968.3 903.2 934.9 1050.3 1255.8 1096.6 1086.4 985.8 1049.3 988.5 1063.4 1134.6 1095.4 927.4 1337.0 876.4 1072.8

± 35.1 ± 35.8 ± 58.7 ± 25.2 ± 6.7 ± 16.5 ± 46.8 ± 47.6 ± 12.1 ± 16.3 ± 28.5 ± 39.0 ± 43.0 ± 4.4 ± 76.4* ± 27.9 ± 41.3 ± 61.8 ± 51.8 ± 28.5 ± 27.7 ± 38.9 ± 42.8 ± 49.0 ± 11.8 ± 54.5 ± 14.2 ± 49.2 ± 44.2 ± 123.8*

110.6 112.7 106.6 103.0 101.8 112.7 108.7 171.2 118.6 101.3 157.4 179.8 180.6 112.4 112.6 189.5 131.5 198.6 150.9 107.8 120.7 201.3 134.7 127.8 105.0 107.8 123.1 197.2 195.7 133.1

± 4.6 ± 2.1 ± 3.2 ± 6.1 ± 2.1 ± 4.2 ± 3.9 ± 6.8 ± 4.7 ± 5.4 ± 4.4 ± 3.4 ± 5.7 ± 5.1 ± 50.8# ± 4.1 ± 4.0 ± 9.6 ± 6.7 ± 3.4 ± 5.5 ± 3.19 ± 6.3 ± 5.4 ± 4.5 ± 2.6 ± 4.4 ± 8.1 ± 7.0 ± 75.0#

578.4 552.2 567.7 594.5 567.2 563.5 408.7 778.5 476.9 564.2 894.4 811.7 773.6 515.5 567.5 942.4 607.6 1104.5 867.8 596.9 620.0 1404.4 856.1 648.7 596.4 712.6 706.6 1224.2 877.5 784.4

± 14.7 ± 4.4 ± 16.6 ± 14.1 ± 16.6 ± 21.8 ± 19.0 ± 20.0 ± 18.3 ± 16.3 ± 27.6 ± 26.0 ± 17.7 ± 16.3 ± 221.4# ± 17.8 ± 11.7 ± 19.3 ± 7.2 ± 10.4 ± 10.3 ± 17.1 ± 16.7 ± 12.5 ± 14.3 ± 16.5 ± 9.0 ± 22.7 ± 17.7 ± 322.5#

3396.54 3995.13 3788.85 3385.52 2849.25 2945.95 3148.56 3433.40 3153.15 3526.01 3177.18 2904.59 3032.78 3183.60 3280.04 2979.58 3492.98 4267.12 3922.23 4203.58 4051.67 3361.52 4171.41 4148.30 4377.38 3842.24 3564.66 3762.98 2991.40 3795.50

± 125.26 ± 99.68 ± 174.94 ± 124.86 ± 86.88 ± 94.87 ± 61.66 ± 136.11 ± 78.33 ± 145.56 ± 43.52 ± 78.24 ± 43.13 ± 62.82 ± 331.84 ± 33.04 ± 57.14 ± 119.97 ± 158.43 ± 66.03 ± 92.53 ± 101.83 ± 193.50 ± 125.50 ± 16.96 ± 83.06 ± 82.08 ± 113.19 ± 112.93 ± 457.73

Results were expressed in dry base as: *mean ± SD or #median ± IR; GA: gallic acid.

Table 2 Mineral content (mg/kg) of white (WS) and red (RS) sorghum hybrids.* Hybrids

Fe

PEX 40730 W PAN 8706 W PEX 9261 W PAN 8648 PAN 8648 W A9941W WS01 S9C474C TOB48W A9947W Jowar Short ACA544 WS02 Jowar Food WS Mean ± SD PEX 9273 10SAR 0025 10SAR 0010 PEX 42353 PEX 42334 PEX 40676 PAN 8918 PEX 9247 PEX 42345 PEX 1282 PEX 41027 PEX 41011 PEX 9269 PAN 8816 RS Mean ± SD

30.41 22.42 25.86 26.91 24.71 29.03 25.37 28.67 32.26 27.57 29.63 23.99 26.28 30.52 27.40 21.99 21.7 19.78 22.24 26.87 21.19 27.04 20.91 23.01 22.07 21.95 23.86 21.45 28.83 23.06

Zn ± 0.01 ± 0.12 ± 0.23 ± 0.07 ± 0.06 ± 0.33 ± 1.84 ± 0.80 ± 0.32 ± 0.53 ± 0.84 ± 1.91 ± 0.86 ± 0.29 ± 2.82 ± 0.11 ± 0.04 ± 0.10 ± 0.19 ± 0.05 ± 0.02 ± 0.09 ± 0.02 ± 0.01 ± 0.01 ± 0.16 ± 0.14 ± 0.06 ± 1.87 ± 2.65

15.38 17.72 16.40 16.69 14.41 11.23 19.10 20.31 17.01 22.65 20.43 18.63 17.93 17.27 18.30 15.17 15.92 12.51 14.54 15.87 18.60 18.37 16.57 19.80 18.04 16.64 17.51 11.68 16.01 16.23

Ca ± 0.31 ± 0.11 ± 0.21 ± 0.14 ± 0.34 ± 0.02 ± 1.52 ± 0.00 ± 0.62 ± 1.56 ± 0.64 ± 0.09 ± 0.67 ± 0.12 ± 2.43 ± 0.24 ± 0.39 ± 0.20 ± 0.17 ± 0.37 ± 0.57 ± 0.81 ± 0.53 ± 0.59 ± 0.48 ± 0.20 ± 0.95 ± 0.38 ± 0.25 ± 2.27

117.33 110.56 110.03 115.06 130.90 146.62 106.69 145.91 139.90 132.34 131.65 159.80 111.46 95.02 125.23 112.31 107.76 121.94 109.83 135.57 126.77 132.77 116.17 111.38 110.69 113.52 117.41 122.37 156.25 121.05

Cu ± 0.08 ± 0.09 ± 0.01 ± 0.06 ± 1.43 ± 1.90 ± 0.73 ± 8.36 ± 3.02 ± 0.90 ± 1.90 ± 0.86 ± 0.95 ± 3.86 ± 18.56 ± 5.59 ± 0.27 ± 0.06 ± 0.19 ± 0.06 ± 0.03 ± 0.15 ± 0.18 ± 0.22 ± 0.17 ± 0.14 ± 0.05 ± 0.26 ± 2.95 ± 13.29

2.83 3.48 2.92 3.36 2.95 3.32 2.58 4.85 2.37 3.09 4.16 2.26 2.70 2.84 3.12 4.61 4.00 2.83 4.72 4.02 3.92 2.79 2.85 4.20 3.92 3.95 3.24 3.83 3.42 3.73

K ± 0.00 ± 0.00 ± 0.01 ± 0.01 ± 0.01 ± 0.10 ± 0.01 ± 0.10 ± 0.06 ± 0.16 ± 0.08 ± 0.01 ± 0.06 ± 0.17 ± 0.70 ± 0.02 ± 0.00 ± 0.01 ± 0.01 ± 0.01 ± 0.02 ± 0.02 ± 0.01 ± 0.02 ± 0.02 ± 0.01 ± 0.01 ± 0.01 ± 0.03 ± 0.62

4115.18 4240.92 3894.73 4254.08 4098.95 2935.71 3707.92 3531.55 4352.87 4137.17 4091.15 3611.92 3739.03 3378.91 3855.55 4053.79 3546.12 3002.94 4563.91 3252.27 3889.69 3846.89 4226.10 5093.48 3968.18 4419.92 3750.08 4326.11 3708.00 3974.82

Mg ± 9.79 ± 6.24 ± 3.13 ± 1.59 ± 295.70 ± 25.02 ± 33.28 ± 6.63 ± 27.55 ± 55.38 ± 34.75 ± 43.18 ± 177.76 ± 253.79 ± 404.73 ± 7.11 ± 49.83 ± 3.22 ± 31.79 ± 8.20 ± 5.70 ± 8.87 ± 13.77 ± 8.75 ± 7.30 ± 10.81 ± 4.08 ± 6.96 ± 248.04 ± 539.59

1548.65 2090.65 1887.66 1548.65 2079.72 1874.28 2057.52 2037.1 1815.25 2321.00 1925.40 1777.67 1954.93 1803.74 1908.73 1849.59 1793.59 1626.81 2179.43 1964.97 2028.75 1688.36 2390.17 2388.72 2116.82 2184.93 1812.92 1990.54 1856.74 1968.14

Na ± 16.39 ± 14.98 ± 14.47 ± 16.39 ± 0.81 ± 17.28 ± 68.87 ± 57.68 ± 35.80 ± 47.55 ± 14.38 ± 116.70 ± 18.22 ± 43.27 ± 209.62 ± 27.97 ± 26.55 ± 23.85 ± 39.85 ± 85.32 ± 30.40 ± 6.31 ± 1.15 ± 2.64 ± 72.45 ± 5.90 ± 15.35 ± 62.25 ± 62.28 ± 211.47

179.75 189.71 165.96 179.75 159.29 250.97 189.97 180.00 232.96 299.39 214.71 220.59 241.15 270.63 212.49 171.68 201.75 189.89 140.61 176.15 194.42 219.83 127.38 133.56 182.03 87.54 175.22 115.73 151.42 161.94

P ± 0.91 ± 0.92 ± 0.64 ± 0.91 ± 2.37 ± 1.35 ± 2.40 ± 1.49 ± 9.14 ± 19.73 ± 0.61 ± 1.58 ± 11.27 ± 11.56 ± 42.01 ± 0.33 ± 0.85 ± 0.30 ± 0.38 ± 2.14 ± 1.07 ± 1.04 ± 1.59 ± 0.21 ± 3.22 ± 0.07 ± 2.67 ± 2.05 ± 12.12 ± 37.09

*Results were expressed as Mean ± SD in dry base.

values of protein, crude fat, dietary fiber, ash, mineral and

polyphenols are within the ranges reported in the bibliography

E.E. Llopart, S.R. Drago / LWT - Food Science and Technology 71 (2016) 316e322

, Van Berkel, & Voragen, 2005). Chemical (Dicko, Gruppen, Traore composition and nutritional value of sorghum can be affected by factors such as genotype, climate, soil type and fertilization (Ebadi et al., 2005). PA, Fe, Zn, Cu, Na and P contents were affected by the color of the grains according to the ANOVA (p < 0.05), PA, Cu, and P being higher in RS and Fe, Zn, and Na in WS. In addition, TPC, FPC and BPC depend on the color (KruskaleWallis test, p < 0.05). BPC were higher than FPC for both types of sorghum and ranged 79e87 and 13e21% respect to TPC, respectively. Awadelkareem, Muralikrishna, El Tinay and Mustafa (2009) also reported that phenolic acids in sorghums are mostly in a bound form. RS had higher content of FPC and BFC than WS, since red hybrids have a more pigmented testa (Waniska, Poe, & Bandyopadhyay, 1989). Physical characteristics of sorghum hybrids and the results of popping are shown in Table 3. RM, BD, AV, and PP presented normal distribution and PP was affected by the color of the grains according to ANOVA (p < 0.05). TW and F% showed not normal distribution, and TW depended on the color of the grains (KruskaleWallis test, p < 0.05). The mean value (4.00) for MR of sorghum hybrids was higher than that reported by Montiel, Elizalde, Santini, and Giorda (2011) for 14 sorghum hybrids (MR: 2.0). Grains with a higher MR are harder (rich in vitreous endosperm) and produce a larger particle size than softer ones (Chandrashekar & Kirleis, 1988). The mean values obtained for BD (1.33 g/mL) and TW (79.36 kg/hL) were similar to that found by Montiel et al. (2011) (1.31 g/mL and 78.40 kg/hL, respectively), F% values ranged from 0 to 59%, while Montiel et al. (2011) and and Jambunathan, Kherdekar, and Stenhouse (1992) reported ranges of 12e73% and 40e100%, respectively. The percentage of floating sorghum grains is lower

319

when they have high proportions of vitreous endosperm, meaning that the lower the flotation, the harder the grains were (Robutti, 1995). Regarding popped grains, AV and PP values (Table 3) were in several higher than those found by Viraktamath, Raghavendra, and Desikachar (1972) who assessed the quality of popped sorghum and found that AV ranged from 7.0 to 11.4 mL/g and PP varied from 21.0 to 74.6%. In order to study the relationship among physicochemical properties of the grains and the ability for popping, a PCA was performed taking into account the results obtained at 250  C and 18% M, since in these conditions higher AV and PP values were achieved. To include the color in the analysis, values of 1 and 2 were assigned to WS and RS, respectively. Jowar Food hybrid did not pop, and for this reason, its physicochemical characteristics were not considered for PCA. PCA analysis showed that two components might explain 75% of cases. Fig. 1 shows that MR, TW, BD, protein content, and AV are represented by the first component with a direct relationship, and F % with an inverse one. The later parameter presented an opposed relationship with the above-mentioned characteristics, as was reported for sorghum by Hallgren and Murthy (1983). It is observed that the harder the grains (i.e. higher MR, TW, and BD and lower F%), the higher AV of popped product was (Montiel et al., 2011). This is because other than the optimum moisture content, the volume of popped grains depends on the breaking of the pericarp at a certain temperature, when the pressure within the core is sufficient (Shimoni, Dirks, & Labuza, 2002). The pericarp generates a strength that keeps a high pressure in the grain, favoring increasing popping volume. Furthermore, MR and protein

Table 3 Milling ratio (MR), test weight (TW), percentage of flotation (F%) and bulk density (BD) before popping sorghum hybrids. Apparent volume (AV), popping performance (PP) and ability for popping (AP) after popping at 250ºC-14%M and 250ºC-18%M. Sorghum

Before popping

Hybrids

MR

PEX 40730 W PAN 8706 W PEX 9261 W PAN 8648 PAN 8648 W A9941W WS01 S9C474C TOB48W A9947W Jowar Short ACA544 WS02 WS Average*# PEX 9273 10SAR 0025 10SAR 0010 PEX 42353 PEX 42334 PEX 40676 PAN 8918 PEX 9247 PEX 42345 PEX 1282 PEX 41027 PEX 41011 PEX 9269 PAN 8816 RS Average*# Range

6.2 ± 0.0 3.7 ± 0.1 5.0 ± 0.1 4.3 ± 0.1 4.7 ± 0.1 4.0 ± 0.1 3.2 ± 0.1 2.9 ± 0.0 2.4 ± 0.0 3.2 ± 0.0 1.7 ± 0.1 1.8 ± 0.1 4.2 ± 0.1 3.6 ± 1.3* 4.2 ± 0.1 3.4 ± 0.0 5.3 ± 0.1 4.5 ± 0.1 5.2 ± 0.1 5.4 ± 0.0 4.0 ± 0.1 3.8 ± 0.0 4.2 ± 0.0 3.9 ± 0.1 4.0 ± 0.1 2.8 ± 0.1 4.0 ± 0.1 6.0 ± 0.1 4.3 ± 0.9* 1.7e6.2

After popping

TW

F%

BD

250  C 14%M

(kg/hl)

(%)

(g/ml)

AV

PP

AP

AV

PP

AP

81.2 ± 0.3 80.7 ± 0.3 80.8 ± 0.3 80.3 ± 0.3 81.1 ± 0.3 78.7 ± 0.3 73.0 ± 0.3 78.9 ± 0.0 78.7 ± 0.3 80.0 ± 0.3 73.2 ± 0.6 73.3 ± 0.2 71.8 ± 0.5 78.9 ± 7.4# 81.6 ± 0.3 79.4 ± 0.1 81.9 ± 0.1 81.3 ± 0.0 82.0 ± 0.4 80.3 ± 0.1 81.0 ± 0.1 80.3 ± 0.2 80.4 ± 0.2 80.9 ± 0.1 80.3 ± 0.2 80.2 ± 0.2 80.5 ± 0.2 81.0 ± 0.1 80.7 ± 1.0# 71.8e82.0

8.0 ± 0.1 13.0 ± 0.1 2.0 ± 0.0 5.0 ± 0.0 7.0 ± 0.0 1.0 ± 0.0 16.0 ± 0.1 10.0 ± 0.0 19.0 ± 0.1 7.0 ± 0.0 58.0 ± 0.3 59.0 ± 0.3 4.0 ± 0.0 8.0 ± 11.0# 4.0 ± 0.0 10.0 ± 0.1 0.0 ± 0.0 0.0 ± 0.0 4.0 ± 0.0 9.0 ± 0.0 3.0 ± 0.0 8.0 ± 0.0 10.0 ± 0.0 6.0 ± 0.0 8.0 ± 0.0 13.0 ± 0.1 8.0 ± 0.1 5.0 ± 0.0 7.0 ± 5.0# 0.0e59

1.5 ± 0.0 1.4 ± 0.0 1.4 ± 0.0 1.7 ± 0.1 1.3 ± 0.0 1.3 ± 0.1 1.2 ± 0.0 1.2 ± 0.1 1.1 ± 0.0 1.2 ± 0.1 1.1 ± 0.1 1.0 ± 0.0 1.1 ± 0.0 1.3 ± 0.2* 1.3 ± 0.0 1.3 ± 0.0 1.5 ± 0.0 1.6 ± 0.0 1.5 ± 0.0 1.4 ± 0.0 1.4 ± 0.1 1.3 ± 0.1 1.3 ± 0.0 1.3 ± 0.0 1.4 ± 0.1 1.4 ± 0.0 1.4 ± 0.0 1.3 ± 0.0 1.4 ± 0.1* 1.0e1.7

10.0 ± 0.0 14.0 ± 0.1 18.4 ± 0.1 17.5 ± 0.1 17.5 ± 0.1 15.3 ± 0.1 13.0 ± 0.1 10.1 ± 0.0 12.8 ± 0.1 11.7 ± 0.0 9.1 ± 0.0 9.1 ± 0.0 16.9 ± 0.1 13.5 ± 3.3* 17.4 ± 0.1 15.7 ± 0.1 14.5 ± 0.1 15.8 ± 0.1 18.9 ± 0.1 6.3 ± 0.1 20.8 ± 0.1 5.9 ± 0.1 16.1 ± 0.1 17.7 ± 0.1 15.6 ± 0.1 15.1 ± 0.1 15.5 ± 0.1 15.5 ± 0.1 15.1 ± 4.1* 5.e20.8

63.6 ± 1.1 70.9 ± 1.0 86.3 ± 1.2 81.1 ± 2.0 81.1 ± 1.9 87.1 ± 2.1 84.7 ± 2.0 86.5 ± 2.1 85.2 ± 1.8 87.3 ± 2.2 68.9 ± 1.3 67.3 ± 1.3 86.0 ± 1.7 79.7 ± 8.4* 86.2 ± 20.1 77.2 ± 1.7 75.5 ± 1.6 73.8 ± 1.6 84.5 ± 1.9 47.1 ± 1.0 78.7 ± 1.7 23.7 ± 0.9 79.5 ± 1.7 77.6 ± 1.6 68.9 ± 1.5 76.6 ± 1.6 79.5 ± 1.6 54.3 ± 1.1 70.2 ± 17.2* 23.7e87.3

5.2 8.0 12.8 11.4 11.5 10.5 8.1 6.9 8.6 8.1 4.6 4.5 10.4 8.5 ± 2.6* 12.2 9.6 9.0 9.5 13.1 2.4 13.2 1.1 10.3 11.1 8.6 9.3 9.9 6.8 9.0 ± 3.5* 1.1e13.2

19.1 ± 0.1 16.6 ± 0.1 16.7 ± 0.1 15.4 ± 0.1 14.4 ± 0.1 12.5 ± 0.1 13.7 ± 0.1 11.4 ± 0.1 13.9 ± 0.1 12.2 ± 0.1 10.3 ± 0.1 11.2 ± 0.1 17.8 ± 0.1 14.2 ± 2.6* 14.9 ± 0.1 13.4 ± 0.1 18.0 ± 0.1 13.6 ± 0.1 16.0 ± 0.1 17.7 ± 0.1 13.2 ± 0.1 13.5 ± 0.1 14.1 ± 0.1 16.3 ± 0.1 13.4 ± 0.1 13.4 ± 0.1 15.2 ± 0.1 18.7 ± 0.1 15.1 ± 1.9* 10.3e19.1

84.7 ± 2.0 72.6 ± 1.9 79.0 ± 1.9 74.5 ± 1.8 70.0 ± 1.7 95.3 ± 2.2 89.3 ± 2.1 88.1 ± 2.1 87.5 ± 2.1 90.2 ± 2.2 80.3 ± 2.0 81.5 ± 1.9 85.7 ± 2.1 83.0 ± 7.2* 63.2 ± 1.2 72.0 ± 1.6 73.2 ± 1.7 71.1 ± 1.6 77.0 ± 1.9 77.3 ± 1.9 68.6 ± 1.3 70.0 ± 1.5 71.0 ± 1.7 70.5 ± 1.5 64.1 ± 1.4 62.2 ± 1.3 71.4 ± 1.6 78.2 ± 1.8 70.7 ± 5.0* 62.2e95.3

13.1 9.7 10.7 9.2 8.2 9.4 8.9 7.9 9.6 8.8 6.0 6.7 11.0 9.2 ± 1.8* 7.7 7.7 10.8 7.8 10.1 11.0 7.3 7.6 8.1 9.3 6.9 6.7 8.7 11.8 8.7 ± 1.6* 6.0e13.1

Results were expressed as: *mean ± SD or #median ± IR; WS: white sorghum, RS: red sorghum.

250  C 18%M

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Fig. 1. Weights of the components of protein content, color, milling ratio (MR), test weight (TW), percentage of flotation (%F), bulk density (BD), apparent volume (AV), popping performance (PP) of hybrid sorghum grains popped at 250 C-18%M.

content are well represented by this component in a direct way. This means that at higher protein content, grains will be harder and higher AV will be reach after pop, as was observed for maize (Soylu & Tekkanat, 2007). The second component of PCA directly represents PP, and inversely, the color of the grains, indicating that WS reached higher yields. No relationship between PP and AV was observed, as was reported by Viraktamath et al. (1972) and Dofing, ThomasCompton, and Buck (1990). As mentioned above, an indicator of popping aptitude was defined (Table 3) in order to predict the ability of sorghum grains to pop. Its relationship with the physicochemical properties was studied through multiple regression. It was found that using RM and color as variables, the following correlation was found: AP ¼ 5.70029 e 1.41194  COLOR þ 1.34105  MR (R2: 0.71) Thus, starting from an unknown sample of sorghum, through the determination of RM and taking into account the color (assigning 1 to WS and 2 to RS), it is possible to predict the AP indicator that will have 71% of cases. Taking into account that a good aptitude for popping may be indicated by a AV of 14 cm3/g and a PP of 80%, and considering an average TW of 80 kg/hL, the value of AP would be equal to or greater than 9. Given a sample of sorghum grains, measuring its RM, considering its color and using the above equation, in 71% of cases correlate with the AP, and if the value is greater or equal to 9, this hybrid would have a good capacity to pop.

3.2. Nutritional properties of popped sorghum In the case of popcorn, it is considered that the volume of pop grains is the most important attribute for consumer (Shimoni et al., 2002), thus AV was considered to select popped samples to be analyzed regarding their nutritional properties. They were PEX 40730 W hybrid popped at 250ºC-18% M and PAN 8918 hybrid popped at 250ºC-14% M. Table 4 shows the results of analysis of raw and flours. Regarding proximal composition (Table 4), it is observed that color significantly affected protein and ash content, both being higher in WS. Popping process did not affect protein and fat content but significantly affected fiber and ash content, causing a reduction of both components of 1.35 and 1.15 times, respectively. The decreasing can be attributed to the loss of shell during the explosion. Sharma, Champawat, and Mudgal (2014), also observed this effect. Respect to minerals, the ANOVA showed that all of them were affected by the effects of process and color, except for P and Cu content that did not change because of color grain. The interaction only was significant for Zn and K. In the lining of sorghum grain there is a large proportion of minerals (Sankara Rao & Deosthale,

1980). Thus, it is expected that the loss of tegument leads to a significant decrease in micronutrient content after popping. The reductions were around 1.1 times. After popping, protein digestibility increased by 1.1 times for WS and RS, regarding their native samples. This was attributed to the fragmentation of the cell walls of vitreous endosperm, which would improve the accessibility of digestive enzymes to proteins (Awadelkareem, Muralikrishna, El Tinay & Mustafa, 2009). The color and the process significantly affected available lysine. Popping caused a decrease of 1.3 and 1.2 times for WS and RS, respectively since the high temperature of popping favors Maillard reaction, as was observed for popcorn (Gupta, Chatterjee, & Singh, 1985). TEAC was higher for RS than WS, and the process decrease the antioxidant capacity of both types of grains. PA content was higher for RS than WS and decrease by the process. After popping, there were not differences among samples. The reduction produced by the process was 1.3 and 1.5 times for WS and RS, respectively. Similarly, Saravanabavan, Shivanna, and Bhattacharya (2013) observed that PA content was higher for RS and that popping reduced 20e25% PA content in sorghum. Regarding mineral bioaccessibility, the values of DFe% and DZn were around 5% or lower. Hemalatha, Platel, and Srinivasan (2007) reported similar values for sorghum (5.51± 0.32% and 4.13± 0.33% for Zn and Fe, respectively). DFe% increased 1.3 and 1.6 times after popping for WS and RS, respectively. DZn% was higher for WS than RS and was reduced by the process 1.9 and 1.4 times, respectively. DCa% was not affected by any of the studied effects. PA/mineral molar ratios can be used to predict bioavailability of minerals of food or diets (Turnlund, King, Keyes, Gong, & Michel, 1984). A PA/Fe molar ratio >1 is considered as indicative of poor Fe bioavailability (Ma, Jin, Piao, Kok, Guusje, 2005). Other studies showed that PA/Zn molar ratios higher than 10e15 progressively inhibited the absorption of Zn, and were associated with a suboptimal Zn state in rats fed with diets based on egg albumin added with PA (0e7.43 g/kg) or Zn (18e144 mg/kg) (Yuwei et al., 2013). Also, in a study conducted in young men confined to a metabolic unit, it was concluded that a diet with a PA/Zn molar ratio higher than 15 lead to a decrease in absorption of Zn, accompanied by an increase in fecal and urinary Zn (Turnlund et al., 1984). On the hand, a molar ratio PA/Ca >0.24 will impair Ca bioavailability (Umeta, West, & Fufa, 2005). In the analyzed samples PA/Fe molar ratios were greater than the critical level (between 21 and 32) which indicates that Fe bioavailability could be affected by phytates. A reduction of PA was observed after popping, which is reflected in increased DFe%, as was observed by Radhakrishnan and Sivaprasad (1980), who also stated that the bioavailability of Fe in sorghum was most affected by PA than the content of pro-anthocyanidins in grains. It was observed that all the samples showed PA/Zn molar ratios above 15 (between 47 and 60), which would affect the availability of this mineral. Similar ratios were reported in sorghum by Stuart, Johnson, Hamaker, and Kirleis (1987). This index decreased after popping, which was not reflected as an increase of Zn accessibility. Other interactions occurring during cooking would produce such behavior. PA/Ca molar ratio was above the critical value (between 3 and 5), but DCa% was not low. FPC and BPC were lower in raw WS than RS, and both were reduced after popping. This resulted in a reduction of TPC, which was 1.3 times and 1.8 times for WS (689.08e519.76 mg AG/100 g) and RS (1605.63e870.39 mg AG/100 g), respectively. This behavior was also observed in popped beans (Sreerama et al., 2008). TEAC values of raw samples were in the range observed for cereals by other researchers (Ragaee, Abdel-Aal, & Noaman, 2006).

E.E. Llopart, S.R. Drago / LWT - Food Science and Technology 71 (2016) 316e322

321

Table 4 Proximate composition (protein, ether extract, total dietary fiber, ash), mineral content, iron, zinc and calcium accessibility (DFe, DZn and DCa %), protein digestibility (%), available lysine (AL), free (FPC) and bound (BPC) phenolic compounds, phytic acid (PA) and antioxidant capacity (TEAC) of raw and popped sorghum flours from PEX 40730 W hybrid sorghum (WS) popped at 250ºC-18% M and PAN 8918 hybrid (RS) popped at 250ºC-14% M. Components Protein (g/100 g) Ether extract (g/100 g) Total Dietary Fiber (g/100 g) Ash (g/100 g) Fe (mg/kg) Zn (mg/kg) Ca (mg/kg) Cu (mg/kg) K (mg/kg) Mg (mg/kg) Na (mg/kg) P (mg/kg) DFe% DZn% DCa% Protein Digestibility (%) Available Lysine (mg/g prot.) PA (mg/100 g) FPC (mg GA/100 g) BPC (mg GA/100 g) TEAC (mmol/g)

Raw PEX 40730 W 11.89 3.08 8.69 1.70 30.61 15.33 117.14 2.89 4181.04 1583.57 184.36 3396.54 2.69 5.27 64.07 90.21 4.68 928.05 110.64 578.44 39.42

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

b

0.01 0.10 0.49b 0.01d 0.24c 0.27a 0.28b 0.06b 90.47d 39.69b 3.74b 125.26b 0.16a 0.47c 5.85 1.10b 0.20c 35.19b 4.63b 14.70b 1.17b

Pop PEX 40730 W 12.03 3.03 6.49 1.53 27.61 13.20 110.54 2.67 3859.00 1479.40 159.87 3179.47 3.50 2.74 67.06 97.20 3.55 687.95 60.30 459.46 30.24

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

c

0.08 0.02 0.46a 0.03b 0.39b 0.75a 0.80a 0.06a 53.73c 97.60a 1.53a 152.27a 0.28b 0.15a 6.02 3.95c 0.04a 16.65a 6.38a 10.55a 1.81a

Raw PAN 8918 10.69 3.03 8.37 1.59 27.57 19.04 133.74 2.85 3758.67 1704.59 226.42 3361.52 2.59 3.69 70.90 79.83 4.88 1049.34 201.26 1404.38 55.65

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

Pop PAN 8918 a

0.02 0.09 0.49b 0.01c 0.59b 0.90b 1.39d 0.07b 100.67b 18.22c 13.21d 101.83b 0.19a 0.13b 6.23 0.89a 0.18c 38.85c 3.19c 17.07d 0.94c

10.71 2.93 6.19 1.34 24.41 14.55 125.93 2.58 3210.07 1513.58 206.13 3048.65 4.17 2.65 65.28 87.08 4.09 682.40 72.52 797.88 32.70

± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ±

p-Value a

0.05 0.04 0.27a 0.00a 2.18a 0.68a 4.06c 0.11a 63.91a 35.51ab 8.43c 80.80a 0.23c 0.44a 5.98 2.31b 0.21b 32.76a 2.44a 2.13c 0.70a

0.0000 0.5430 0.0098 0.0002 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0057 0.0055 0.0044 0.9903 0.0056 0.0051 0.0005 0.0001 0.0000 0.0001

Results were expressed in dry base as x ± SD. Different letters in a row mean significant differences among samples (p < 0.05). GA: gallic acid.

Antioxidant capacity was higher for RS than WS. However, there were not differences after popping, with reductions of 1.3 times and 1.7 times for WS and RS, respectively. Similarly, amaranth popping reduced 35% the antioxidant capacity expressed as the content of tocopherols (Ogrodowska, Zadernowski, Czaplicki, Derewiaka, & Wronowska, 2014). TEAC was directly correlated with TPC (r ¼ 0.9815). Polyphenols are quantitatively the major antioxidants in the diet and have more in vitro antioxidant activity than vitamins and carotenoids. It is expected that the decrease in TPC was reflected in a reduction of TEAC, since sorghum grains have antioxidant activities highly related to their phenolic content (Dicko et al., 2005). Popping reduced TPC and TEAC. This effect may be due, not only to the process conditions (moisture and temperature), but also to the loss of a part of the shell during the grain exploiting. In a study carried out with RS whole grain flours precooked by extrusion at lez, 182  C and 14%M (Llopart, Drago, De Greef, Torres & Gonza 2013) and of WS under the same conditions, reductions in the contents of TPC and TEAC were also observed. However, compared to fruits and vegetables, whose TEAC ranges 6e37, and 4.5e14 mmol/g, respectively (Miller et al., 2000) whole sorghum flours precooked by popping have high antioxidant capacity. 4. Conclusions The physicochemical analysis of 28 sorghum hybrids showed that the color affected composition, and the harder the grain (higher MR, TH, and BD, protein content and lower F%), the higher apparent volume of popped grain was. The performance was inversely related to the color, white hybrids having higher technological aptitude. An indicator of the ability for sorghum popping was developed (AP). It can be determined through the color grain and milling ratio in 71% of cases. If the value of AP is greater or equal to 9, the sample would be appropriate for popping. Regarding nutritional properties, the losses of sells by popping did not significantly affect protein and ether extract, but ash, total dietary fiber, phytic acid, and minerals were significantly reduced. Although DFe% increased after popping (1.3 and 1.6 times for WS and RS, respectively), DZn% was reduced (1.9 and 1.4 times for WS

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