Breadmaking Properties of Flour Produced From Irradiated Wheat Carolina S. Singer*, Susy F. Sabatoº, Carmen C. Tadini* *Food Eng. Lab., Chemical Eng. Dept., Escola Politécnica, São Paulo University, Brazil, P.O. Box 61548, 05424-970, SP, Brazil, Phone: +551130912258, Fax: +551130912255,
[email protected] e
IPEN-CNEN/SP, Radiation Technology Center, São Paulo, Brazil. Av. Lineu Prestes, 2242, 05508-900, SP, Brazil
Written for presentation at the 2006 CIGR Section VI International Symposium on FUTURE OF FOOD ENGINEERING Warsaw, Poland 26-28 April 2006 Abstract. Gamma radiation technology applied on foods is growing progressively to improve their preservation, storage and distribution. The aim of this study was to verify the influence of irradiation on wheat on the physicochemical and rheological properties of flour and, in consequence, its roll on breadmaking. Wheat grains were submitted to four different irradiation doses (0.0, 0.5, 1.0 and 2.0 kGy), and then milled into flour. Physicochemical and rheological analyses were conducted on the resulting flour. ANOVA indicated that different irradiation doses influenced neither the water content nor the protein content of the flours. The water absorption and stability of flour, parameters obtained by the farinograph analysis were also not influenced by irradiation dose. The Falling Number decreased significantly with the increase of irradiation dose. This may have occurred due to change in starch gelatinization caused by irradiation. Color parameters (L, a, b) did not show statistically significant differences. Dough extensograph parameters (maximum resistance, extensibility) were not influenced by irradiation dose. This was confirmed by the dough texture analyses results, which did also not show significant differences. Irradiation doses did not affect the dough development and the gas retention capacity measured by rheofermentometer. French bread was produced, and two triangle difference tests were conducted, comparing bread from wheat irradiated at 2.0 kGy and non-irradiated wheat, and wheat irradiated at 1.0 kGy and non-irradiated wheat. Both sensory analyses showed that there were no general significant differences between irradiated and non-irradiated bread. Keywords. Gamma radiation, breadmaking, flour, rheological properties.
Introduction Nowadays, food treatment with irradiation is one of the most modern, secure and efficient ways for its preservation. The irradiation process is approved by important international organizations such as Codex Alimentarius and Food and Drug Administration (FDA), and is used in more than 30 countries around the world. This process does not induce radioactivity to food (ICGFI, 1992). Irradiation process provides disinfestations, sterilization, increases shelf life and maintains product nutrients. Studies in international literature report that irradiation applied on wheat, besides lowering microbiological and entomological levels, can have a positive effect on breadmaking. According to Köksel, Sapirstein, Celik & Bushuk (1998), gamma radiation has important effects on cereal grain quality, besides its roll of food protection. These authors reported that irradiation doses higher than 10 kGy applied on wheat causes weakening of dough mixture properties, due to change on wheat proteins. However, this effect is smoother for lower doses. Rao, Hoseney, Finney, & Shogren (1975) studied the effect of gamma radiation on wheat on its breadmaking properties in doses up to 10 kGy. Besides reporting their results, they discussed about different researches from other specialists. They showed that doses up to 3.0 kGy do not change significantly flour characteristics, and in consequence do not influence the bread making process. However, doses higher than 5.0 kGy caused a reduction in bread volume and damaged baking quality. The aim of this study was to verify the influence of irradiation, on doses of 0.0, 0.5, 1.0 and 2.0 kGy, on wheat on the physicochemical and rheological properties of flour and, in consequence, its roll on breadmaking.
Materials and Methods Argentinean untreated wheat grains from the same batch were portioned into 0.5kg bags and irradiated in normal atmosphere and at room temperature, in a 60Co Gamma cell 220 (AECL), with doses of 0.0, 0.5, 1.0 and 2.0 kGy. Dosimetry was done using Amber routine dosimeter (Harwell, United Kingdon) and dose rate was established using Fricke reference dosimeter to plot calibration curves. The whole dosimetry system is in IDAS program from International Atomic Energy Agency. Irradiated and non-irradiated wheat were milled into flour using a Brabender Quadrumat laboratory scale wheat mill. The resulting flour was submitted to analyses.
Physicochemical analyses Water content was determined according to AACC 44-15A method (AACC, 1995). Crude protein content was determined by semi-micro Kjeldahl method, based on AACC 46-13 method (AACC, 1995). Measurements of water absorption and dough stability were determined by analysis using a farinograph (Brabender OHG, Duisburg, Germany) according to AACC 54-21 method, constant flour weight procedure (AACC, 1995). Flour color was analyzed using a Color Quest XE colorimeter (Hunterlab). Three dimensions L, a and b were determined. The L values give a measure of the lightness of the product color, from 100 for perfect white to zero for black, as the eye would evaluate it. The
redness/greenness and yellowness/blueness are denoted by a and b values, respectively (Hunterlab, 2004). Falling Number was determined using Falling number 1800 equipment (Perten Instruments), according to ICC Standard nº107/1 methods (ICC, 1995).
Rheological analyses Dough extensibility and maximum resistance to an extension were determined using an extensograph (Brabender OHG, Duisburg, Germany) according to AACC 54-10 method (AACC, 1995). The same parameters were determined by a dough texture analyzer TA-XT2-i (SMS), using the accessory A/KIE according to DOU1/KIE method (SMS, 1995). Dough development and gas retention capacity were studied using a CHOPIN rheofermentometer (Tripette & Renaud). The dough was prepared and analyzed according to CHOPIN protocol, as described in Kanemaru, Tavares, Singer, Hilsenrath, Sabato & Tadini (2005).
Sensory analysis For this analysis, French bread was manufactured from flour produced from irradiated and nonirradiated wheat. Forty-five non-trained panelists (20 male, 25 female) took part in the sensory analysis, which consisted of a difference triangle test, used to find out if there is significant sensorial difference between two different products (Meilgaard, Civille & Carr, 1987). Two triangle tests were conducted, in which panelists had to tell the difference between bread produced from wheat irradiated at 2.0 kGy and from non-irradiated wheat, and wheat irradiated at 1.0 kGy and non-irradiated wheat.
Statistical analysis For all analyses, two repetitions were done. ANOVA and Tukey HSD mean tests were performed in all results using the statistical program Statgraphics for Windows v4.0 (Manugistics), at a confidence interval of 95%.
Results and Discussion Physicochemical analyses Color, water and crude protein contents, farinograph parameters and Falling Number results of wheat flour analyses are summarized in Table 1. Water content results are similar to those obtained by Kanemaru et al. (2005). The results show that irradiation dose did not affect significantly flour water content. This was also noticed by Silva (2003) and Marathe, Machaiah, Rao, Pednekar & Rao (2002), who studied irradiated wheat flour in doses up to 6.0 kGy and 1.0 kGy, respectively. Crude protein content was also not influenced by irradiation dose, which implies that the irradiation did not alter the milling efficiency, giving similar rate of extraction. Similar results were obtained by Köksel et al. (1998). Water absorption is the amount of water that flour can absorb until the dough consistency reaches 500 BU (Brabender Units). Dough stability is the time needed before dough consistency starts to decline from 500 BU line. Both properties were not influenced by irradiation dose. Silva, Reginato-d´Arce & Spoto (2002) and Marathe et al. (2002) observed an increase of
water absorption with irradiation dose applied on wheat flour. This might suggest that the effects of irradiation on wheat flour and on wheat grains are different for farinograph properties. ANOVA indicated that none of the color dimensions, L, a, b, were influenced by different doses of irradiation. According to Marathe et al. (2002), all color parameters of wheat flour irradiated with doses between 0.25 and 1.0 kGy did not show statistically significant differences. Falling Number is an indication of a-amylase enzyme activity on flour. Irradiation caused a significant decrease of Falling Number. This may have occurred due to change in starch gelatinization caused by irradiation. Similar results were obtained by Kanemaru et al. (2005), Silva et al. (2002) and MacArthur & D´Appolonia (1983). Table1. Physicochemical mean results of flour produced from irradiated wheat. _________ Property Irradiation doses (kGy) Tukey HSD 0.0 0.5 1.0 2.0 5% Water content (%) 15.2a 14.8a 15.1a 15.0a 0.8 10.6a
Protein content (%) a
absorption (%) a
17.7
57.6 a
17.6
Color L 0.4
a
11.5 313
d
a
11.5
a
57.9
17.7
M.T
a
a
88.9 0.4
a
a
10.6a
0.4
a
a
89.1 0.4
0.6 FN (s)
a
10.5a a
58.0
10.6a a
57.9
0.5 Water 2.5 Stability (min)
0.4 89.1
a
89.0
a
1.3 a
0.1 b
11.1 477
a
a
428
11.4 b
a
409
c
18 Same letter within a row are not significantly different (p> 0.05) by Tukey HSD
Rheological analyses Results of rheological measurements obtained from extensograph and texture analyzer are summarized in Table 2. The extensograph and texture analyzer give information about the viscoelasticity of dough. The analysis difference is that the amount of sample used in texture analysis is much smaller. A combination of good resistance and good extensibility means desirable dough properties. Results show that irradiation did not influence the parameters measured by the extensograph. Kanemaru et al. (2005) did also not find significant differences in maximum resistance and dough extensibility for the different irradiation doses applied on wheat. Texture analysis results confirm what was observed in the extensograph analysis, also not being influenced by irradiation dose.
Table 2. Rheological mean results of flour produced from irradiated wheat. Property Irradiation doses (kGy)
Tukey HSD
0.0
0.5
1.0
2.0
5%
809a 154a
745a 154a
778a 162a
745a 160a
176 56
Maximum resistance (N)
0.32a
0.35a
0.32a
0.34a
0.31
Extensibility (mm)
17.1a
18.6a
19.2a
18.9a
9.4
Extensograph Maximum resistance (UE) Extensibility (mm) Texture analysis
Same letter within a row are not significantly different (p> 0.05) by Tukey HSD
Rheofementometer parameters are summarized in Table 3. The height of maximum dough development under constraint, Hm, is related to the bread volume. T1 refers to the time of maximum dough development, and h is the height of the dough at the end of the test. None of these parameters varied significantly, showing that irradiation dose, up to 2.0 kGy, does not change bread volume. However, Urbain (1986) reported that bread made from flour irradiated on moderate doses (up to 2.0 kGy) might show an increase in volume, although higher doses cause a volume decrease. The weakening coefficient of dough, WC, calculated by the relation: (Hm-h)/Hm, was significantly influenced by irradiation dose, however, no tendency was found. As for the parameters obtained from the gas release curve, TX is the apparent time of dough's porosity, VT refers to the total volume of gas production, VR to the gas volume retained by dough at the end of the test and VL to the volume of CO2 released by dough during its fermentation. TX and VT were not influenced by irradiation. VR and VL results showed significant differences, however, no tendency was found. Retention coefficient, RC, represents the amount of gas retained by dough at the end of fermentation, and is obtained by the relation: VR/VT. This parameter is strongly related to the quality of dough. RC results suggest that irradiation does not change the resistance of the gluten network.
Sensory analysis Both triangle tests results, between bread from non-irradiated wheat and from wheat irradiated at 1.0 kGy, and bread from non-irradiated wheat and from wheat irradiated at 2.0 kGy, showed that no sensorial difference was found between bread made from irradiated and non-irradiated wheat. Zaied, Abdel-Hamid & Attia (1996) studied the acceptance of bread produced with wheat flour irradiated at 2.0, 4.0 and 8.0 kGy. They reported that only bread from flour irradiated at 4.0 and 8.0 kGy showed lower acceptance levels than control (non-irradiated). Rao, Vakil, Bandyopadhyay & Sreenivasan (1978) reported that no sensorial alterations were observed in sweet bread made from wheat irradiated at doses up to 2.0 kGy.
Table 3. Rheofermentometer parameters mean results of the dough produced from irradiated wheat. Property Irradiation doses (kGy) Tukey HSD 0.0
0.5
a
1.0
a
2.0
a
5%
a
65.6
64.3
59.2
62.5
20.9
104.3a 41.3a
105.0a 54.1a
99.0a 29.6a
104.3a 42.0a
24.2 26.0
TX(min)
75.8a
80.3a
78.0a
78.0a
28.5
VT (mL)
1090a
1089a
1124a
1152a
154
VR (mL)
a
1040
a
b
a
163
VL (mL)
ab
Dough development curve Hm (mm) T1 (min) h (mm) Gas release curve
1029
1081
1090
50
60ab
a
44
b
62
17
WC (%)
36.9ab
15.9a
50.1b
32.9ab
33.3
RC (%)
95.4a
94.5a
96.2a
94.7a
2.0
Calculated param eters
Same letter within a row are not significantly different (p> 0.05) by Tukey HSD Hm: maximum height (mm) T1: time (min) at Hm. h: height at end of test (mm) TX: time (min) of gas release VT: total volume of CO2 (mL) VR: retention volume of CO2 (mL) VL: lost volume of CO2 (mL) WC: weakening coefficient of dough (%) RC: retention coefficient of dough (%)
Conclusions The present study shows that gamma irradiation in doses up to 2.0 kGy applied on wheat has no significant influence on most of the physicochemical and rheological properties of flour and sensorial properties of bread produced from this wheat. Water and crude protein content, water absorption, stability and color of flour produced from irradiated wheat were not altered with irradiation dose. The same occurred to dough resistance and extensibility and rheofermentometer parameters of dough development and gas release during fermentation. A sensory analysis showed that there was no significant sensorial difference between bread produced from irradiated and non-irradiated wheat. However, Falling number results, which indicate a-amylase activity on flour, showed a steep decrease with the increase of irradiation dose. A hypothesis for this event is a change in starch gelatinization caused by irradiation. Acknowledgements To CAPES (National Agency for Graduate Human Resources) for research grant.
To Moinho Pacífico and Cereal Laboratory of State University of Campinas for technical support.
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