1
Effect of different fibers on batter and gluten-free layer cake properties 1
Márcia Arocha Gularte
1,2
, Esther de la Hera
3
, Manuel Gómez
3
,
Cristina M. Rosell
1
2
¹ Food Science Department, Institute of Agrochemistry and Food Technology (IATA-3
CSIC), Avda Agustín Escardino 7, 46980-Paterna, Valencia, Spain. E-mail: 4
crosell@iata.csic.es 5
2
University Federal of Pelotas – Food Science Department (UFPel-DCA), Brazil 6
3
Universidad de Valladolid - Ingenierías Agrarias de Palencia (Departamento 7
Tecnología de los Alimentos), Spain. 8
9
Running title: Cake enrichment in fibers 10
Correspondence should be sent to: Cristina M. Rosell. E-mail: crosell@iata.csic.es 11
Tel 34 963900022, Fax 34 963636301 12
13
ABSTRACT 14
The effect of different fibers, added individually or in combination, to improve the 15
functional properties of gluten free layer cakes was examined. Soluble (inulin and guar 16
gum), and insoluble (oat fiber) fibers were used to replace up to 20% of rice flour in gluten 17
free layer cakes formulation. The incorporation of fibers increased the batter viscosity, with 18
the exception of inulin. Fiber enriched gluten free cakes containing blends of oat fiber-inulin 19
resulted in improved specific volume. Significantly brighter crust and crumb was obtained in 20
the presence of fibers, excepting the crumb of oat-guar gum containing cake. Fibers and its 21
blends increased the crumb hardness; but the smallest effect was observed with the addition 22
of oat, individually or combined with inulin. Enriched cakes increased significantly their 23
dietary fiber content, which was connected to the nature of the fibers added. Fibers 24
significantly affected the in vitro hydrolysis of starch fractions, being the most pronounced 25
2
effect the decrease in the slowly digestible starch. Overall combination of oat fiber-inulin 26
resulted in better gluten-free cakes. 27
28
Highlights: 29
• Insoluble and soluble fiber incorporation in gluten free layer cakes was examined 30
• Gluten free cakes containing blends of oat fiber-inulin have better specific volume 31
• Combination of soluble and insoluble fibers provides enriched gluten free cakes 32
33
Key words: gluten free; cakes; fibers; starch; rice flour. 34
35
1. Introduction 36
Breakfast cereals and bakery products are the most preferred vehicles for fiber enrichment 37
(Rosell, 2011). Traditionally, wholemeal cereals were eaten with that purpose, but lately 38
alternative fibers from different sources are available, like fruit extracts, resistant starch, 39
beta-glucans and so on (Rodrígues, Jiménez, Fernándes-Bolaños, Guillén & Heredia, 2006). 40
More attention should be paid to gluten free bakery products that are prepared with gluten-41
free cereals and commercial grain products and often tend to have reduced quantities of 42
proteins, B vitamins, iron, and fiber compared with products containing gluten (Thompson, 43
Dennis, Higgins, Lee & Sharrett, 2005; Matos & Rosell, 2011). Therefore, a re-design of the 44
gluten free bakery goods is needed for obtaining gluten free baked products with similar 45
nutritional composition to that of their gluten counterparts. Those products would allow 46
celiac patients and/or population with other allergic reactions and intolerances caused by 47
proteins or another component of cereals to meet dietary guidelines without changing their 48
dietary pattern. 49
50
3
Research on gluten free cakes has been focused on the effect of wheat flour replacement by 51
rice flour in traditional recipes, as steamed leavened rice cakes (Mohamed & Hamid, 1998; 52
Perez & Juliano, 1988), layer cakes (Bean et al., 1983; Perez & Juliano, 1988) and muffins 53
(Johnson, 1990). Some authors have also used some hydrocolloids, emulsifiers or enzymes 54
for improving the quality of those cakes (Preichardt et al., 2011; Ronda et al., 2009; Sumnu 55
et al., 2010; Turabi et al., 2008), but scarce investigations were aimed at determining the 56
nutritional profile of those products. 57
Different attempts have been made for protein enrichment of gluten free products with soy 58
bean or legume proteins (Marco & Rosell, 2008 a, b; Gularte, Gómez & Rosell, 2011). 59
However, scarce research has been carried out with high levels of purified fibers. Different 60
fiber sources like cereals bran, legume outer layer and processing by-products of apple and 61
potato industry have been used for enriching wheat cakes and muffins. Gómez, Moraleja, 62
Oliete, Ruiz & Caballero (2010a) studied the effect of insoluble fibers, obtained from fruits, 63
cereals, modified celluloses and resistant starch, on the quality of wheat layer cakes. Results 64
showed that acceptable fiber enriched wheat based cakes could be obtained when fiber 65
addition only goes up to 10% (w/w, wheat flour), and in general fiber incorporation results 66
in low volume and minor acceptance. 67
Numerous commercial fibers are available in the market, which differed in solubility, 68
particle size, hydration properties and viscosity, among other characteristics (Rosell, Santos 69
& Collar, 2009). Inulin is a non-digestible polysaccharide and acts as prebiotic by 70
stimulating the growth of ‘healthy’ bacteria in the colon (Gallagher, Gormley & Arendt, 71
2004). Guar gum is a galactomanan polymer used mainly as thickener and stabilizer. 72
Dartois, Singh, Kaur & Singh (2010) suggested that the physiological action of 73
hydrocolloids in the upper gut could be related to their ability to produce high viscosity in 74
the gut lumen, thereby affecting the nutrient absorption and postprandial plasma nutrient 75
4
levels. Lately, oat fibers are being used as insoluble fibers that contained cellulose, 76
hemicellulose and lignin. In spite of its nutritional role, no study has been carried out about 77
the effect of this insoluble fiber on the cakes and batters, neither on the gluten free cakes. 78
Regardless the extensive use of fibers in food technology, there is no information about the 79
individual and combined effect of soluble and insoluble fibers and their possible synergistic 80
action concerning the quality parameters of gluten free cakes. The objective of this study 81
was to investigate the potential of different dietary fibers, soluble and insoluble, on batter 82
properties and on the technological and nutritional quality of gluten free layer cakes. The 83
effect of those fibers on in vitro starch digestibility was also considered due to the relevance 84
of starch in gluten free bakery products. 85
2. Materials and methods 86
2.1 Materials 87
Rice flour (7.85% of protein and particle size<200µm) from Harinera los Pisones (Zamora, 88
Spain) was used. Inulin (Orafti
®
HPX, Beneo-orafti) and guar gum (Guar gum – 3500, 89
EPSA, Spain) were used as soluble fibers, and oat fiber (Vitacel HF 600, J. Rettenmaier & 90
Sönne, Rosenberg, Germany) as source of insoluble fiber. Sugar, sunflower oil, pasteurized 91
whole eggs, fresh milk and double-action baking powder were purchased from the local 92
market. Pancreatin from porcine pancreas (Cat. No. P-1625, activity 3_USP/g) was 93
purchased from Sigma Chemical Company (St. Louis, MO, USA). Amyloglucosidase (EC 94
3.2.1.3., 3300 U/mL) and glucose oxidase–peroxidase assay kit GOPOD (Cat. No. K-95
GLUC) were purchased from Megazyme (Megazyme International Ireland Ltd., Bray, 96
Ireland). 97
2.2 Methods 98
2.2.1 Cake preparation 99
5
A single-bowl mixing procedure was used for making yellow layer cakes. The basic recipe 100
and the fiber enriched formulations replacing up to 20g/100g rice flour are detailed in Table 101
1. All ingredients were mixed during 1 min at speed 4, and 9 min at speed 6 using a Kitchen-102
Aid Professional mixer – KPM5 (KitchenAid, St. Joseph, Michigan, USA). 180 g of cake 103
batter were placed into rectangular (109 mm x 159 mm), metallic, oil coated pans (430ml of 104
capacity), and were baked in an electric oven ST-02 (Salva Industrial S.A., Lezo, 105
Guipuzcoa, Spain) for 30 min at 190 ºC. After baking, the cakes were removed from the 106
pans, left at room temperature for one hour to cool down, and put into plastic pouches to 107
prevent drying. Two different sets for each cake recipe were made in different days. Four 108
cakes from the same batter were used for physical measurements that were carried out one 109
day after baking. One cake from each set was freeze dried for further determination of the in 110
vitro enzymatic hydrolysis of starch. 111
2.2.2 Batter measurements 112
Batter density was measured using an Elcometer 1800 (Elcometer, Manchester, UK), which 113
is a cup that consisted of a 50ml cylindrical container and a cover with a hole for removing 114
excess of liquid. The cup is initially weight empty for calibration and then after filling with 115
the batter. Density was calculated by dividing the weight and the volume. Each formulation 116
was measured twice. 117
Viscosity of batter was measured using a Rapid Viscoanalyser (RVA-4) (Newport Scientific 118
model 4-SA, Warriewood, Australia). Batter sample (28 g) was placed in the RVA 119
aluminum canister with a plastic paddle that ensures the uniformity of the sample. Viscosity 120
of the batter with recorded at 30ºC after one minute stirring at 160rpm. The reported values 121
are means of duplicate measurements. 122
2.2.3 Cake quality evaluation 123
