Abstract
The pasting and gel textural properties of corn starch in syrup at different concentrations were investigated by Rapid Visco Analyzer (RVA) and Texture profile analysis (TPA) tests. The results showed that the pasting temperatures of corn starch greatly increased, especially at higher sugar concentration. Increasing concentration of syrup caused an increase in peak, trough and final viscosity of corn starch. Peak viscosity and the disintegration rate of starch increased in the following order: fructose syrup> maltose syrup> glucose syrup. Increasing syrup concentration to 13%, 25% and 50% resulted in a lower retrogradation rate than the control. When the maltose syrup concentration increased to 50%, the retrogradation rate decreased to 14.30% from 33.38%. The highest hardness was observed when the syrup concentration was 25%. There was a particular low hardness when the concentration of syrup was 50%. The springiness of starch gels in syrup was similar at different concentrations.
Introduction
Corn starch is a valuable ingredient to the food industry, being widely used as a thickener, gelling agent, bulking agent and water retention agent [1]. Pasting properties, gelatinization and subsequent textural properties of starch are key functional properties that determine many applications of starch in the food industry [2]. Native starch undergoes various physicochemical changes during thermal processing. Specifically, when heated in water, starch granules swell, followed by disruption of their crystalline structures [3]. The rising viscosity has been ascribed to the swelling of the starch granules as they absorb water until they burst. The viscosity maximum is reached when the granules are fully swelled, and the subsequent decrease results from the less rigid arrangement of the individual molecules released by granules rupture [4]. Subsequently, gelatinized starch molecules are re-associated in an ordered structure. During this heating and cooling process, the texture of the resultant starch pastes changes, thereby forming viscoelastic gels. However, the structure and property of starch are highly dependent on its sources and also varies under different processing conditions [5].
Recently, some studies on the pasting properties, gelatinization and textural properties of starch–sugar composites have been reported. Peak viscosity, trough viscosity and final viscosity of wheat and potato starches increased as the concentration of sucrose, glucose, and glycerol increased. For both starches peak viscosity increased in the following order: glucose> sucrose>glycerol [2]. Sharma et al. [6] found that the pasting temperature increased with the increase of the sugar concentration in cassava starch–water system, while peak viscosity and breakdown viscosity decreased with the increase of the sugar concentration. Perry et al. [7] reported that the addition of sugars and other polyols to starch-water systems elevates the starch gelatinization temperature. Sugars delay starch gelatinization by increasing the gelatinization temperature [8]. Gelatinization temperature of wheat and potato starches were increased by sucrose, glucose and glycerol in the order of sucrose>glucose>glycerol. Gel hardness of wheat starch was increased following the order glucose>sucrose>glycerol [2].
Syrup is a kind of sticky solution containing high levels of sugar. Syrup and sugar is important ingredient in many starch based foods. Saleem et al. [9] demonstrated material properties of semi-sweet biscuits and biscuits contained 1.3% glucose and 21% sugar. Secchi et al. [10] studied the shelf life of Amaretti cookies and two batches of Amaretti cookies contained 18% and 22% sugar. A gummy confection consists of high proportions of sucrose and syrup (60%), combined with starch [11].
Currently, in most studies, the effect of sugar on starch gelatinization is investigated by using differential scanning calorimetry. The present studies on pasting properties of starch are contradictory. For example, the peak viscosity and breakdown viscosity of cassava starch decreased with increase in the sugar concentration [6], but peak viscosity and breakdown point of wheat and potato starches increased as the concentration of sucrose, glucose, and glycerol increased [2]. However, no systematic studies have been reported on textural properties of starch in sugar or syrup. Therefore the purpose of this study was to investigate the influence of corn starch addition on glucose, fructose and maltose syrup at different concentrations (from 0% to 50%). The pasting and textural properties were analyzed in order to better understand the interaction between starch and syrup. A Rapid Visco Analyzer (RVA) has been generally employed to investigate the pasting properties of starch by monitoring its viscosity during heating and cooling. In addition, the textural analysis of starch gel has been carried out using a texture profile analysis (TPA). Based on this study, we can systematically understand the pasting and textural properties of corn starch in syrup and the addition of syrup to corn starch in suitable proportions can be a feasible alternative to formulation of starch based foods.
Materials and Methods
Materials
Corn starch (amylose content 26.33%) was from Shandong Zhucheng starch company, China. Glucose, fructose and maltose syrup (moisture content 25%) were purchased from Shandong Luzhou food Co., Ltd., China.
Table 2. RVA values of corn starch in fructose syrup at different concentrations.
| Fructose syrupconcentrations/% | PastingTemperature/°C | Peakviscosity/RVU | Troughviscosity/RVU | Finalviscosity/RVU | Breakdown/RVU | Disintegrati-onrate/% | Setback/RVU | Retrogr-adation rate/% |
| 0 | 77.20±0.14a | 235.79±2.65a | 170.04±1.36a | 248.75±1.06a | 65.75±4.01b | 27.88±1.39b | 78.71±2.42b | 33.38±0.65c |
| 1 | 76.90±0.57a | 273.42±0.94b | 188.25±4.60b | 285.79±3.01b | 85.17±3.65c | 31.15±1.44bc | 97.54±1.59c | 35.67±0.70c |
| 3 | 76.90±0.07a | 286.46±1.12c | 195.38±4.54b | 296.42±0.24c | 93.08±5.66c | 31.80±1.85bc | 103.04±4.77c | 35.27±1.53c |
| 13 | 78.40±0.57b | 403.38±0.88d | 270.79±4.89c | 371.29±0.53d | 138.59±3.01d | 32.87±1.07bc | 106.50±4.36c | 24.91±1.14b |
| 25 | 82.00±0.57c | 585.17±0.82e | 409.25±9.55d | 554.46±0.06e | 175.92±2.72e | 30.06±1.53bc | 145.21±2.49d | 24.82±1.66b |
| 50 | 95.40±0.14d | 846.49±2.30f | 807.67±0.82e | 807.75±0.71f | 38.82±2.12a | 4.59±0.36a | 0.08±0.12a | 0.00±0.00a |
All data represent the mean of three determinations.
Mean± standard deviation.
Means with the same letter in each column are not significantly different (p<0.05).
Methods
Pasting properties of corn starch
The pasting properties of the starch were evaluated with the Rapid Visco Analyzer (RVA-4, Newport Scientific, Warriewood, Australia). Corn starch (3.0 g, 14 g/100 g moisture basis) was weighed directly in the RVA canister and syrup was added to obtain a sample weight of 28.0 g. The concentration of syrup was 0%, 1%, 3%, 13%, 25% and 50%. A programmed heating and cooling cycle was used, where the samples were held at 50°C for 1 min, heated to 95°C at 12°C/min, held at 95°C for 2.7 min, before cooling from 95 to 50°C at 12°C/min and holding at 50°C for 2 min. Parameters recorded were pasting temperature, peak viscosity, trough viscosity (minimum viscosity at 95°C), final viscosity (viscosity at 50°C), breakdown viscosity (peak viscosity - trough viscosity) and setback viscosity (final viscosity - trough viscosity) [12]. All measurements were replicated thrice. All tests were replicated three times.
Textural properties of starch gels
The starch prepared in the RVA was poured into small aluminum canisters and stored at 4°C to cause gelation. The gels formed in the canisters were evaluated for their textural properties by texture profile analysis (TPA) using the TA/XT2 texture analyzer (Stable MicroSystems, Surrey, England). Each canister was placed upright on the metal plate and the gel was compressed at a speed of 0.5 mm/s to a distance of 10 mm with a cylindrical plunger (diameter = 5 mm). The compression was repeated twice to generate a force–time curve from which hardness (height of first peak) and springiness (ratio between recovered height after the first compression and the original gel height) was determined. Five repeated measurements were performed for each sample and their average was taken [13].
Statistical analysis
All experiments were conducted at least in triplicate, for which mean values and standard errors were determined. Also, experimental data were analyzed using Analysis of Variance (ANOVA), and expressed as mean values ± standard deviations. Differences were considered at significant level of 95% (P<0.05). Pearson’s correlation coefficients among parameters were calculated using SPSS v17.0 software.
Results and Discussion
Pasting Properties of Corn Starch
Pasting results of corn starch in syrup at different concentrations were presented (Table 1 to Table 3). From Table 1 to Table 3, we could see that there was no significant difference in pasting temperatures when the concentration of syrup was 0%, 1% and 3%. But when the concentration of syrup was 13%, 25% and 50%, pasting temperatures of corn starch increased significantly. Similar results were reported by Sharma et al. [6]. The high pasting temperature of starch indicated its higher resistance towards swelling [14]. The competition between sucrose and starch, through association with available water molecules, leads to a decrease in water activity in the mix and restrains the swelling of starch [15]. The increasing concentration of syrup caused an increase in peak viscosity, trough viscosity and final viscosity of corn starch. For instance, peak viscosity of corn starch in fructose syrup at 25% concentration was more than twice than that at 0% concentration. Peak viscosity of corn starch increased in the following order: fructose syrup> maltose syrup> glucose syrup. Comparing the three kinds of syrup, we could found corn starch in glucose syrup had the lowest peak viscosity, trough viscosity and final viscosity. Maybe because it was more difficult for starch granules to move than in water and could cohere together better, leading to close packing concentration of swollen corn starch granules. Similar results were reported by Richardson et al. [16]. Also in syrup, the hydration of corn starch granules was inhibited. Similar results were reported by Zhou et al. [17]. Previously, Mantzari et al. [18] demonstrated that the increase in viscosity of starch examined was proportional to the sorbitol content increase. This could be attributed to the fact that the external surface of the amylose helices bears hydroxyl groups which could interact with the hydroxyl groups of sorbitol to form hydrogen bridges. Sharma et al. [6] reported that the peak viscosity of cassava starch decreased with increase in the sugar concentration. The fact that the results of this study were opposite to those of the former study may be because the raw materials were different.
Table 1. RVA values of corn starch in glucose syrup at different concentrations.
| Glucose syrupconcentr-ations/% | Pastingtemperature/°C | Peakviscosity/RVU | Troughviscosity/RVU | Finalviscosity/RVU | Breakdown/RVU | Disintegrati-onrate/% | Setback/RVU | Retrogr-adationrate/% |
| 0 | 77.20±0.14a | 235.79±2.65a | 170.04±1.36a | 248.75±1.06a | 65.75±4.01c | 27.88±1.39d | 78.71±2.42ab | 33.38±0.65d |
| 1 | 77.30±0.28a | 244.17±2.83b | 173.13±3.12a | 261.92±0.47a | 71.04±2.95c | 29.09±1.10d | 88.79±2.65b | 36.36±0.66d |
| 3 | 77.10±0.14a | 253.29±1.12c | 182.04±1.00a | 266.00±0.94a | 71.25±2.12c | 28.13±0.71d | 83.96±0.06ab | 33.15±0.12d |
| 13 | 78.60±0.14b | 320.92±0.71d | 245.83±1.89b | 331.42±0.01b | 75.09±1.59c | 23.40±0.76c | 85.59±6.90ab | 26.67±2.40c |
| 25 | 82.60±0.28c | 413.71±0.41e | 360.58±0.71c | 425.21±0.65c | 53.13±0.29b | 12.84±0.08b | 64.63±1.36a | 15.62±0.34a |
| 50 | 95.05±0.07d | 532.49±2.06f | 534.17±0.79d | 636.83±1.74d | −1.68±0.06a | −0.32±0.02a | 102.66±2.86c | 19.28±1.00b |
All data represent the mean of three determinations.
Mean±standard deviation.
Means with the same letter in each column are not significantly different (p<0.05).
Table 3. RVA values of corn starch in maltose syrup at different concentrations.
| Maltose syrupconcentrations/% | Pastingtemperature/°C | Peakviscosity/RVU | Troughviscosity/RVU | Finalviscosity/RVU | Breakdown/RVU | Disintegrati-onrate/% | Setback/RVU | Retrograd-ationrate/% |
| 0 | 77.20±0.14b | 235.79±2.65a | 170.04±1.36a | 248.75±1.06a | 65.75±4.01ab | 27.88±1.39cd | 78.71±2.42a | 33.38±0.65d |
| 1 | 76.25±0.21a | 274.17±0.82b | 189.04±1.00b | 287.75±1.06b | 85.13±0.71c | 31.05±1.52d | 98.71±2.06b | 36.00±0.64e |
| 3 | 76.80±0.57ab | 280.75±0.82b | 196.79±5.60b | 296.50±1.30c | 83.96±4.77bc | 29.91±1.79cd | 99.71±4.30bc | 35.52±1.64de |
| 13 | 78.80±0.00c | 372.88±1.00c | 273.50±5.42c | 372.92±2.01d | 99.38±6.42dc | 26.65±1.65c | 99.42±1.41bc | 26.66±0.31c |
| 25 | 82.45±0.07d | 506.50±2.95d | 414.17±2.49d | 515.08±3.18e | 92.33±13.44c | 18.23±2.54b | 100.91±7.31bc | 19.92±1.33b |
| 50 | 94.70±0.00e | 765.17±2.54e | 716.92±3.42e | 826.33±0.24f | 48.25±2.96a | 6.31±1.36a | 109.41±3.65c | 14.30±0.34a |
All data represent the mean of three determinations.
Mean± standard deviation.
Means with the same letter in each column are not significantly different (p<0.05).
Breakdown was measured of the cooked starch to disintegration [13]. Leached amylose is more or less aligned in the direction of flow that contributes to the breakdown [6]. Breakdown value is peak viscosity value minus trough viscosity value. We defined the disintegration rate to measure the disintegration speed of starch paste and its role was better than breakdown value because peak viscosity and trough viscosity were changing at the same time. The disintegration rate is the ratio of breakdown value to peak viscosity value. There was no significant difference in disintegration rate when the concentration of glucose syrup was 1%, 3%, fructose syrup was 1%, 3%, 13% and 25%, and maltose syrup was 1%, 3% and 13%. However the disintegration rate of corn starch decreased when the concentration of glucose syrup was 13%, 25% and 50%, fructose syrup was 50% and maltose syrup was 25% and 50%. It really showed that corn starch in fructose syrup disintegrated more easily than in glucose and maltose syrup. The disintegration rate of corn starch increased in the following order: fructose syrup> maltose syrup> glucose syrup. Molecular corn starch ruptured and had interaction with different syrup resulting in different disintegration rate. At 50% concentration of the three kinds of syrup, the disintegration rate of corn starch decreased. In Table 1 to Table 3, we can see the trough value is closed to the peak viscosity value indicating that disintegration of starch in high concentration syrup was slight when the syrup concentration was 50%. The change may be attributed to the fact that high concentration of syrup reduced the proportion of amylose leaching. Similar results were reported by Ahmed and Williams [19]. Setback value was determined by final viscosity value minus trough viscosity value. The retrogradation rate was defined to indicate how quickly a short-term retrogradation and its role was better than setback value, because final viscosity and trough viscosity were changing at the same time. The retrogradation rate is the ratio of setback to peak viscosity. When the concentration of syrup was low, for instance 1% and 3%, the retrogradation rate of starch showed little change. In addition, increasing syrup concentration to 13%, 25% and 50% resulted in a lower retrogradation rate than the pure starch showing short-term retrogradation of starch was slow in the high concentration syrup solution. There was more or less molecular interaction among sugar, amylose and amylopectin, leading to a decrease in the extent of amylose leaching and it was more difficult to associate directionally, so the retrogradation rate was lower in the high concentration syrup solution.
Textural Properties of Corn Starch Gels
The textural properties of corn starch gels in syrup at different concentrations determined using Texture profile analysis (TPA) tests were shown in Fig. 1 and Table 4. Images of corn starch gels in syrup at different concentrations were shown in Fig. 2.
Figure 1. The hardness values of corn starch gels in syrup at different concentrations.
Table 4. The springiness values of corn starch gels in syrup at different concentrations.
| Syrup concentrations/% | Glucose syrup | Fructose syrup | Maltose syrup |
| 0 | 0.99±0.01b | 0.99±0.01b | 0.99±0.01b |
| 1 | 0.98±0.00b | 0.98±0.03b | 0.95±0.00b |
| 3 | 1.00±0.03b | 0.97±0.00b | 0.97±0.01b |
| 13 | 0.98±0.00b | 0.95±0.01b | 0.96±0.00b |
| 25 | 0.97±0.00b | 0.98±0.01b | 0.97±0.02b |
| 50 | 0.79±0.00a | 0.79±0.01a | 0.81±0.04a |
All data represent the mean of three determinations.
Mean± standard deviation.
Means with the same letter in each column are not significantly different (p<0.05).
Figure 2. Images of corn starch gels in syrup at different concentrations.
A: Corn starch gels in glucose syrup in different concentrations: a (0%), b (1%), c (3%), d (15%), e (25%) and f (50%). B: Corn starch gels in fructose syrup in different concentrations: a (0%), b (1%), c (3%), d (15%), e (25%) and f (50%). C: Corn starch gels in maltose syrup in different concentrations: a (0%), b (1%), c (3%), d (15%), e (25%) and f (50%).
The Hardness of Corn Starch Gels in Glucose, Fructose and Maltose Syrup
Hardness value is the force at maximum compression during first bite [11]. Fig. 1 showed the hardness results of corn starch gels in syrup at different concentrations. It can be seen that when the concentration of syrup was low, the change of hardness values was slight. When concentration of the three kinds of syrup was increased to 13% and 25%, we can see the hardness values of corn starch gels increased dramatically. The highest hardness values were observed when the syrup concentration was 25%. The reason why the hardness increased may be because in syrup-starch system, free water decreased leading to an increase of amylose leaching concentration relatively. Starch molecules were more likely to crash and easier to rank directionally to form three dimensional network structures resulting in an increase in gel hardness. Gunaratne et al. [2] reported that sucrose and glucose increased the hardness of wheat starch gel. They proposed that sucrose and glucose could create more junction zones on amylose chains, thus changed the ordering and intermolecular association of amylose chains, thus resulting in a strong amylose gel matrix network. Gel hardness of wheat starch was increased following the order glucose>sucrose>glycerol. The results indicated the occurrence of starch–polyhydroxy interaction which reinforces the starch granules [2]. There was a particularly low hardness value when the syrup concentration increased to 50%. This was because the syrup concentration was too high to form a powerful gel (Fig. 2).
The Springiness of Corn Starch Gels in Glucose, Fructose and Maltose Syrup
Springiness value is the distance or length of compression cycle during the second bite [11]. We can see the springiness value increased. From this study, the springiness values of starch gels in glucose, fructose and maltose syrup at different concentrations (0%, 1%, 3%, 13%, and 25%) were similar. The syrup at the concentrations (1%, 3%, 13% and 25%) did not make the springiness of corn starch gels worse (Table 4), suggesting that it had little influence on the corn starch gel’s “rubbery” feeling in the mouth. In Fig. 2, the starch gels all looked very powerful at 0%, 1%, 3%, 15% and 25% concentration. But when the concentration of syrup was 50%, the springiness of starch gel decreased because it could not form a good gel. In Fig. 2, the starch gels looked like viscous and soft sludge separating out a lot of sugar solution.
Conclusion
The pasting and textural properties of corn starch in glucose, fructose and maltose syrup at different concentrations were observed. The competition between syrup and starch, through association with available water molecules, led to a significant increase in pasting temperature when the concentration of syrup was 13%, 25% and 50%. The peak viscosity, trough viscosity and final viscosity of corn starch in different syrup increased and peak viscosity increased in the following order: fructose syrup> maltose syrup> glucose syrup. Disintegration rate of corn starch increased in the following order: fructose syrup> maltose syrup> glucose syrup. When the concentration of syrup was low, for instance 1% and 3%, the retrogradation rate of starch showed little change. In addition, increasing syrup concentration to 13%, 25% and 50% resulted in a lower retrogradation rate than the pure starch. Increasing the concentration of the three kinds of syrup to 13% and 25%, we can see the hardness of starch gels increased dramatically. There was a particular low hardness value when the syrup concentration increased to 50%. The springiness of starch gels in glucose, fructose and maltose syrup at different concentrations (0%, 1%, 3%, 13%, 25%) were similar.
Acknowledgments
We thank Professor Ying Li (College of Food Science and Engineering, Qingdao Agricultural University) for her help with statistical analysis.
Funding Statement
The authors have no support or funding to report.
References
- 1. Singh N, Singh J, Kaur L, Singh SN, Singh GB, et al. (2003) Morphological, thermal and rheological properties of starches from different botanical sources. Food Chemistry 81: 219–231. [Google Scholar]
- 2. Gunaratne A, Ranaweera S, Corke H (2007) Thermal, pasting, and gelling properties of wheat and potato starches in the presence of sucrose, glucose, glycerol, and hydroxypropyl beta-cyclodextrin. Carbohydrate Polymers 70: 112–122. [Google Scholar]
- 3. Zhu F, Cai YZ, Sun M, Corke H (2009) Effect of phytochemical extracts on the pasting, thermal, and gelling properties of wheat starch. Food Chemistry 112: 919–923. [Google Scholar]
- 4. Winter SS, Loiselle AA (1985) The effect of salts upon starch granule rupture. Journal of Colloid Science 13: 576–583. [Google Scholar]
- 5. Kim Y, Yoo SH, Park KH, Shim JH, Lee S (2012) Functional characterization of native starches through thermal and rheological analysis. Journal of the Korean Society for Applied Biological Chemistry 55: 413–416. [Google Scholar]
- 6. Sarma R, Oberoi DPS, Gill BS (2009) Effect of sugar and gums on the pasting properties of cassava starch. Journal of Food Processing and Preservation 33: 401–414. [Google Scholar]
- 7. Perry PA, Donald AM (2002) The effect of sugars on the gelatinisation of starch. Carbohydrate Polymers 49: 155–165. [Google Scholar]
- 8. Mezreb K, Goullieux A, Ralainirina R, Queneudec M (2006) Effect of sucrose on the textural properties of corn and wheat extrudates. Carbohydrate Polymers 64: 1–8. [Google Scholar]
- 9. Saleem Q, Wildman RD, Huntley JM, Whitworth MB (2005) Material properties of semi-sweet biscuits for finite element modelling of biscuit cracking. Journal of Food Engineering 68: 19–32. [Google Scholar]
- 10. Secchi N, Stara G, Anedda GR (2011) Campus M (2011) Effectiveness of sweet ovine whey powder in increasing the shelf life of Amaretti cookies. LWT - Food Science and Technology 44: 1073–1078. [Google Scholar]
- 11. Marfil PHM, Anhê ACBM, Telis VRN (2012) Texture and Microstructure of Gelatin/Corn Starch-Based Gummy Confections. Food Biophysics 6: 12–20. [Google Scholar]
- 12. Kaur M, Sandhu KS (2010) In vitro digestibility, structural and functional properties of starch from pigeon pea (Cajanus cajan) cultivars grown in India. Food research international 43: 263–268. [Google Scholar]
- 13. Sandhu KS, Singh N (2007) Some properties of corn starches II: Physicochemical, gelatinization, retrogradation, pasting and gel textural properties. Food Chemistry 101: 1499–1507. [Google Scholar]
- 14. Seetharaman K, Tziotis A, Borras F, White PJ (2001) Thermal and functional characterization of starch from Argentinean corn. Cereal Chemistry 78: 379–386. [Google Scholar]
- 15. Maaurf AG, Che Man YB, Asbi BA, Junainah AH (2001) Gelatinisation of sago starch in the presence of sucrose and sodium chloride as assessed by differential scanning calorimetry. Carbohydrate Polymers 45: 335–345. [Google Scholar]
- 16. Richardson G, Langton M, Bark A, Hermansson AM (2003) Wheat starch gelatinization – the effect of sucrose, emulsifiers and the physical state of the emulsifier. Starch 55: 150–161. [Google Scholar]
- 17. Zhou H, Wang J, Li J, Fang X, Sun Y (2011) Pasting properties of Angelica dahurica starches in the presence of NaCl, Na(2)CO(3), NaOH, glucose, fructose and sucrose. Starch-Stärke. 63 (6): 323–332. [Google Scholar]
- 18. Mantzari G, Raphaelides SN, Exarhopoulos S (2010) Effect of sorbitol addition on the physicochemical characteristics of starch-fatty acid systems. Carbohydrate Polymers 79: 154–163. [Google Scholar]
- 19. Ahmed FB, Williams PA (1999) Effect of sugars on the thermal and rheology properties of sago starch. Biopolymers 50: 401–412. [DOI] [PubMed] [Google Scholar]