Skip to main content
NCBI home page
Journal of Food Science and Technology logoLink to Journal of Food Science and Technology
. 2013 Dec 11;52(4):2033–2042. doi: 10.1007/s13197-013-1229-y

Influence of calcium fortification on physical and rheological properties of sucrose-free prebiotic milk chocolates containing inulin and maltitol

Nevzat Konar 1,✉, Ender Sinan Poyrazoglu 1, Nevzat Artik 1
PMCID: PMC4375207  PMID: 25829583

Abstract

In the present study, chocolates were investigated that had been prepared according to the composition specified as a result of this previous work (9.00 % w/w inulin and 34.0 % w/w maltitol) Certain physical (particle size distribution [PSD], brightness, chroma, water activity and hardness) and rheological features of the samples resulting from the addition of calcium carbonate in different quantities (300, 450, 600, 750 and 900 mg calcium carbonate to 100 mg milk chocolate) were studied. Both the Herschel-Bulkley and Casson models were used to investigate the rheological findings. It was determined by comparing certain rheological (rate index, Casson yield stress and Casson viscosity) and physical (chroma and hardness) parameters that samples containing 409.5 mg calcium (nearly 41.0 % of the RDA of calcium) per 100 g chocolate did not show significant differences from samples from the control group. Furthermore, these calcium-containing samples were shown to exhibit positive differences in other physical properties (brightness and water activity) that could be noteworthy and significant with respect to visual quality and shelf life.

Keywords: Chocolate, Maltitol, Calcium, Inulin, Prebiotic

Introduction

Chocolate is consumed all over the world, by all segments of society and by people of all ages. Recently, consumers have become increasingly concerned with the nutritional status of foodstuffs. Since chocolate is a potential source of many essential minerals, it can contribute to a healthy diet (Ieggli et al. 2011). Calcium, one of these elements, is an essential mineral for a variety of physiological and biochemical functions (Aguilar et al. 2012). Different researchers have shown that calcium intake is insufficient during particular stages of life (Miller 1989). Recent evidence suggests that calcium-rich diets not only reduce the risk of cardiovascular disease but also play a direct role in the prevention and treatment of obesity (Zemel et al. 2004). A higher consumption of calcium-rich foods has been recommended in order to avoid the significant repercussions that calcium deficiency may have upon health care and the economy (Aguilar et al. 2012).

In addition to its key role in the maintenance of skeletal integrity, dietary calcium is now well-recognised as playing an important part in modulating the risk of chronic diseases. The modulation of blood pressure by dietary calcium has been well-established through numerous well-controlled studies over the last 20 years (Zemel et al. 2004). Childhood and adolescence are critical times of development during which optimal peak bone mass must be established, and inadequate consumption of calcium during these years increases the risk of osteoporosis and bone fractures later in life (Matkovic 1996).

The prevalence of dietary calcium deficiency is not known, but there is evidence suggesting that people of all ages, worldwide, fail to consume adequate amounts of calcium (Van der Hee et al. 2009). The fortification of a number of foods that do not naturally contain calcium–such as orange juice, other beverages and ready-to-eat cereals–is becoming commonplace in the US. About 43 % of the US population–and almost 70 % of older women–reported calcium intake from supplements, based on a national survey of supplement intake conducted between 2003 and 2006 (Bailey et al. 2010; Ross et al. 2011).

The Food and Nutrition Board of the Institute of Medicine (IOM) of US has set a recommended daily allowance (RDA) for calcium of 1000 mg per day, based on estimates of the requirements of both genders throughout the life cycle (Institute of Medicine 2010). The tolerable upper limit for calcium has also been established as 2000 mg per day (Horn 2012). In chocolates, calcium concentrations depend on the cocoa and milk powder contents. Milk chocolate, which is the most preferred chocolate among children, as well as a high percentage of adults (Belscak-Cvitanovic et al. 2012), contains a significantly varying amount of calcium than dark chocolate does; the amount of calcium contained in these types of chocolates can satisfy approximately 4.50–25.0 % of the RDA value in the case of 100 g chocolate consumption per day (Chekri et al. 2012; Sager 2012). However, chocolate consumption at lower levels results in a decrease in this ratio. For example, in Italy, the mean chocolate intake has been calculated as 9 g per day. In India, the consumption rate of chocolate for children has been estimated at 20 g per day (Dahiya et al. 2005; Sager 2012; Sepe et al. 2001). Therefore, it is believed that chocolates may also be a product that could benefit by being enriched with calcium. CaCO3 was used in our study as the calcium source. Calcium supplements vary in their calcium contents, with the largest percentage of calcium (nearly 40 % per unit mass) provided by CaCO3 (this is also the most cost-effective source and is readily available in some antacids). Other salts, such as citrate, lactate and gluconate, contain 21, 14 and 9.3 % calcium, respectively (Krupa-Kozak et al. 2012).

Chocolate quality is often determined by sensory evaluation and physical (such as colour, hardness, water activity) and rheological measurements. Relevant information related to colour has be acquired from modern technologies such as computer vision and calibrated colour imaging analysis according to the HunterLab and CIELab models (Afoakwa et al. 2008; Briones and Aguilera 2005; Jahns et al. 2001; Hatcher et al. 2004; Lawless and Heymann 1998). Colour changes are likely to be specific to each chocolate sample (Aguilera et al. 2004). In previous studies, differences in colour parameters were found to vary with the particle size distribution, packaging conditions and storage (Aguilera et al. 2004; Mexis et al. 2010). Hardness plays an important role in the sensory assessment of chocolate (Viaene and Januszewska 1999). The hardness of chocolates has been related to the type of fat present and its content, the type of sugar, tempering conditions, conching temperature and particle size distribution (PSD) (Afoakwa et al. 2008; De Clerq et al. 2012; Jovanovic and Pajin 2004; Kieran Keogh et al. 2003; Konar 2013). PSD has a significant impact on the rheological and instrumental textural properties of chocolates. In previous studies, Beckett (2000) stated that PSD influences chocolate rheology, with the specific surface area (SSA) and the mean particle size (D[4,3]) specifically influencing yield stress. Smaller particle sizes in chocolates are known to improve sensory properties (Ziegler et al. 2001). In previous studies, it has been reported that the rheological properties of chocolate are affected also by processing (refining, conching and tempering) as well as composition (amount of fat, amount and type of emulsifiers) (Afoakwa et al. 2009; Schantz and Rohm 2005; Varveck 2004).

The use of maltitol in chocolate production is important because it makes chocolates “tooth-friendly” and “sugar-free.” Furthermore, the addition of inulin makes it possible to produce a product in which prebiotic activity can be observed. Prebiotics have been associated with a variety of health benefits, including an increase in the bioavailability of minerals, particularly that of calcium (Charalampopoulus and Rastall 2012). Therefore, it important to produce a calcium-fortified foodstuff containing a prebiotic compound that can be consumed by all age and socioeconomic groups. In our previous works (Konar 2013; Konar et al. 2013), we studied the effects of substituting fine sugar with isomalt and maltitol in milk chocolate samples that contain inulin (9.0 % w/w). The use of varying conching temperatures in the sample-preparation process and the effects of these temperatures on the physical and rheological properties of the chocolates were examined. It was concluded that maltitol is a more suitable substitute for fine sugar than isomalt in milk chocolates containing inulin. In the present study, the effects of calcium (Ca) fortification at various levels on the rheological properties (such as yield stress, viscosity and rate index) and physical properties (such as color [brightness, hue angle and chroma], water activity and hardness) of non-sucrose prebiotic milk chocolate samples that contain inulin and maltitol, were examined.

Materials and methods

Materials

The following substances were used for the preparation of the milk chocolate samples: cocoa butter, cocoa mass (Altinmarka, Istanbul, Turkey), sugar (SMS Kopuz, Istanbul, Turkey), milk powder (Besel, Konya, Turkey), soy lecithin (Bremtag Chemistry, Istanbul, Turkey), polyglycerol polyricinoleate (PGPR) (Palsgaard, Zierikzee, Netherlands), vanillin (Ekin Chemistry, Istanbul, Turkey), inulin (Beneo Orafti, Oreye, Belgium), maltitol (Roquette Frenes, Lestres, France) and calcium carbonate (CaCO3; assay ≥ 99.0 %, Sigma-Aldrich, Gillingham, Dorset). All materials were obtained from Tayas Food Company (Gebze, Kocaeli, Turkey).

Apparatus

A pilot-scale chocolate line and tempering apparatus (Aasted, Farum, Denmark), pilot-scale refiner (Lehman, Asslen, Germany) and pilot-scale conch (BSA Schneider Anlagentechnik, Aachen, Germany) were used for preparing chocolate samples. In addition to general laboratory equipment, a Flame Atomic Absorption Spectrophotometer (FAAS, PerkinElmer Analyst 700, PerkinElmer, Norwalk, CT, USA), a TA-TXPLUS Texture Analyser (Microstable Systems, UK), an LA-300 Laser-Scattering Particle Size Distribution Analyser (Horiba Scientific, USA), a CR400 colorimeter (Konica Minolta, Japan), a Master Water Activity Measurement device (Novasina, Switzerland) and a rheometer (Brookfield R/S Plus, USA) were used for analysis.

Sample preparation

Each sample group was prepared in lots of 10 kg using the formulations presented in Table 1. For this purpose, the melted fat components (comprising 20 % of the total cocoa butter) and the dry powders (fine sugar, milk powder and cocoa mass, maltitol, inulin and CaCO3) were mixed until homogeneous while being warmed to 40 °C. Calcium carbonate (CaCO3) at various levels (300, 450, 600, 750 and 900 mg/100 g chocolate) was used as the source of calcium. At the end of the mixing and warming, the chocolate mass (containing approximately 5.98 % fat) was first pre-refined on a pilot-scale 3-roll refiner (Lehmann, Aaelen, Germany) and then mixed again and warmed to 50 °C. To achieve a mean particle size of 20 μm, the gap size/pressure between the rollers of the 3-roll refiner was adjusted and the particle size distribution was measured using a laser-diffraction particle size analyser (Horiba, USA), as described in the discussion of Particle Size Distribution below. After measuring the particle size, dry conching was performed for 45 min, and the remaining cocoa butter (80 % of the total), vanilla, soy lecithin and PGPR were then added (resulting a fat content of 24.0 %). The total conching time was 4.50 h at 55 °C.

Table 1.

Formulations used for the chocolate samples

Ingredient Control (K) Sample
A B C D E
Maltitol (g) 34.00 34.00 34.00 34.00 34.00 34.00
Cocoa butter 24.00 24.00 24.00 24.00 24.00 24.00
Cocoa mass 12.45 12.45 12.45 12.45 12.45 12.45
Whole powdered milk 20.00 20.00 20.00 20.00 20.00 20.00
Soy lecithin 0.30 0.30 0.30 0.30 0.30 0.30
PGPR 0.22 0.22 0.22 0.22 0.22 0.22
Vanilla 0.03 0.03 0.03 0.03 0.03 0.03
Inulin 9.00 9.00 9.00 9.00 9.00 9.00
Calcium carbonate 0.00 0.300 0.450 0.600 0.750 0.900
Calciuma (mg/100 g) 169.8 ± 9.9 287.9 ± 11.0 351.3 ± 8.9 409.5 ± 10.4 468.3 ± 13.8 529.9 ± 9.7
Open in a new tab

aCalcium content of milk chocolate samples determined by FAAS, presented as mean value ± SD. Experiments were performed in triplicate

Afterwards, a three-stage tempering process (33–35, 24–25 and 25–26 °C) was implemented (temper index value, as measured by a temper meter [Chocometer, Aasted Farum, Denmark]: 5.50–6.00). Subsequently, the moulding and vibration process (Aasted Farum, Denmark) was conducted at 27–30 °C. After 20 min of cooling (Aasted Farum, Denmark) at 5 °C, the process was completed. Samples were output at temperatures between 13 and 15 °C, and subsequently stored away from light and heat prior to analysis.

Calcium content determination

The calcium content of the milk chocolate samples was determined according to a method published by the Association of Analytical Communities (AOAC; Method 985.35, 2010) by usingan FAAS (PerkinElmer Analyst 700).

Particle size distribution

A method for determining the particle size distribution of each sample was adapted from the method used by Afoakwa et al. (2008). A LA-300 Laser-Scattering Particle Size Distribution Analyser (Horiba, USA) was used. Approximately 0.20 g of each chocolate sample was dispersed in vegetable oil (refractive index, RI: 1.45) at ambient temperature (20 ± 2 °C) until an obscuration of 0.20 was obtained. Ultrasonic dispersion was maintained by stirring for 2 min to ensure that the particles were freely dispersed. The size distribution was quantified as the relative volume of particles in different size bands and presented as size distribution curves. Data were analysed based on Mie theory. The obtained particle size distribution parameters included the following: D[4,3] (μm), median; D90 (μm), diameter for which 90 % of particles were smaller in size; specific surface area (cm2/cm3); D10 (μm), diameter for which 10 % of particles were smaller in size; [(D90–D10)/D50] (μm), span; and standard deviation (St Dev).

Hardness measurement

The mechanical properties of the chocolates, such as the hardness, were measured using a TA-TXPlus Texture Analyser (Stable Micro Systems, UK) according to the method used by Konar (2013). Results for the hardness (N) are expressed as the mean value of 5 replicates conducted on different samples from the same lot of each chocolate.

Water activity

The water activity of the chocolates was measured using a Lab-Master aw (Novasina, Switzerland) according to the method used by Konar (2013). Aw values of each sample were measured in triplicate at after a follow-up day of sample preparation.

Colour measurement

Instrumental analyses for colour measurement were performed according to the method used by Konar (2013). The colour parameters in this study were brightness (L*) and chroma (C* = [(a*2) + (b*2)]1/2). All data were expressed as the mean value of 5 replicates conducted on different samples from the same lot of each chocolate.

Rheological measurement

Rheological properties of the milk chocolate samples were measured using a rheometer (Brookfield R/S Plus, USA) according to the method used by Sokmen and Gunes (2006), with some modifications. Each chocolate sample was incubated at 50 °C for 75 min, melted, then transferred to the rheometer and sheared at a rate of 5.00 s−1 for 10 min at 40 °C prior to beginning the measurement cycles. The shear rate was ramped up from 0.50 to 60.0 s−1 over a period of 120 s and subsequently ramped down from 60.0 to 0.50 s−1. During each cycle of ramping up and then down, 50 measurements were taken. Each measurement cycle was repeated 30 times consecutively until thixotropy was eliminated from the samples. The data from the 30th measurement were analysed using both the Casson model and the Herschel-Bulkley model. From the best fit of these models to the data, certain rheological parameters, such as the yield stress, viscosity and rate index, were determined.

Statistical analysis

Quantitative data are expressed as mean values. Results were analysed using the Tukey test (SPSS 15.0, SPSS Inc., Chicago, IL.). Values at P < 0.01 were considered significant.

Results and discussion

Calcium fortification

Chekri et al. (2012), studying the mineral content of various foodstuffs, reported that the calcium content of chocolate samples (n = 10), as determined by the FAAS Method, varied between 45 and 173 mg/100 g. Powdered milk and cocoa mass may be specified as the essential sources of calcium in chocolates before enrichment. These compounds are present in the composition of the product in different ratios depending on the type of chocolate. Therefore, it can be concluded that the type of chocolate is one of the decisive factors in predicting calcium content. Data obtained in previous studies also confirm this hypothesis. Sager (2012) reported the calcium contents of milk chocolate and dark chocolate as about 150–250 mg/kg and 50–100 mg/kg, respectively. The calcium content determined for the non-enriched control samples in the present study (169.8 ± 9.9 mg/100 g) was consistent with the values obtained in these previous studies. Furthermore, it was determined that this control value satisfies approximately 17 % of the RDA suggested by IOM (Institute of Medicine 2010) for calcium (1,000 mg) assuming 100 g of milk chocolate are consumed per day. The daily tolerable upper limit for calcium (2,000 mg) would be obtained by consuming 1,179.9 g of the control chocolate samples in a day.

The calcium contents of the samples labelled A, B, C, D and E were found to be 287 ± 11.0, 351.3 ± 8.90, 409.5 ± 10.4, 468.3 ± 13.8 and 529.9 ± 9.70 mg/100 g respectively. Given the quantities of CaCO3 used in the preparation of the samples and the determined calcium contents, it was determined that a homogeneous CaCO3 distribution was present in the chocolate samples. Furthermore, given these calcium contents, it was determined that 100 g of the samples labelled A, B, C, D and E contained enough calcium to satisfy 28.7, 15.1, 41.0, 46.8 and 53.0 % of the RDA for calcium, respectively.

Particle size distribution

An unpleasant texture has been found to occur when too many coarse particles are present in the chocolate (Bolenz et al. 2006). These coarser particles (size larger than 30 μm) lead to a gritty or sandy product. Grittiness is a textural defect in chocolate, but it is one of many possible defects, including difficulty in swallowing, poor melting, and hardness. In some cases, grittiness represents a minor issue (Do et al. 2007). Thus, in this study we investigated the PSD of calcium-fortified chocolate samples. The data resulting from this analysis can provide information as to whether or not variation in the determined PSD values is a factor that can predict rheological variations observed in the product. The largest particle size (D90), smallest particle size (D10), mean (D[4,3]), median (D[3,2]), span and specific surface area (SSA) of each sample group are given in Table 2. Also, representative PSD curves of different milk chocolate samples are shown in Fig. 1.

Table 2.

PSD values for chocolate samples

Sample SSA (cm3/cm2) D90 (μm) D10 (μm) D[4,3] (μm) Span D[3,2] (μm) SD
K 5,389.6f 39.2853f 5,2108a 19.6265e 2.1566c 15.7999b 14.4070
A 5,417.9e 43.1004a 5.0525b 20.8417a 2.3563a 16.1474a 16.4289
B 5,489.6d 42.2058c 5.0152b 20.4176b 2.3586ab 15.7682b 16.1404
C 5,505.5c 40.4751e 5.0051b 19.9824c 2.3293b 15.2384e 15.4952
D 5,583.6b 42.5457b 4.9965b 20.0134c 2.5261ab 14.8643d 15.5888
E 5,707.2a 40.6167d 4.7370c 19.6944d 2.2939bc 15.6415c 14.5529
Open in a new tab

SSA specific surface area, D 90 largest particle size, D 10 smallest particle size, D [4,3] mean, D [3,2] median, SD standard deviation. For each parameter, mean values followed by the same letter are not significantly different (P < 0.01)

Fig. 1.

Fig. 1

Open in a new tab

Representative PSD curves for milk chocolate samples

Traditionally, continental European chocolate has been described as having a fineness of 15–22 μm particle diameter, while North American chocolate has a corresponding value of 20–30 μm (Afoakwa et al. 2009). Typically, values around 20 μm are used for standards (Schumacher et al. 2009). In this study, a mean particle size (D[4,3]) of 20 μm was the target for all samples. The observed values for the produced samples were within the range of 19.6265–20.8417 μm (Table 2). The differences between D[4,3] values were statistically significant (P < 0.01), it is believed that they are at a tolerable level, and that they might be due to deviations in the sample preparation procedures. However, it is noteworthy that the values of both SSA, which is another important PSD parameter, and span varied directly with the amount of CaCO3 in the sample. The value of D10 was also found to vary inversely with CaCO3 content. No correlation between the other parameters described above and CaCO3 content was found.

Previous studies have also shown that SSA is inversely correlated with the different components of the PSD (Afoakwa et al. 2009; Beckett 1999; Sokmen and Gunes 2006; Ziegler and Hogg 1999), as was observed in this study. As a result, it was concluded that a variation in PSD may occur depending on the CaCO3 content of chocolate, and that it is possible to observe a variation in the rheological, sensory and textural properties of the product due to this PSD variation.

Colour

In this study, the CIELab model was used to determine the brightness (L*) and chroma (C*) for each chocolate sample. The L* value for the control samples was determined to be 37.8 ± 0.23, while this value varied between 38.8 ± 0.11 and 38.3 ± 0.63 in case of samples to which CaCO3 had been added (Table 3). The brightness values for all of the calcium-enriched chocolates were higher than that of the control (P < 0.01), and this value was observed to vary directly with calcium content, with the exception of the sample to which 900 mg of CaCO3 was added. Thus, it is believed that the enrichment of milk chocolate samples with CaCO3 may result in an increase in brightness and an improvement in visual quality.

Table 3.

Some physicochemical properties of chocolate samples

Sample Brightness (L*) Chroma (C*) Water activity (aw) Hardness (N)
K1 37.8d ± 0.23 15.4ab ± 0.11 0.22a ± 0.00 11.4a ± 0.41
A 38.3c ± 0.63 15.0c ± 0.65 0.21ab ± 0.00 11.3a ± 0.30
B 38.6ab ± 0.60 15.1bc ± 0.33 0.21ab ± 0.01 11.4a ± 1.46
C 38.5bc ± 1.04 15.4ab ± 0.45 0.21ab ± 0.01 11.4a ± 1.46
D 38.8a ± 0.11 15.4ab ± 0.59 0.21b ± 0.00 11.4a ± 0.50
E 38.4bc ± 1.07 15.5a ± 0.81 0.19c ± 0.01 11.3a ± 0.91
Open in a new tab

Five replicates of the hardness and colour (L* and C*) experiments were performed. Water activity experiments were performed in triplicate. All data are reported as mean value ± SD. For each parameter, mean values followed by the same letter are not significantly different (P < 0.01)

In previous studies, differences in L* (38.3–43.5) and C* (11.0–14.4) were found to vary with the process conditions and storage (Aguilera et al. 2004; Mexis et al. 2010). In this study, chroma values varied within narrow ranges, such as 15.0 ± 0.65–15.5 ± 0.81 (Table 3); however, statistically significant variations were determined between the sample groups (P < 0.01). No obvious correlation between this variation and the calcium content or the quantity of supplementary CaCO3 added could be established.

Hardness

The data from our study (Table 3) showed that calcium fortification cannot be considered as one of the factors affecting hardness, provided that all features of the chocolate and production process used in the study are taken into account. No statistically significant variation between all sample groups could be determined with respect to hardness.

Farzanmehr and Abbasi (2009) studied milk chocolates containing inulin. These researchers obtained different hardness values (10.1–15.0 N) for samples of different compositions. In the present study, the hardness values were determined within narrow ranges, such as 11.3 ± 0.30–11.4 ± 1.46 N. Similar samples, containing also calcium in addition to inulin and maltitol, were produced in this study.

Good chocolate should have a smooth, soft, velvety texture, while poor quality chocolate feels hard, grainy or waxy (Aidoo, et al. 2011). Therefore, the fact that enriching the calcium content of the chocolate samples by using CaCO3 as a calcium source did not cause an undesired variation in hardness and can be considered to be a favourable result.

Water activity

Prebiotic chocolate samples were produced using inulin (9.00 %, w/w). Inulin is a hydrophilic substance; therefore, it may influence the water activity of the foodstuff to which it is added. On the other hand, maltitol, which is used as a bulk sweetener, has a moderate hygroscopicity. In a previous study, the water activity of control samples (0.22 ± 0.003) was determined to be lower than that of samples containing inulin, which exhibited water activity values in the range between 0.40 and 0.50. However, this value may be influenced by the raw materials and processing conditions, particularly the refining and conching steps (Biquet and Labuza 1988; Rossini et al. 2011; Vercet 2003). For example, Farzanmehr and Abbasi (2009), using 10.45 g/100 g inulin in the preparation of milk chocolate samples, found a water activity value of 0.34. In a previous study (Konar 2013) in which the samples were prepared using 9.00 g/100 g inulin and 34.0 g/100 g maltitol, identical to the samples used in the present study, water activity was determined to lie within the range of 0.22–0.24. Another reason for lower water activities determined in the present study may be the fact that water activity was measured on the day following the day of sample preparation.

In the present study, measured water activity values were in the range between 0.21 ± 0.00 and 0.19 ± 0.01 for the calcium-enriched chocolate samples (Table 3). Water activity varied inversely with the quantity of CaCO3 used in preparation of the samples. Although all samples showed significant variation in water activity as compared to the control (P < 0.01), no significant variation was observed between sample groups A, B and C, which were prepared with 300, 450 and 600 mg of CaCO3, respectively (P < 0.01). Sample group E, prepared using the largest quantity of CaCO3 (900 mg), found to be the sample having the lowest water activity (0.19 ± 0.01).

In general, it can be concluded that calcium fortification in the milk chocolates prepared in this study may offer advantages with respect to shelf life and storage stability, provided that fortification does not have an adverse effect on the sensory features of the product.

Rheology

Molten chocolate is a non-Newtonian fluid with a yield stress, which can be characterised using a number of mathematical models, including the Bingham, Herschel-Bulkley and Casson models (Konar 2013). With regard to techniques for characterizing the rheological properties, the International Confectionary Association (ICA, previously IOCCC) suggests the use of rotational viscometers with concentric cylinders, to be used in conjunction with the Casson equation. The Casson model was also applied to the data from the present study. However, Sokmen and Gunes (2006), who investigated the effects of different bulk sweeteners, such as maltitol, isomalt and xylitol, as well as the particle size distributions of these sweeteners on the rheological properties of molten chocolates, stated that the Herschel-Bulkley model fit the data more appropriately than did the Casson and Bingham models. In our previous study characterising milk chocolate containing inulin and maltitol, we also used the Herschel-Bulkley model (Konar 2013). In the present study, the Herschel-Bulkley model showed the best fit for predicting rheology, except in the case of sample group D. Therefore, the related rheological parameters, such as yield stress, viscosity and rate index, along with Casson yield stress and viscosity, are given with together at Table 4. Also, plots of viscosity versus shear rate of milk chocolate samples which containing various quantities of calcium, are shown in Fig. 2.

Table 4.

Rheological measurements for chocolate samples

Herschel-Bulkley Casson
Sample Yield stress (Pa) Viscosity (Pa.s) Rate index Standard error Yield stress (Pa) Viscosity (Pa.s) Standard error
K1 6.70c 4.30c 0.92ab 5.26 2.14c 2.57a 6.43
A 5.31d 3.30e 0.88b 5.80 0.86e 2.57a 6.50
B 4.74e 4.18d 0.90ab 3.26 1.51d 2.54a 5.05
C 7.91b 4.42b 0.91ab 7.22 2.71a 2.52a 8.71
D 3.50f 6.29a 0.97a 3.44 2.49b 3.16b 5.63
E 12.0a 3.29e 0.97a 7.50 2.83a 2.32a 4.72
Open in a new tab

For each parameter, mean values followed by the same letter are not significantly different (P > 0.01)

Fig. 2.

Fig. 2

Open in a new tab

Plots of viscosity versus shear rate of milk chocolate samples containing various quantities of calcium

Examining the rate index (RI) values for all of the samples showed similar values across the range of samples (0.88–0.97). Almost all of the calcium-fortified samples (A, B, C, D and E), as well as the control sample (K), were found to be pseudoplastic (shear-thinning) (0 < RI < 1). The variation between the rate index value for samples D and E, containing the highest quantities of CaCO3, was not found to be significant (P < 0.01), nor was the variation in rate index between the control sample and the samples from groups B and C. Adding a small amount of CaCO3 (300 mg) to the control samples was found to reduce significantly the RI value. As this amount increased (450 mg and 600 mg), the RI value reached a level that did not vary significantly in comparison to the control. Adding higher amounts of CaCO3 increased the RI value by a statistically significant amount. It is noteworthy that the final achieved value of rate index (0.97), for the chocolates enriched with the largest quantities of calcium, was very close to the value associated with a shear-thickening property. It is believed that this is due to the increased calcium level increasing the intensity of interactions between calcium and the powdered milk proteins found in the chocolate.

Examining the yield stress values obtained by using the Herschel-Bulkley model, it was found that significant variations were present between the samples (P < 0.01), but such variations could not be associated with the varying amounts of calcium. The viscosity values obtained using this model showed that RI values increased with increasing calcium content, except in the case of samples from group E.

Although the best fit was obtained by using the Herschel-Bulkley model, it was found that viscosity values obtained by using the Casson model produced more meaningful results. The viscosity values calculated using this model varied between 2.57 and 3.16 Pa.s. No significant variation between the samples was observed with respect to the Casson viscosity values (P < 0.01), with the exception of sample D. On the other hand, as the CaCO3 content of the chocolates increased across the range of samples, Casson yield stress values first decreased in sample group A relative to the control group, then subsequently increased for the other sample groups. Although the difference between the Casson yield stress (2.83 Pa) of sample group E, which had the highest calcium enrichment, and that of the control group (2.14 Pa) is statistically significant (P < 0.01), this was considered to be a tolerable difference.

Considering the type and quantity of the calcium resource used in the present study, it has been concluded that calcium enrichment does cause variations in the rheological properties of the milk chocolate samples containing inulin and maltitol, but that the magnitude of this variation generally changes depending on the amount of calcium that is used.

Conclusions

The properties of calcium-enriched chocolates were compared with control samples in the present study. Certain physical features of calcium-enriched milk chocolate samples, such as hardness, do not change significantly, while other physical features change favourably with regard to the visual quality and shelf life of the product. However, variations in rheological features could not be clearly correlated with the level of calcium enrichment. It is noteworthy and significant that either no significant difference was observed between the samples containing 409.5 mg/100 g calcium and the control samples with respect to certain rheological (RI, Casson yield stress and Casson viscosity) and physical (chroma and hardness) parameters, or that a tolerable difference in these properties was observed. In addition, other physical properties changed (brightness and water activity) in favour of improved visual quality and shelf life. Consuming 100 g of this calcium-enriched product can satisfy approximately 41 % of the RDA of calcium; however, further studies using in vivo methods should be conducted to determine the correlation between the bioavailability of calcium and the presence and amount of prebiotic substances in chocolates.

References

  1. Afoakwa EO, Paterson A, Fowler M, Vieira J. Particle size distribution and compositional effects on textural properties and appearance of dark chocolates. J Food Eng. 2008;87:181–190. doi: 10.1016/j.jfoodeng.2007.11.025. [DOI] [Google Scholar]
  2. Afoakwa EO, Paterson A, Fowler M, Vieira J. Microstructure and mechanical properties related to particle size distribution and composition in dark chocolate. Int J Food Sci Technol. 2009;44(1):111–119. doi: 10.1111/j.1365-2621.2007.01677.x. [DOI] [Google Scholar]
  3. Aguilar MC, Mateos C, Meseguar I, Para M. Calcium availability in breakfast cereals: effect of other food components. Eur Food Res Technol. 2012;235:489–495. doi: 10.1007/s00217-012-1773-0. [DOI] [Google Scholar]
  4. Aguilera JM, Michel M, Mayor G. Fat migration in chocolate. Diffusion or capillary flow in particulate solid? A hypothesis paper. J Food Sci. 2004;69(7):R167–R174. doi: 10.1111/j.1365-2621.2004.tb13615.x. [DOI] [Google Scholar]
  5. Aidoo H, Sakyi-Dawson E, Abbey L, Tano-Debrah K, Saalia FK. Optimisation of chocolate formulation using dehydrated peanut-cowpea milk to replace dairy milk. J Sci Food Agric. 2011;92(2):224–231. doi: 10.1002/jsfa.4563. [DOI] [PubMed] [Google Scholar]
  6. Bailey RK, Dodd KW, Goldman JA, Gahche JJ, Dwyer JT, Mosfegh AJ, Sempos CT, Picciano MF. Estimation of total usual calcium and vitamin D intake in the United States. J Nutr. 2010;140(4):817–822. doi: 10.3945/jn.109.118539. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Beckett ST. Industrial chocolate manufacture and use. 3. Oxford: Blackwell; 1999. [Google Scholar]
  8. Beckett ST. The science of chocolate. Cambridge: The Royal Society of Chemistry; 2000. pp. 85–103. [Google Scholar]
  9. Belscak-Cvitanovic A, Komes D, Berkovic M, Karlovic S, Hecimovic I, Jezek D, Bauman I. Innovative formulations of chocolates enriched with plant polyphenols from Rubus idaeus L. Leaves and characterization of their physical, bioactive and sensory properties. Food Res Int. 2012;48:820–830. doi: 10.1016/j.foodres.2012.06.023. [DOI] [Google Scholar]
  10. Biquet B, Labuza TP. Evaluation of the moisture permeability characteristics of the chocolate films as an edible moisture barrier. J Food Sci. 1988;53(4):989–998. doi: 10.1111/j.1365-2621.1988.tb13516.x. [DOI] [Google Scholar]
  11. Bolenz S, Amtsberg K, Schape R. The broader usage of sugars and fillers in milk chocolate made possible by the new EC cocoa directive. Int J Food Sci Technol. 2006;41:45–55. doi: 10.1111/j.1365-2621.2005.01023.x. [DOI] [Google Scholar]
  12. Briones V, Aguilera JM. Image analysis and changes in surface color of chocolate. Food Res Int. 2005;38:87–94. doi: 10.1016/j.foodres.2004.09.002. [DOI] [Google Scholar]
  13. Charalampopoulus D, Rastall RA. Prebiotics in foods. Curr Opin Biotechnol. 2012;23(2):187–191. doi: 10.1016/j.copbio.2011.12.028. [DOI] [PubMed] [Google Scholar]
  14. Chekri R, Noel L, Millour S, Vastel C, Kadar A, Sirot V, Leblanc JC, Guerin T. Calcium, magnesium, sodium and potassium levels in foodstuffs from the second French Total Diet Study. J Food Compos Anal. 2012;25:97–107. doi: 10.1016/j.jfca.2011.10.005. [DOI] [Google Scholar]
  15. Dahiya S, Karpe R, Hedge AG, Sharma RM. Lead, cadmium and nickel in chocolates and candies from suburban areas of Mumbai, India. J Food Compos Anal. 2005;18:517–522. doi: 10.1016/j.jfca.2004.05.002. [DOI] [Google Scholar]
  16. De Clerq N, Moens K, Depypere F, Ayala JV, Calliauw G, De Greyt W, Dewettinck K. Influence of cocoa butter refining on the quality of milk chocolate. J Food Eng. 2012;111(2):412–419. doi: 10.1016/j.jfoodeng.2012.01.033. [DOI] [Google Scholar]
  17. Do T-AL, Hargreveas JM, Wolf B, Hort J, Mitchell JR. Impact of particle size distribution on rheological and textural properties of chocolate models with reduced fat content. J Food Sci. 2007;72(9):E541–E552. doi: 10.1111/j.1750-3841.2007.00572.x. [DOI] [PubMed] [Google Scholar]
  18. Farzanmehr H, Abbasi S. Effects of inulin and bulking agents on some physicochemical, textural and sensory properties of milk chocolate. J Texture Stud. 2009;4:536–553. doi: 10.1111/j.1745-4603.2009.00196.x. [DOI] [Google Scholar]
  19. Hatcher DW, Symons SJ, Manivannan U. Developments in the use of image analysis fort he assesment of oriental noodle appearance and colour. J Food Eng. 2004;61:109–117. doi: 10.1016/S0260-8774(03)00192-4. [DOI] [Google Scholar]
  20. Horn G. Sources of dietary calcium in patients attending an osteoprosis clinic. Nutr Diet Suppl. 2012;4:55–60. doi: 10.2147/NDS.S31772. [DOI] [Google Scholar]
  21. Ieggli CVS, Bohrer D, do Nascimento PC, de Carvalho LM. Determination of sodium, potassium, calcium, magnessium zinc and iron in emulsified chocolate samples by flame atomic absorption spectrometry. Food Chem. 2011;124(3):1189–1193. doi: 10.1016/j.foodchem.2010.07.043. [DOI] [PubMed] [Google Scholar]
  22. Institute of Medicine . Dietary reference ıntakes for calcium and vitamin D. Washington, DC: National Academies Press; 2010. [PubMed] [Google Scholar]
  23. Jahns G, Nielsen HM, Paul W. Measuring image analysis attributes and modelling fuzzy consumer aspects for tomato quality grading. Comput Electron Agric. 2001;31:17–29. doi: 10.1016/S0168-1699(00)00171-X. [DOI] [Google Scholar]
  24. Jovanovic O, Pajin B. Influence of lactic acid ester on chocolate quality. Trends Food Sci Technol. 2004;15:128–136. doi: 10.1016/j.tifs.2003.09.011. [DOI] [Google Scholar]
  25. Kieran Keogh M, Murray CA, O’Kennedy BT. Effects of selected properties of ultrafiltered spray-dried milk powders on some properties of chocolate. Int Dairy J. 2003;13:719–726. doi: 10.1016/S0958-6946(03)00124-9. [DOI] [Google Scholar]
  26. Konar N. Influence of conching temperature and some bulk sweetners on physical and rheological properties of prebiotic milk chocolate containing inulin. Eur Food Res Technol. 2013;236:135–143. doi: 10.1007/s00217-012-1873-x. [DOI] [Google Scholar]
  27. Konar N, Ozhan B, Artik N, Dalabasmaz S, Poyrazoglu ES. Rheological and physical properties of inulin-containing milk chocolate prepared at different process conditions. CyTA J Food. 2013 [Google Scholar]
  28. Krupa-Kozak U, Altamirano-Fortoul R, Wronkowska M, Rosell CM. Breadmaking performance and technological characteristic of gluten-free bread with inulin supplemented with calcium salts. Eur Food Res Technol. 2012;235:545–554. doi: 10.1007/s00217-012-1782-z. [DOI] [Google Scholar]
  29. Lawless HT, Heymann H. Sensory evaluation of food: principles and practices. New York: Chapman & Hall; 1998. [Google Scholar]
  30. Matkovic V. Nutrition, genetics, and skeletal development. J Am Coll Nutr. 1996;15:556–569. doi: 10.1080/07315724.1996.10718630. [DOI] [PubMed] [Google Scholar]
  31. Mexis SF, Badeka AV, Riganakos KA, Kontominas MG. Effect of active and modified atmosphere packaging on quality retention of dark chocolate with hazelnuts. Innov Food Sci Technol. 2010;11:177–186. doi: 10.1016/j.ifset.2009.09.001. [DOI] [Google Scholar]
  32. Miller DD. Calcium in the diet: food source, recommended intakes and nutritional availability. Adv Food Nutr Res. 1989;33:103–156. doi: 10.1016/S1043-4526(08)60127-8. [DOI] [PubMed] [Google Scholar]
  33. Ross AC, Taylor CL, Yaktine AL, Del Valle HB. Dietary reference ıntakes for calcium and vitamin D. Washington: National Academy of Sciences; 2011. pp. 36–37. [PubMed] [Google Scholar]
  34. Rossini K, Norena CPZ, Brandelli A. Changes in the colour of white chocolate during storage: potential roles of lipid oxidation and non-enzymatic browning reactions. J Food Sci Technol. 2011;48(3):305–311. doi: 10.1007/s13197-010-0207-x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  35. Sager M. Chocolate and cocoa products as a source of essential elements in nutrition. J Nutr Food Sci. 2012;2:123. doi: 10.4172/2155-9600.1000123. [DOI] [Google Scholar]
  36. Schantz B, Rohm H. Influence of lecithin-PGPR blends on the rheological properties. LWT Food Sci Technol. 2005;38(1):41–45. doi: 10.1016/j.lwt.2004.03.014. [DOI] [Google Scholar]
  37. Schumacher AB, Brandelli A, Schumacher EW, Macedo FC, Pieta L, Klug TV, de Jong EV. Development and evaluation of a laboratory scale conch for chocolate production. Int J Food Sci Technol. 2009;44:616–622. doi: 10.1111/j.1365-2621.2008.01877.x. [DOI] [Google Scholar]
  38. Sepe A, Costantini S, Ciaralli L, Ciprotti M, Giordano R. Evaluation of aluminum concentrations in sample of chocolate and beverages by electrothermal atomic absorption spectrometry. Food Addit Contam. 2001;18:788–796. doi: 10.1080/02652030118615. [DOI] [PubMed] [Google Scholar]
  39. Sokmen A, Gunes G. Influence of some bulk sweetners on rheological properties of chocolate. LWT Food Sci Technol. 2006;39:1053–1058. doi: 10.1016/j.lwt.2006.03.002. [DOI] [Google Scholar]
  40. Van der Hee RM, Siret S, Slettenarr M, Duchateau GSM, Rietveld AG, Wikinson JE, Quail PJ, Berry MJ, Dainty JR, Teucher B, Fairweather-Tait SJ. Calcium absorption from fortified ice cream formulations compared with calcium absorption from milk. J Am Diet Assoc. 2009;109(5):830–835. doi: 10.1016/j.jada.2009.02.017. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Varveck AN. Flow of molten milk chocolate from an efflux viscometer under vibration at various frequincies and displacements. Int J Food Sci Technol. 2004;39(4):465–468. doi: 10.1111/j.1365-2621.2004.00805.x. [DOI] [Google Scholar]
  42. Vercet A. Browning of white chocolate during storage. Food Chem. 2003;81(3):371–377. doi: 10.1016/S0308-8146(02)00452-1. [DOI] [Google Scholar]
  43. Viaene J, Januszewska R. Quality function deployment in the chocolate industry. Food Qual Prefer. 1999;10:377–385. doi: 10.1016/S0950-3293(99)00007-5. [DOI] [Google Scholar]
  44. Zemel MB, Thompson W, Milstead A, Morris Campbell P. Calcium and dairy acceleration and fat loss during energy restriction in obese adults. Obes Res. 2004;12(4):582–590. doi: 10.1038/oby.2004.67. [DOI] [PubMed] [Google Scholar]
  45. Ziegler G, Hogg R. Particle size reduction. In: Beckett ST, editor. Industrial chocolate manufacture and use. New York: Chapman & Hall; 1999. pp. 182–199. [Google Scholar]
  46. Ziegler GR, Mongia G, Hollender R. Role of particle size distribution of suspended solids in defining the sensory properties of milk chocolate. Int J Food Eng. 2001;4:353–370. [Google Scholar]

Articles from Journal of Food Science and Technology are provided here courtesy of Springer

RESOURCES