In current study four different samples of milk chocolate were prepared by replacing a part of cocoa butter with 0, 10, 20 and 30% of animal fat constituting control and three treatments in ascending order, to improve its textural quality during storage in tropical regions. The quality characteristics of the milk chocolate samples were assessed on the basis of pH, proximate analysis, sensory evaluation, antioxidant activity, calcium and cholesterol content. With the increase in the amount of animal fat replaced, a significant (P<0.05) decrease in sensory attributes and a significant (P<0.05) increase in cholesterol content was observed in third and fourth treatment. However the pH and proximate parameters showed non-significant difference.
Cocoa butter constitutes the continuous phase and is responsible for the dispersion of the other constituents in the preparation of chocolate. Cocoa butter is responsible for the hardness of chocolate at room temperature and pleasant mouth feeling due to its melting at body temperature (Quast et al., 2011). There have been many efforts to replace cocoa butter at different levels for chocolate production for technological and economic reasons. Such cocoa butter alternatives are categorized as cocoa butter equivalents (CBEs), cocoa butter substitutes (CBSs) and cocoa butter replacers (CBRs). These are mostly mixtures of various vegetable fats and usually consist of palm and palm kernel oil, shea butter, salfat and kokum butter etc. In addition, a large variety of other vegetable oils can also be used (Lipp and Anklam, 1998). Enzymatically modified beef tallow as a substitute for cocoa butter was used in dark chocolate preparation and the modified tallow had no detrimental effect on the crystallization of cocoa butter after proper tempering of the chocolates. Modified tallow did not soften the chocolate, infact modified lipids reduced bloom rates according to Osborn and Akoh (2002). Animal fat having higher melting point than cocoa butter can be used to replace some part of cocoa butter in chocolate preparation for improving its firmness at higher temperatures above body temperature. Inclusion of animal fat to some extent along with major part of cocoa butter as fat component of chocolate, can help in checking the melting away of chocolates at higher temperatures. The study was designed to optimize the level of animal fat in the form of goat fat that can replace a part of cocoa butter in the preparation of milk chocolate without any adverse effect its sensory characteristics.
The study was undertaken to optimize the level of animal fat that can be used to replace cocoa butter in milk chocolate without altering its sensory attributes and study the effect of animal fat on milk chocolate on the basis of proximate analysis, sensory evaluation and physic-chemical properties.
Material and Methods
Various ingredients used for preparation of milk chocolate under study included cocoa powder, cocoa butter, milk solids, sugar, soy lecithin (code RM637, was procured from Hi Media), animal fat (goat fat as a source of animal fat was purchased from local market of Jammu and processed in the lab by heating in hot air oven at 75oC for 15 minutes). Aluminum foil was used for packaging of product with use of LDPE around that as an outer layer. Aluminum foil and Low density polyethylene film pouches (200 µm thickness) in natural colour were purchased from the local market of Jammu. These pouches were sterilized by U.V. light and were used for packaging. The chemicals used for estimation of different parameters were of analytical grade and were obtained from standard firms (Qualigens, CDH, Hi Media etc.)
Formulation and Processing
For the preparation of milk chocolate, the method of Jeffery et al. (1977) for manufacturing a shaped, heat-resistant chocolate product with some modifications was used. First of all milk chocolate was prepared by thorough mixing following ingredients, cocoa solids, cocoa butter, animal fat, milk solids, sugar, emulsifier (being added after half of conching time is over) and ethyl vanillin in traces and said percentage being based on the total weight of the milk chocolate so as to produce an emulsion. The emulsion is then subjected to conching process for minimum 6 hours in a wet grinder. This is followed by tempering of the chocolate at 30 – 40oC for 15 – 20 minutes. Emulsion is now put into moulds of choice to obtain milk chocolate of desired shape. It was then wrapped in aluminium foil followed by LDPE packaging. Formulation of four chocolate samples for the optimization of animal fat in the preparation of milk chocolate is presented in Table 1.
Table 1: Optimization of animal fat in the preparation of milk chocolate
|Ingredient||Milk Chocolate||Milk chocolate with 10 % cocoa butter replaced with animal fat||Milk chocolate with 20 % cocoa butter replaced with animal fat||Milk chocolate with 30 % cocoa butter replaced with animal fat|
|Ethyl vanillin||0.1 % (traces)||0.1 % (traces)||0.1 % (traces)||0.1 % (traces)|
In this study four samples were prepared by replacing cocoa butter in milk chocolate with animal at 0, 10, 20 and 30 % levels and the samples were designated as control (C), treatment 1 (T1), treatment 2 (T2) and treatment 3 (T3).
pH estimation was done according to Trout et al. (1992). Ten grams of chocolate sample was homogenized with 50 ml distilled water by using Ultra Turrex T 10 tissue homogenizer (Janke and Kenkel, IKA labor Technik, Germany) for 30 seconds. The pH of the suspension was recorded by immersing the electrode of digital pH meter (product code 35613424, Oakton instruments, Singapore) directly into the suspension.
The moisture, protein, fat and ash content of milk chocolates were determined by standard methods as described by AOAC (1999) using hot air oven, Kjeldahl assembly, Soxhlet extraction apparatus, muffle furnace respectively.
Estimation of Cholesterol
Preparation of Lipid Extract
The lipid extract of milk chocolate samples was prepared by the method described by Folch et al. (1957). 5 g of sample was taken in a 50 ml beaker and 20 ml of solvent containing chloroform: methanol in the ration of 2:1 v/v was added to it. The beaker was allowed to stand at room temperature with occasional stirring for 6 – 8 hours. The mixture was then filtered through Whatman No. 1 filter paper and residue was again extracted with 10 volumes of chloroform: methanol solution (2:1 v/v) for 2 hours and filtered through Whatman No. 1 filterpaper. The filtrate was evaporated to dryness and the process was repeated three times. In order to break the proteolipids, 1/10th volume of lipid extract choloroform: methanol: water (64: 32: 4 v/v/v) solution was added to the dried lipid residue. This was evaporated to dryness at 55oC and this step was repeated twice. The dried lipid residue now obtained was dissolved in 100 ml of chloroform: methanol (2:1 v/v) and then filtered and held by vigorous shaking with 1/5th volume of 0.9% NaCl to remove non-lipid impurities from the lipid extract. Allow it to stand overnight at room temperature. The chloroform layer was collected, evaporated to dryness at 55 – 60°C and the process was repeated 3-4 times followed by making final volume 5 ml with chloroform. The lipid extract prepared was stored for further analysis at -18oC after addition of 0.5% of butylated hydroxyl toluene prepared in chloroform.
Assay of Total Cholesterol
Total cholesterol in the lipid extract of milk chocolate was estimated by modified Tschugaeff reaction described by Hanel and Dam (1995). 100 microlitre of each cholesterol solution (1mg/ml) and lipid extract were separately taken into test tubes and evaporated to dryness. Add 4 ml of chloroform and 2 ml of ZnCl2 reagent (prepared by dissolving 40g anhydrous zinc chloride in 153 ml glacial acetic acid at 80oC for 2 hrs. and filtered through Whatman No.1 filter) and 2 ml of acetyl chloride to each test tube followed by heating in water bath at 60oC for 10 minutes. Blank was prepared by adding 4 ml chloroform 2 ml of ZnCl2 reagent and 2 ml of acetyl chloride in a test tube and it was heated along with samples at 60oC. The optical density of the coloured complex was measured at 528 nm in Systronics UV – VIS Spectrophotometer and expressed as mg cholesterol/100g of milk chocolate. For preparation of calibration curve cholesterol concentration vs optical density is presented in Fig. 1. Calibration curve as depicted in Fig. 2 was drawn and the equation was calculated in Microsoft excel spread sheet. The linear correlation between standard cholesterol concentration and absorbance was expressed with the equation y = f(x) and r2 value. Where, y = absorbance, x = standard concentration and r2 = correlation coefficient.
Ten panelists rated the intensity of each sensory descriptor for each sample, in triplicate. The acceptance of the chocolate samples was conducted with semi-trained panelist from SKUAST Jammu. A nine-point structured hedonic scale (1= disliked extremely and 9 = liked extremely) was used in the acceptance test to evaluate the appearance, taste, aroma, hardness, mouth feel and overall acceptability of the samples according to Iwe (2010).
Fig.1: Cholesterol concentration vs. optical density graph at 528 nm
Fig. 2: Calibration curve of cholesterol concentration vs. absorbance at 528 nm
The result will be analyzed statistically for analysis of variance and least significant difference tests as per Snedecor et al. (1997). In significant effects, least significant differences were calculated at appropriate level of significance for a pair wise comparison of treatment means.
Results and Discussion
Mean values of proximate analysis, cholesterol content and pH have been presented in Table 2, Fig. 3 and Fig. 4 respectively.
Table 2: Effect of animal fat on proximate parameters of milk chocolate (Mean ± SE)*
|Parameter||C||T 1||T 2||T 3|
|Moisture (%)||1.515 ± 0.02||1.503 ± 0.04||1.508 ± 0.01||1.505 ± 0.02|
|Protein (%)||7.78 ± 0.33||7.78 ± 0.24||7.79 ± 0.22||7.79 ± 0.20|
|Fat (%)||40.68 ± 0.33||40.57 ± 0.38||40.91 ± 0.29||40.72 ± 0.15|
|Ash (%)||2.37 ± 0.04||2.40 ± 0.05||2.41 ± 0.02||2.43 ± 0.03|
|Carbohydrates (%)||47.64 ± 0.49||47.73 ± 0.45||47.36 ± 0.27||47.55 ± 0.40|
*Mean SE with different superscripts in a row differs significantly (p<0.05). n = 6 for each treatment
Fig. 3: Effect of animal fat on the cholesterol content of milk chocolate
Fig. 4: Effect of animal fat on the pH of milk chocolate
Sensory scores of the same are presented in Table 3. The mean values for pH showed non-significant increase with the increase in the level of animal fat. There was non-significant difference in the mean values of proximate parameters with increase in the level of animal fat and this might be because only the vegetable fat i.e. cocoa butter was replaced by animal fat that too at very low levels i.e. at 10, 20 and 30 % level. This did not bring much change in the mean values of proximate parameters under study. Mean values for cholesterol content of T2 and T3 was significantly (P<0.05) higher than T1 and control.
Table 3: Effect of animal fat on sensory evaluation of milk chocolate (Mean ± SE)*
|Parameter||C||T 1||T 2||T 3|
|Appearance||8.55 ± 0.14||8.56 ± 0.15||8.56 ± 0.12||8.55 ± 0.11|
|Taste||8.19 ± 0.22a||8.21 ± 0.18a||7.19 ± 0.20b||5.81 ± 0.35c|
|Aroma||8.20 ± 0.16a||8.06 ± 0.19a||7.06 ± 0.39b||6.01 ± 0.37c|
|Hardness||8.21 ± 0.18a||8.08 ± 0.26a||7.06 ± 0.31b||5.91 ± 0.26c|
|Mouthfeel||8.07 ± 0.28a||7.95 ± 0.21a||6.66 ± 0.30b||5.22 ± 0.37c|
|Overall acceptability||8.25 ± 0.24a||8.22 ± 0.17a||7.10 ± 0.23b||5.49 ± 0.28c|
*Mean SE with different superscripts in a row differs significantly (P<0.05). Mean values are scores on 9; Point descriptive scale. n = 21 for each treatment
However the mean values for cholesterol were nonsignificantly higher in T1 and T2 as compared to control and T3 respectively. The increase in cholesterol content with the increase in the level of animal fat in milk chocolate must be because of higher cholesterol content in animal fat (USDA, 2016) where cocoa butter contain no cholesterol. All the sensory attributes showed significant (P<0.05) decrease in T2 and T3 except for appearance which remained comparable to control in all treatments. The decrease in sensory attributes was due to the sensory characteristics of animal fat especially flavor and aroma which increased with increase in the level of animal fat. Based on the findings, especially sensory attributes treatment 1 (T1) i.e. milk chocolate containing cocoa butter replaced with 10 % animal fat was optimized.
|Photograph of control(C)||Photograph of treatment (T1) sample|
|Photograph of treatment (T2) sample||Photograph of treatment (T3) sample|
Fig.: Photographs of milk chocolate containing animal fat at three different levels as a vegetable fat replacer
Milk chocolate is one of the extremely liked and desired ready to eat snack. It is not only a huge demand in kids but in adults also. The study was designed keeping in mind the melting away of chocolate at higher temperatures. Inclusion of animal fat does prevent the melting away of chocolate at temperatures upto 40 degree Celsius. Although at higher levels i.e. 20 and 30 % of cocoa butter replacement with animal fat there was improvement in firmness and textural properties of chocolate but the sensory attributes were compromised. However at 10 % replacement of cocoa butter with animal fat was found suitable based on sensory attributes. Inclusion of animal fat can also lower the cost of milk chocolate, which is an expensive item. There is further scope of using animal fat at different levels for replacing cocoa butter or cocoa butter substitutes especially those substitutes which have very low melting points. This might make it possible for the people from lower socio economic group to afford such a relishing snack.
I consider myself very fortunate to have worked under the guidance of Dr. S. Kumar, Associate Professor and Head, Sher-e-Kashmir University of Agricultural Sciences and Technology- Jammu, J&K. He has been a great support throughout this study including my PhD programme. Then I would like to thank Dr A. Kumar and Dr Z.F. Bhat both are Assistant Professor, Sher-e-Kashmir University of Agricultural Sciences and Technology. Their experience and constant suggestions in technical programme of the study made it a success. All the authors would like to thank Sher-e-Kashmir University of Agricultural Science and Technology, Jammu for financial as well as technical support.