Descriptive sensory analysis of heat‐resistant milk chocolates

Abstract Sensory attributes of six heat‐resistant chocolates were compared with the standard chocolate using a trained sensory panel who were trained using the Sensory Spectrum method. The panel evaluated the chocolates using three tactile and ten oral attributes at 24, 29, and 38°C. The panel demonstrated consistent rating of the various samples. ANOVA showed that all of the 13 sensory attributes (Firmness to touch, Stickiness to fingers, Snap, Abrasiveness, Hardness with incisors, Fracturability, Cohesiveness of mass, Time to melt, Firmness with tongue, Adhesiveness to teeth, Number of particles, Oily mouthcoating, and Chocolate messiness) were significantly different across the samples. A higher degree of heat resistance was identified by the panelists for the low‐fat gelatin and polyol samples at 38°C. Principal component analysis revealed two principal components; the first pricipal component described the variability due to temperature, and the second principal component described the variability brought about by the various technologies.


| 2807
DICOLLA et AL. Finkel, 2005;Kempf, 1958;Takemori et al., 1992). All these subjective attributes make it difficult to compare differences in the heatresistant chocolates described in the literature and patents. Stortz and Marangoni (2011) have provided a review of composition and processes for production of heat-resistant chocolate.
Increasing the melting point of the fat is the easiest way to improve the heat resistance of chocolate (Pease, 1985). A secondary nonfat structure resulting from adding water, monosaccharides, amorphous sugars, polyols, fiber, starch, or protein can create heat resistance in chocolate (Afoakwa, Paterson, & Fowler, 2007;Finkel, 1990;Friedman, 1921;Killian & Coupland, 2012;Kruger & Freund, 2001;Lopez, Pariein, & Datalle, 2010). Afoakwa et al. (2007) in reviewing the textural attributes of chocolates observed that chocolate melts in the mouth as a continuous fat phase which then inverts into a continuous water phase into which the sugar particles dissolve. A chocolate that was slow to solvate required greater effort for the tongue to compress it. The coarseness of the chocolate was observed in the inverted syrup, while a smoother chocolate was perceived as creamier. The fat and cocoa particles provided a mouthcoating sensation. Voltz and Beckett (1997) noted that only a few particles greater than 30 μm made a chocolate taste gritty while a very finely ground chocolate was difficult to swallow (Voltz & Beckett, 1997). As such, Afoakwa et al. (2007) considered the processing steps of refining, a particle size reduction step, and conching, where water was evaporated and fat and emulsifier were added, as determining many of the textural attributes of chocolate. Tempering and hardening of chocolate, where the fat was solidified into the optimum hardness, provided the remaining textural attributes of chocolate.
Sensory texture of chocolate has been extensively studied. Rodríquez, Jorge, and Beltrán (2000) observed dark, milk, and white chocolates differed by fragility, hardness, and melting. Andrea-Nightingale, Lee, and Engeseth (2009) described dark and milk chocolates with sensory-texture terms of hardness, cohesiveness, toothpacking, chewiness, fatty mouthcoating, toothpacking, and melting. Cagindi and Otles (2007) differentiated dark, milk, and white chocolates held at 20 and 30°C up to 12 weeks based on sensory-texture evaluations at 20°C. Guinard and Mazzucchelli (1999) differentiated milk chocolates with varying levels of sugar and fat using sensory-texture attributes of fatty/oily, gritty, hard, melting rate, mouthcoating, vanishing, and viscous. Haedelt, Beckett, and Niranjan (2007) differentiated aerated milk chocolates with texture attributes of hardness and melting time. Liang and Hartel (2004) showed that milk chocolates made with different types of milk powders (spray-dried, roller-dried, and fluidized bed) differed in "rate of meltdown while chewing," "textural smoothness upon melting," and "over all mouth coating sensation." Voltz and Beckett (1997)  Sensory evaluation of heat-resistant chocolates has been reported, but to a much lesser extent. The majority of the patents describe an informal sensory evaluation of the heat-resistant chocolate. Some heat-resistant chocolates were reported to have a coarser or rougher texture (Giddey & Dove, 1984;Schubiger & Rostagno, 1965), especially in those with added water (Davila & Finkel, 2005). Giddey and Dove (1984) developed a chocolate that remained stiff at 50°C yet would melt in the mouth. Ogunwolu and Jayeola (2006) (Murray, Delahunty, & Baxter, 2001). In Flavour Profile Method and Profile Attributes Analysis (FPM/PAA), a small panel selects, defines, and rates attributes using panel-identified standards focusing on the flavors of the foods to be rated. In Texture Profile Method (TPM), a list of texture attributes with predefined ratings anchored with preidentified standards is used to train the panelists. In Quantitative Descriptive Analysis (QDA ® ), panelists use common-language attributes largely without anchoring to standard foods (except to resolve disagreements). In quantitative flavor profiling technique (QFPT), the panelists use the lexicon of flavorists wherein the scale is anchored extensively with standards. In the Sensory Spectrum method (SM), the panelists select appropriate attributes whose range is anchored by standard foods. In free choice profiling (FCP), panelists use their own attributes and as many as they wish and without any response-calibrating standards.
Training in these descriptive sensory methods also differs (Murray et al., 2001). In FPM/PAA, a small panel of 4-6 panelists are trained approximately for 2-3 weeks. In TPM, at least 10 panelists are trained for as many as 130 hr over a 6-to 7-month period. In QDA, panelists are trained for 10-15 hr. In QFPT, the panelists are highly trained flavorists. In SM, the panelist brings a basic understanding of the physiology and psychology of sensory perception.
In FCP, the panelists are consumers of the particular type of product to be tested and are not trained.
The results from FPM/PAA are highly discriminating but use technical language that requires interpretation to a wider audience (Murray et al., 2001). The TPM describes food throughout its oral mastication, but the food standards to which it is anchored may not exist in other cultures or may disappear or change over time. In QDA, the differences in panelists' ratings are used to discriminate between samples, but such differences are difficult to compare with other panels or may drift over time. Presuming one has a pool of flavorists to draw from, the description provided by QFPT is considered free of erroneous terms, while requiring interpretation for a wider audi-

| MATERIAL S AND ME THODS
Standard milk chocolate and six heat-resistant milk chocolates were evaluated in this study (Table 1).

| Ingredients
The ingredients used for making these chocolate samples were as follows: pure cane extra-fine granulated sugar (Domino), pasteurized and spray-dried nonfat dry milk (

| Standard milk chocolates (S)
A standard milk chocolate was produced as a reference based on formulas from Beckett (1999) and Stauffer (2000). The standard milk chocolate was prepared by following the steps of mixing, refining, conching, standardizing, tempering, molding, hardening, and demolding (Dicolla, 2009). The chocolate was refined in a 3-roll refiner (29.5-cm-width rolls, Bühler AG) to a particle size of approximately 30 μm. The conched chocolate was standardized to bring the fat content to the specifications of the sample formulation. The standardized chocolate was tempered using the seed method. The tempered chocolate mass was molded into 10-g squares, cooled, and demolded. During refining, the particle size was determined using a micrometer (Mitutoyo IP 65). The refined flake was dispersed in mineral oil at approximately 1:1 v/v and a drop squeezed between

Regular-fat gelatin (R) Polyol (P) Starch (H)
Fat content ( the anvil surfaces of the micrometer. The particle size was the extent the micrometer could be closed.

| Milk chocolate with corn syrup solids (C)
Corn syrup solids milk chocolate was reproduced based on the U.S. Patent 2904438 (O'Rourke, 1959). CSS (20 DE) were added to chocolate before refining, and the subsequent processing steps were similar to the standard milk chocolate. After the chocolate was demolded, it was exposed to 80% relative humidity at 28°C for 24 hr and then put in storage.

| Milk chocolate with added emulsion (E)
This formulation was based on European Patent 1673977 A1 (Simbürger, 2006

| Milk chocolate with low fat and gelatin (L)
This chocolate sample was adapted from a light chocolate sample according to US Patent Application 2009/0311409 (Luccas, Efraim, & Vissotto, 2009). This formula used a hydrolyzed collagen ingredient, Instant Gel Schoko ® , in order to replace cocoa butter without affecting the sensorial characteristics of the chocolate. All ingredients were mixed and refined together except for the milk fat and emulsifiers, which were added one hour before the end of conching.
The chocolate was then tempered and molded in the same fashion as the standard milk chocolate and then put into storage.

| Milk chocolate with regular fat and gelatin (R)
The sample of regular-fat gelatin is formulated with 4.94% Instant Gel Schoko ® but with a finished fat content similar to the standard milk chocolate. The same mixing, refining, conching, tempering, and molding procedures used for low-fat gelatin were applied to the regular-fat gelatin.
TA B L E 2 Sensory attributes selected by the sensory panel for characterizing heat-resistant milk chocolate

Sensory attributes Definition
Tactile Firmness to touch The degree to which the product deforms when pressing down with the index finger.

Stickiness to fingers
The degree to which the surface of the sample adheres to the fingers when being lightly touched.

Snap
The amount of force it takes to break the product in half with the fingers.
Oral Abrasiveness Degree to which the sample feels scratchy when rubbed with equal pressure on tip of tongue.
Hardness with incisors Measure the amount of force required to bite completely through the sample with incisors.

Fracturability
The force with which a material crumbles, cracks, or shatters when placing the sample between molars and biting completely down at a fast rate.
Adhesiveness to teeth Force required to remove material that sticks to the teeth after expectorating.

Time to melt
The time it takes the chocolate to begin to melt when massaged with the tongue.

Cohesiveness of mass
The degree to which a chewed sample holds together in a mass when chewing sample five times with molar on one side of mouth and moving sample to tongue.

Firmness with tongue
The amount of force required to compress a semisolid sample, placed between the tongue and palate with a flat tongue.
Number of particles Number of particles perceived by tongue when mass is gently manipulated between tongue and palate.
Oily mouthcoating The amount of oily residue felt by the tongue when moved over the surfaces of the mouth after expectorating.

| Milk chocolate with polyol
Polyol sample was made based on U.S. Patent 6841186 (Davila & Finkel, 2005). Glycerin was added to the standard chocolate after it was standardized. The mass was mixed for an additional 20 min in order to reduce the viscosity. The polyol milk chocolate was then tempered and molded.

| Milk chocolate with starch (H)
Starch chocolate was made based on Ogunwolu and Jayeola (2006), where regular corn starch was added before the refining of ingredients. The subsequent steps were performed in the same fashion as the standard milk chocolate sample.

| Storage conditions
All of the chocolate types including the standard milk chocolate were stored for 2-3 months, unwrapped at 21°C and 40%-60% relative humidity prior to sensory evaluation. Three batches of polyol chocolate were prepared and used as the reference in the sensory study.

| Sensory analysis
The The panelists were trained in a 4-hr session for this study. The panel selected 13 attributes (three tactile and 10 oral) by consensus to evaluate the chocolate samples (Table 2). They also selected standards for the various attributes (Tables 3 and 4), and they selected the polyol sample as a reference sample ( TA B L E 6 Differences in the score for each of the attributes for the coded polyol sample and the panel agreed upon rating for the reference sample by panelist (P) for each attribute at each temperature (T in C). Attributes are as follows: Firmness to touch (  and 38C were determined in the environmental chambers (Table 5).
A ballot was created for each temperature and displayed a horizontal 15-cm line scale for each attribute in the order listed in Table 2 with markings on each attribute line scale for the scores of standards (Tables 3 and 4) and the reference sample (Table 5;  Environmental chambers were controlled at three conditions: 24°C and 50% relative humidity (RH), 29°C and 30% RH, and 38°C and 30% RH. The first condition at 24°C and 50% RH is considered typical in-store condition when chocolate is ideally consumed. The second condition at 29°C and 30% RH is considered the upper limit for chocolate handling although less than ideal.  The third condition of 38°C and 30% RH mimics a warm-temperate climate summer day or a tropical climate.
Evaluations of the chocolate samples were conducted in five sessions, taking approximately 3 hr each. The samples were left between 16 and 20 hr in the respective environmental chambers allowing the samples to equilibrate before analysis at each temperature. Panelist was given three squares each of three different coded chocolate samples and seven squares of the reference samples. Attributes were evaluated in the order shown in Table 2.
It took approximately 5 min for each panelist to evaluate the thirteen attributes for one sample and 15 min for the three coded samples. Each chocolate sample was evaluated three times in a randomized fashion blocked by temperature and evaluated at least once at each temperature during each session by every panelist.
The reference sample (polyol) was presented at random three times at all three temperature as a coded chocolate sample to assess panel consistency.

| Statistical analysis
Statgraphics (StatPoint Inc) was used for all of the statistical analysis, and they are described below.

| Sensory data analysis
The results from the descriptive sensory panel were analyzed by a

| Principal component analysis
Principal component analysis (PCA) on the sensory data was conducted. Principal components with eigenvalues greater than 1.0 were retained.

| RE SULTS AND D ISCUSS I ON
The reference sample (polyol) was presented at random three times at all three temperatures as a coded chocolate sample to assess panel consistency. Table 6  suggesting these samples had the most substantial heat-resistant structure. It has been reported that the heat-resistant structure is a product of the nonfat phase (Stortz & Marangoni, 2011), and instrumental characterization of the melted state has been used to characterize heat-resistant technology (Anon, 2016;Dicolla, 2009;Wang, Baker, Worthing, Gonzalez, & Mongia, 2014;Wang et al., 2015).
The interaction of P × T was significant for nine attributes (FH, SF, SN, HI, CH, TM, FT, NP, and CM), and this was also evident from the comments from the panelist that the conditions at 38°C and 30% RH for 15 min were at the limit of comfort. The most variability between panelists occurred at 38°C (Figure 3). Fang, Clausen, and Fanger (1998) explained that at higher temperatures, lower humidity would be more comfortable, as has been routinely touted in arid southern Arizona. The consistency of the replicates was indicated in the lack of significant F-values for replicate or its interactions (R × T and R × S).
Given the multidimensional nature of the analysis of the data by individual attributes, PCA provided a convenient way to reduce the data to fewer orthogonal dimensions. Two principal components (PC) were identified describing 81% and 11% of the variation in the attribute scores for the samples at different temperatures (Table 8).

| CON CLUS IONS
The overall goal of this study was to identify sensory attributes for de-

ACK N OWLED G M ENTS
Not applicable.

CO N FLI C T O F I NTE R E S T
The authors do not have any conflicts of interest with respect to this study.

E TH I C A L R E V I E W
The sensory analysis and testing protocols were reviewed and ap-