Effects of particle size distribution and composition on rheological properties of dark chocolate

Control of chocolate viscosity is vital to its quality and production cost, and directly influenced by solids particle size distribution (PSD) and composition. Effects of PSD and composition on rheological properties of molten dark chocolate were investigated by varying PSD [D₉₀ (90% finer than this size) of 18, 25, 35 and 50 μm], fat 25, 30 and 35% and lecithin (0.3 and 0.5%) using a shear rate-controlled rheometer. PSD, fat and lecithin content significantly affected all rheological parameters, with significant interaction among factors. Increasing particles size gave significant reductions in Casson plastic viscosity, Casson yield value, yield stress, apparent viscosity and thixotropy, with greatest effect with 25% fat and 0.3% lecithin, which reduced with increasing fat and lecithin contents. Statistical analysis revealed that fat exerts the greatest effect on the variability in all the rheological properties followed by PSD and lecithin. PSD, fat and lecithin could be manipulated to control dark chocolate rheology, influencing quality whilst reducing production cost.     

Relationship between rheological,textural and melting properties of dark chocolate as influenced by particle size distribution and composition

In dark chocolate, rheological properties during processing are influenced by particle size distribution (PSD), fat and lecithin contents with consequential effects on finished texture and melting characteristics. Multivariate regression, correlation and principal component analyses (PCA) were used to explore their interrelationships. A 4 × 3 × 2 factorial experiment was conducted with varying PSD [D ₉₀ (90% finer than this size) of 18, 25, 35 and 50 μm], fat (25, 30 and 35%) and lecithin (0.3 and 0.5%). Rheological properties (yield stress and apparent viscosity), textural properties (firmness, index of viscosity and hardness) and melting index (duration) were respectively measured using shear rate-controlled rheometer, TA.HD Plus texture analyzer and differential scanning calorimetry. The PSD, fat and lecithin contents significantly influenced all rheological, textural properties and some melting characteristics. Increasing particles sizes reduced yield stress, apparent viscosity, firmness, index of viscosity, hardness and melting index of products with greatest influence with 25% fat and 0.3% lecithin, reduced with increasing fat and lecithin contents. There were high correlation (r = 0.78–0.99) and regression coefficients (R ² = 0.59–0.99) among the rheological, textural and melting index indicating their high inter-relationships. In PCA, the rheological, textural and melting index accounted for >95% variance in the data.     

Optimization of Maillard reaction products from casein-glucose using response surface methodology

Response surface methodology (RSM) was applied to optimize the processing parameters of casein-glucose Maillard reaction for improving the emulsifying ability and antioxidant activity. The effect of heating time, temperature and initial pH on Maillard reaction products (MRPs) was evaluated. Emulsifying ability and reducing power were taken as response values. An increase of temperature in range and initial pH were associated with an enhanced emulsifying ability and reducing power of the MRPs. Substrate concentration 20%, casein-glucose ratio 1:2, heating time 132.7 min, temperature 100.2 °C and initial pH 12.0 were optimum conditions for the improved emulsifying ability and antioxidant activity of the MRPs. The predicated results for optimum reaction conditions coincided well with experiments values.     

Microstructure and mechanical properties related to particle size distribution and composition in dark chocolate

Composition in dark chocolate was varied and the effects determined on microstructure, using light microscopy, and mechanical properties of molten and tempered chocolates, using a TA.HD Plus Texture Analyser. Compositional parameters were particle size distribution (PSD) (D₉₀ of 18, 25, 35 and 50 μm), fat (25%, 30% and 35%) and lecithin (0.3% and 0.5%) contents. Micrographs revealed wide variations in sugar crystalline network structure and inter-particle interaction strengths related to PSD and fat level. Samples containing 25% fat had more crystal agglomerates, well flocculated with greater particle-to-particle interaction strengths than those with higher (30% and 35%) fat contents. Increasing the D₉₀ to 35–50 μm caused broadening of the PSD, with particles becoming coarser, which were similar at all fat levels. Mechanical analysis showed that PSD, fat and lecithin content significantly influenced firmness of molten chocolate and hardness of solid (tempered) chocolate with significant interactions among factors. Particle size was inversely correlated with firmness (1235–173 g) and hardness (7062–5546 g). Greatest effect of PSD was with 25% fat and 0.3% lecithin. With higher fat and lecithin contents, the PSD influence was reduced. It was concluded that PSD, fat and lecithin contents and their interactions were central to mechanical properties of dark chocolates.     

Colour degradation and quality parameters of sonicated orange juice using response surface methodology

Freshly squeezed orange juice was subjected to sonication at amplitude levels ranging from 40 to 100% at a constant frequency of 20 kHz for different times (2-10 min) and pulse durations of 5 s on and 5 s off. Hunter colour values (L^∗, a^∗ and b^∗), pH, °Brix, titratable acidity, cloud value and browning index were measured. Response surface methodology (RSM) based on two factor five level central composite design was applied to determine the effect of amplitude level and sonication time on juice quality parameters. There was no significant difference (p < 0.05) on pH, °Brix and titratable acidity. The model predictions for critical quality parameters of Hunter colour values (L^∗, a^∗ and b^∗), cloud value and browning index were closely correlated to the experimental results obtained. RSM was demonstrated to be an effective technique to model the effect of sonication on juice quality while minimising the number of experiments required.     

Optimization of microbial transglutaminase activity in ice cream using response surface methodology

In order to determine the maximum activity range of transglutaminase (TG) in ice cream, the central composite design was used and the TG concentration along with the reaction time and temperature were evaluated. The rheological behavior of the ice cream mix that provided the best response and the determination of the protein cross-linking by electrophoresis (SDS-PAGE) were evaluated. It was observed that the TG increased the consistency index and favored the pseudoplastic behavior of the ice cream samples. The maximum response (0.69 Pa sⁿ) was obtained using a TG concentration of 4 U g⁻¹ protein at 56.8 °C with a reaction time of 90 min. The protein cross-linking was confirmed by electrophoresis, which showed that κ-casein was more susceptible to attack from TG than whey proteins.     

Effect of extraction conditions on lycopene extractions from tomato processing waste skin using response surface methodology

Skin, rich in lycopene, is an important component of waste originating from tomato paste manufacturing plants. A central composite design with five independent variables, namely solvent/meal ratio (20:1, 30:1, 40:1, 50:1, and 60:1 v/w); number of extractions (1, 2, 3, 4 and 5); temperature (20, 30, 40, 50 and 60 °C); particle size (0.05, 0.15, 0.25, 0.35 and 0.43 mm); extraction time (4, 8, 12, 16 and 20 min) was used to study their effects on lycopene extraction. The experimental values of lycopene ranged between 0.639 and 1.98 mg/100 g. The second order model obtained for extracted lycopene revealed a coefficient of determination (R²) of 0.99 and a standard error of 0.03. Maximum lycopene (1.98 mg/100 g) was extracted when the solvent/meal ratio, number of extractions, temperature, particle size and extraction time were 30:1 v/w, 4, 50 °C, 0.15 mm and 8 min, respectively.     

Optimization of enzymatic degumming process for rice bran oil using response surface methodology

Response surface methodology was used to determine the optimum processing conditions for enzymatic degumming of rice bran oil. Reaction time, enzyme dosage, level of water added and temperature were the factors investigated with respect to phosphorus and free fatty acids contents. A D-optimal design, with four variables and two response functions, was employed to study the effect of the individual variables on the response functions. For each response, second-order polynomial models were developed using multiple linear regression analysis. Applying desirability function method, optimum operating conditions were found to be reaction time of 4.07 h, enzyme dosage of 50 mg/kg, added water of 1.5 ml/100 g and temperature of 49.2 °C. At this optimum point, phosphorous and free fatty acids contents of degummed oil were found to be 8.86 mg/kg and 2.01 g/100 g as oleic acid, respectively.     

Optimization of ingredient levels for manufacturing malted milk beverage using response surface methodology

The malted milk beverage was prepared with varying levels of milk fat, wort and stabilizer–emulsifier mix using response surface methodology. Milk fat had a significant effect on all sensory attributes at the linear, quadratic or interactive levels. Wort level affected the flavour of the beverage at the linear ( P <  0.01) term. The addition of stabilizer–emulsifier mix enhanced the overall acceptability of the product by significantly affecting the flavour ( P <  0.01) and mouthfeel ( P <  0.01). The optimum levels of ingredients to manufacture acceptable quality malted milk beverages were 1.93 g/100 g milk fat, 62.96 g/100 g wort and 0.09 g/100 g stabilizer–emulsifier mix.     

Response surface optimization and characteristics of rambutan (Nephelium lappaceum L.) kernel fat by hexane extraction

Response surface methodology (RSM) was used to study the effect of moisture content (1.59-18.41 g/100 g), extraction time (2.3-10.7 h) and particle size (0.09-2.11 mm) on the fat yield from rambutan kernels using hexane extraction. The physical and chemical characteristics of rambutan fat were also determined. The optimum conditions obtained from response surface analysis was 4.99 g/100 g moisture, 1.05 mm particle size and 9.2 h extraction time. Under these optimum conditions, the maximum fat yield was 37.35 g/100 g. The extracted fat was a white solid at room temperature. The physical and chemical characteristics of the extracted fat compared well with those of conventional fats. The high level of arachidic acid (∼ 34.3 g/100 g fat) and low iodine value in rambutan kernel fat permits the use of the fat, especially where oxidation may be a concern, without its being subjected to hydrogenation.     

Optimisation of osmotic dehydration of carrot cubes in sucrose-salt solutions using response surface methodology

Osmotic dehydration of carrot cubes in ternary solution of water, sucrose and sodium chloride at different solution concentrations, temperatures and process durations were analysed for water loss and solute gain during osmotic dehydration. The osmotically pre-treated carrot cubes were further dehydrated in a cabinet dryer at 65 °C and were then rehydrated in water at ambient temperature of water for 10–12 h and were analysed for rehydration ratio, shrinkage and overall acceptability after rehydration. The process was optimised for maximum water loss, rehydration ratio and overall acceptability of the rehydrated product, and for minimum solute gain and shrinkage of rehydrated product by response surface methodology. The optimum conditions of various process parameters are 50°B+10% w/v aqueous sodium chloride concentration, 46.5 °C solution temperature and 180 min process duration.     

Process optimisation for fractionating Jerusalem artichoke fructans with ethanol using response surface methodology

Optimal conditions for fructan precipitation from Jerusalem artichoke concentrate by adding ethanol were established by response surface methodology. The combination of the starting syrup concentration (9.9–40 °B), ethanol-to-syrup (E/S) ratio (2.3:1–15.7:1) and precipitation temperature (3.1–62 °C) was varied at design points of a central composite rotatable design. Significant regression models describing the changes of average chain length, fructan precipitation yield and purity value of fructans were developed with the coefficient of determination greater than 0.8. The results suggested that higher syrup concentration resulted in an increased fructan yield, but further increase in concentration had a reverse effect on average chain length and purity values. The optimum conditions for fractionating fructan composition by ethanol were estimated to be 32 °B initial syrup concentration, E/S ratio of 13 and temperature of 42 °C.     

Optimization of antioxidant peptide production from grass carp sarcoplasmic protein using response surface methodology

The sarcoplasmic protein was extracted from the muscle of grass carp, a Chinese freshwater carp, and was hydrolyzed with five proteases to produce antioxidant peptides. Papain hydrolysate was found to have the greatest activity against lipid peroxidation. Response surface methodology (RSM) was applied to optimize the hydrolysis conditions (including enzyme to substrate ratio, time and temperature). The minimum EC₅₀ value (317.25 μg/mL) which signified the maximum antioxidant activity was obtained at an enzyme to substrate ratio of 0.79%, an incubation time of 5.69 h and an incubation temperature of 52.15 °C, which was in agreement with the predicted value (313.99 μg/mL) estimated by RSM within a 95% confidence interval. Also, it was found that moderate denaturation of the sarcoplasmic protein and a modest increase in the degree of hydrolysis promoted the antioxidant activities of the hydrolysates. Oligopeptides (< 3 kDa) contributed more to the antioxidant activity than polypeptides.     

Expansion characteristics of a nutritious extruded snack food using response surface methodology

Response surface methodology was used to analyze the effect of screw speed (220–340 rpm), feed moisture (11.0–15.0%, wet basis) and feed rate (22.0–26.0 kg/h, wet basis) on the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally balanced extruded snack food. Regression equations describing the effect of each variable on the responses were obtained. Responses were most affected by changes in screw speed followed by feed moisture and feed rate (P<0.05). Expansion and porosity increased with screw speed and feed moisture whereas the opposite was observed for bulk density. Radial expansion was found to be a better index to measure the extent of expansion than the axial and overall expansions, indicated by a higher correlation coefficient.     

Impact of particle size distribution on rheological and textural properties of chocolate models with reduced fat content

ABSTRACT:  With an increasing consumption of lipids nowadays, decreasing the fat content in food products has become a trend. Chocolate is a fat-based suspension that contains about 30%wt fat. Reducing fat content causes an increase in the molten chocolate viscosity. This leads to 2 major issues: difficulties in the process and a loss of eating quality in the final product, reported to have poor in-mouth melting properties, remain hard, and difficult to swallow. Literature shows that optimizing the particle size distribution (PSD), that is, having one with an increased packing fraction, can decrease the viscosity of highly concentrated suspensions. This study focuses on the impact of the PSD and fat content on the rheological properties, melting behavior, and hardness of chocolate models (dispersions of sugar in fat). We show that optimizing the PSD while reducing the fat content to a critical amount (22%wt) can decrease the viscosity of the molten material and reduce the hardness of the crystallized chocolate models. Melting in the mouth, characterized by an in vitro collapse speed, is faster for the samples with an optimized PSD. The decrease in the viscosity by optimizing the PSD in systems with a constant fraction of medium phase is based on the decrease of interparticle contact, reducing the particle aggregates strength, and structure buildup during flow or meltdown. In its crystallized state, the particle network is less interconnected, providing less resistance to breakage and meltdown.     

Optimizing conditions for anthocyanins extraction from purple sweet potato using response surface methodology (RSM)

Optimization for purple sweet potato (Ipomoea batatas (L.) Lam) anthocyanins (PSPAs) extraction was investigated using response surface methodology in this paper. PSPAs were extracted using acid-ethanol at different extraction temperature (40-80 °C), time (60-120 min) and solid-liquid ratio (1:15-1:30). The combined effects of extraction conditions on PSPAs yield and color attributes (expressed as L*, C* and H) were studied using a three-level three-factor Box-Behnken design. The results showed that The highest yield (158 mg/100 g dw) of PSPAs were reached at the temperature 80 °C, extraction time 60 min, and solid-liquid ratio 1:32. PSPAs yield indicated a high and significant correlation with L^* (P<0.05; r=−0.961) and it was significantly affected by extraction temperature (P<0.01) and solid-liquid ratio (P<0.05).     

Optimisation of ingredients for a low‐fat,Chhana‐based dairy spread using response surface methodology

The effect of ingredients, viz. chhana, skimmed milk powder (SMP), maltodextrin and whey powder, on sensory and texture responses of a low‐fat chhana‐based spreads was studied and its formulation was optimised using response surface methodology. In linear and quadratic terms, chhana and SMP significantly influenced all the responses. The interaction term between maltodextrin and chhana was the most effective in influencing texture parameters. Optimisation suggested 55.6% chhana, 6.2% SMP, 4% maltodextrin, 2% whey powder, 1.5% edible salt, 1.5% enzyme‐modified cheese, 0.5% sodium tripolyphosphate, 0.5% trisodium citrate, 0.3% glycerol monostearate and 28% water with desirability of 0.889, as the best levels of these ingredients in a formulation that also contained 1.5% edible salt, 1.5% enzyme‐modi ed cheese, 0.5% sodium tripolyphosphate, 0.5% trisodium citrate, 0.3% glycerol monostearate and 28% water on a w/w basis.     

Determination of pesticide residues in milk using a QuEChERS-based method developed by response surface methodology

Response surface methodology (RSM) was employed to optimise a rapid and easy sample preparation method for the determination of 14 different pesticide residues in milk. The recovery of each pesticide was investigated by a QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe)-based method with respect to 3 variables, the amounts of sodium acetate (Na Acetate), primary secondary amine (PSA), and octadecylsilane (C₁₈). After optimisation, the maximum predicted recovery was the 99.73% rate for myclobutanil under the optimised conditions of 1.70 g Na Acetate, 600.00 mg PSA, and 489.96 mg C₁₈. The recovery rates of the other 9 hydrophilic pesticides were ranged from 82.01% to 98.84%. However, the recovery rates for the 4 lipophilic pesticides (2,4′-DDE, 4,4′-DDE, 2,4′-DDT, and 4,4′-DDT) were <80% because they were removed by C₁₈ along with the other fatty compounds. This method could be implemented in many laboratories to reduce inspection time and cost.     

Optimization of the process variables for the preparation of processed paneer using response surface methodology

Models capable of predicting the quality and yield of processed paneer have been developed using response surface methodology to determine the optimum processing conditions. Three and four-dimensional response surfaces were drawn and the individual contour plots of the different responses were superimposed, and regions meeting the maximum sensory score (29.50–30.75) and yield (9.50–10.50 g/100 g) were identified at 70.1±2.0 °C at 4.85±0.23 pH and 2.908±0.113 g/kg stabilizer concentration. These predicted values for optimum process conditions were in good agreement with experimental data.     

Optimization of enzymatic hydrolysis of immature citrus (Citrus unshiu Marcov.) for flavonoid content and antioxidant activity using a response surface methodology

Food Science and Biotechnology - Immature citrus with peel was enzymatically treated for production of a hydrolysate with enriched bioactive components and higher antioxidant activity. The effects...