Dulce De Leche Research Articles

Sensory evaluation of "dulce de leche" with coffee and whey using different affective data analysis methods

This study sought to evaluate the acceptance of "dulce de leche" with coffee and whey. The results were analyzed through response surface, ANOVA, test of averages, histograms, and preference map correlating the global impression data with results of physical, physiochemical and sensory analysis. The response surface methodology, by itself, was not enough to find the best formulation. For ANOVA, test of averages, and preference map it was observed that the consumers' favorite "dulce de leche" were those of formulation 1 (10% whey and 1% coffee) and 2 (30% whey and 1% coffee), followed by formulation 9 (20% whey and 1.25% coffee). The acceptance of samples 1 and 2 was influenced by the higher acceptability in relation to the flavor and for presenting higher pH, L*, and b* values. It was observed that samples 1 and 2 presented higher purchase approval score and higher percentages of responses for the 'ideal' category in terms of sweetness and coffee flavor. It was found that consumers preferred the samples with low concentrations of coffee independent of the concentration of whey thus enabling the use of whey and coffee in the manufacture of dulce de leche, obtaining a new product.

PHYSICOCHEMICAL AND RHEOLOGICAL CHARACTERIZATION OF “DULCE DE LECHE”

ABSTRACTPhysicochemical and rheological characterization of “dulce de leche,” a milk‐based sauce especially popular in South America, was carried out on different types of commercial products (traditional, confectionery, reduced calories or reduced fat). Proximal composition, solid content, water activity, pH and color (Minolta Co., Ramsey, NJ) were evaluated. A controlled stress rheometer (Haake RS600; ThermoGap, Karlsruhe, Germany) was used to perform flow curves, dynamic oscillatory test in the linear viscoelastic range and creep‐recovery experiments. Although in all samples, η decreased with increasing γ′, corresponding to shear‐thinning behavior, clear differences were found in the rheological characteristics of different types of products. Experimental dynamic data were successfully modeled using the Baumgärtel–Schausberger–Winter equation to predict the mechanical relaxation spectrum. Satisfactory prediction of other mechanical properties was validated using creep experiments.PRACTICAL APPLICATIONSIn spite of the differences in composition and rheological behavior of the several types of “dulce de leche” studied, it was possible to analyze the rheological characteristics of all systems and model the obtained results using the broadened Baumgärtel–Schausberger–Winter (BSW) model as a representation of the relaxation spectra to convert dynamic data into time domain. The parameters of the BSW model were used to explain structural characteristics of the systems; thus, the overall microstructural pattern of “dulce de leche” might be similar, and the differences observed would be mainly explained by the level of interactions among macromolecular components. Using the discrete spectrum obtained from the BSW model, it was possible to calculate other viscoelastic properties of interest; thus, the proposed methodology is a useful tool, especially for establishing a rheological data bank and analyzing viscoelastic experiments of this type of product.

Viability of Staphylococcus xylosus during shelf-life of dulce de leche prepared by vacuum evaporation

In this research an innovation in the manufacture of dulce de leche by vacuum evaporation is presented, based on the addition of Staphylococcus xylosus. The culture growth, lactic acid bacteria, pH, acidity, water activity, and lactose and sucrose contents were monitored. The cell counting of S. xylosus varied from log10 6.22cfu g-1 to log10 6.83cfu g-1. Lactic acid bacteria naturally occurring in the milk varied from log10 3.62cfu g-1 to log10 4.38cfu g-1 (90th day of storage). The pH was favourable to the growth of S. xylosus, showing the viability of using this culture in this kind of product.

Pathogenic microorganism survival in dulce de leche

In order to evaluate the survival of Salmonella typhimurium, Listeria monocytogenes, Escherichia coli O157:H7 and Staphylococcus aureus in dulce de leche, aliquots of this sweet were experimentally contaminated with these pathogenic microorganisms at 10 3 (C1) and 10 1 (C2) bacterial cells per gram, and later analysed to evaluate microorganism viability after storage for 0, 1, 2, 3, 5, 10, 20 and 30 days. Salmonella and L. monocytogenes were recovered from all aliquots. E. coli O157:H7 and S. aureus were recovered from all aliquots at C1 concentration, and up to the 5th and 10th day, respectively, at C2 concentration. Relevant public-health danger pathogenic microorganisms were found to survive up to 30 days in dulce de leche.

Estudo do efeito da adição de soro de queijo na qualidade sensorial do doce de leite pastoso

O presente trabalho teve como objetivo realizar uma avaliação do perfil sensorial de cinco amostras de doce de leite pastoso formuladas com diferentes concentrações de soro de queijo em pó ou in natura. Os atributos sensoriais avaliados foram aparência, aspecto geral, cor, sabor, textura e intenção de compra. Os resultados foram analisados através de ANOVA e pelo teste de Tukey e mostraram que não houve diferença significativa entre as amostras, sendo assim, a utilização de soro de queijo na fabricação do doce de leite pastoso é uma ótima alternativa para a indústria de laticínios, pois possibilita a obtenção de um produto com qualidade nutricional, de baixo custo e infere ao soro não só caráter de efluente das indústrias alimentícias, mas complemento da alimentação humana.

CONSUMER ATTITUDE TOWARD SHELF‐LIFE LABELING: DOES IT INFLUENCE ACCEPTANCE?

ABSTRACT The aims of the present work were to study consumer attitudes toward shelf‐life labeling and to evaluate if shelf‐life information affects consumer acceptability, rejection to consume and rejection to repeat purchase. Six samples of dulce de leche with different plastic flavor intensities were presented to a panel of 50 consumers, who scored their overall acceptability and indicated their intention to consume and to repeat purchase of the samples. They also answered a multiple‐choice questionnaire regarding their attitude toward shelf‐life labeling. Knowing that the samples were near the end of their shelf life did not affect acceptability scores or consumer rejection to consume. Thus, consumer perception of the product was not affected by knowing that it was close to expiration. This is in agreement with the fact that most consumers (75%) first try an expired product before deciding what to do. PRACTICAL APPLICATIONSNinety‐five and seventy‐nine percent of the consumers stated that they read shelf‐life information at purchase and consumption stage, respectively, which suggests the importance of proper shelf‐life labeling.Consumer rejection to repeat purchase was higher than rejection to consume. Thus, consumers seemed to consume a product although they might not actually like it or buy it again. Thus rejection to purchase or repeat purchase could be a more conservative criterion than rejection to consume in order to estimate sensory shelf lives or acceptance limits for sensory defects.

Influence of temperature on accelerated lactose crystallization in dulce de leche

The aims of the present work were to study the crystallization of lactose in dulce de leche and to evaluate the influence of temperature on this process. Samples of approximately 1 g were placed in plastic containers and stored at –5, 5, 20 and 35°C for 25 days. Lactose crystal and lactose crystal agglomerate numbers and size were measured by using an optical microscope. Results suggested that stirring and placing a small sample of dulce de leche in a small container induced lactose crystallization. Lower storage temperatures resulted in an increase of crystal and agglomerate number but in a decrease of crystal and agglomerate size. The effect of temperature on crystal and agglomerate growth rates could be attributed to the effect of temperature on viscosity, as lower temperatures resulted in decreased crystal mobility in dulce de leche and therefore reduced crystal and agglomerate growth rate.

Consumer reaction to changes in sensory profile of dulce de leche due to lactose hydrolysis

The effect of lactose hydrolysis on the sensory profile of dulce de leche and consumer reaction to this process using overall acceptability data and survival analysis calculations was examined. Lactose hydrolysis caused marked changes in the sensory profile of dulce de leche, particularly for flavor and texture, leading to a decrease in consumer overall acceptability and intent to purchase the product. Survival analysis methodology was used to estimate the consumer rejection percentage to purchase dulce de leche as a function of lactose hydrolysis percentage. Using a Weibull distribution, lactose hydrolysis percentage corresponding to a 10% consumer rejection was calculated as 4.6 ± 0.4%, in agreement with calculations from least significant difference in overall acceptability, suggesting that both methodologies might provide similar results. Survival analysis could be used to estimate limits for ingredient replacement or changes in manufacturing processes that cause complex sensory changes in the product, leading to consumer rejection.

CONSUMER PERCEPTION OF SANDINESS IN DULCE DE LECHE

ABSTRACT Sandiness, one of the most common defects of dulce de leche, is caused by lactose crystallization. In order to study consumer reaction to the presence of different levels of this defect, survival analysis statistics was applied to the consumer acceptance/rejection data of the samples. Limits for this defect were estimated by working with 10% and 25% consumer rejection probabilities. The consumers were also asked to score the sample sandiness according to their perception, using a 9‐point scale. Cluster analysis and correspondence analysis performed showed the heterogeneity of the consumer responses toward sandiness in dulce de leche. Significant correlations were established between consumer sandiness and the number of crystals and sandiness as measured by a panel of trained assessors, the latter being the best indicator of sandiness as perceived by the consumers. It could be established that the consumers' and assessors' sandiness perception is clearly influenced by the presence of agglomerates, their size distribution and number. PRACTICAL APPLICATIONSSandiness is an important defect for a segment of consumers who rejected samples with high levels of sandiness, suggesting the importance of avoiding the occurrence of this defect. Survival analysis methodology was used to estimate the maximum level of sandiness in dulce de leche before consumers reject it. As sandiness is a sensory defect that often limits the shelf life of dulce de leche, the calculated sensory limits could be used in future studies to estimate the sensory shelf life of dulce de leche.

Características físico-químicas e utilização em alimentos de amidos modificados por tratamento oxidativo

The use of modified starches in foods is made to improve characteristics that the native cannot confer. The objective of this work was to evaluate physicochemical characteristics of starches from several botanical sources after chemical modification with H2O2 considering technological properties of interest to the food industry. The modified starches were used in dulce de leche and starch gum and the sensorial acceptance of these products was verified. The chemical treatment included the suspension of the native starches in a 0.01% Fe2SO4, followed by addition of 1.25% H2O2 at pH 3.0 and reaction time of 15 min at 45 °C. After this period the starch was recovered by filtration, washed and oven-dried at 45 °C for 24 hours. The modified starches had higher expansion, carboxyl content, reducing power and susceptibility to syneresis. There was a decrease in the viscosity peak of the modified starches especially when the samples were analyzed in pH 7.0. The sensorial evaluation indicated that dulce de leche produced with addition of Peruvian carrot modified starch and regular corn acid-modified starch were the preferred samples. The starch gum made with modified starch of Peruvian carrot reached the second position on global preference between the panelists.

GROWTH OF EUROTIUM CHEVALIERI IN MILK JAM: INFLUENCE OF PH, POTASSIUM SORBATE AND WATER ACTIVITY

ABSTRACT Milk jam (dulce de leche) is a typical Argentine sweet spread prepared by milk evaporation to about 70% w/w total solids at atmospheric pressure with added sucrose, glucose and vanillin. Growth of xerophilic molds represents a severe problem in this type of intermediate moisture product. This study evaluated the growth response of Eurotium chevalieri in milk jam with different potassium sorbate (KS) concentrations (0, 500, 1,000, 1,500 and 2,000 ppm) at selected water activity (aw) values (≅0.80 and 0.85) and two pH levels (≅5.5 and 6.0) stored at room temperature (25C) for 90 days. Growth curves were characterized by the modified Gompertz model, and the effect of the independent variables on the estimated parameters (maximum specific growth rate, vm, and lag time, λ) was analyzed through polynomial equations. Growth of E. chevalieri was prevented for at least 90 days when the addition of 1,000 ppm KS was combined with a decrease in aw to 0.80 and ph 5.5. The boundary between growth and nongrowth of E. chevalieri as a function of aw, pH, KS and storage time was also predicted by means of the probabilistic model using logistic regression, which provided a wide range of formulation possibilities depending on the targeted shelf life.

PREFERENCE MAPPING OF TEXTURE OF DULCE DE LECHE

ABSTRACT The texture of 12 commercial samples of dulce de leche was characterized by means of texture profile analysis. Two sensory manual texture attributes (hardness and ropiness) were evaluated by a panel of 11 trained assessors. A panel of 50 consumers evaluated the texture acceptability of the samples using a 9‐point structured scale. Consumers showed highly significant different degrees of liking for the texture of the evaluated samples of dulce de leche. Clusters identified with Pearson's correlation coefficient showed opposite preference patterns and provided more useful information regarding market segmentation than clusters identified with Euclidean distances. External preference mapping and partial least squares regression showed that hardness was a driver of liking for one segment of consumers, whereas for the other one it was a driver of disliking. When all the consumers were considered, external preference mapping indicated that the ideal texture of dulce de leche would be intermediate, showing the importance of identifying preference patterns and suggesting that data averaging in consumer preferences might affect information recovery, and may lead to wrong conclusions. Different preference mapping techniques were compared; it was found out that when the relationship between acceptability and texture attributes was not linear, external preference mapping showed the best results.

INSTRUMENTAL METHODS TO CHARACTERIZE NONORAL TEXTURE OF DULCE DE LECHE

ABSTRACT Three different instrumental texture methods (vane yield stress determination, forward extrusion and penetration tests) were used to characterize nonoral texture of 13 commercial samples of dulce de leche, a type of sweetened condensed milk. Two sensory nonoral texture attributes (hardness and ropiness) were evaluated by a panel of 11 assessors, trained in descriptive analysis of dairy product's texture. All the studied instrumental methods showed high reproducibility and high discriminating ability between samples. Those instrumental parameters that are related to the firmness of dulce de leche (yield stress, extrusion force, hardness, modulus and adhesiveness) were highly correlated to sensory hardness. No instrumental parameter was able to reflect the sensory ropiness of the samples. From all the instrumental methods used to characterize the nonoral texture of dulce de leche, yield stress seems the most appropriate to be used in quality control programs, because it showed the highest discriminating ability and it has the advantage of being a quick and direct method.

Growth Response of Eurotium chevalieri, Aspergillus fumigatus and Penicillium brevicompactum in Argentine Milk Jam

Milk jam ( dulce de leche) is a typical Argentine sweet spread prepared from milk concentrated by evaporation to about 70% w/w total solids at atmospheric pressure with added sucrose, glucose and vanillin. Growth of xerotolerant moulds represents a severe problem in this type of product with high sugar concentration. This work aimed at analysing the influence of water activity (aw range 0.74–0.85), pH (5.5 and 6.0) and the addition of 1,000 ppm potassium sorbate on Eurotium chevalieri, Aspergillus fumigatusand Penicillium brevicompactumgrowth response in milk jam stored at 25 °C or 35 °C during 90 days. Growth curves were successfully modelled by applying the modified version of Gompertz equation. There were proposed polynomials equations relating time to detection, λ, with two independent variables: potassium sorbate and water activity at pH 6.0. Some useful combinations of these factors were found to assure inhibition of mould growth during a critical storage period. Results might contribute to optimise manufacture conditions and/or milk jam composition to obtain a safer product when failure occurs during the hot filling process or when the product is stored for a long period of time.

Loss of available lysine during processing of different dulce de leche formulations

Dulce de leche is a dairy‐based confectionery product prepared by heat concentration of milk and sugar, which can be partially replaced by other sugars. The effect of different formulations commonly used in the manufacture of this product on the rate of available lysine loss by Maillard reactions was examined. The replacement of 10% of sucrose by glucose increased by 90% the rate of lysine glycation, while the rise with fructose was only 30%. The use of skim milk led to a low fat product with the same available lysine content as the traditional one. Dulce de leche prepared with lactose‐hydrolysed milk had a very low available lysine value.

Sensory Shelf Life of Dulce de Leche

The objectives of this research were to determine the sensory cutoff points for dulce de leche (DL) critical descriptors, both for defective off-flavors and for storage changes in desirable attributes, and to estimate the shelf life of DL as a function of storage temperature. The critical descriptors used to determine the cutoff points were plastic flavor, burnt flavor, dark color, and spreadability. Linear correlations between sensory acceptability and trained panel scores were used to determine the sensory failure cutoff point for each descriptor. To estimate shelf life, DL samples were stored at 25, 37, and 45°C. Plastic flavor was the first descriptor to reach its cutoff point at 25°C and was used for shelf-life calculations. Plastic flavor vs. storage time followed zero-order reaction rate. Shelf-life estimations at different temperatures were 109 d at 25°C, 53 d at 37°C, and 9 d at 45°C. The activation energy, necessary to calculate shelf lives at different temperatures, was 14,370±2080 cal/mol.

Lubricated squeezing flow viscometry for dulce de leche (milk sweet) Viscometría de extensión biaxial sin fricción de dulce de leche

Commercial samples of dulce de leche (milk sweet, caramel jam) of two types, made by two different manufacturers were squeezed between two parallel Teflon® plates, 64 mm in diameter. The initial height of the samples was about 8 mm and they were compressed to 0.4 mm at rates of 0.1, 0.2, 0.3 and 0.4 mm/s. After the samples had reached the final height, they were allowed to relax for about 3 min. The force-height relationships, when plotted on logarithmic coordinates, had a clearly discern ible linear region, with slope in the range of -1.1 to -1.5. The apparent stress at pre-selected heights was used as a measure of the product consistency. The experimental scatter of these stresses was in the order of the 10%, small enough to detect differences between the different brands and monitor rate effects. The latter did not conform to theoretical predictions based on the power law model, most probably because of the products' considerable apparent yield stress on the experimental time scale. An empirical formula to describe the rate effect was developed and found to be appropriate for all the products tested. The yield stress itself was manifested in the magnitude of the residual stress after relaxation. It could also be used as a measure of consistency which provided the same ranking of the samples as the apparent stress at a fixed height.

Viability of lactic acid microflora in different types of yoghurt

The suitability of three culture media (Skim milk agar, M17 agar and MRS agar, incubated under aerobic and anaerobic conditions) to obtain total and differential counts of yoghurt bacteria, was assayed. A total of 25 samples of different yoghurt types (set, skimmed set, drinking, and set with “dulce de leche”) obtained with the culture IA, were used. The lactic microflora viability was studied at 6°C and 12°C. Skim milk agar (aerobiosis) was the most useful medium for total and differential counts of Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus. Cell viability depended on the yoghurt type and the storage temperature. On the basis of a minimum value of 10 7 CFU g −1, the shelf life of yoghurts at 6°C was longer than 60 days, with the exception of the drinking type (45 days). At 12°C, shelf life was identical for the skimmed drinking yoghurt but lower for the other yoghurt types. Both the storage temperature and the yoghurt type should be taken into account when shelf life is specified on the basis of the lactic microflora content.

Carbohydrates and risk of stomach cancer in Uruguay

Carbohydrates and risk of stomach cancer in Uruguay

RHEOLOGICAL CHARACTERIZATION OF “DULCE DE LECHE” BY DYNAMIC AND STEADY SHEAR MEASUREMENTS

ABSTRACTRheological properties of three commercial samples of the typical Argentine sweet spread “Dulce de Leche” (common, low calorie and confectionery types) were measured by transient tests (constant shear rate time dependency) using rotational viscometry and dynamic measurements with oscillatory rheometry. All the samples showed a strong time dependency but no recovery of the structure was detected in a 24‐h period. A prominent overshoot was evidenced in all transient assays; at long times, the Leider‐Bird model converges to the power law equation. The linear‐viscoelastic range for the confectionery “Dulce de Leche” determined by the dynamic test ranged up to a limit deformation of 9% whereas the other two types had a range up to 3.5%. The behavior of the three types of “Dulce de Leche” was intermediate between a concentrated solution and a gel but the confectionery type was closer to a gel‐like behavior than the other two. Differences found in the rheological behavior of the three “Dulce de Leche” types were related to their different compositions and the presence or absence of thickening agents.