INFLUENCE OF UNIAXIAL COMPRESSION RATE ON RHEOLOGICAL PARAMETERS AND SENSORY TEXTURE PREDICTION OF COOKED POTATOES

The effect of uniaxial compression rate (20–1000 mm/min) on the parameters: Stress (σ_ftrue), strain (ε_fHencky) and work to fracture (W_f), modulus of deformability (E_d), maximum slope before fracture (E_max) and work during 75% compression (W_total) was investigated for ten potato varieties. Multivariate data analysis was used to study the correlation between and within the sensory and nonsensory measurements by Principal Component Analysis (PCA) which showed σ_ftrue, E_max, W_f, and W_total to explain the same type of information in the data, and ε_fHencky versus E_d another type of information in the data. The deformation rate had a large effect on ε_fHencky. Nine sensory texture attributes covering the mechanical, geometrical and moistness attributes were evaluated. Relationships between uniaxial compression data at various deformation rates and the sensory texture attributes were studied by Partial Least Squares Regression (PLSR). A minor effect of deformation rate on the correlation with the sensory texture properties was obtained. Mechanical properties were predicted to a higher extent than the geometrical attributes and moistness. The prediction of the mechanical, geometrical and moistness attributes increased largely by using uniaxial compression supplemented by chemical measures such as dry matter and pectin methylesterase, but here no relevant effect of deformation rate was obtained.     

Physical Properties, Sensory Attributes, and Consumer Preference of Pear Fruit Leather

ABSTRACT: Pear fruit leathers were prepared by drying a mixture of pear juice concentrate, pectin, corn syrup, and water at 70°C for 8 h. The effects of ingredients on texture, color, microbial growth, moisture content (MC), water activity (a_w), glass transition temperature (T_g), and sensory attributes were investigated. Pectin was the most significant independent variable that affected the properties of interest. This was followed by initial moisture content and corn syrup. Glass transition temperature (T_g) was not useful for predicting microbiological attributes but had strong correlations with instrumental and sensory hardness and chewiness. The results from partial least squares analysis (PLS) indicate instrumental hardness, chewiness, and cohesiveness could be used to predict their corresponding sensory attributes. The consumer liking of pear fruit leather could be increased by raising their fruit aroma, sweetness, tartness, and shininess.     

PREDICTION OF INSTRUMENTAL AND SENSORY TEXTURAL CHARACTERISTICS OF MAHON CHEESE FROM ULTRASONIC MEASUREMENTS

Ultrasonic velocity was related to sensory and instrumental texture measurements. A semi-logarithmic model (Weber-Fechner) was used to relate the sensory and instrumental texture measurements. The ultrasonic velocity ranged from 1650 to 1723 m/s for the softest and hardest cheese, respectively. As expected from theoretical equations, the ultrasonic velocity was related to the square root of the instrumental measurements. The deformability modulus (r²=0.93) and the slope in puncture (r²=0.85) were the most closely related parameters. A model developed from the relationship between sensory and instrumental texture and the relationship between ultrasonic velocity and instrumental texture, was used to relate velocity to sensory measurements. Elasticity (r²= 0.84) and firmness (r²= 0.81) were the sensory attributes which best correlated with ultrasonic velocity. From the obtained results, it was concluded that ultrasonic velocity measurements could be used to assess instrumental and sensory properties of Mahon cheese texture nondestructively, and therefore could be used for grading purposes.     

RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY ANALYSIS OF TEXTURE AND COLOR OF POTATO CHIPS

The instrumental and sensory analysis of the texture and color of commercial potato chips were compared. The instrumental measurement was a puncture test with an Intron Universal Testing Machine, and the parameters used were fracture force, deformation and stiffness. The instrumental color quantification was a computerized video image analysis technique, and the color was expressed as L*a*b* values. Sensory evaluation of texture and color was performed by a sensory panel especially trained in evaluating potato chips. The sensory attributes were "hardness", "chewiness", "crunchiness", and "tenderness" for texture analysis, and "yellow color", "burnt aspect", "sugar colored aspect" and "transparency" for color analysis. The factor analysis of the sensory attributes indicated that texture can be divided into two principal components, one represented by "hardness", "crunchiness" and "chewiness", and the other by "tenderness" alone. The factor analysis of the color can be divided into two principal components, one including "yellow color" and "burnt aspect", and the other "sugar colored aspect" and "transparency". Discriminant analysis showed that "tenderness" and "crunchiness" could predict correctly over 90% of the data. Fracture force correlated well with all of the sensory attributes (R² > 0.76), and L* with the sensory color attributes (R² > 0.79). The "Tenderness" was the individual sensory attribute which had the highest correlation (R²= 0.95) with fracture force.     

Energy content, sensory properties, and microbiological shelf life of German bologna-type sausages produced with citrate or phosphate and with inulin as fat replacer

ABSTRACT:  The aim of this study was to determine the feasibility of reducing energy content (9% to 48%) in bologna-type sausages by replacing fat with inulin and to study the effects of substituting citrate for phosphate in the traditional sausage formula. German-type mortadella was produced, and fat was replaced with increasing amounts of inulin as a frozen gel to yield 3%, 6%, 9%, and 12% inulin in the final product. In another part of the study, citrate was substituted for the phosphate in the recipe. All sausages produced were sliced, packaged under a modified atmosphere (70% N₂, 30% CO₂), and stored for 23 d at +7 °C. Sausage quality was determined by chemical and instrumental texture profile analyses, color measurement, sensory evaluation, and microbiological testing. Replacing fat with inulin led to significant energy content reductions of up to 47.5% (with 12% inulin). However, the sensory properties of these sausages were also different from those of the control mortadella: fracturability fell, hardness and adhesiveness rose, and color became darker. In general, the substitution of citrate for phosphate significantly reduced the negative effects of inulin. There were no significant differences in microbiological stability between different inulin batches but there were significant differences between phosphate and citrate batches. Overall, the energy content of bologna-type sausages produced with citrate and with up to 6% inulin as a fat replacer was 22% lower than that of the control sausages. Furthermore, the sensory attributes (texture, color) of these 6% inulin–citrate sausages were comparable to the control sausages, and the sausages were microbiologically stable for 23 d of storage.     

RHEOLOGY OF RICE-FLOUR PASTES: RELATIONSHIP OF PASTE BREAKDOWN TO RICE QUALITY, AND A SIMPLIFIED BRABENDER VISCOGRAPH TEST

Flours from 21 nonwaxy rice cultivars, varying in amylose-equivalent (AE) content and eating quality, were pasted at 12–13% concentration at 95C and then further cooked at the same temperature for another 60 min. The fall in apparent viscosity, measured in a coaxial cylinder viscometer, of the 95C–50 min as compared to that of the 95C–0 min paste (paste breakdown, bd _p ) was calculated. The bd _p values were inversely correlated to the sensory and viscoelastograph hardness of cooked rice as well to the AE contents. Paste breakdown was clearly a fundamental attribute of rice quality. It appears that starch granule rigidity/fragility, as determined by its AE, is the basic element in rice quality. This principle was then used to devise an abridged Brabender viscograph procedure. The slurry concentration was adjusted, by a simple technique described, to give a predetermined viscosity value at 95C. Then the paste was heated for another 10 min at 95C. The breakdown at 95C (BD₉₅) of the samples correlated excellently with their total and insoluble AE, sensory and instrumental measures of cooked-rice texture, and with bd _p .     

The Effect of Brine Ingredients on Carrot Texture during Thermal Processing in Relation to Pectin Depolymerization due to the β-Elimination Reaction

ABSTRACT:  Thermal texture degradation of carrots was studied at a temperature of 100 °C in aqueous solutions containing sodium chloride, citric acid, ascorbic acid, and ethylenediaminetetraacetic acid (EDTA) at different concentrations. To enhance the texture of the final product, the carrot samples were pretreated at 65 °C for 30 min in an aqueous calcium chloride solution (5 g/L). For all case studies considered, the pH of the solutions was adjusted to pH = 6.0. In parallel, both the changes in degree of esterification (DE) and the progress of the β-elimination reaction of carrot pectin under the same conditions were investigated. The kinetic parameters for texture degradation (rate constant k_t and final texture value [TP_∞/TP₀]) were estimated using a fractional conversion model. The results indicate that both the rate constant for texture degradation ( k_t ) and the rate constant for the β-elimination reaction ( k_b ) increased with increasing additive concentration, while the final texture values (TP_∞/TP₀) and DE decreased with increasing additive concentration in all systems studied. A high correlation was observed between the relative rate constant for texture degradation and the relative rate constant for the β-elimination reaction on the one hand, and the relative final texture value and the relative rate constant for the β-elimination reaction on the other hand, suggesting that the influence of the solutes on texture degradation can be explained by their influence on the β-elimination reaction.     

Influence of exposure to light on the sensorial quality of minimally processed cauliflower

ABSTRACT:  The impact of lighting on minimally processed cauliflower packaged in 4 different film types (PVC and 3 P-Plus) has been measured and quantified. The effect on the sensorial quality of storage at 4 °C in darkness and partial or continuous lighting was evaluated. The gas concentrations in the packages and the weight losses were also determined. Atmosphere composition inside the packages depended on both the permeability of the film used for the packaging and exposure to light. Samples stored with lighting maintained the gaseous exchange between plant tissue and the atmosphere inside the packages for longer periods than in samples kept in darkness. This prompted a greater loss of water vapor as well as the development of atmospheres with low levels of O₂ and high levels of CO₂ in the samples packed with less permeable films. The most important aspect in sensory evaluation was color. In instrumental color evaluation, coordinates h * and L * were the main means for estimating color evolution. The presence of light accelerated browning in the cut zones. The development of abnormal coloring in these areas marked the end of shelf life for minimally processed cauliflower. Among the sensory attributes studied, color was the most affected by exposure to light. Samples packed in P-Plus 120 film displayed the lowest level of color deterioration in the cut zones. However, under lit conditions, the low permeability of this film caused atmospheres with very low O₂ contents and high CO₂ contents. These atmospheres produced a loss of texture and the development of off-odors.     

RELATIONSHIP BETWEEN INSTRUMENTAL AND SENSORY PARAMETERS OF COOKED SWEETPOTATO TEXTURE1

This study compared two instrumental methods, namely uniaxial compression and texture profile analysis (TPA), with sensory evaluation in describing the textural properties of cooked sweetpotatoes. The steamed cooked samples (1.35 × 2.2 cm cylinder) of four cultivars and six selections were subjected to a trained texture profile panel for sensory ratings and the two instrumental methods for determination of the mechanical properties. Factor analysis indicated that the 15 sensory variables were grouped into 3 main factors, namely moistness-firmness (factor 1), particles (factor 2), and fiber (factor 3). Among the instrumental parameters, shear stress of compression and fracturability, hardness, and gumminess of TPA correlated highly (R = 0.73–0.95) with both the mouthfeel and mechanical-type sensory notes. These parameters of the two instrumental methods were linearly related (R²≥ 0.95) and could be converted from one to another with a high degree of reliability. Regression equations based on shear stress significantly explained (R²= 0.71–0.91) eight of the sensory notes. These instrumental parameters can be good predictors of cooked sweetpotato texture.     

潮州牛肉丸质构的感官评定与仪器分析

质构是潮州牛肉丸品质的决定因素,为正确合理地评价潮州牛肉丸质构特性,对感官评定与仪器分析2种方法进行比较。选用11种市售潮州牛肉丸,采用质地剖面检验法进行感官评定,质构仪(质构剖面分析模式,剪切力模式,穿刺模式)进行仪器分析。运用主成分分析从潮州牛肉丸质构的感官评定与仪器分析数据中提取出2个独立主成分,这2个主成分解释了74.486%的数据,并把样品分成了3类。对感官评定与仪器分析结果进行相关性分析,发现感官评定与仪器分析结果之间存在广泛的程度不同的相关性(r=-0.622～0.896,P<0.05或P<0.01)。以主要感官指标为因变量,仪器分析指标为自变量,进行逐步回归分析,得到具有统计意义的感官硬度、弹性、紧密性、多汁性和易嚼性的预测方程(R2adj=0.696～0.907)。     

DEVELOPMENT AND PROPERTIES OF SOYBEAN SPREADS

Soybean spreads were developed by concentrating soymilk with the addition of sugar, sorbitol, sodium citrate, carrageenan and refined bleached and deodorized (RBD) palm olein. Soymilk was prepared by 3 extraction methods: soaking in water (control), blanching at 85C with sodium bicarbonate (NaHCO₃) solution and acid treatment using HCl. Three different types of soybean spreads were developed using these soymilks. The spreads were evaluated for their proximate composition, pH, water activity (A_w), color, spreadability, sensory characteristics and storage stability. Sensory and spreadability results showed that soybean spread from blanched and alkali-treated soymilk was most acceptable and showed better spreadability than the others. It was more yellowish in color, possessed lower A_w and firmer texture. The shelf-life of all three types of spreads at refrigerated temperature were at least 30 days.     

Effect of Thermal Process Time on Quality of "Shrimp Kuruma" in Retortable Pouches and Aluminum Cans

ABSTRACT:  The effect of processing time on biochemical, sensory characteristics, and instrumental texture profiles of "Shrimp Kuruma" in retortable pouches and aluminum cans with equal pack weight and lethality was studied. Processing in pouches resulted in a 35% reduction in processing time compared to cans for equal lethality ( F ₀ 8.0). Thermal processing resulted in a 14% loss of water in canned samples compared to 9% in pouched products. Thermal processing resulted in an increase in the volatile compounds and a decrease in the oxidation products in both canned and pouched samples. Products processed in pouches were rated as lighter in color, more succulent, and more desirable in firmness compared to products in cans. Chewiness and hardness showed a significant difference ( P < 0.05) between the 2 treatments.     

A NUMERICAL APPROACH TO COMPUTE TEXTURAL ATTRIBUTES OF COOKED RICE BY EXTRUSION TESTING

The cooked rice extrusion testing system consisted of a piston disc and a sample container with a pot base insert of one outlet. S _init (N/m) and S _max (N/m) are the slopes of the force–deformation curve in the packing and compression stages, respectively, and in the original method they are graphically drawn. Here, however, they were numerically computed as the differential of force to distance. The S _init and S _max from the numerical and drawing methods were compared in terms of data reproducibility and accuracy as described by coefficient of variation (CV) and correlation coefficient (CC), respectively. The numerically computed S _init and S _max showed lower CV: the new method, 0.03–0.06 and 0.03–0.06; the original method, 0.18–0.39 and 0.03–0.14, respectively. S _init by the new method showed higher CC with the adhesiveness of the samples: the new method, − 0.99; the original method, − 0.4. Therefore, the new method proved to be better in data accuracy and reproducibility.

PRACTICAL APPLICATIONS

The extrusion test is a practical instrumental method for measuring the textural properties of cooked rice. Nevertheless, its force–deformation curves are difficult to analyze quantitatively. This study attempted to improve the existing method for curve data analysis by applying a numerical method to compute the instrumental parameters. Based on the findings, this new method provided better data reproducibility and accuracy, and in terms of the instrumental parameters, can facilitate the implementation of cooked rice quality control in the field.     

Effectiveness of active and modified atmosphere packaging on shelf life extension of a cheese tart

This study evaluated the shelf life extension of a cheese cake subjected to modified atmosphere (MAP) and active packaging (AP). Cheese cakes were packaged under different N₂/CO₂ ratios (70/30 and 20/80) (MAP batches), by placing a sachet of an iron oxide-based oxygen absorber inside trays (AP batch) and with air (air batch). Changes in microbial growth, in-package gas composition, chemical–physical parameters including texture and sensory attributes were monitored for 48 days at 20 °C. AP allowed a mould-free cheese cake shelf life of 48 days, MAP extended the shelf life of samples packaged under 30% and 80% CO₂ up to 14 and 34 days, respectively, whereas tarts stored with air spoiled after 7 days. MAP resulted in a significant increase in hardness after 14 days of storage, whereas AP tarts recovered the initial texture after 48 days. Panellists judged AP tarts over the acceptability threshold during the whole shelf life of cheese tarts.     

豆腐质构的感官评定与仪器评价的相关性分析

为探索最能反映豆腐感官质构的仪器指标,选取了四种市售鲜豆腐作为研究对象,采用豆腐质构仪器测定中常用的二次压缩和插入试验进行仪器指标测定,同时进行分析型感官质构评定试验,并对两者测定指标之间进行了相关性分析。结果表明:压缩试验中的5项仪器指标（硬度、弹性、咀嚼性、凝聚性及胶粘性）除凝聚性外,其余4项均与感官质构评价指标间存在较好的相关性,其中硬度与感官质构硬度相关性显著（r=0.952,P<0.05）;插入实验中的3项仪器指标（表观破断应变ε、表观破断应力σ、表观弹性率E）均与感官质构评价指标间存在较好的相关性,其中表观破断应力σ与感官硬度、细腻性之间相关性显著（r=0.989, ?0.978,P<0.05）。综合考虑,仪器评价指标中的硬度及表观破断应力可以代替感官评定指标客观准确的评价豆腐质构的好坏,在豆腐的实际生产中及豆腐质构的科研中也可考虑仅选用这两个仪器指标。     

Vane Yield Stress of Starch Dispersions

ABSTRACT: Yield stresses of 5% (wt/wt) cross-linked waxy maize, tapioca, and Amioca starch dispersions (SDs) were measured with the vane method at different rotational speeds ( N ). The static (σ_0S) and dynamic (σ_0d) yield stress values of each SD were measured before and after breaking down its structure under continuous shear, respectively. The difference (σ_0S - σ_0d) was associated with the stress required to break the internal bonds (σ_b). Values of total yield stress (σ₀=σ_0S) and σ_b, and shear rate were related by power law relationships. The contribution of viscous and network stresses were estimated from an energy balance model. Textural characteristics of the SDs were analyzed in a texture map.     

Texture of Vacuum Microwave Dehydrated Apple Chips as Affected by Calcium Pretreatment, Vacuum Level, and Apple Variety

ABSTRACT: The effects of calcium pretreatment, vacuum level, and apple variety on the texture of apple chips, processed using a combination of air drying and vacuum microwave dehydration (VMD), were determined. Pretreatment of apple slices by immersion in 1-5% aqueous CaCl₂ significantly increased crispness of chips as determined by instrumental and sensory analysis; however above 1%, chips were perceived as bitter. Higher vacuum applied during VMD significantly lowered density and increased crispness of chips. This effect was mediated by the vaporization of water in the interior of the chip, which caused expansion of the tissue. Chips made from Fuji apples had higher calcium contents, and were crisper than Red and Golden Delicious apple chips. Microstructure of the chips evaluated by scanning electron microscopy indicated that chips with thicker cell walls and large internal voids were crisper.