CONSUMER PREFERENCE AND MECHANICAL PROPERTY ASSESSMENT OF MAINE WILD BLUEBERRIES FOR THE FRESH PACK MARKET1

Maine wild fresh blueberries were purchased from a cooperative twice (tests 1 and 2) during the 1997 field season and used to determine the relationship of consumer preference and textural properties. Berry diameter was used to establish 3 size classes and a consumer panel evaluated teaspoon-sized samples and indicated their opinion of flavor, texture and overall quality attributes using a 9-point hedonic scale. Ranked preference for size was conducted in a separate area following the acceptability evaluation. At the same time the consumer samples were drawn, three berries were subsampled and subjected to a compression test. Two replications of the test were made to evaluate texture/sensory interactions of Maine wild blueberries throughout the harvest period; test 1, one week into the four-week harvest. Based on size class, there were no significant differences in acceptability attributes; however, differences were detected in the mechanical tests. Slight differences in consumer preference were detected in test 2, which took place three weeks into the harvest cycle, and significant differences were also found in the mechanical tests. Differences between test 1 and 2 can be attributed to blueberry maturity. These results compare with previously published data on Maine wild blueberries.     

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.     

QUALITY OF 'CLIMAX' BLUEBERRIES AFTER LOW DOSAGE ELECTRON BEAM IRRADIATION

Fruit of ‘Climax’ rabbiteye blueberries (Vaccinium ashei Reade) were irradiated by a linear accelerator at 0, 0.25, 0.5, 0.75, 1.0, and 1.25 kGy and evaluated for various quality attributes after storage for 1, 3, 7, or 14 days at 1C plus 2 days at 15C, respectively. Weight loss increased during storage and averaged 4.2% after the final inspection and was not affected by irradiation dosage. About 5% of total berries were decayed after 14 days at 1C, about 6% after the final inspection at 15C, but decay was not affected by the level of irradiation. Electrolyte leakage, skin color, total soluble solids, acidity, and pH were also not affected by irradiation dosage. There was a significant decline in berry firmness, flavor, and texture as dosage increased. Berries treated at 1.0 kGy or above were softer and had lower flavor and texture preference scores than berries treated at lower dosages or nontreated berries.     

INSTRUMENTAL AND SENSORY CHARACTERIZATION OF COOKED POTATO TEXTURE

Uniaxial compression, Texture Profile Analysis (TPA) and chemical measurements were related to sensory texture evaluation of potato quality during storage. Principal component analysis grouped the varieties into three types of variation: mealiness versus firmness and springiness (PC1), moistness versus adhesiveness (PC2) and hardness versus adhesiveness and moistness (PC3). In uniaxial compression the variable 'stress', 'work up to fracture' and 'total work during compression' described the same type of information in the data. These uniaxial data and most of the TPA data were highly correlated. Uniaxial compression data (stress, strain, modulus of deformability), starch structural data (area, roundness, aspect ratio), specific gravity and pectin methyl esterase activity discriminated between the varieties and harvest times. Partial Least Squares Regression showed stress, strain, modulus of deformability and specific gravity to be the most important variables in distinguishing between two groups of sensory texture attributes explaining 65% of the total variance in the sensory data. Coefficients of correlation between predicted and measured sensory attributes were in the range 0.36–0.79. The TPA data were not found to be relevant substitutions for the sensory attributes.     

SENSORY AND OBJECTIVE EVALUATION OF A RESTRUCTURED BEEF PRODUCT

A study was undertaken to determine the effect of connective tissue, flake size and NaCl level on the texture of restructured beef steakettes; to examine the effect of these factors on the acceptability of restructured steakettes; and to develop sensory and instrumental texture profiles of the product. Restructured beef steakettes were manufactured with two levels of connective tissue (high, low), three flake sizes (3 mm, 6 mm, 13 mm) and three NaCl levels (0.25%, 0.50%, 0.75%). The textural attributes of these products were measured by a trained sensory panel and by objective measures of compression texture profile analysis, Warner-Bratzler shear and three tensile tests. Most sensory texture attributes could be predicted accurately using instrumental methods. Reduction of the sensory attributes by Principal Components Analysis revealed two underlying dimensions of connective tissue and bind strength. A consumer panel rated steakettes manufactured with 6 mm flakes and 0. 75% NaCl at either connective tissue level to be the most acceptable of the 18 products manufactured for this study.     

Varietal Comparison of The Chemical,Physical, and Mechanical Properties of Five Colored Table Grapes

The visual attributes of table grapes, their chemical constituents, and mechanical properties are involved in consumer acceptability because they are correlated to sensory perception. Usually, instrumental measurements are preferred to the sensory evaluations because they reduce variations in subjective judgments and can be carried out more easily. In this work, chemical-physical attributes and texture properties of five black table grapes (Alphonse Lavallée, Black magic, Cardinal, Perlon, Regina nera) were studied in order to identify significant varietal differences. Spectrophotometric and HPLC methods and texture analysis test were used to evaluate color index, sugars and acid composition, phenolic characteristics, and mechanical properties of the skin and the pulp of berries. Many differences were found among varieties in technological maturity indexes, hydroxycinnamic acid, anthocyanin content and profile, and relative CIE L*, a*, b* parameters, but the more relevant differences were found in mechanical properties. Principal component analysis showed that the texture profile analysis parameters (hardness, cohesiveness, gumminess, and resilience) and berry skin characteristics (break skin energy, skin modulus of elasticy) were the best indices able to fulfill the aim of this work. Almost all of the parameters showed differences among cultivars, confirming their importance in the characterization of the variety as well as in the assessment of potential consumer acceptability. In particular, the cultivars demonstrated different reactions to the compression test; thus, the texture analysis parameters can be appropriate to explain varietal differences and to allow their differentiation.     

UNIAXIAL COMPRESSION OF UF-FETA CHEESE RELATED TO SENSORY TEXTURE ANALYSIS

Rheological characteristics of seven Feta cheeses with different textures and produced from ultrafiltered milk (UF-Feta cheeses) were evaluated by uniaxial compression and sensory texture analysis. The effect of uniaxial deformation rate (50–2500 mm/min) on four rheological parameters: Stress at fracture s?_f), Hencky strain at fracture (?_f), deformability modulus (E) and work to fracture (W_f) was examined. Three Principal Components (PC) described 76, 16 and 4% respectively, of the variation in the uniaxial compression data set (4 parameters at 12 deformation rates). Statistically α_f, E and W_f described the same type of information in the data set. Six sensory texture attributes of the UF-Feta cheeses were evaluated by a sensory texture panel: nonoral firmness, nonoral brittleness, nonoral spreadability, oral crumbliness, oral firmness and oral stickiness. One PC described 93% of the variation in the sensory texture data and grouped the sensory variables into two negatively correlated groups: nonoral firmness nonoral brittleness, oral firmness and oral crumbliness versus nonoral spreadability and oral stickiness. Correlations and Partial Least Squares regression (PLS) between instrumental and sensory texture variables showed that nonoral and oral firmness were the nonoral and oral sensory variables best predicted from instrumental measurements. α_f, E and W_f were all able to predict nonoral and oral firmness. Of the instrumental parameters, α_f generally gave the best correlation to nonoral firmness at all deformation rates. Above a deformation rate of 50 mm/min correlations between α_f and nonoral firmness were almost independent of deformation rate, and at any deformation rate correlations between α_f and oral firmness     

Quality of electron beam irradiation of blueberries (Vaccinium corymbosum L.) at medium dose levels (1.0-3.2 kGy)

We assessed the effect of electron beam irradiation of packaged fresh blueberries at doses greater than 1.0 kGy on the quality attributes of the fruits. Irradiation experiments were conducted using a 10 MeV (18 kW) linear accelerator with single beam fixture. Fruits were stored at 5 °C and 70.4% RH for 14 days and tested at days 0, 3, 7 and 14 for physico-chemical, textural, microstructural, and sensory characteristics. Control samples consisted of non-irradiated fruits. Irradiation at doses higher than 1.1 kGy did affect (P<0.05) the texture of blueberries as the fruits became considerably softer and less acceptable throughout storage. Only irradiation at 3.2 kGy affected the color of blueberries by the end of storage. Irradiation slightly reduced the respiration rates of the blueberries by the end of storage. In terms of overall quality, texture and aroma, only fruits exposed to 3.2 kGy were found unacceptable by the sensory panelists. Irradiation at the dose levels used in this study did not affect the density, pH, water activity, moisture content, acidity and juiciness of blueberries. Electron beam irradiation of blueberries up to 1.6 kGy is a feasible decontamination treatment that maintains the overall fruit quality attributes.     

VISCOELASTIC CHARACTERIZATION OF RICE GEL

Rice flour dispersions with 15–25% solids were subjected to microwave heating for 0–75 s and samples were subjected to oscillatory frequency sweep between 0.01–10 Hz. The initial rapid increase in storage modulus (G¹) with frequency decreased to a plateau at higher frequencies. An increase in G¹ and complex viscosity (η*) with an increase in the time of treatment or concentration of solid indicate the extent of sol-gel transformation. The sensory data on hardness, elasticity and stickiness also followed similar trend. Principal component analysis (PCA) of the sensory results indicate that a minimum treatment time of 45 s is needed to achieve a rice gel with acceptable sensory characteristics. The G' values were modeled (0.936 ≤ r ≤ 0.988, P ≤ .01) by the 4-element spring-dashpot model.     

COMPARISON OF TWO INSTRUMENTAL METHODS WITH SENSORY TEXTURE OF PROTEIN GELS2

The textural attributes of 8 different heat-induced protein gel preparations evaluated by torsion failure testing and Instron texture profile analysis (TPA) were compared to sensory ratings by a trained texture profile panel. The gels presented a wide range of textural properties as determined by the instrumental and sensory parameters. Among the instrumental parameters, true shear strain at failure was the most frequent and significant predictor of sensory notes. Initial shear modulus and 50% compression force had the poorest correlations with sensory notes. Comparison of the two instrumental tests produced high correlations between shear stress at failure and TPA hardness; true shear strain at failure and TPA cohesiveness; and, initial shear modulus and 50% compression force. High correlations were also observed among various panel notes. Canonical correlation analyses showed that sets of linear combinations of parameters from each one of the 3 tests (torsion, TPA or sensory) were highly correlated to sets from either of the other two. Regression equations relating each of the instrumental tests to sensory notes were developed. Of the torsion failure parameters, the logarithm of true shear strain most commonly appeared in the equations. Of the TPA parameters, cohesiveness and its logarithm were the terms that were most frequent. High R² values were obtained for regression equations developed for predicting torsion failure parameters based on TPA parameters.     

Improvements in Canned Lowbush Blueberry Quality

Individually quick frozen lowbush (wild) blueberries (Vaccinium angusrifolium) were canned with 0, 1500, or 3000 ppm calcium from chloride or lactate salts and 0, 0.25, or 0.50% citric acid in water. Physical and pH changes were measured at 0, 6, and 12 mo, and sensory evaluations were made at 3 and 9 mo post-canning. Calcium increased firmness and berry calcium content. Calcium chloride and citric acid reduced pH and increased hue angle and off-flavor; calcium lactate increased drained weight and pH but reduced hue. Response surface methodology predicted changes in calcium lactate-treated berries, but not CaCl₂-treated berries. Optimal conditions were 1200–1800 ppm calcium lactate at 3–6 mo storage.     

FULL UNIAXIAL COMPRESSION CURVES FOR PREDICTING SENSORY TEXTURE QUALITY OF COOKED POTATOES

The prediction of six different sensory texture attributes of twenty-seven potato samples based on uniaxial compression curve features and full uniaxial compressions curves is reported. The data set comprised five varieties, sorted in dry matter bins, and sampled at two storage times. The predictions of most of the sensory texture attributes from full compression curves performed better than just using curve features. Furthermore, force-deformation curves are shown to give slightly better predictions than stress-strain curves. For most of the texture attributes better predictions were obtained using uniaxial compression data from raw potato samples as compared to cooked samples. This study is meant to open up a debate on interpreting the information in uniaxial compression curves in relation to sensory texture quality. Multivariate analysis can handle this and can further give insight about where in the curve the information relevant for the predictions of the sensory attributes is found.     

Radiation Processing of Minimally Processed Pineapple (Ananas comosus Merr.): Effect on Nutritional and Sensory Quality

ABSTRACT:  Radiation processing of minimally processed pineapple at a dose of 2 kGy was investigated. Effect of this treatment on different quality parameters like vitamin C content, total carotenoids content, sensory attributes, texture, and color was determined over a storage period of 12 d at 8 to 10 °C. Results showed that the irradiation treatment showed no significant effect ( P > 0.05) on total vitamin C content of pineapple samples but a significant decrease ( P ≤ 0.05) in vitamin C during storage period in both controls as well as irradiated samples was observed. However, total carotenoids were not affected by irradiation and were stable during the whole storage period as well ( P > 0.05). Sensory evaluation studies revealed that irradiation had no significant effect ( P > 0.05) on the ratings of any of the sensory attributes of pineapple samples. Taste panelists could not differentiate between control and irradiated samples. Textural studies showed no significant effect ( P > 0.05) of irradiation as well as storage period on the firmness of the central edible region of pineapple samples. Color attributes of both control and irradiated samples showed slight variation during the storage period of 12 d. However, irradiation at 2 kGy did not have a significant effect ( P > 0.05) on all color coordinates. Thus, radiation processing with 2 kGy did not affect significantly the nutritional value as well as the sensory quality of minimally processed pineapple samples.     

Use of a Combination Process of Osmotic Dehydration and Freeze Drying to Produce a Raisin-Type Lowbush Blueberry Product

A raisin-type product was prepared from lowbush blueberries using a sequence of osmotic dehydration, freeze drying, and thermal plasticization. Qualities of osmotically dehydrated blueberries, residual syrup, and final products were studied using various ratios of berry and sugar. An accelerated storage test was also conducted. IQF berries were preferred to fresh berries as a starting material, and a berry/sugar ratio of 3:1 or 4:1 was appropriate. Final products had good texture, flavor, overall acceptability, and a predicted shelf life of 16 and 64 months at 25° and 5°C storage, respectively.     

PREDICTION OF SENSORY TEXTURE OF FETA CHEESE MADE FROM ULTRAFILTERED MILK BY UNIAXIAL COMPRESSION AND SHEAR TESTING

The ability to predict sensory texture properties of Feta cheese made from ultrafiltered milk (UF-Feta) from uniaxial compression, small shear deformation measurements (frequency sweep, strain sweep, relaxation) and indices of proteolysis was studied. In principal component analysis (PCA) some of the instrumental variables were highly correlated, e.g. the moduli from uniaxial compression and shear measurements; and strain at fracture from uniaxial compression and indices of proteolysis. PCA of the six sensory attributes determined by a trained panel showed that mainly one type of information was present in the sensory results. Partial Least Squares regression (PLS) of all results revealed that stress at fracture from uniaxial compression was the individual instrumental parameter having the highest correlation with the sensory texture attributes. Of these, the three firmness attributes were best predicted by the instrumental parameters. As the shear measurements were not very useful for prediction of sensory texture properties by themselves, and as the increase in prediction precision by inclusion of these measurements was marginal, it is suggested that either stress at fracture alone, or together with three other parameters from uniaxial compression should be used to describe texture properties of UF-Feta cheese.