A comparative study for the quantitative determination of soluble solids content,pH and firmness of pears by Vis/NIR spectroscopy

Visible and near infrared (Vis/NIR) spectroscopy was investigated to determine the soluble solids content (SSC), pH and firmness of different varieties of pears. Two-hundred forty samples (80 for each variety) were selected as sample set. Two-hundred ten pear samples (70 for each variety) were selected randomly for the calibration set, and the remaining 30 samples (10 for each variety) for the validation set. Partial least squares (PLS) and least squares-support vector machine (LS-SVM) with different spectral preprocessing techniques were implemented for calibration models. Different wavelength regions including Vis, NIR and Vis/NIR were compared. It indicated that Vis/NIR (400–1800 nm) was optimal for PLS and LS-SVM models. Then, LS-SVM models were developed with a grid search technique and RBF kernel function. All LS-SVM models outperformed PLS models. Next, effective wavelengths (EWs) were selected according to regression coefficients. The EW-LS-SVM models were developed and a good prediction precision and stability was achieved compared with PLS and LV-LS-SVM models. The correlation coefficient of prediction (r_p), root mean square error of prediction (RMSEP) and bias for the best prediction by EW-LS-SVM were 0.9164, 0.2506 and −0.0476 for SSC, 0.8809, 0.0579 and −0.0025 for pH, whereas 0.8912, 0.6247 and −0.2713 for firmness, respectively. The overall results indicated that the regression coefficient was an effective way for the selection of effective wavelengths. LS-SVM was superior to the conventional linear PLS method in predicting SSC, pH and firmness in pears. Therefore, non-linear models may be a better alternative to monitor internal quality of fruits. And the EW-LS-SVM could be very helpful for development of portable instrument or real-time monitoring of the quality of pears.     

Effect of water content and storage time on white pan bread quality: instrumental evaluation

 The firmness of white pan bread was measured using compression and bending tests to determine the influence of the water content of the dough on bread quality and on the changes taking place with storage time. Three sample breads were prepared using different flours and three different water contents, and firmness was tested at 24, 48 and 72 h. For gluten-enriched flours, higher water contents tended to bring about a decrease in compression force and bending values, improving shelf-life by reducing the increase in firmness over time. Received: 24 March 1997     

A comparison of various rheological properties for modelling the kinetics of thermal softening of potato tissue (c.v. Monalisa) by water cooking and pressure steaming

The kinetics which can be used to describe thermal softening of potato tissue by water cooking and pressure steaming were established and the temperature dependence of rheological and textural properties, using six different instrumental objective methods as firmness indicators, was determined within the temperature range of 100–122 °C. In water cooking at 100 °C and in steaming at 100, 112 and 117 °C, the thermal softening was best expressed by one simple pseudo first-order kinetic mechanism, which was considered to be the response to the changes in the pectic material in the cell wall and interlamellar region. Tension energy was the best rheological property for establishing the kinetics of softening of potato by water cooking, whereas maximum shear force was the best method of representing the tissue softening by steaming, using first-order models. Steaming at 122 °C caused overcooking of the tissue, even for short times. At this high temperature, rheological parameters (compression, tension and creep compliance) and textural properties from Texture Profile Analysis (TPA) fitted second-order models. When second-order models were used, the Arrhenius equation was significant for chewiness, indicating that this textural property can be useful for detecting overcooking caused by prolonged pressure steaming in the experimental temperature range.     

Changes in quality and phenolic compounds of virgin olive oils during objectively described fruit maturation

The effect of fruit ripening on the quality of the oil extracted and on the changes in the amount of phenolic compounds was determined in two olive varieties (Olea europaea, cvs. Arbequina and Picual) in two crop seasons, characterized by showing the same mean temperature and different rainfalls. Maturation level was evaluated using six methods: Harvest date, ripening index (RI), fruit skin colour, fruit firmness, and amount of chlorophylls and carotenoids in the oil. Oil quality, evaluated using the parameters established to determine the quality level of virgin olive oils (acidity, K₂₃₂, K₂₇₀, peroxide index, and panel test), was not affected by fruit ripening or by the increase in rainfall of the season. However, the changes in oil stability and phenolic compounds in the oils extracted during fruit ripening strongly differed according to the variety, the maturity level of the fruit and the crop season tested. Fruit skin colour and firmness allowed a better discrimination at the initial maturity stages than the other methods tested.     

Water status of cooked white salted noodles evaluated by MRI

Transverse relaxation time (T₂)-weighted images and T₂ maps of white salted noodles (WSN) were investigated by magnetic resonance imaging technique. T₂-weighted images and T₂ maps clearly showed the differences in water status between noodles. The migration of moisture from surface regions to central regions of boiled WSN at different migration rates were investigated during storage. The distribution of T₂ values changed differently depending on the cooking and storage times. The small differences in T₂ values between surface region and central region of noodles cooked for 5 and 15 min were attributed to the limited water absorption during short cooking time, which resulted in high firmness. The changes in starch granules morphology observed under scanning electron microscope and the increase of noodle firmness measured by texture analyzer were significantly affected by the water status in noodles. The water status can be controlled by the cooking time.     

红喜士苹果采后1-MCP处理对常温贮藏效果的影响

试验表明,1-MCP(1-甲基环丙烯)处理可以明显减缓红富士苹果硬度的降低,保持可滴定酸的含量,维持红富士苹果良好的商品品质和风味,延长货架期。     

The genetic relationship between enzymatic activity of cathepsin B and firmness of dry-cured hams

This study aimed to investigate the genetic relationship between enzymatic activity of raw hams and firmness of dry-cured hams. Instrumental firmness and sensory panel firmness scores were obtained from 2058 and 3275 dry-cured hams, respectively. On a sub-sample of 988 raw hams for dry-curing, enzymatic activity of cathepsin B was determined through a fluorimetric analytical method. A multiple-trait animal model was used to estimate heritability and genetic correlations of these traits. Estimates of heritability were moderate, ranging from 0.11 for sensory panel firmness scores to 0.25 for cathepsin B activity. Genetic correlations between firmness measures on dry-cured hams and enzymatic activity of raw hams were low. The efficiency of a selection program aimed to reduce the incidence of excessive softness in dry-cured hams on the basis of enzymatic activity of cathepsin B of raw hams is expected to be very limited.     

Effect of high hydrostatic pressure pretreatment on drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera (Aloe barbadensis Miller) gel

The effect of High Hydrostatic Pressure (HHP) and other pretreatments on the drying kinetics, antioxidant activity, firmness and microstructure of Aloe vera gel was investigated during convective drying at 70 °C. The pretreatments analyzed were high hydrostatic pressure, blanching, enzymatic and microwaves. Simulation of drying curves was studied through the application of several mathematical models such as Newton, Henderson and Pabis, Page, Modified Page, Wang and Singh, and Weibull. Among them, the Weibull model provided the best fit for the experimental data. All pretreatments increased the water diffusion coefficient compared to the control sample. Microwaves followed by HHP presented the fastest drying rates. All pretreatments modified the microstructure and hence the texture of the product. HHP and microwaves increased firmness while blanching and enzymatic treatments produced a softer final product. Blanching, microwaves and HHP enhanced A. vera antioxidant activity. However, the HHP pretreated samples showed the highest antioxidant activity compared to the rest. Based on these results, HHP together with convective drying offers the chance of producing dried aloe with high antioxidant attributes.     

Effect of chloride salt mixtures on selected attributes and mineral content of fermented cracked Aloreña olives

Sodium chloride is essential in table olive fermentation, storage and packing to guarantee safety and flavor. However, consumers are progressively concerned about sodium intake. In this work, the effect of selected attributes and mineral contents of fermented cracked Aloreña olives as a function of different chloride salt mixtures were studied, using a simplex lattice design with constrains (NaCl + CaCl₂ + KCl = 0.110 kg/l). The best fruit colour was observed at half proportions of KCl and NaCl or CaCl₂; optimum firmness was around the centre of the triangular coordinates but close to the line connecting CaCl₂ and NaCl vertexes; and the best overall quality was obtained in the 0.037 kg/l NaCl and 0.073 kg/l KCl mixture. The concentrations in the fermented olive flesh of the involved elements depended on their initial levels and on the CaCl₂ × NaCl and CaCl₂ × KCl interactions. Results demonstrate that sodium chloride can be replaced in table olives, at least partially, with potassium or calcium chlorides.