ABSTRACT : View final version online for free until July 3, 2015, on ScienceDirect: http://www.sc... more ABSTRACT : View final version online for free until July 3, 2015, on ScienceDirect: http://www.sciencedirect.com/science/article/pii/S0168169915001209 Abstract: To meet consumer demands, the need for quick and accurate methods for quality assessment of fresh fruits is increasing constantly. This study presents a comparison of three different models for mass estimation of mango fruits (cv. ‘Nam Dokmai’) calculated by simple linear regression (SLR), multiple linear regression (MLR) and artificial neural network (ANN). Three dimensions (length, maximum width, and maximum thickness) were manually measured and included as parameters for model building. Calibration and validation were carried out on independent data sets with 820 samples (2010–2012) and 61 samples (2014), respectively. This allowed it to establish a high-performance model that can be used for further mass-size estimation in a machine-vision system. For the SLR, an existing equation for mass estimation was modified to calculate an adjusted coefficient for accurate mass estimation. A MLR model was proposed to obtain the intercept, the slopes of the three parameters length, maximum width and maximum thickness as well as the random error. In addition, an ANN model was used as it allows the network to learn linear and nonlinear relationships between inputs and outputs. Performance evaluation of three different models was based on a compilation of different statistical error parameters and goodness-of-fit measures and the outcomes of the models were compared. ANN was found to be the most accurate and robust model for mass estimation with a root mean squared error (RMSE) of 6.55 g, mean absolute percentage error (MAPE) of 1.62%, and coefficient of efficiency (E) of 0.99 after validation. Therefore, it can be applied for mass estimation of mango fruits with highest accuracy and success rate of 96.7% compared to the other models in this study.
2011 Louisville, Kentucky, August 7 - August 10, 2011, 2011
ABSTRACT Bell pepper (Capsicum Annuum L.) is a fruit rich in pigments such as chlorophylls, antho... more ABSTRACT Bell pepper (Capsicum Annuum L.) is a fruit rich in pigments such as chlorophylls, anthocyanins and carotenoids which is dried to produce spices. The aim of this research was to test the feasibility of laser light for predicting moisture content changes during drying. Green (532 nm) and red light (635 nm) were applied to the pepper tissue at different drying conditions. Detection of discoloration during the drying process using a CCD camera was also investigated by comparing of the RGB color values with CIE L*, a*, b* color coordinates measured by a Minolta Colorimeter. Cross validation analysis showed the highest correlation between laser light at wavelengths of 532 and 635 nm for yellow pepper (R=0.93). On the contrary, the behavior of green and red light in samples with corresponding colors raises questions for the ability to predict moisture content changes. Additional studies are still required to determine the suitability of digital images as an alternative method to the colorimeter for the evaluation of color change during drying of bell pepper. The described optical technology may represent a basis for future in-line quality monitoring of drying processes.
This study explored the effects of calcium chloride (CaCl2) and calcium lactate (Ca-L) pretreatme... more This study explored the effects of calcium chloride (CaCl2) and calcium lactate (Ca-L) pretreatments prior to osmotic dehydration on physicochemical characteristics and consumer acceptance of dried papaya. Three different calcium concentrations [0.5, 1.5 and 2.5% (w/v)] were applied to samples before they were soaked in a 30 °Brix sucrose solution and subsequently dried at 70 °C. The results showed that the dried samples treated with calcium exhibited significantly lower moisture content, water activity, apparent density and shrinkage, while volume was higher when compared to the control. Calcium applications did not obviously influence sugar content of samples and maintained the quality of dried papaya in terms of colour and textural characteristics. Calcium chloride at 2.5% (w/v) was found to particularly impart undesirable bitterness to the dried papaya. In contrast, using 2.5% (w/v) Ca-L provided the best acceptance scores. Thus, the use of Ca-L could be an alternative to CaCl2 in the pretreatment of fruits prior to drying as it offers improved quality.
International Journal of Food Science & Technology, 2011
ABSTRACT Litchi is a significant cash crop in Thailand, but marketing is constrained by the peris... more ABSTRACT Litchi is a significant cash crop in Thailand, but marketing is constrained by the perishable nature of the fruit. Drying can extend the shelf life of the fruit; however, in Thailand drying technology is still in its early stages of development. With the aim of improving locally available small-scale drying equipment, the performance of a litchi batch-dryer by a farmers’ cooperative near Chiang Mai was studied. Drying conditions, energy consumption and product quality were monitored over three trials. Energy performance was analysed using instantaneous indices, leading to suggestions for possible design-modifications. About 29.8% of the heat input was used for moisture evaporation, 38.4% was lost via unsaturated exhaust air and 17.6% was lost to the ambient environment. An optimum air flow rate, one that minimises exhaust heat losses without increasing the drying time, was calculated. Temperature and air flow within the drying chamber varied, resulting in a non-uniform batch. To improve performance, a new design for the drying chamber air inlet is recommended.
Papaya has been identified as a valuable source of nutrients and antioxidants, which are benefici... more Papaya has been identified as a valuable source of nutrients and antioxidants, which are beneficial for human health. To preserve the nutritional properties after drying, appropriate storage specifications should be considered. This study aimed to investigate the quality and stability of air-dried papaya in terms of quality dynamics and behavior of bio-active compounds during storage for up to 9months in two packaging materials: aluminum laminated polyethylene and polyamide/polyethylene. Samples with moisture content (MC) of 0.1328gg(-1) and water activity (aw) of 0.5 were stored at 30°C and relative humidity (RH) of 40-50%. The MC, aw, degree of browning (DB) and 5-hydroxymethylfurfural (HMF) content were found to notably increase as storage progressed. On the contrary, there was a significant decrease in antioxidant capacity (DPPH, FRAP and ABTS), total phenolic (TP) and ascorbic acid (AA) contents. Packaging in aluminum laminated polyethylene under ambient conditions was found to better preserve bio-active compounds and retard increases in MC, aw and DB, when compared to polyamide/polyethylene.
This article presents the thin-layer drying of peeled litchi, which was conducted under controlle... more This article presents the thin-layer drying of peeled litchi, which was conducted under controlled conditions of temperature and relative humidity. It was observed that the drying temperature has some influence on the drying rates of peeled litchi, so that the higher the temperature the less the drying time. Eight different thin-layer models were fitted to the experimental data of peeled
ABSTRACT : View final version online for free until July 3, 2015, on ScienceDirect: http://www.sc... more ABSTRACT : View final version online for free until July 3, 2015, on ScienceDirect: http://www.sciencedirect.com/science/article/pii/S0168169915001209 Abstract: To meet consumer demands, the need for quick and accurate methods for quality assessment of fresh fruits is increasing constantly. This study presents a comparison of three different models for mass estimation of mango fruits (cv. ‘Nam Dokmai’) calculated by simple linear regression (SLR), multiple linear regression (MLR) and artificial neural network (ANN). Three dimensions (length, maximum width, and maximum thickness) were manually measured and included as parameters for model building. Calibration and validation were carried out on independent data sets with 820 samples (2010–2012) and 61 samples (2014), respectively. This allowed it to establish a high-performance model that can be used for further mass-size estimation in a machine-vision system. For the SLR, an existing equation for mass estimation was modified to calculate an adjusted coefficient for accurate mass estimation. A MLR model was proposed to obtain the intercept, the slopes of the three parameters length, maximum width and maximum thickness as well as the random error. In addition, an ANN model was used as it allows the network to learn linear and nonlinear relationships between inputs and outputs. Performance evaluation of three different models was based on a compilation of different statistical error parameters and goodness-of-fit measures and the outcomes of the models were compared. ANN was found to be the most accurate and robust model for mass estimation with a root mean squared error (RMSE) of 6.55 g, mean absolute percentage error (MAPE) of 1.62%, and coefficient of efficiency (E) of 0.99 after validation. Therefore, it can be applied for mass estimation of mango fruits with highest accuracy and success rate of 96.7% compared to the other models in this study.
2011 Louisville, Kentucky, August 7 - August 10, 2011, 2011
ABSTRACT Bell pepper (Capsicum Annuum L.) is a fruit rich in pigments such as chlorophylls, antho... more ABSTRACT Bell pepper (Capsicum Annuum L.) is a fruit rich in pigments such as chlorophylls, anthocyanins and carotenoids which is dried to produce spices. The aim of this research was to test the feasibility of laser light for predicting moisture content changes during drying. Green (532 nm) and red light (635 nm) were applied to the pepper tissue at different drying conditions. Detection of discoloration during the drying process using a CCD camera was also investigated by comparing of the RGB color values with CIE L*, a*, b* color coordinates measured by a Minolta Colorimeter. Cross validation analysis showed the highest correlation between laser light at wavelengths of 532 and 635 nm for yellow pepper (R=0.93). On the contrary, the behavior of green and red light in samples with corresponding colors raises questions for the ability to predict moisture content changes. Additional studies are still required to determine the suitability of digital images as an alternative method to the colorimeter for the evaluation of color change during drying of bell pepper. The described optical technology may represent a basis for future in-line quality monitoring of drying processes.
This study explored the effects of calcium chloride (CaCl2) and calcium lactate (Ca-L) pretreatme... more This study explored the effects of calcium chloride (CaCl2) and calcium lactate (Ca-L) pretreatments prior to osmotic dehydration on physicochemical characteristics and consumer acceptance of dried papaya. Three different calcium concentrations [0.5, 1.5 and 2.5% (w/v)] were applied to samples before they were soaked in a 30 °Brix sucrose solution and subsequently dried at 70 °C. The results showed that the dried samples treated with calcium exhibited significantly lower moisture content, water activity, apparent density and shrinkage, while volume was higher when compared to the control. Calcium applications did not obviously influence sugar content of samples and maintained the quality of dried papaya in terms of colour and textural characteristics. Calcium chloride at 2.5% (w/v) was found to particularly impart undesirable bitterness to the dried papaya. In contrast, using 2.5% (w/v) Ca-L provided the best acceptance scores. Thus, the use of Ca-L could be an alternative to CaCl2 in the pretreatment of fruits prior to drying as it offers improved quality.
International Journal of Food Science & Technology, 2011
ABSTRACT Litchi is a significant cash crop in Thailand, but marketing is constrained by the peris... more ABSTRACT Litchi is a significant cash crop in Thailand, but marketing is constrained by the perishable nature of the fruit. Drying can extend the shelf life of the fruit; however, in Thailand drying technology is still in its early stages of development. With the aim of improving locally available small-scale drying equipment, the performance of a litchi batch-dryer by a farmers’ cooperative near Chiang Mai was studied. Drying conditions, energy consumption and product quality were monitored over three trials. Energy performance was analysed using instantaneous indices, leading to suggestions for possible design-modifications. About 29.8% of the heat input was used for moisture evaporation, 38.4% was lost via unsaturated exhaust air and 17.6% was lost to the ambient environment. An optimum air flow rate, one that minimises exhaust heat losses without increasing the drying time, was calculated. Temperature and air flow within the drying chamber varied, resulting in a non-uniform batch. To improve performance, a new design for the drying chamber air inlet is recommended.
Papaya has been identified as a valuable source of nutrients and antioxidants, which are benefici... more Papaya has been identified as a valuable source of nutrients and antioxidants, which are beneficial for human health. To preserve the nutritional properties after drying, appropriate storage specifications should be considered. This study aimed to investigate the quality and stability of air-dried papaya in terms of quality dynamics and behavior of bio-active compounds during storage for up to 9months in two packaging materials: aluminum laminated polyethylene and polyamide/polyethylene. Samples with moisture content (MC) of 0.1328gg(-1) and water activity (aw) of 0.5 were stored at 30°C and relative humidity (RH) of 40-50%. The MC, aw, degree of browning (DB) and 5-hydroxymethylfurfural (HMF) content were found to notably increase as storage progressed. On the contrary, there was a significant decrease in antioxidant capacity (DPPH, FRAP and ABTS), total phenolic (TP) and ascorbic acid (AA) contents. Packaging in aluminum laminated polyethylene under ambient conditions was found to better preserve bio-active compounds and retard increases in MC, aw and DB, when compared to polyamide/polyethylene.
This article presents the thin-layer drying of peeled litchi, which was conducted under controlle... more This article presents the thin-layer drying of peeled litchi, which was conducted under controlled conditions of temperature and relative humidity. It was observed that the drying temperature has some influence on the drying rates of peeled litchi, so that the higher the temperature the less the drying time. Eight different thin-layer models were fitted to the experimental data of peeled
Image processing techniques are increasingly applied in sorting applications of agricultural prod... more Image processing techniques are increasingly applied in sorting applications of agricultural products. This work has assessed the use of image processing for inspecting surface color of two Thai mango cultivars. A computer vision system (CVS) was developed and experiments were conducted to monitor peel color change during the ripening process. Conversion of RGB to CIE-LAB values was done via image processing and prediction models were developed to estimate color parameters from CVS data. Performance evaluations showed insufficient prediction for L values (R2 = 0.42-0.58), but better results for A and B values (R2 = 0.90-0.95 and 0.80-0.82, respectively). Compared to the calculated color values hue angle and chroma, a yellowness index computed from intermediate XYZ values was found to be much more adept at accurately predicting peel color from CVS data. Correlations were strong for both cultivars (R2 = 0.93 for ‘Nam Dokmai' and R2 = 0.95 for ‘Maha Chanok'). Results from classification analysis indicated satisfactory results for classifying fruits according to ripeness based on yellowness. Success rates of true positives in the categories unripe, ripe and overripe ranged 72{\%}-92{\%} for ‘Nam Dokmai' and 98{\%}-100{\%} for ‘Maha Chanok'. Therefore, it was shown that the CVS was capable of producing accurate color values for the two mango cultivars investigated. The findings of this study can be incorporated for development of a robust system for quality prediction and establishment of a CVS for automatic grading and sorting of mangos.
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