Determination of surface color of‘all yellow’mango cultivars using computer vision

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.

Optimal physicochemical properties of dried litchis for Thai consumers

The litchi is a fruit essential for the economies of several Southeast Asian countries,but markets regularly reject it,mainly due to spoilage.Drying extends the shelf-life of litchis,but in Thailand the optimal characteristics of the dried product have not yet been determined.The purpose of this study was to determine the optimum physicochemical properties of dried litchis-those suitable for Thai consumers.The dried fruits were submitted to physicochemical measurement and consumer evaluation,with datasets subsequently integrated using circular ideal-point regression analysis.Response surface methodology was then used to predict the optimum physicochemical properties of the fruits.It was found that Thai consumer preferences with regard to dried litchis are for the fruits to be of golden-yellow color(L*ranging around 54;H ranging around 79°),to have a soft flesh(SMF ranging between 13 and 14 kN/100 g)and to have a sweet taste(TSS:TA ranging between 25 and 28).The results may be used in the future to prescribe pretreatments and drying conditions.

Generalized single-layer model for drying kinetics of unpeeled-longan

Dried longan fruit has become an important export product of Thailand.Knowledge about drying kinetics is essential to optimize the drying process.In this study,drying kinetics of unpeeled longan fruits was investigated by varying the parameters as follows:air temperature 50~90℃,relative humidity 4%~20%,air velocity 0.2~0.5 m/s,and size of the fruits.The drying curves of longan fruit,dried in a single layer,were strongly affected by the temperature of the drying air and fruit size but less dependent on relative humidity and velocity of the drying air.Eight single-layer drying models were selected from literature to identify suitable ones for fitting moisture ratio curves to data obtained from the drying experiments.Both,the proportional and exponential coefficient of drying time in the‘Page’model could be given in a generalized function for each of the investigated drying parameters.Moreover,the two coefficients could be correlated to all drying parameters simultaneously.This allowed establishing a generalized‘Page’model for estimating drying curves for any value of temperature,fruit size,relative humidity and air velocity within the range of performed experiments.The analysis also revealed an inner correlation between the two‘Page’coefficients,which opens new doors for further research on the application of the‘Page’model for describing drying processes.