Non-destructive evaluation of apple maturity using an electronic nose system

Abstract

The apple growers and packaging houses are interested in methods that can evaluate the quality of apples non-destructively. Harvested fruits are a mixture of immature, mature, and over mature fruits, thereby posing a great problem in deciding their end use and storage time. It is expected that the technique developed from the present project could be effectively used to classify the harvested fruit into immature, mature and over mature apples, rapidly and nondestructively. It would also help the growers to predict the optimum dates to harvest the fruits.York and Gala were the varieties of apples that were used in this study and were obtained from Virginia Tech College of Agriculture and Life Sciences Kentland Farm. Apples were harvested at different times resulting in different maturity groups (immature, mature and ripe).Gala apples were harvested on three dates with an interval of 10 days, while York apples were harvested on four dates with an interval of 14 days. They were stored at 0 o C until sampled. For each harvest date, the experiments were conducted in two sets (10 each) on two consecutive days. First the ethylene levels were measured, followed by gas chromatograph and electronic nose. Then the maturity indices were measured.Three maturity indices, starch index, firmness and soluble solids were used as the three variables for the statistical analysis to identify and categorize the fruits into three maturity categories referred as immature, mature and over mature fruits. Apples were also categorized into three maturity groups based on the emanation levels of the aroma compounds evolved from the fruits. Then electronic nose sensor responses were categorized into the above maturity categories, and their effectiveness was determined using a statistical procedure called Discriminant Analysis (DA). From the DA cross validation results the correct classification percentage for Gala andYork apples into maturity groups was 95%. The Electronic nose sensor's effectiveness to categorize the same observations based on sensor responses in to the above classified maturity categories was 83% correct in case Gala apples and 69% for York apples. The EN sensors response data were analyzed by the EN system software and the correct classification percentage for Gala was 83% and for York was 81%. Aroma-based categorization for Gala apples was 100% correct, while the electronic nose for the same analysis was 80%.Based on the three physical parameters, an objective evaluation of maturity could be accomplished. Principal Component Analysis, Canonical Discriminant Analysis and DA results demonstrated that the electronic nose could be used to classify apples into three identified maturity-based groups. The EN sensors (Gala apples), could also classify the apples into aromabased categories. Thus, it can be concluded that the EN system holds promise as non-destructive evaluation technique to determine the maturity of an apple.iv Acknowledgements

Optimal Illumination-Detection Distance and Detector Size for Predicting Braeburn Apple Maturity from Vis/NIR Laser Reflectance Measurements

“…The maturity of apples indicated by the Streif index has already been predicted directly in other studies using electronic nose measurements (Pathange et al 2006;Saevels et al 2003) and optical measurement techniques like Vis/ NIR spectroscopy (Peirs et al 2001) or time resolved spectroscopy (Vanoli et al 2011). Optical techniques show advantages in automated mechanical harvesting as the apple maturity can be detected under field conditions in a fast, reliable and non-destructive way.…”

Sensors for product characterization and quality of specialty crops—A review

“…Fruit aroma, or any other volatiles related to the process, are potential indicators of the physiological condition of the fruit, which can be used to develop consistent and reproducible non-destructive techniques to evaluate fruit quality from harvest to consumer (Pathange et al, 2006).…”

“…The technique of global aroma analysis by means of EN has been considered very promising during the last 15 years as a non-destructive tool to evaluate fruit quality, as shown in the comprehensive review of Peris and Escuder-Gilabert (2009), from different points of view: shelf-life investigation to assess "Jonagold" (Saevels et al, 2003) and "Pinklady" (Brezmes et al, 2001a) apples quality during shelf-life, to monitor tomato fruit with different storage time (Gómez et al, 2008); harvest date determinations in mandarins (Gomez et al, 2006), apples (Saevels et al, 2003) and mango fruit (Lebrun et al, 2008), to classify "Gala" apples at harvest in different maturity degrees (Pathange et al, 2006), faults detection as to detect freeze damage in oranges (Tan et al, 2005) or apples defects as mealiness and skin damage in "Cox" (di Natale et al, 2001) and "Red Delicious" apples (Li et al, 2007), and for blueberry fruit disease detection and classification (Li et al, 2010).…”

Electronic nose with polymer-composite sensors for monitoring fungal deterioration of stored rapeseed

“…The technique was developed at the end of the last century (Olsson et al, 2000;Oshita et al, 2006). At the current stage of evolution of sensor technology, a device like the e-nose offers new possibilities not only for assessment of grain quality but generally in food (Loutfi et al, 2015), cosmetic, or pharmaceutical industries, as well as in environment control and clinical disease diagnosis (Casalinuovo et al, 2006;Guz et al, 2015;Pathange et al, 2006;Peris and Escuder, 2009).…”