ANALYSIS OF VOLATILE ORGANIC COMPOUNDS TO PREDICT APPLE RIPENING AND SHELF-LIFE

Abstract

Apple fruits have enormous nutritional value. Fruit ripening is a complex and dynamic process that affects the quality, taste, and aroma of fruits. Ripeness is an important factor in fruit quality control, as it determines the market value and consumer acceptance of the fruit. However, assessing fruit ripeness can be challenging, as it requires subjective methods, such as visual inspection, palpation, and taste testing. Moreover, these methods can be destructive, time-consuming, and unreliable, as they are affected by factors, such as experience, environmental conditions, and fruit variability. The VOC profiling of three apple cv. ‘Golden Delicious’, ‘Red Delicious’ and ‘Shireen’ five different ripening stages (RS1. RS2, RS3, RS4 and RS5) were analyzed by solid phase microextraction and gas chromatography-mass spectrometry (SPME-GC-MS). Each cultivar contain fifteen VOCs biomarkers contributed a lot in the discrimination of the different ripening stages as those VOCs showed a strong correlation between the change in their concentrations and the ripening time point. Those VOCs were considered as a biomarker for further shelf life prediction and Fruit Fruit nose sensor for the non-invasive identification of the ripening and quality of ‘Golden Delicious’, ‘Red Delicious’ and ‘Shireen’ apples. Cold storage may trigger an alteration in the non-volatile and volatile components of apple fruits. This study aimed to evaluate the time-course changes in the metabolite composition in terms of the non-volatile and volatile components of apple cv. Golden Delicious under low-temperature storage conditions. Time-course changes in the metabolite composition of apples during cold storage at 4oC were evaluated by gas chromatography-mass spectrometry (GC-MS) based metabolite profiling at six different post-harvest storage time points (0, 15, 30, 45, 60, and 90 days). The variations in the metabolic profiles were monitored mainly focusing on primary metabolites (organic acid, sugar, sugar alcohol, amino acids, and fatty acids) providing nutrition and taste, as well as volatile components that contributes to the fruit aroma. Changes in the secondary metabolite profile were investigated by high-performance liquid chromatography analyses. Significant changes in the physicochemical properties and compositions of the primary metabolites, secondary metabolite, and volatile organic compounds (VOCs) were observed in Golden Delicious apples kept under low temperature storage. Partial least squares discriminant analysis of VOCs emitting from the six storage time points identified 13 shelf-life biomarker VOCs, which can discriminate between the duration of cold storage of apples. Volatile components (VCs) can be used as a non-invasive biomarker to predict the shelf-life and quality attributes of apples during postharvest storage at low temperature (4oC). In this work, the VC profile of intact ‘Red Delicious’ apple at five postharvest storage stages (0, 15, 30, 45, and 60 days) was established using gas chromatography–mass spectrometry analyses. VC profile identified a total of 36 VCs. Then by combining GC-MS-based volatilomics data together with PLS-based multivariate statistical analyses and BP-ANN-based machine learning tool, biomarker volatiles were identified. Those biomarker volatiles were used for the non-destructive prediction of fruit shelf-life and quality attributes. Our study clearly demonstrated that, by using quantitative data of biomarker volatiles, both PLS models can be used successfully to predict the shelf life of ‘Red Delicious apple’ under storage conditions. Volatiles such as propyl hexanoate, propyl 2-methylbutanoate, 2-methylbutyl propionate, ethyl hexanoate, butyl acetate, comes out as best biomarker for shelf-life prediction by PLS model. Another BP-ANN model was used with 10 biomarker volatiles for the accurate prediction of three important quality attributes, such as sugar, TSS and firmness. This will ensure better fruit quality and higher economic returns. The optimum organoleptic quality and shelf life of apples are obtained by harvesting them at the proper stage of ripening. Alpha-farnesene was the best analyte to follow the ripening changes in the tiny amount compared to the other VOCs, thus we selected it for further study as a potential biomarker. We developed portable optical scanning equipment that includes a salkowaski test for the digital quantification of important plant volatiles. Our fruit ripening E-Nose-based VOC-sensing technology employs colorimetrically, which produces remarkable detection sensitivity. It is selective for the farnesene with the Salkowski test reagent. Additionally, we showed that even when operating under challenging circumstances, our fruit nose sensor is reliable and reproducible in signal reading. Additionally, the sensor is expected to cost only 25 rupees per test, and the fruit ripening E-Nose costs around $30, which is a lot less money than commercial fruit nose sensors. The two primary aspects of this work's invention are as follows: first, this gadget can determine an apple's maturity stage, including NR (close to ripe, which indicates that the fruit is not yet ready for harvesting), FR (full ripe, which indicates that the fruit is suitable for harvesting), and OR (overripe, apples crossed the harvesting stage and will have short shelf-life). The system also forecasts some qualities of apple fruits, including hardness, TSS levels, and sugar content. The cultivars of ‘Golden Delicious’, ‘Red Delicious’, and ‘Shireen’ apples all be handled by the fruit-nose sensor with ease. This work utilised signal colour variations instead, which are simple to detect and quantify using inexpensive sensor hardware. On the other hand, there aren't many applications for gas detection that have been shown off, and there aren't any sensor systems for detecting apple fruit ripening in the field that was precise, colorant-based, quick, or non-invasive yet either. An environment for testing that is stable and repeatable is provided by the use of glass vials to collect volatile gas from non-detached samples. The quickest sample-to-result time could be less than 30 min for field testing. This design may be more advantageous than other E-Nose senor in terms of long-term monitoring of ripening fruits and analysis of the larger numbers of samples to more efficiently detect the ripening status of apple fruit in fields.