Authors: Swapnil D. Deshmukh
Department of Horticulture
Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola
Nowadays, people pay more and more attention to their health; fruit consumption is increasing due to not only their good taste and appearance, but also the health benefits from their vital components such as phenolics, polysaccharides, proteins, vitamins and minerals. Increasing consumer demand for high quality fruits has need to develop and adopt advanced technologies in post-harvest in terms of growing demand for quality products.
What is quality?
Quality means degree of superiority or excellence. A combination of characteristics attributes and properties that gives the value to human and enjoyments. Quality can be judge by five senses such as touch, sight, smell, taste and hearing. There are mainly two component of quality i.e. internal and external quality. Appearance, flavor, texture, nutritive value, and defect factors are generally recognized as the five quality factors of fruits.
What is non destructive method?
Today, measuring the quantity and quality of agricultural products without any injuries has a special position in post-harvesting and processing of agricultural products. In this regard, various non-destructive methods i.e. means quality evaluation of fruits without damaging fruit sample have been developed to detect internal properties of crops which many of them come to the practical application as used in the grading system. These methods are replacing traditional ones which were too expensive, unreliable, difficult and exhausting. On the other hand, the power of human visual perception is too limited because of the human narrow band of the electromagnetic spectrum which cause the human decision with errors and even impossible about identifying the quality factors such as flavour in fruits, the amount of nutrients, texture and internal injuries, near about all physico-chemical properties and defects are judged by these methods.
Why nondestructive methods?
The first and most important reason for using nondestructive method is export rejection. If growers cannot fulfill the quarantine needs and meet their quality requirement, the export consignment may reject. From consignment randomly a sample of fruit is taken to estimate the quality of batch, but the sample may not ensure the quality of whole batch. Other reasons are sample not destroyed, quick and almost instantaneous, simultaneously determination of many parameters, online application for bulk handling etc.
Non destructive methods –
In recent years, on one hand, nondestructive methods of fruit quality assessment have get momentum; on the other hand, considerable assay have been made to expand these nondestructive methods. Most of these methods are based on optical, vibrational, transmission, an electrical etc. characteristic, which is subsequently correlated with various physicochemical quality parameters.
- Near Infrared Spectroscopy – This method is no longer new; as it started in early 1970, just after some reports from America. The use of near-infrared spectroscopy as a rapid and often nondestructive technique for measuring the composition of biological materials has been demonstrated for many commodities. NIR as a nondestructive method for quality evaluation was started for the determination of sugar content in intact peaches, Satsuma orange and similar other soluble solids. Similarly, a nondestructive optical method for determining the internal quality such as sucrose content, sorbitol content, etc. It also use for grading citrus. Now various NIR spectrometers are available and are being used commercially. Some modifications in these available spectrometers, especially for holding the intact samples, are reported. It is based on electromagnetic radiation between visible wavelength and near infrared wavelength.
- X-ray and computerized tomography (CT) - X-ray imaging is an established technique to detect strongly attenuating materials and has been applied to a number of inspection applications within the agricultural and food industries. It is use for detection of bruises, water core and internal browning of apples, injury in papaya,maturity of peaches, freeze damage, dry sections and granulation in oranges, split pit in peaches and changes of peach internal structure during ripening.
- Ultrasonics and Acoustic Technology - Ultrasonic vibrations are above the audible frequencies (> 20 kHz). These waves can be transmitted, reflected as they interact with material. Wave propagation velocity, attenuation and reflection are important parameters used to evaluate the tissue properties of fruits. Through this technique ripening, firmness, maturity and other internal quality of fruits judged.
- Magnetic Resonance Imaging - The nuclear magnetic resonance technique, often referred as magnetic resonance imaging (MRI) involves resonant magnetic energy absorption by nuclei placed in an alternating magnetic field. The amount of energy absorbed by the nuclei is directly proportional to the number of a particular nucleus in the sample such as the protons in water or oil. There are many applications of NMR in agriculture. The simplest among them is the determination of seeds in orange, hallow heart, invisible bruises and translucency in over ripe pineapple, internal defects such as pits, dry regions, insect bodies air filled cavities etc., moisture and oil content in avocado.
- Fluorescence technique - Fluorescence refers to the property of light emitted by molecules of a particle when they are excited by photons. Short wavelength light such as UV light is used. The main application concern chlorophyll inflorescence. Eg. The chlorophyll fluorescence yield decrease with the ripening of papaya fruits. The instrument used named as portable fluorimeter. Also used to monitor grape maturation specially monitoring anthocynin accumulation.
- Electronic Nose - An Electronic Nose, also called an Artificial Olfactory System, is a machine that is designed to detect and discriminate among complex odors using sensor arrays. The sensor array consists of broadly tuned sensors that are treated with a variety of odor-sensitive biological or chemical materials. During ripening, fruits release volatiles in their surrounding atmosphere. On that basis maturity of fruits, monitoring fermentation process etc. can be judge. E-nose technique is simple, rapid and appears to be useful for discriminating fruits. It can detect chemicals in concentrations so small that people could not smell them. It can also detect chemicals that people find "odorless" and toxic in nature. It doesn't suffer from "odor fatigue," the human tendency to grow insensitive to smells that start small and increase gradually.
- Multispectral and Hyperspectral Imaging - Although digital color cameras (RGB) have been designed to acquire the same red, green, and blue bands captured by the human eye, the extraction of quality aspects corresponding to small contrasts in the images (bruises, ripeness stages, etc.) remains very challenging. These very small differences might be detected with more advanced image processing algorithms; however, the computation costs are very often too high for use in the food industry. Instead of trying to detect these very small differences, it might be more efficient to enhance the contrast. Multi- and hyperspectral imaging aims to combine the spectral information content and discriminating power of point spectroscopy with the spatial information content of machine vision. In multispectral imaging, images are acquired at a small number of wavebands (5--10), whereas many more wavebands are included in hyperspectral imaging.
Future tendencies –
- The future lies in the fusion of different methods to provide systems that gives more global information on each fruit.
- Integration of such methods should ensure consumer purchase quality product.
- There is a need for a concerted effort by various Indian research institutes for accelerated development of low cost non-destructive methods for quality evaluation of major fruits of India in order to have major share in the world market.
- NDT provides constitutional variation of the fruits. These are now available for many quality attributes.
- Their accurate quantification, leading to better characterization, improved quality and safety evaluation results.
- It is gaining a good momentum in the global horticulture industry. As these methods are instantaneous and can simultaneously determine many parameters, could be used for bulk handling of produce.
About Author / Additional Info:
I am currently pursuing Ph. D. in Horticulture from Dr. P.D.K.V.,Akola