ReviewCleaner quality control system using bioimpedance methods: a review for fruits and vegetables
Graphical abstract
Introduction
Nowadays the trend is a healthier diet, so decreasing the intake of meat and dairy, and increasing fish (Sánchez-Muros et al., 2014) and seasonal fruit and vegetable products, are needed (López et al., 2015). Due to the very rapid development of technology as well as the increased demand of quality food, vegetables and fruits are more under spotlights for enhancing their healthy characteristics. Engineering practices should be revised continuously to address methodological innovations (Halbe et al., 2015) to reach quality standards production at technical levels. Quality is a term that is frequently used as a multilayered expression that can be usually neutrally or positively occupied (Butz et al., 2005). The origin of the term “Quality” is the Latin word “Qualitas” pointing to the nature or property attribute of the object. Because quality exists only in the minds of the consumer, it may also be defined as the result of all interactions of this consumer (or observer) with a product and its circumstances, the market and its circumstances, and the social situation of the consumer himself. Site measurement of the weight of fruits on the harvester may enhance their market value and present a significant advance in precision agriculture (Qarallah et al., 2008). Thus, quality literally reflects the “acceptability” when speaking in the minds of the consumers. In the agricultural field, optical impression is an essential criterion for a product to be judged as “fresh”, and this implies necessarily that special expectations about its internal components are created (Chilar et al., 1987).
Quality of food can be determined through four main factors, as by Bourne classification (Bourne, 2002). First of all, the appearance that involves the shape (Clement et al., 2013), size, color and brightness (Clement et al., 2012). Second, comes the flavor which includes the smell and the taste. The texture of the product comes third by considering the physical stimulus that born through the part of the body contact with food; this phenomenon is known as the “sense of touch”. Last but not least the amount of macronutrients (carbohydrates, lipids and proteins) and micronutrients (minerals, vitamins and fibers) which are combined and referred to as the nutrition factor. Apart from some other characteristics, the freshness of vegetables is determined considerably by the water content and the concentration of valuable constituents whereby these items often change rapidly during postharvest decay (Butz et al., 2005).
Seeking an efficient treatment and straightforward marketing, for the producers of agricultural products, the concept of quality involves the cultivation of specific factors such as resistances and potential of yield, as well as uniformity of the harvest products when it comes to size, shape and color. The set of processes occurring from the stage of growth to the development of the fruit, known as maturity, is highly interesting for the producers since it reflects the point of maximum quality (Watada et al., 1984). A major indicator of the maturity in fruits is the color, except for the fruits that change color after harvest, this factor becomes less deciding (López, 2003). From the marketing side, merchant is also interested in freshness and durability, whereas the processing industry has to contemplate the suitability for processing and preservation. Finally, the consumer should buy the produce in the consciousness to receive tasty commodities with nutritionally valuable and health-promoting contents. The consumer decision to purchase the fruit is essentially directed by the appearance of the product that is considered as primary attribute evaluating the first visual contact, and it is followed by texture and flavor (Mitcham et al., 1996).
From electrical perspective, impedance spectrometry is a simple low-cost technique that has a lot of potential to characterize fruits non-destructively in vivo, at the site of harvest and storage. By studying the passive electrical properties of the fruit or vegetable under measure, their impedance can be determined, using a multifrequency impedance analyzer by observing the electrical response of their tissue to the passage of the external power (Ortiz Meléndez, 2014).
In order to increase consciousness of quality in the food and health sector, it is strongly needed to enhance the research activities regarding a defined quality control and its preservation during marketing; but above all, it is essential to explore the possibilities of evaluating quality parameters of agricultural products and of integrating this into control processes. Applying bioimpedance spectroscopy on fruits and vegetables seeking better quality control constitutes an integration management system of high relevance with the journal scope. Such non-destructive studies aiming to avoid and reduce deficiencies in the agricultural production don't hold positive effects only on public health but have great economical impact on the consumption control as whole. Linking environmental impact directly with kind of economic performance reflects the sustainability of an eco-efficient system (Müller et al., 2014). Thus, such a qualified yield based on electrical engineering advances contributes to a cleaner environment and forms a life cycle assessment with healthier performance.
This being said, this paper is the outcome of an intensive review on bioimpedance measurements effected over several horticultural products detecting changes in various quality parameters listed above. Bioimpedance, being an electrical non-destructive characterization tool, contributes as an essential management system in enhancing the quality of fruits and vegetables.
Section snippets
Academic literature review method
In the review presented, the experiments considered for each fruit and vegetable are all peer-reviewed papers from international journals and conference proceedings. The review is organized to highlight the value of quality food products to what it brings at the consumers health level. Defining the concept of quality drives automatically to enlighten the concept of electrical characterization and particularly impedance spectroscopy. The review covers all main definitions, mechanisms and
Bioimpedance measurement
From the harvest side to reach the cool storage, the characterization of fruits has been an important issue in the automatic sorting of fruits. These characterization techniques can be divided between non-destructive and destructive techniques. It has been known that automatic sorting of fruit today, accompanied with the help of robotic arms follow preferably non-destructive fruits techniques in contrast with what used to happen earlier.
This review focuses on the newly non-destructive
Bioimpedance applications data
In the goal of elaborating a cleaner production control, the review focuses on the newly non-destructive techniques applied on a variety of fruits and vegetables along with their proper description. Old destructive experiments will be resumed in the analysis section later for purposes of comparison with the newly applied non-destructive techniques.
Results and discussions
As mentioned earlier, for analysis purposes, Table 2 presents, in chronological order, different vegetables and fruits on which destructive bioimpedance measurement were applied, with their appropriate authors, objective of the study and their principal conclusions.
With destructive methods, the following products strawberry, Kiwi, kaki and nectarine were measured for the same frequency range going from 50 Hz to 1 MHz. While the avocado and pear were measured under a frequency ranging 214 Hz to
Conclusions
This review summarizes the potential of bioimpedance spectroscopy to detect electrical characteristics in fruit and vegetables which will enhance the quality production parameters. It offers a comprehensive overview of bioimpedance techniques focussed on electrical characteristics of vegetables and fruits. For the cleaner control elaboration, non-destructive techniques for different species are presented and the wide variety of equipment available in the market for impedance measurements in the
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