Volume 3 Special Issue 1 2009
New trends in postharvest management of fresh produce I

Guest Editor

Dharini Sivakumar

University of Pretoria, South Africa

CONTENTS AND ABSTRACTS

Elazar Fallik, Sharon Alkalai-Tuvia, Yaacov Perzelan (Israel) The Influence of Preharvest Practices and Postharvest Treatments on Sensory Characteristics of Fresh and Fresh Cut Produce (pp 1-6)

Full Text [PDF]

ABSTRACT

Invited Review: Observation of consumer expectations regarding food quality provides the basic for any successful food production and marketing. This is also true for fresh fruits and vegetables which are increasingly valued as an important part of the diet. Traditional quality evaluation of fruits and vegetables is associated, primarily, with appearance attributes, such as size, shape, surface color and defects; tactile characteristics, such as firmness or hardness; and internal quality attributes, such as sugar and/or oil content, vitamins and internal defects and disorders. However, sensory attributes play an important role in a consumer’s decision to purchase fresh or fresh-cut fruit or vegetables. Preharvest practices such as cultivation, growing system, soil type, and fertigation, as well as harvest practices, such as choice of the stage of maturity and postharvest treatments, such as controlled or modified atmosphere packaging, coating, and physical or physicochemical treatments may affect the sensory and flavour attributes of fresh and fresh-cut product. The goal of this mini review is to summarize the information that has been published during the last 4 years on preharvest practices and postharvest treatments that affect the sensory characteristics of fruits and vegetables, marketed as fresh, or fresh-cut products.

Satoru Kondo (Japan) Fruit Ripening and Characteristics Regulated by Physiologically Active Substances (pp 7-11)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: Fruit color and aroma volatile compounds are important factors that determine fruit quality. The effects of jasmonates (jasmonic acid and methyl jasmonate) on fruit color development differed between climacteric and nonclimacteric fruit. Jasmonates, and jasmonates combined with an ethylene action inhibitor stimulated greater anthocyanin accumulation in apples regardless of fruit growth stages. The expression of UDP-glucose:flavonoid 3-O-glucosyltransferase (UFGluT) anthocyanin biosynthetic gene was increased in the skin of fruits treated with jasmonates and these fruits also had much higher anthocyanin content than untreated controls. In contrast, jasmonates did not influence anthocyanin accumulation in sweet cherries. The impact of jasmonate application on volatile compound production was dependent on fruit ripening stage; jasmonates increased the volatiles in preclimacteric fruit, but decreased the volatiles in climacteric fruit. In addition, jasmonates influenced 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) and ACC oxidase (ACO) gene transcription. In pears (Pyrus communis L.), jasmonate application at the preclimacteric stage stimulated ethylene production and the expression of the ACS and the ACO messenger RNA (mRNA) levels. In contrast, the accumulation of ACS mRNA levels in fruit treated with jasmonate at the climacteric stage was low and ethylene production also decreased. Some types of physiologically active substances may play a protective role against chilling injury. For example, endogenous polyamines were linked to the degree of chilling injury in mangosteens. Additionally, EC₅₀ values of superoxide (O₂^-) and 1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity were also associated with the degree of chilling injury.

Clément Vigneault, Gaétan Bourgeois, Vicky Toussaint, Denis Charlebois, Denyse I. LeBlanc (Canada) Potential for Modelling Postharvest Quality of Fresh Fruit and Vegetables (pp 12-22)

Full Text [PDF]

ABSTRACT

Invited Review: For fresh fruit and vegetables, models that use temperature and relative humidity data measured throughout the cold chain and quality parameters measured at specific steps need to be developed to predict the produce quality that can be expected subsequently based on the environmental conditions. The development of such models requires data on physiological and microbial quality changes and on disease development in a wide variety of fresh fruit and vegetables as a function of time, temperature and relative humidity. Unfortunately, the availability of this type of data is relatively limited. One of the challenges in developing such models is defining the parameters that best describe the overall quality of fresh produce, given that the ideal parameters probably vary considerably depending on the type of produce. Associated with this is the challenge of finding the best tool for measuring the various aspects (physiological, microbial, pathological, etc.) of horticultural produce quality at any point along the field-to-fork continuum. Once these challenges have been resolved, systems could be developed to record ambient conditions (temperature and relative humidity) for each load of fresh produce and to use models to predict produce quality at various steps in the cold chain. Such systems could be used by producers, shippers, wholesalers and retailers to identify the optimum market for a particular load of fresh produce.

Sylvie Bureau (France) The Use of Non-destructive Methods to Analyse Fruit Quality (pp 23-34)

Full Text [PDF]

ABSTRACT

Invited Review: This article is divided into three parts. The first part, the most important one, deals with spectroscopic methods. Different regions of the electromagnetic spectrum are useful for fruit quality characterisation, in particular the visible and near-infrared regions. Concerning the visible one, studies have been carried out on apple, apricot, cherry, mango, peach, red table grape and tomato, when the near-infrared one has been used on apple, apricot, bayberry, citrus, kiwi, lemon, mango, peach, pear, red bell pepper and tomato. Results of other spectroscopic methods such as time-domain reflectance spectroscopy, multi- and hyperspectral imaging, fluorescence, nuclear magnetic resonance and magnetic resonance imaging were obtained on apple, grape berry, kiwifruit, mandarin, olive, papaya, peach, pear, plum and tomato. The second part concerns the studies of mechanical properties based on impact, acoustic and ultrasonic responses, which were developed and tested on apple, avocado, peach, pear, plum, tomato and watermelon. The third part presents the analysis of volatile compounds using the principle of electronic nose applied on apple, mandarin, peach, pear and tomato. According to the researched fruit quality traits, the adequate methods will be different for the assessment of colour, firmness, soluble solids or volatiles or for the detection of internal defects like brown heart. However, methods are developed to improve the fruit management and thus the general fruit quality for consumers.

Guglielmo Costa, Massimo Noferini, Giovanni Fiori, Patrizia Torrigiani (Italy) Use of Vis/NIR Spectroscopy to Assess Fruit Ripening Stage and Improve Management in Post-Harvest Chain (pp 35-41)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: Fruit “quality” is a concept encompassing sensory and mechanical properties, nutritive values, safety and defects. Fruit quality has declined, determining consumer dissatisfaction, largely due to the wrong harvest date; in addition, quality is badly defined since the parameters mainly considered are fruit size and skin color. Other attributes such as flesh firmness, sugar content, acidity and aroma, are perceived by the consumer as fruit global quality, are seldom considered by the farmer and by other individuals along the chain. Up to now, several studies have been carried out on fruit quality assessment by using traditional methods, which are affordable and fast, but do not consider other quality traits, as antioxidant power, aroma volatile emission, soluble sugars and organic acids content. The assessment of these parameters is time consuming and requires sophisticated equipments (i.e. HPLC, GC-MS). Moreover, destructive analyses can be performed only on a limited number of fruit. In recent years, extensive research has been focused on the development of non-destructive techniques for assessing internal fruit quality attributes allowing extending the assessment to a high number of fruit, to repeat the analysis on the same samples monitoring their physiological evolution, and to achieve real-time information on several fruit quality parameters at the same time. Among the non-destructive techniques, visible/Near Infra Red spectroscopy (vis/NIR) can be efficiently used for determining traditional fruit quality traits and concentration of the main organic acids and simple sugars. In addition, this technique allows defining a new maturity index strictly related to fruit ethylene emission and ripening stage. This index, called “Absorbance Difference” index (I_AD), which can be used for precisely determining harvest date, and for grouping harvested fruit in homogeneous classes which show a different evolution of the ripening syndrome during shelf-life.

Gustavo Polenta, Silvina Guidi, Claudia B. González (Argentina) The Application of Stress Treatments to Prevent the Development of Chilling Injury (pp 42-48)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: The control of temperature is the most important tool to avoid postharvest losses during the commercialization of fruits and vegetables. However, one problem usually found during the cold storage of commodities of tropical and subtropical origin is the development of physiological disorders collectively known as chilling injury. Although chilling injury can be prevented by maintaining the commodity at temperatures above the critical threshold, these temperatures cause a significant reduction in the shelf life. Different mechanisms have been proposed to explain both, the physical and biochemical bases of this phenomenon. Over the last years, the theory that oxidative stress may be involved in chilling injury has gained importance. According to this theory, an oxidative unbalance causing an excessive production of reactive oxygen species (ROS) would be the responsible for initiating the damage. Due to consumer concerns about the presence of chemicals in food, the use of physical techniques to avoid the development of chilling injury has been considered in many studies. According to this approach, the exposure of fruit to a stress may be used as a strategy to protect the commodity from the subsequent stress represented by the cold storage. From a biochemical point of view, evidence has been found that links this protective effect with the synthesis of a group of proteins known as heat shock proteins (HSP). The present review discusses the application of different stress treatments and the link between treatment application and HSP production. It is also discussed the role played by these protein in the protection and their potential use as biochemical markers to optimize the application of stress treatments.

Atef M. Elansari (Egypt) Design Aspects in the Precooling Process of Fresh Produce (pp 49-57)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: Temperature is the most single important factor which affects the storage life and the quality of fresh produce. The process of precooling is the removal of field heat as soon as possible after harvest since field heat arrest the deterioration and senescence process. The precooling process can be achieved via different methods. Forced air precooling is the most common technique and is adapted to many commodities. The classification of the forced air precooling process includes wet deck system and the dry coil technique. Wet deck system is a mechanism which provides air of low temperature and higher level of relative humidity which minimizes the weight loss of produce during the process of cooling. Dry coil system uses a direct expansion or secondary coolant coil sized to operate at a small temperature difference which will maintain a high relative humidity of the leaving air stream. An evaluation of both systems is presented through the current study that exhibits a description of the theory behind each system and its different components. Through this study, it is aimed to promote interest in precooling and encourage its use on a more widespread basis via the illustration of the different systems details.

Peter M. A. Toivonen (Canada) Benefits of Combined Treatment Approaches to Maintaining Fruit and Vegetable Quality (pp 58-64)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: The use of combined treatments to manage fruit and vegetable quality has been successfully applied in commercial practice, particularly for apples. This historical success is well documented. Unfortunately, the extensive use of combined treatments has not been adopted as a general principle to optimize produce quality, shelf life and safety. The thesis of this review is to discuss the basis for the effectiveness of combined treatment approaches and also discuss potential combined treatments that could significantly improve quality, shelf life and safety of a wide range of fruit and vegetable products. The use of molecular tools in the evaluation of synergistic physiological responses to combined treatments is also discussed.

Mª Alejandra Rojas-Graü, Robert Soliva-Fortuny, Olga Martín-Belloso (Spain) Edible Coatings as Tools to Improve Quality and Shelf-Life of Fresh-Cut Fruits (pp 65-72)

Full Text [PDF]

ABSTRACT

Invited Review: The current worldwide trend for a healthier lifestyle has triggered a rise in the demand and consumption of minimally processed commodities. Minimal processing operations need to be designed to protect fruits and vegetables against undesirable deleterious consequences of mechanical bruising such as browning, off-flavor development and texture breakdown. The search for methods to retard these negative effects is of great interest to all the stakeholders involved in the production and preservation of fresh-cut fruits. In this sense, edible coatings can be regarded as a strategy to maintain the original properties of intact vegetable tissues. The artificial semipermeable barrier, a polymeric edible coating, contributes to shelf-life extension by reducing migration of moisture and solutes, gas exchange, respiration and oxidative reactions, and the associated physiological disorders. Edible coatings can additionally act as carriers of antibrowning, antimicrobials, colorants, flavouring agents, nutrients or even probiotic organisms. Edible coatings may be composed of polysaccharides, proteins, lipids or a blend of these compounds. Their composition determines the barrier properties of the layer with regard to the transfer of moisture, gases, solutes and/or volatiles when applied on a food system. This review is an update about the state of the art of the development of edible coatings for fresh-cut fruits, as an alternative to the currently used preservation approaches.

Sean X. Liu (USA) Antimicrobial Coatings for Ensuring Safety of Fresh Produces (pp 73-79)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: Safety of fresh produce has been a perennial issue for the industry in the US despite tightening up regulations and implementing good manufacturing practice. The diversity of crops and labor-intense operations in the fresh produce production created a unique set of contamination routes that are not common in other food productions. New technologies and procedures have been developed to minimize the occurrences of in-production and shipping/distribution contaminations; however, in order to be effective, these proactive measures have to be implemented and practices consistently, which is not totally reassuring given the inevitability of human errors or occasional incompetence. As a consequence, in recent years, many researchers have been looking into development of passive protection of fresh produce from contamination through antimicrobial coatings of fresh produces or antimicrobial packaging materials that are used in fresh produce packing. This review critically examines the current technologies and developments in antimicrobial coatings and antimicrobial food packaging materials as a food safety tool for fresh produce producers.

Peter Sholberg (Canada) Control of Postharvest Decay by Fumigation with Acetic Acid or Plant Volatile Compounds (pp 80-86)

Full Text [PDF]

ABSTRACT

Invited Mini-Review: Stored pome, stone fruit and berry crops are subject to postharvest decay if they are not protected against plant pathogens such as Botrytis cinerea, Penicillium expansum, Monilinia spp., or Rhizopus stolonifer. Decay in table grapes primarily caused by B. cinerea is prevented by frequent fumigations with sulfur dioxide over the storage period. Although there are many advantages to the use of fumigation, it is used infrequently for the control of postharvest decay. Studies on a wide range of materials that can be used as fumigants has identified several that appear to be good candidates for use on berries, pome fruit, and stone fruit to prevent postharvest decay. In this review the focus is on two classes of naturally occurring chemicals used as fumigants, acetic acid and plant volatile compounds. The first that is discussed is acetic acid usually applied as a vapor of glacial acetic acid or occasionally as vinegar. Details are presented on its use for both large and small volumes of produce as well as its use as a sanitizing agent for storage rooms and bins. Results from several published studies with a wide range of crops and under various conditions of temperature and humidity are summarized. These results provide a good picture of the efficacy of AA vapor and its potential to cause phytotoxicity on certain crops. Two compounds identified as plant volatiles, hexanal and 2-trans-hexenal, are discussed in detail. In this review the emphasis is placed on their ability to inhibit postharvest pathogens and their use in an overall postharvest strategy in combination with 1-methylcyclopropene (1-MCP).

Nikos G. Tzortzakis (Greece) Essential Oil: Innovative Tool to Improve the Preservation of Fresh Produce – A Review (pp 87-97)

Full Text [PDF]

ABSTRACT

Invited Review: The degree of fresh produce safety obtained with the currently applied preservation methods seems to be not sufficient. The interest in the possible use of natural compounds to prevent microbial growth has notably increased in response to the consumer pressure to reduce or eliminate chemically synthesized additives in foods. This review examines the potency of essential oils as natural antimicrobial agents from plants, outlining the ranges of microbial susceptibility and factors affecting antimicrobial action. Moreover, an overview on the application of essential oils and/or components during storage on fruit quality related attributes as well as the impacts of essential oil on fruit coating edible films are demonstrated. Undesirable organoleptic effects can be limited by careful selection of essential oils according to the type/sensitivity of fresh commodity.