Using innocative technologies to increase the quality of Hayward Variety
It is extremely important to establish the quality of cv Hayward fruits (Actinidia deliciosa A. Chev. C.F. Liang et A.R. Ferguson), commonly known as “kiwi fruit,” and the stage of ripeness reached at the time of harvest because they influence both the post-harvest progress of the fruits and their storage under refrigeration, and the development of the typical colour, flavour and fragrance that determine acceptability for consumers (Costa et al. 2011).
Hence, the stage of ripeness must be defined with the utmost precision by applying rigorous procedures, and adequate techniques and instruments for the purpose.
The standard that currently defines the marketing quality of the Actinidia cv Hayward fruits is established by European regulations.
Though some new indexes have been recently considered, namely the content of dry substance, colour of the seeds and the number of days to reach full bloom, the criterion used conventionally to determine the right degree of ripeness of Actinidia deliciosa fruits is the Refractive Index (expressed in °Brix). Changes in the soluble solid content of the fruits can be determined with common refractometers, which are simple instruments that are normally used both in the field and in the laboratory to monitor the progress of soluble solids and the achievement of required standards.
To be precise, the fruits are harvested when the soluble solid content reaches 6.2° Brix or more, while marketing requires a minimum soluble solid content of 9.5°Brix. Unfortunately, measurements recorded with the Refractive Index have some limits, including the need to destroy the sample of fruits examined, whose number is generally inadequate to appropriately describe the heterogeneous ripeness of the fruits in the batch considered.
In fact, it is common knowledge that, in the case of Actinidia deliciosa, fruits of a same plant present extensive variability (Smith et al., 1994), and that the external appearance of the fruit prevents any differences from being noticed (Costa et al. 2003). Hence, the scarce number of fruits considered in determining the Refractive Index prevents adequate evaluation of the ripeness of a general batch of fruits, both “on the field” and “in the warehouse.
This implies subsequent difficulties in managing the stored fruits (choice of the most appropriate technique – normal or controlled atmosphere) and marketing phases.
Aware of the agronomic and storage problems that can affect the quality of cv Hayward fruits, the “Kiwifruit of Italy” Consortium decided to pursue a rigorous programme dictated by cultivation and harvesting rules to improve and standardise the quality of fruits in order to ensure optimal management of the pre-harvest and post-harvest phases, and to make a success with a high quality product both on the Italian market and on foreign markets.
In fact, the Consortium is aware of the problems that arise already from the field, and which can influence the quality of the fruits both during harvest and post-harvest phases. Said aspects include, for example, the right choice of buds to be left during winter pruning, careful cross-pollination, nutrition techniques focused on maintaining a balance between the vegetal and production frameworks, etc. Extensive expertise in these fields is already part of the technical know-how possessed by the Kiwifruit of Italy Consortium, and will be stated and strengthened by drawing up dedicated production rules for cv Hayward fruit.
The Consortium is also aware of the negative consequences of “early harvesting” of the fruits in recent years in terms both of poor product quality – with a subsequent loss of image of kiwi fruit “Hayward” in the eyes of the customer – and difficulties related to the subsequent refrigeration of said fruits.
In fact, it is known that visual inspection does not detect any change in colour of the skin or softening of the pulp that might clearly reveal the stage of ripeness achieved at the time of harvest in order to guide the operators in defining the most appropriate time of harvest. Complicated procedures were drawn up in the past to solve issues related to the definition of the time of harvest. providing reliable indications required very long analysis periods and destruction of the sample.
Considering the limits of the methods currently proposed, of the characteristics of the information demanded today and the potential offered by certain new recent non-invasive instruments, the programme of the “Kiwifruit of Italy” Consortium particularly focuses on defining the best time of harvest, also taking into account agronomic management, cultivated area, and climate of the year.
The Consortium also proposes a new analysis procedure for Actinidia deliciosa fruits.
Said procedures can define the stage of ripeness of the fruits in real time and indicate the right time for harvesting, besides the variability of features presented by the batch considered. The “Kiwifruit of Italy” Consortium has, therefore, requested the department of Agricultural Sciences of the University of Bologna to define a sampling procedure in view of creating a database with extensiveinformation about the hayward product.
Said information will then be processed to develop a software that will be used by member companies of the Consortium itself to improve management of information and products, obtaining homogeneous high quality fruits that meet customer requirements both on Italian markets and, especially, on international ones.
This project exploits cutting edge instruments that do not require the sample of fruits considered to be destroyed, thus allowing a considerable increase in the number of items in the sample, and improving reliability of the tests required to define the quality of the fruits. visible light and near infrared spectroscopy (vis/NIR), a non- destructive technique that is currently available and that has been adopted for the past ten years, is particularly promising and, assuredly, the most tested (Nicolaï et al., 1994; Costa et al. 2003).
The procedure for sampling on the field, which underpins the Kiwifruit of Italy project, will, therefore, monitor the growth of the fruits in a combined manner with automatic callipers that can transmit data directly to an IT support, and ripeness with the vis/NIR simplified Kiwi-meter (Fig. 2) that reports ripeness with the IAd index.
Tests started this year and will continue for another 2 years. work will be carried out in partnership between the research group of prof.
Guglielmo Costa of the department of Environmental Sciences, University of Bologna, and the technical compartment of the Kiwifruit of Italy Consortium.
Massimo Noferini, Elisa Bonora, Guglielmo Costa Dipartimnento di Scienze agrarie, Scuola di agraria e medicina veterinaria, Alma Mater Studiorum, Università di Bologna