Emerging postharvest technologies to enhance safety and quality of fresh fruits. TECHNOPOSTHARVEST

Funder

Organizational Unit

Publications

Study of modes of action of the biocontrol agent metschnikowia and auensis pbc-2

Publication . Manso, Teresa; Vero, Silvana; González, M. Belén; Nunes, Carla; Nunes, Carla

Metschnikowia andauensis NCYC 3728 (PBC-2) is an effective antagonist against the postharvest pathogens Penicillium expansum, Botrytis cinerea and Rhizopus stolofiner on pome fruits, however its mode of action is unknown. The ability of this strain to produce inhibitory compounds in 4 distinct media (PDA, NYDA, YPDA, CJA) at 3 temperatures (1, 25, 30 ºC), was investigated. It was also assayed the competition for iron in media with different iron concentrations and characterized the capability of PBC-2 produce and secrete fungal cell wall lytic enzymes, like chitinase, protease, and glucanase in a culture media with fungal pathogen cell wall as unique carbon source. M. andauensis PBC-2 did not show any inhibition zone to cope pathogens in any of the tested media. The results obtained in this study suggest that the production and secretion of lytic enzymes is not the main or more important mode of action of the new biocontrol agent PBC-2, since the production of chitinase was observed only past 5 and 7 d of incubation, and the production of -1.3-glucanases and proteases was not observed, which mean that the biocontrol agent PBC-2 have more than one mechanism of action.

2010Book part

Open Access

X-ray computed (micro) tomography for detecting internal defects in fruit

Publication . Verboven, Pieter; Tri Ho, Quang; Herremans, Els; Lammertyn, Jeroen; Nicolaï, Bart; Nunes, Carla

Internal disorders in horticultural products are not revealed by external visual symptoms. Non-destructive and non-invasive monitoring techniques are required to detect the occurrence and investigate development of internal disorders. X-ray CT allows visualization and analysis of plant materials with a resolution down to a few micrometers, and without sample preparation or chemical fixation. X-ray tomography is based on X-ray radiography: an X-ray beam is sent on a sample and the transmitted beam is recorded on a detector. The level of transmission of these rays depends mainly on the mass density and mass absorption coefficient of the material. The resulting image is superimposed information (a projection) of a volume in a 2D plane. The classical way to retrieve 3D information is to perform a large number of radiographs while rotating the sample between 0° and 180°. The filtered back-projection algorithm can then be used to reconstruct the volume of the sample from these radiographs. Compared to two-dimensional radiography used in medicine and linescan radiography applied on grading machines, X-ray computer tomography (CT) is the most powerful technique from the horticultural research point of view, since two and three dimensional images can be reconstructed from the accumulated data to study internal physical and physiological processes. Most internal disorders like woolliness in nectarines, hollow heart in potato, core breakdown in pears, watercore in apples and spongy tissue in mango affect the density and water content of the internal tissue and, hence, are detectable by means of X-ray measurements. For in vivo observations, high resolution submicron tomography has up to recently only been achieved on relatively dry -or hard- biological samples, such as plant seeds. We have shown, however, that by means of synchrotron radiation X-ray sources, it has now become feasible to image plant tissues at a resolution of less than one micrometer.

2010Book part

Open Access

Effect of electrolyzed water as a disinfectant for fresh-cut fruit

Publication . Graça, Ana; Salazar, Miguel; Quintas, Célia; Manso, Teresa; Nunes, Carla; Nunes, Carla

In fresh-cut processing the disinfection is the most important step. This process can affect the quality and the safety of the end product as well as its shelf life. Chlorine is the most used disinfectant in fresh-cut industry but due to its association with environmental and health risks, the development of alternative sanitizers is emergent. Electrolyzed water (EW) may be an alternative to the use of chlorine sanitizers and both acidic electrolyzed water (AEW) and neutral electrolyzed water (NEW) can be used with this purpose. In fact, several studies have shown that EW can be effective in reducing pathogenic bacteria on the surface of fruits and vegetables. This manuscript presents a review of electrolyzed water approaches, its antimicrobial activity in fresh-cut produce and the results of a study undertaken in our laboratory to evaluate the disinfection efficacy of AEW and NEW on fresh-cut apples and oranges. Fresh-cut apples and fresh cut oranges were inoculated with a suspension of Listeria innocua and fresh-cut oranges with Escherichia coli at a concentration of 107 cfu mL-1 and treated with the different solutions. Untreated freshcut fruits were used as control. The best sanitizing treatment for both pathogens and fruits was AEW at 200 ppm of free chlorine applied during 5 minutes.

2010Book part

Open Access

New developments in alternative methods to control postharvest fruit decay

Publication . Nunes, Carla; Nunes, Carla

Public concern in food safety and the increase of pathogen resistant populations has enhanced the interest in developing methods to control postharvest fruit decay alternative to fungicides. According to their nature alternative methods can be classified as biological, chemical or physical. This article reviews research on alternative postharvest disease control methods and explores new possibilities of research to improve their efficacy.

2010Book part

Open Access