Modelling quality of fresh-cut tomato based on stage of maturity and storage conditions

M. Moreira Lana

Research output: Thesisinternal PhD, WU

Abstract

Fresh-cut or minimally processed vegetables are those which have been trimmed and/or peeled and/or cut into 100% usable product and still maintain freshness. Contrary to other processing methods (freezing, canning and drying for example) the minimal processing operations reduce the shelf life in relation to the raw material (intact product).In this thesis the changes in quality of tomato fruits after cutting into transversal slices were analysed and quantified in relation to the stage of maturity of the fruit at harvest and to the storage temperature. Quality was analysed in relation to some attributes related with organoleptical (firmness) visual (colour and translucency) and nutritional (lycopene content and total antioxidant activity) quality.The firmness of the tomato pericarp, evaluated through puncture tests, decreased exponentially during storage. Within a maturity stage, the firmness decreased only slightly during storage and major difference was found in the initial firmness at the different stages of maturity.The optical properties were evaluated through video image analysis and expressed as RGB (Red,Green,Blue) colour aspects. A mathematical model was used to describe the changes in the RGB colour aspects resulting from two different processes namely changes in colour due to the production and/or degradation of pigments (maturation) and development of translucency due to watersoaking of the pericarp. It incorporated in a single equation the effects of time, temperature, stage of maturity and background over which the tomato slices were imaged. Both translucency and maturation resulted in a decrease of the RGB values. The development of translucency was highly determined by the stage of maturity of the fruit at harvest and rather independent of temperature. Changes in colour due to maturation were much less pronounced. Using a spectrophotometric technique (Kubelka-Munk analysis) to evaluate the development of translucency these findings were confirmed.Changes in lycopene content were evaluated by HPLC. Cutting did not change the lycopene accumulation when the slices were kept at low temperature, while lycopene production predominated over degradation at temperature higher than 8 o C. The antioxidant activity of fresh-cut and intact tomato fruits was assessed by a radical (ABTS) scavenging method. Cutting induced a reduction of the hydrophilic antioxidant activity, while the lipophilic antioxidant activity was not affected. The antioxidant activity of both fractions increased with maturation.In short, the post cutting life based on appearance was shorter than that based on textural and nutritional value. The greatest range of changes happened in the first 2 days of storage for all quality attributes. The stage of maturity determined the initial values as much as the rate of decrease (or increase) along storage of each attribute. The effect of temperature although present was far lower than the effect of stage of maturity. For a short period (less than 1 week) the low temperature was efficient to prevent most of the deleterious changes in quality (softening, over-ripening, loss of antioxidants) but not to prevent water-soaking of the pericarp and translucency development.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Wageningen University
Supervisors/Advisors
  • van Kooten, Olaf, Promotor
  • Tijskens, Pol, Co-promotor
  • Dekker, Matthijs, Co-promotor
Award date14 Sep 2005
Place of Publication[S.l.]
Print ISBNs9789085042594
Publication statusPublished - 2005

Keywords

  • solanum lycopersicum
  • tomatoes
  • harvesting
  • crop quality
  • ripening stage
  • maturity stage
  • postharvest physiology
  • storage
  • colour
  • image analysis

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