The work on changes occurring in the nutritional and functional quality of ready-to-eat (RTE) products has been coordinated by Manuela Pintado and Ana Amaro, scientists at Universidade Catolica Portuguesa.The objective of the work was to report a detailed overview of the changes that occur in the nutritional and functional composition of the fresh products, as a consequence of specific processes and storage conditions (isolated or combined) and also as a consequence of processing steps during the production line (through nutritional and functional audits).
Processing and storage conditions are known to affect quality of RTE rocket leaves, with package atmosphere and low temperature as key factors in quality maintenance throughout processing to consumption. However, information on rocket leaves nutritional and functional quality affected by modified atmosphere and storage temperature is scarce.
In order to generate recommendations to optimize phytochemical preservation of rocket leaves during processing, a nutritional audit of the processing line of a fresh-cut vegetables enterprise was performed.
Furthermore, the effect of passive and active modified atmosphere and temperature conditions during storage on phytochemical quality of RTE rocket leaves was evaluated and the relative changes determined. From a nutritional and functional point of view it is important to understand the consequences of processing and storage in fresh-cut fruits composition in order to select the best technological conditions required for the preservation of fruit and vegetables health benefits.
Fruit processing conditions can be described through representative flowcharts with the identification of the process variables. However, integrated information about the effect of each processing step on phytochemical properties of the processed fruits is still lacking. A nutritional and functional audit of postharvest handling systems and processing lines of a fresh-cut fruit enterprise was performed and the effects of the production process upon the nutritional and phytochemical composition of melon and strawberry were determined.
Furthermore, the effect of active modified atmosphere and temperature conditions during storage on phytochemical quality of fresh-cut melon and strawberry was evaluated and the relative changes determined. The integration of these results contributes to the understanding of the effects of processing and storage conditions on overall quality of RTE fruit and vegetables and provide useful information for developing processes aimed at the modulation of nutritional quality and shelf-life extension.
The main conclusions of this work are:
1. Most nutritional quality parameters are affected by the different steps that constitute the production flowcharts. The processing steps that can be highlighted as mostly affecting these products phytochemical content are the decontamination step and packaging, most of the times decreasing nutritional value when comparing with the products at reception.
2. In order to reduce rocket leaves respiration rate and thus metabolism, initial oxygen levels inside the packages should be reduced. On the other hand, nutritional and functional compounds were better maintained in higher oxygen availability throughout storage in Permeable packages. These results strain the need to re-assess oxygen availability inside different film packages as a tool to modulate wild rocket leaves nutritional quality.
3. Active modified atmosphere packaging significantly affected RTE rocket leaves and fresh-cut melon nutritional and functional quality. The results show that too low O2 concentration may be detrimental to nutritional quality of RTE rocket leaves and fresh-cut melon. Initial low O2 levels (5%) in packages may stimulate wound response, enhancing enzymatic activity and the production of phenolic compounds.
4. Regarding storage temperature, 5ºC was beneficial for most phenolic compounds production and accumulation during storage, antioxidant activity and ascorbic acid maintenance of RTE fruits and vegetables, being therefore the selected storage temperature to reduce nutritional quality loss after processing and during storage.
5. As for package selection, the increase in total phenolic compounds and better maintenance of overall nutritional quality in filmed packages may be attributed to the stress that the tissue was subjected to many of these packages, because being filmed with a very low oxygen transmission rate, allowed the oxygen levels to decrease and the carbon dioxide levels to increase, due to tissue respiration during storage, while most of clamshell packages allowed the gas exchange and kept the package atmosphere close to normal atmospheric conditions.
6. Finally, addressing cutting size, throughout commercial storage of fresh-cut fruits (6-7 days), overall nutritional quality is more constant and better maintained in commercial sized cubes (2.5 cm) and halves, in fresh-cut melon and strawberries, respectively.
For further info:
Manuela Pintado - mpintado@porto.ucp.pt
Ana Amaro - aamaro@porto.ucp.pt