Preservation of hermaphrodite and female papaya fruits (Carica papaya L?., Cv Sunrise, Solo group) by freezing: physical, physico-chemical and sensorial aspects

 The physical, physico-chemical and sensorial changes that occur during the freezing and frozen storage of hermaphrodite and female papaya slices (Carica papaya L., cv Sunrise, Solo group) were studied. Samples were evaluated by panellists throughout a 1-year period of storage at –24°C; the panellists described the fruit in terms of physico-chemical measurements of texture (firnmess and total pectins content), colour [L, a _L , b _L , peroxidase (POD) and polyphenoloxidase (PPO) activities] and flavour/taste [soluble solids content, pH, tritatable acidity and quality index (^oBrix/acidity)], and ranked them in order of preference. Desserts prepared from frozen slices of hermaphrodite and female papaya fruits mixed with orange, lemon and sugar were also evaluated. The freezing process itself did not result in significant changes in the more commonly assessed quality parameters of texture, colour and flavour/taste. However, during storage at –24°C, changes in sensorial characteristics occurred that became more evident as storage continued (≤ 9 months). Nevertheless, these quality changes can be masked by using these papaya slices as an ingredient in fruit products, with frozen female papaya slices being especially suitable for this purpose. Received: 1 August 1997 / Revised version: 14 November 1997     

Effect of refrigerated storage on vitamin C and antioxidant activity of orange juice processed by high-pressure or pulsed electric fields with regard to low pasteurization

A better knowledge of the effect of refrigerated storage on the nutritional and antioxidant characteristics of foods processed by emerging technologies with regard to thermal traditional technology is necessary. Thus, freshly squeezed orange juice was processed by high-pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV/cm/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of vitamin C and antioxidant activity was studied just after treatment and during 40 days of refrigerated storage at 4 °C. The determination of total vitamin C (ascorbic acid plus dehydroascorbic acid) was achieved by HPLC whereas the antioxidant activity was assessed by the measurement of the DPPH• radical scavenging. Just after treatment, all treated orange juices showed a decrease lower than 8% in vitamin C content compared with the untreated one. At the end of refrigerated storage, HP and LPT juices showed similar vitamin C losses (14 and 18%, respectively) in relation to untreated juice, although HP juices maintained better the vitamin C content during more days than LPT juices. Regarding antioxidant activity, after 40 days at 4 °C, differences among treated juices were no significant in terms of antiradical efficiency (AE=1/EC₅₀T_EC50). HP and PEF may be technologies as effective as LPT to retain antioxidant characteristics of orange juice during refrigerated storage.     

Water-soluble hollow nanocrystals from self-assembly of AIEE-active Pt(II) metallomesogens

Luminescent hollow micro-and nanocrystals have been successfully obtained taking advantage of the self-assembly behavior and the aggregation-induced emission enhancement properties of several bispyrazolate Pt(II)metallomesogens decorated with four terminal alkyl chains.Oil-in-water droplets have been used to confine the Pt(II)compounds and drive them to be self-assembled via intermolecular Pt…Pt interactions into spherical aggregates of about 200 or 50 nm.Evaporation of the oil phase generates highly-stable aqueous dispersions of nanocrystals that emit a bright orange light as a result of the existence of³MMLCT excited states.Different methods and conditions have been tested for studying the effect of several parameters such as the temperature and the stirring speed in the final particle size and in the polydispersity index.Moreover,the micro-and nanocrystals are able to entrap hydrophobic drugs between the alkyl chains of the compounds,forming stable dispersions of drug-loaded capsules in water.The droplet method is applied in the area of metallomesogens for the first time to synthesize self-assembled Pt(II)nanocapsules,which opens a new field of study that could allow the use of these liquid crystal materials in biomedical applications.     

Analysis of network function sharing in Content Delivery Network-as-a-service slicing scenarios

Video content consumption is currently dominating the mix of traffic observed in Internet service provider (ISP) networks. The distribution of that content is usually performed by means of content delivery network (CDN) caches storing and delivering multimedia. The advent of virtualization is calling attention to the CDN providers as a use case for virtualizing the cache function. In parallel, there is a trend for sharing network infrastructures as a way of reducing deployment costs by ISPs. Then, an interesting scenario emerges when considering the possibility of sharing virtualized cache functions among ISPs which are sharing a common physical infrastructure, mostly considering that those ISPs offer similar video content catalogs to end users. Furthermore, when deciding to share the caches among ISPs, it is interesting to understand the impacts due to limiting the storage capacity at the edge sites. This paper investigates through simulations the potential efficiencies that can be achieved when sharing a virtual cache function if compared with the classical approach of independent virtual caches operated per ISP, as well as the implications of limiting the storage capacity of the caches at the edge.     

Development of a Measure Cell to Assess by Amperometry Dissolved Oxygen in Vegetable Oils

Dissolved oxygen in vegetable oils is an important component of oil degradation over time. Various methods for the determination of dissolved oxygen in oils are proposed in the literature leading to very variable results. An amperometric method associated with a cell of measurement in dynamic mode makes it possible to determine the conditions of stability of the measurements of the relative dissolved oxygen concentration (RDOC, mg L⁻¹) and the electrolysis current intensity (ECI) (nA) in seed oils and virgin olive oils. The effects of oxygenation/deoxygenation time and temperature on RDOC measurements are investigated. For virgin olive oils, the RDOC in bottles closed for eight weeks varies from 0 to 0.9 mg L⁻¹. The nature of the fruitiness and the filtration of the oils have no influence on the RDOC. The monitoring of RDOC and ECI during the flow of virgin olive oil in a column open to air, simulating an industrial tank, shows differences in dissolved oxygen concentration due to a faster flow of oil in the center of the column than at the walls. This result is validated by a similar experiment with nitrogen inerting the column and by a numerical simulation. Practical applications: Knowledge of the oxygen dissolved in vegetable oils is an important factor in limiting the autoxidation phenomenon to increase their shelf life. The development of a cell for measuring the relative dissolved oxygen concentration (RDOC) in vegetable oils and its conditions of use, provides a tool for the RDOC applicable to the different stages of the manufacturing process and during storage or packaging. The RDOC measurement is particularly useful during long storage in tanks whether inerted or not.