INFLUENCE OF CHEMICAL TREATMENT ON QUALITY OF CUT APPLE (cv. JONAGORED)

The quality of a new variety of apple, ‘Jonagored’, after peeling and cutting was evaluated during ten days of storage in air at 4C. The objective was to evaluate the shelf-life of apple cubes by detecting the limiting parameter and to test the influence of different chemical dips on the cut apple quality with the aim of extending shelf-life. Color, i.e. browning at the cut surface, was found to be the critical quality parameter determining the shelf-life of the cut apple to less than three days. There were no significant differences between the dip treatments in measurements of CIE values. When apple cubes were treated with ascorbic acid, ascorbic acid plus calcium chloride or ascorbic acid plus calcium chloride and citric acid, the 0.75% ascorbic acid dip was found to be the most effective preservation treatment in terms of reducing color change of the cut surface. Both 0.75% ascorbic acid and 0.75% ascorbic acid plus 0.75% calcium chloride inhibited the loss of firmness of apple cubes. When citric acid was added to the dip treatment, there were color changes similar to those of the control.     

Numerical analysis of the ENF and ELS tests applied to mode II fracture characterization of cortical bone tissue

The objective of this work is to verify numerically the adequacy of the ENF and the ELS tests to determine the fracture toughness under mode II loading of cortical bovine bone tissue. A data‐reduction scheme based on the specimen compliance and the equivalent crack concept is proposed to overcome the difficulties inherent to crack monitoring during its growth. A cohesive damage model was used to simulate damage initiation and growth, thus assessing the efficacy of the proposed data‐reduction scheme. The influences of the initial crack length, local strength and toughness on the measured fracture energy were analysed, taking into account the specimen length restriction. Some limitations related to spurious influence on the fracture process zone of the central loading in the ENF test, and clamping conditions in the ELS test were identified. However, it was verified that a judicious selection of the geometry allows, in both cases, a rigorous estimation of bone toughness in mode II.     

EFFECTS of CONTROLLED ATMOSPHERE ON QUALITY of MINIMALLY PROCESSED APPLE (cv. JONAGORED)

Controlled atmosphere (2% O₂+ 4% to 12% CO₂) storage was found to be advantageous over air storage in terms of overall preservation of fresh-cut apple (cv. Jonagored). After 3 days, CA-stored apple cubes were firmer, showed better color and higher content of fructose and soluble solids content than air-stored cubes. In relation to color preservation this benefit was increased when CO₂ in the atmosphere was increased to 12% CO₂. Controlled atmosphere storage showed no advantage over air storage in relation to sensory evaluation of firmness and flavor.     

Influence of intralaminar cracking on the apparent interlaminar mode I fracture toughness of cross‐ply laminates

One of the major difficulties in interlaminar fracture tests of multidirectional laminates is the high tendency for intralaminar cracking and the resulting wavy crack propagation. Experimental work showed that this occurred in double cantilever beam (DCB) tests of cross‐ply laminates having a starter crack on a 0°/90° interface. Moreover, under steady‐state propagation conditions, the apparent values of the critical strain energy release rate G_Ic were two times higher than those of 0°/0° specimens. In this paper, a finite‐element‐based progressive damage model was used to simulate crack propagation in cross‐ply specimens. The results showed that transverse cracking alone cannot be responsible for the above difference of G_Ic values. Therefore, the higher propagation G_Ic values for cross‐plies must be attributed to the more extensive fibre bridging observed and to plastic deformations of the 90° interfacial ply.     

Interlaminar fracture studies in Portugal: past,present and future

This paper reviews the state‐of‐the‐art in interlaminar fracture testing of composite materials, with particular emphasis on the work performed in Portugal over the last 15 years. Early work, carried out within the ESIS Polymer and Composite Technical Committee, was concerned with improving test methods on unidirectional [0°]_n specimens. The focus was on the mode I double cantilever beam (DCB) test and on mode II end‐notched flexure (ENF) and end loaded split (ELS) tests. In spite of some remaining controversy on mode II testing, the main issue nowadays is fracture toughness measurement on multidirectional specimens. Remaining difficulties are discussed in the light of the most recent work. Guidelines for ongoing and future research are also presented.     

POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED 'JONAGORED' APPLES (MALUS DOMESTICA)

The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA‐treated apple cubes.     

COMPARATIVE STUDY OF MICROENCAPSULATION OF CASEIN HYDROLYSATES IN LIPOSPHERES AND LIPOSOMES

The encapsulation in lipospheres and in liposomes was used with the aim of masking the bitterness of casein hydrolysates for dietetic of pharmaceutical purposes. Papain was used for preparing three casein hydrolysates, employing different temperatures and E:S ratios. The percentage of encapsulation of these preparations was measured by second derivative spectrophotometry (SDS). Lipid oxidation over a period of 60 days, was followed by quantifying the 2-thiobarbituric acid reactive substances (TBARS). Other analysis were performed for characterizing these vesicles, including the sensory evaluation and the measure of hydrophobicity. The results showed that these two encapsulation systems were equally efficient in reducing the hydrophobicity and the bitterness of casein hydrolysates. SDS was a useful tool in the characterization of these preparations. It is a quick and relatively low-cost method, and indicated that the encapsulation rate in lipospheres (65%) was higher than in liposomes (59%). The TBARS method revealed the chemical stability of these preparations over the period of study (60 days).     

QUALITY OF PINK TOMATOES (cv. BUFFALO) AFTER STORAGE UNDER CONTROLLED ATMOSPHERE AT CHILLING AND NONCHILLING TEMPERATURES

Greenhouse-grown pink tomatoes (cv. Buffalo) were stored in air or in a controlled atmosphere (CA) of 4% O₂ plus 2% CO₂, to study the effect of CA at chilling and nonchilling temperatures on fruit quality characteristics. Tomatoes could be stored in CA at 12C for three weeks with no major changes in fruit appearance. CA was effective in delaying color development and ripening at this temperature. The soluble solids content was lower after CA storage, but no significant differences in firmness, pH or titratable acidity were observed between storage in air or CA. Storage in CA at 12C was also effective in reducing decay. However, at 6C, fruit showed high incidence of decay after both air and CA storage. CA did not alleviate chilling injury symptoms relative to air-stored samples and may have caused CO₂ injury. Water loss was greater under CA at both temperatures.