Carmen Fuster

Pineapple fruit : morphological characteristics, chemical composition and sensory analysis of Red Spanish and Smooth Cayenne cultivars

Abstract Some physical (weight, size, shape, texture and colour), physico-chemical (pH, titratable acidity and soluble solids), chemical (soluble sugars and organic acids) and biochemical (total dietary fibre, peroxidase activity and soluble protein) characteristics and sensorial attributes (appearance, flavour, odour, colour, firmness and acceptability) of pineapple ( Ananas comosus L.) fruit were studied, in order to assess nutritional properties and consumer acceptability of the local Red Spanish and imported Smooth Cayenne cultivars. Significant differences ( P ≤0.05) were found between size, shape and colour of the cultivars, and also between other objective (lightness, green colour, total acidity, soluble solids, total dietary fibre, peroxidase activity, fructose and glucose) and subjective (colour) measurements. Values of texture, fibre content and soluble solids to acid ratio were lower in the Red Spanish cultivar, while peroxidase activity and soluble protein were higher. Taste panelists preferred the appearance, colour and firmness of the Red Spanish pineapple slices.

Effects of blanching and freezing on the structure of carrots cells and their implications for food processing

Blanching and freezing effects are focused on the microscopic structure, whether the softening of frozen vegetables (carrots) is related to changes in pectic substances or to firmness. Under light and electron microscopy, in the frozen raw samples, some cells were disrupted, producing cavities. The cytoplasm was destroyed and enclosed in a very thin layer inside the cell, and the organelles attached to the plasmalemma had almost disappeared. The formation of a transparent region close to the plasmalemma was observed, as a result of the extraction of some altered materials (hemicellulose, cellulose, pectin). The cell walls in the blanched samples appeared quite different from those in the frozen samples. They did not display tissue disruption as in the frozen samples, but the organelles in the cytoplasm were also altered. We also report substantial vesicle formation (swollen walls) in the cell wall, and a dark granular material inside. When the blanched samples were also frozen, compartmentalization of the material inside was observed. The pectin content was higher in the frozen and frozen blanched samples than in the raw and blanched samples. The semithin and ultrathin structure was in accordance with the objective values obtained by Kramer/Shear cell, where the greatest damage occurred to the samples in the freezing process.

Changes in soluble sugars of two pineapple fruit cultivars during frozen storage

Abstract Sugar changes taking place during freezing and frozen storage of two pineapple fruit cultivars, Smooth Cayenne and Red Spanish, were studied. Pineapple fruit was frozen as slices in a cold room at −18 °C and stored at this temperature for a 12-month period. The sugar content was measured by high-performance liquid chromatography (HPLC) and compared to the total soluble solids determined by refractive index. Both were linearly related. HPLC identified the major components as fructose, glucose and sucrose. A high correlation was observed between the different sugars in the two cultivars during frozen storage. Freezing preservation of pineapple fruit slices led to minimal changes in soluble solids and sugar content (fructose, glucose and sucrose) after 1 year of frozen storage.

Freezing preservation of four Spanish kiwi fruit cultivars (Actinidia chinensis, Planch) : chemical aspects

ZusammenfassungEs wurden die chemischen Veränderungen durch Tiefgefrieren und Gefrierlagerung von vier Kiwisorten (Monty, Bruno, Abbot und Hayward) untersucht. Die Kiwifrüchte wurden in Scheiben ohne vorherige Behandlung im Luftstrom bei−18 °C eingefroren und zwölf Monate gelagert. Es wurden geringe Veränderungen im Wassergehalt beobachtet. Durch das Gefrieren hat die gesamte titrierbare Säure der Kiwischeiben keine bedeutsamen Veränderungen erfahren, nur bei den Scheiben der Montysorte gab es einen 20%igen Abbau. Bei allen Sorten ändert sich der pH-Wert parallel zum titrierbaren Säuregrad. Keine signifikanten Veränderungen zeigten sich beim Zuckergehalt während der Gefrierlagerung. Der Ascorbinsäure-Gehalt nahm zwischen 10–25% in Abhängigkeit von der Kiwisorte ab. Der Chlorophyllgehalt nahm bei allen Sorten ab, aber diese Veränderung zeigte nur bei langen Lagerzeiten einen geringen Farbverlust. Diese Veränderungen sind abhängig von der Abnahme in −a/b und der Zunahme in L (Glanz).SummaryChemical changes taking place during freezing and frozen storage of four kiwi fruit cultivars (Monty, Bruno, Abbot, and Hayward) were studied. Kiwi fruit was air-blast frozen as slices without any previous treatment and stored at−18° C for a 12-month period. Freezing preservation of kiwi fruit slices led minimal changes in moisture content. The total aciditiy of kiwi fruit slices decreased slightly during the freezing process; only frozen slices of Monty showed a 20% decrease. The pH values changed in parallel with the total acidity values obtained. No important changes related to the sugar content were associated with the freezing preservation of kiwi fruit slices. Freezing produced a decrease of 10–25% in the ascorbic acid content depending of the cultivar considered. The chlorophyll content diminished in all kiwi fruit slices during frozen storage but this decrease produced only a slight perceptible change in the visual colour of frozen slices stored during prolonged periods. These changes were directly related to the observed decrease in −a/b and increase in L (brightness) Hunterlab values.

Freezing preservation of four Spanish mango cultivars (Mangifera indica L.): chemical and biochemical aspects

ZusammenfassungEs wurden die chemischen und biochemischen Veränderungen durch Tiefgefrieren und Gefrierlagerung von vier spanischen Mangosorten (Smith, Lippens, Palmer und Davis-Haden) untersucht. Die Mangos wurden in Scheiben ohne vorherige Behandlung im Luftstrom eingefroren und ohne Veränderung in der Restfeuchtigkeit bei −18 °C für vier Monate gelagert. Durch das Gefrieren sank bei allen Sorten der Gehalt an titrierbarer Säure und der pH-Wert stieg an, während sich bei der Gefrierlagerung keine weiteren Veränderungen ergaben. Keine signifikanten Veränderungen zeigten sich bei den Gehalten an löslichen und reduzierenden Substanzen und Gesamtzucker. Der Gehalt an Ascorbinsäure undβ-Carotin hatte nach 120 Tagen Gefrierlagerung erheblich abgenommen. Die Sorte Davis-Haden zeigte dabei den geringsten Unterschied zur frischen Frucht. Die Aktivität der Enzyme Peroxidase (POD; EC 1.11.1.7) und Polyphenoloxidase (PPO; EC 1.14.18.1) wurde durch das Gefrieren verringert und während der Gefrierlagerung wurde keine Reaktivierung beobachtet. Die PPO-Aktivität am Ende der Lagerung war niedrig (<20% der frischen Frucht), während die POD-Aktivität im Vergleich hÖher war (>40% der frischen Frucht). Die verbleibende Aktivität der POD könnte zu einem Qualitätsabfall in gefrorenen Mangoscheiben führen.SummaryChemical and biochemical changes taking place during freezing and frozen storage of four Spanish mango cultivars: Smith, Lippens, Palmer and Davis-Haden were studied. Mango was air-blast-frozen as slices without any previous treatment and stored at −18 °C for a 4-month period. Freezing preservation of mango slices did not lead to changes in moisture content. The titrable acidity of the slices decreased as the pH increased in all cultivars due to the freezing process; no changes were found in these parameters throughout frozen storage. The behaviour of soluble solids and reducing and total sugar contents showed that no important changes appeared in the cultivars considered. Ascorbic acid andβ-carotene contents decreased considerably after 120 days frozen storage, being Davis-Haden the mango cultivar showing values of those parameters closest to the raw fruits. Peroxidase (POD; EC 1.11.1.7) and polyphenoloxidase (PPO; EC 1.14.18.1) activities slowed down after freezing, and no regeneration was found throughout frozen storage. The final PPO activity was low (<20% as compared to the raw fruit) whereas the POD activity was higher (>40% raw fruit). The remaining POD activity might cause deteriorative changes in the final quality of frozen mango slices.

Non-Volatile Organic Acids, pH and Titratable Acidity Changes in Pineapple Fruit Slices During Frozen Storage

Effects of freezing and frozen storage on pH, titratable acidity and non-volatile organic acids of two pineapple fruit cultivars, Smooth Cayenne and Red Spanish, were studied. Pineapple fruit was frozen as slices in a cold room at -18°C and stored at this temperature for a 12 month period. A negative correlation was found between pH and titratable acidity in the two cultivars throughout frozen storage (r = -0.67 for Smooth Cayenne and r = -0.71 for Red Spanish). Non-volatile organic acids were determined by high performance liquid chromatography. The major components were citric and L-malic acids. A high correlation was found between these two acids during frozen storage (r = 0.75 in Smooth Cayenne and r = 0.78 in Red Spanish). There were significant differences (P < 0.01) in pH and titratable acidity between the two studied varieties after a year of frozen storage. Significant differences (P ≤ 0.05) were found in pH values during frozen storage in cv Smooth Cayenne and in citric and L-malic acids in cv Red Spanish. Freezing preservation of pineapple fruit slices led to minimal chemical changes after a year of frozen storage.