Olga Martín-Belloso

New advances in extending the shelf-life of fresh-cut fruits: a review

Minimally processed products are one of the major growing segments in food retail establishments. However, fresh-cut fruits are still under study because of the difficulties in preserving their fresh-like quality during prolonged periods. This paper intends to review the most significant contributions regarding preservation of fresh-cut fruits without a significant modification of its sensorial properties and provides an overview about the last published advances. It covers aspects concerning conditions suggested by authors in each one of the processing steps such as washing, sanitation, cutting, dipping treatments and/or preservation under modified atmospheres, as well as those works studying the influence of these operations on the shelf life and quality extension of fresh-cut fruit products without modification of their sensorial properties.

Comparison of some biochemical characteristics of different citrus fruits

The goal of this investigation was to evaluate the antioxidant properties of some citrus fruits. The contents of dietary fibre, total polyphenols, essential phenolics, ascorbic acid and some trace elements of lemons, oranges and grapefruits were determined and compared with their total radical-trapping antioxidative potential (TRAP). There were no significant differences in the contents of total, soluble and insoluble dietary fibre in the studied peeled fruits or their peels. The contents of total, soluble and insoluble dietary fibre in peels were significantly higher than in peeled fruits (P < 0.05 in all cases). The peeled lemons, oranges and grapefruits contain 164 10.3; 154 10.2 and 135 10.1 and their peels 190 10.6; 179 10.5 and 155 10.3 mg/100 g of total polyphenols, respectively. The content of total polyphenols in peeled lemons and their peels was significantly higher than in peeled oranges and grapefruits and their peels, respectively. The content of total polyphenols in the peels was significantly higher than in peeled fruits (P < 0.05 in all cases). The same results were obtained in the investigation of essential phenolics and ascorbic acid. The content of Fe in peeled lemons and their peels was significantly higher than in peeled oranges and grapefruits and their peels, respectively. Also the TRAP was significantly higher in peeled lemons and their peels than in peeled oranges and grapefruits and their peels, respectively. In all three fruits, the TRAP was significantly higher in peels than in peeled fruits (P< 0.05). In conclusion, lemons possess the highest antioxidant potential among the studied citrus fruits and are preferable for dietary prevention of cardiovascular and other diseases. The peels of all citrus fruits are rich in dietary fibres and phenolic compounds and suitable for industrial processing. # 2001 Published by Elsevier Science Ltd. All rights reserved.

Influence of particle size on lipid digestion and β-carotene bioaccessibility in emulsions and nanoemulsions

The interest in incorporating carotenoids, such as β-carotene, into foods and beverages is growing due to their potential health benefits. However, the poor water-solubility and low bioavailability of carotenoids is currently a challenge to their incorporation into many foods. The aim of this work was to study the influence of particle size on lipid digestion and β-carotene bioaccessibility using corn oil-in-water emulsions with different initial droplet diameters: large (d43≈23μm); medium (d43≈0.4μm); and small (d43≈0.2μm). There was a progressive increase in the mean particle size of all the emulsions as they passed through a simulated gastrointestinal tract (GIT) consisting of mouth, stomach, and small intestine phases, which was attributed to droplet coalescence, flocculation, and digestion. The electrical charge on all the lipid particles became highly negative after passage through the GIT due to accumulation of anionic bile salts, phospholipids, and free fatty acids at their surfaces. The rate and extent of lipid digestion increased with decreasing mean droplet diameter (small≈medium≫large), which was attributed to the increase in lipid surface area exposed to pancreatic lipase with decreasing droplet size. There was also an appreciable increase in β-carotene bioaccessibility with decreasing droplet diameter (small>medium>large). These results provide useful information for designing emulsion-based delivery systems for carotenoids for food and pharmaceutical uses.

Non-thermal food preservation: Pulsed electric fields

The use of electric discharges to inactivate microorganisms and enzymes in food products has evolved since the 1920s from the ‘ElectroPure process’ (ohmic heating process) to the use of high-intensity pulsed electric fields in the 1990s. The non-thermal inactivation of microorganisms and enzymes using electric fields was demonstrated in the 1960s with a variety of microorganisms suspended in simulated food systems. A variety of liquid foods and beverages, including orange, apple and peach juices, pea soup, beaten eggs and skim milk, has been successfully processed during the 1980s and 1990s by several research groups. Little by little, the food industry is demonstrating increasing interest in this promising emerging technology; furthermore, it is expected that it will soon be adopted to process several liquid food products.

Characterisation of low-fat high-dietary fibre frankfurters

Two different peach dietary fibre (DF) suspensions (17 and 29%) were used to obtain low-fat high-DF frankfurters (20-5% fat) which were compared to an all-meat control (25% fat). The viscosity of the meat batters increased with DF content. The protein (11.5±0.6%) and collagen (1.4±0.1%) contents of frankfurters were not affected by DF addition, and the higher the DF content, the lower the pH (6.4 to 5.8) due to the fibre solution acidity. The DF was effective in retaining added water in low-fat frankfurters since their cooking losses were similar to those of the controls (5.5±0.1%). Low-fat frankfurters were darker and browner than the controls and only high fibre addition significantly decreased the textural parameters. Sensory evaluation indicated that low fat-high DF frankfurters (20, 15 and 10% fat) were as acceptable as the all-meat frankfurters.

Comparative content of some bioactive compounds in apples, peaches and pears and their influence on lipids and antioxidant capacity in rats

The aim of this study was to compare some bioactive compounds in apples, peaches and pears and their influence on lipids and antioxidant capacity in rats. The content of total polyphenols (g/100g) was 0.23 +/- 0.03; 0.22 +/- 0.03 and 0.68 +/- 0.1 in peeled fruits and 0.48 +/- 0.04, 0.47 +/- 0.04 and 1.2 +/- 0.12 in peels of peaches, pears and apples, respectively. Caffeic, p-coumaric and ferulic acids and the total radical-trapping antioxidative potential (TRAP) values in peeled apples and their peels were significantly higher than in peaches and pears, respectively. Contrarary, no significant differences in the content of dietary fiber among the studied fruits were found. The content of all studied indices in peels was significantly higher than peeled fruits (p < 0.05 ). A good correlation between the total polyphenols and the TRAP values was found in all fruits. Diets supplemented with apples and to a less extent with peaches and pears have improved lipid metabolism and increased the plasma antioxidant potential especially in rats fed with added cholesterol. The highest content of biologically active compounds and the best results in the experiment on rats makes apple preferable for dietary prevention of atherosclerosis and other diseases.

Characterization of dietary fiber from orange juice extraction

Abstract Residues from orange juice extraction are potentially an excellent source of dietary fiber (DF), because this material is rich in pectin and may be available in large quantities. Chemical and physical characteristics of DF obtained from orange pulp were determined for three varieties of oranges. Total DF content reached quite high values: 35.4–36.9% dry matter (DM). Orange DF was rich in pectins (15.7–16.3% DM), as well as cellulose and hemicellulose (16.6–18.1% DM) and lignin (2.2–3.0% DM). The product showed a relatively high water holding capacity (7.3–10.3 g water/g fiber), high oil absorption property (0.9–1.3 g oil/g fiber) and low caloric value (3519–3735 cal/g). Chemical analyses of orange DF concentrate showed low contents of protein, fat and ash (8.1–10.1%, 1.5–3.0% and 2.6-3.1% DM, respectively). The orange DF color ranged from yellow to light orange. These characteristics suggested many potential applications such as, clouding agent in beverages, thickener and gelling agent as well as binder, texturizer and low calorie bulk ingredient.

Comparison of the contents of the main biochemical compounds and the antioxidant activity of some Spanish olive oils as determined by four different radical scavenging tests.

The aim of this study was to compare the contents of the main biochemical compounds and the antioxidant capacity of five Spanish olive oils by four different antioxidant tests and to find out the most valuable oil for disease preventing diets. Fatty acids, sterols and individual antioxidant compounds in Arbequina, Hojiblanca, Extra Virgin, Picual and Lampante Spanish olive oils were determined. Antioxidant activities were done as well using different radical scavenging activities: total radical-trapping antioxidative potential by ABAP (TRAP-ABAP), radical scavenging activity by DPPH (RSA-DPPH), antioxidant assay by beta-carotene-linoleate model system (AA-beta-carotene) and total antioxidant status by ABTS (TAA-ABTS). The highest content of all studied antioxidant compounds (353; 329; 4.6 and 2.7 mg/kg for tocopherols, tocotrienols, polyphenols and o-diphenols, respectively) was found in Extra Virgin oil. Also the highest antioxidant capacity was observed in Extra Virgin oil (668 nM/ml; 29.4%; 40.4% and 2.64 mM TE/kg for TRAP-ABAP, RSA-DPPH, AA- beta-carotene and TAA-ABTS, respectively). The correlation between total phenols and antioxidant capacities measured by four methods was very high, but the highest for the beta-carotene (R = 0.9958). In conclusion, the best method for determination of the antioxidant capacity of olive oils is the beta-carotene test. Extra Virgin olive oil has high organoleptic properties and the highest antioxidant activity. The above-mentioned makes this oil a preferable choice for diseases preventing diets.

Characterisation of peach dietary fibre concentrate as a food ingredient

Abstract Insoluble and soluble dietary fibre (DF) fractions of peach DF concentrate, obtained by an enzymatic-chemical method, were analysed for neutral sugars, uronic acids and Klason lignin. Proximate composition, energy value, colour and water- and oil-holding capacities were also determined. Total DF constituted 31–36% dry matter (DM) of the concentrate and insoluble DF was its major fraction (20–24% DM). The high proportion of soluble fraction (11–12% DM) in the peach DF concentrate, in comparison with cereal brans, was noticeable. Insoluble and total dietary fibre contents significantly decreased throughout the harvest time of the original fresh fruit. Results suggested that peach DF concentrate may be not only an excellent DF source but an ingredient in the food industry because it showed a high affinity for water (9.12–12.09 g water/g fibre) and low energy (3.723–3.494 kcal/g). However, the use of this material could affect the colour and pH of the final product.

Antimicrobial Activity of Essential Oils on Salmonella Enteritidis, Escherichia coli, and Listeria innocua in Fruit Juices

The antimicrobial properties of essential oils (EOs) and their derivatives have been known for years. However, the information published about the minimal effective concentration of EOs against microorganisms in fruit juices is scarce. In this study, both MIC and MBC of six EOs (lemongrass, cinnamon, geraniol, palmarosa, or benzaldehyde) against Salmonella Enteritidis, Escherichia coli, and Listeria innocua were determined by the agar and broth dilution methods, respectively. All of the six EOs inhibited the microbial (Salmonella Enteritidis, E. coli, and L. innocua) growth at a concentration from 1 microl/ ml (MIC). These studies led to choosing the three most effective EOs. Lemongrass, cinnamon, and geraniol were found to be most effective in inhibiting the growth of the microorganisms and thus were used for the MBC analysis. On this last point, significant differences (P < 0.05) among EOs, their concentrations, and culture media (apple, pear, and melon juices, or tryptone soy broth medium) were found after comparing the results on MBC for each microorganism. A concentration of 2 microl/ml from lemongrass, cinnamon, or geraniol was enough to inactivate Salmonella Enteritidis, E. coli, and L. innocua in apple and pear juices. However, in melon juice and tryptone soy broth medium, concentrations of 8 and 10 microl/ml from cinnamon, respectively, or 6 microl/ml from geraniol were necessary to eliminate the three microorganisms, whereas lemongrass required only 5 micro/ml to inactivate them. These results suggest that EOs represent a good alternative to eliminate microorganisms that can be a hazard for the consumer in unpasteurized fruit juices. The present study contributes to the knowledge of MBC of EOs against pathogenic bacteria on fruit juices.