Esperanza Mollá

Quality attributes of strawberry during ripening

Abstract A study of the organic acid and soluble sugar contents in strawberry fruits was carried out. These compounds were separated, identified and quantified using high-performance liquid chromatography with diode array spectroscopic detection and refractive index detection, for organic acids and soluble sugars, respectively. Strawberry fruits were analysed at six development stages, from fruit set to senescence. Changes in these parameters were studied during development and ripening. Titratable acidity, pH, reducing sugars and soluble solids, as well as phenolic compounds and pectic substances, were also determined. Different sugar:acid ratios were used as a quality index. Strawberry fruits with the best quality characteristics for consumption were obtained on day 28 from fruit set.

Characterization of Industrial Onion Wastes (Allium cepa L.): Dietary Fibre and Bioactive Compounds

The food industry produces a large amount of onion wastes, making it necessary to search for possible ways for their utilization. One way could be to use these onion wastes as a natural source of high-value functional ingredients, since onion are rich in several groups of compounds, which have perceived benefits to human health. The objective of this work is to gain knowledge of any differences between the different onion wastes obtained from industry and non-commercial bulbs to use them as food ingredients rich in specific compounds. The results showed that brown skin and top–bottom could be potentially used as functional ingredient rich in dietary fibre, mainly in insoluble fraction, and in total phenolics and flavonoids, with high antioxidant activity. Moreover, brown skin showed a high concentration of quercetin aglycone and calcium, and top–bottom showed high concentration of minerals. Outer scales could be used as source of flavonols, with good antioxidant activity and content of dietary fibre. However, inner scales could be an interesting source of fructans and alk(en)yl cystein sulphoxides. In addition, discarded onions (cvs Recas and Figueres) could be used as a good source of dietary fibre, and cv Recas also as a source of phenolics compounds.

Starch, Functional Properties, and Microstructural Characteristics in Chickpea and Lentil As Affected by Thermal Processing

Changes in starch, functional, and microstructural characteristics that occurred in chickpea and lentil under soaking, cooking, and industrial dehydration processing were evaluated. Available starch in raw legumes represented 57-64%, and resistant starch (RS) is a significant component. As a result of cooking, available starch contents of soaked chickpea and lentil were significantly increased (21 and 12%, respectively) and RS decreased (65 and 49%, respectively) compared to raw flours. A similar trend was exhibited by dehydration, being more relevant in lentil (73% of RS decrease). The minimum nitrogen solubility of raw flours was at pH 3, and a high degree of protein insolubilization (80%) was observed in dehydrated flours. The raw legume flours exhibited low oil-holding capacities, 0.95-1.10 mL/g, and did not show any change by thermal processing, whereas water-holding capacities rose to 4.80-4.90 mL/g of sample. Emulsifying activity and foam capacity exhibited reductions as a result of cooking and industrial dehydration processing. The microstructural observations were consistent with the chemical results. Thus, the obtained cooked and dehydrated legume flours could be considered as functional ingredients for food formulation.

Study of total fructan and fructooligosaccharide content in different onion tissues

The objective of this work was to determine the fructan and fructooligosaccharide (FOS) content of different onion tissues in order to evaluate the potential use of onion by-products from the food industry as a source of FOS and fructans. Assays with two methods were carried out to optimise the extraction procedure. The main FOS, namely kestose (GF2), nystose (GF3) and fructofuranosylnystose (GF4), were measured directly using standard sugars. The method for total fructans was based on enzymatic treatment (Novozym 230) of ethanolic/aqueous extract followed by determination of released fructose and glucose by HPLC. Data showed a clear predominance of GF2 in every onion tissue and no occurrence of highly polymerised fructans. The tissues richest in fructans were the fleshy layers, so that the outer two fleshy layers turn out to be the best onion by-product as a possible fructan source. © 2000 Society of Chemical Industry

Effect of sterilisation on dietary fibre and physicochemical properties of onion by-products

Food industries are forced to develop productions without secondary residues. Therefore, there is a considerable emphasis on the recovery, recycling and upgrading of wastes. The possibility has been suggested for the conversion of onion waste into food ingredients, but with a stabilisation treatment being necessary. The objective of this work was to study the effect of sterilisation on fibre fractions, fibre composition and physicochemical properties of onion by-products to evaluate the use of sterilised onion by-products as a source of fibre. Sterilisation produced insoluble dietary fibre decreases and soluble dietary fibre increases, improving the soluble:insoluble ratio. Uronic acids of insoluble dietary fibre were partly solubilised and losses of cellulose and Klason lignin were observed. Physicochemical properties slightly changed with sterilisation. Sterilised by-products showed less oil holding capacity, cation exchange capacity and swelling capacity than control ones, although their physicochemical properties were generally higher than those of cellulose. Therefore, sterilisation would be considered a good method to stabilise onion by-products to use as a potential dietary fibre ingredient.

Effects of gibberellic acid (GA3) on strawberry PAL (phenylalanine ammonia-lyase) and TAL (tyrosine ammonia-lyase) enzyme activities

Gibberellic acid (GA 3 ) treatments (30 and 60 μg litre -1 ) were applied to young plants (Fragaria ananassa cv Chandler). Fruits were harvested at various developmental stages (14, 21, 28 and 35 days from fruit set). Weight and size, phenolic compounds (total polyphenols and anthocyanins) and enzyme activities, phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) were determined. Our aim was to obtain detailed information about PAL and TAL activities related to the strawberry colour during development and ripening processes and to determine the effects of exogenous treatments of GA 3 on PAL and TAL activities. Exogenous treatments of GA 3 improve weight, size and colour of strawberry fruits, and affect PAL and TAL activities. We found that the anthocyanin content and PAL activity are enhanced by the exogenous treatment of GA 3 in the range of 30 μg litre -1 . However, with the higher GA 3 treatment, only the anthocyanin content is affected in that way. These findings suggest that gibberellic acid effect on PAL, TAL and ultimately anthocyanin enhancement is dosage related and saturation of the response occurs at 30 μg litre -1 .

Pectin changes during the development and ripening of eggplant fruits

Abstract In developing and ripening eggplant fruits (Semi-round striped, Purple long and Black round), the main pectin fractions, water-, ammonium oxalate-, and alkalisoluble, were estimated up to maturity and ripening. The determinations were made using the m-hydroxydiphenyl assay, which was automated resulting in a rapid and sensitive method to quantitatively determine the pectic substances. For all cultivars studied, total pectic polysaccharides decreased during the initial growth period and after 15 days showed a slightly increasing trend. The concentration of water-soluble pectic substances decreased until 28 days, as did the oxalate-soluble fraction. These two pectin fractions increased during the development period between 28 and 42 days while the alkali-soluble (protopectin) fraction decreased. The increase of protopectin before physiological maturity, and its subsequent decrease with fruit ripening and softening, indicated the involvement of this fraction in the texture maintenance of eggplant fruits.

Cadmium binding capacity of cocoa and isolated total dietary fibre under physiological pH conditions

Cadmium binding capacity of cocoa and isolated total dietary fibre (TDF) was investigated in vitro under simulated physiological pH conditions. The effect of Cd 2+ retention on the bioavailability of essential endogenous minerals was also studied. The sample was mixed with buffered Cd 2+ solution and, after equilibration, the residue was separated for quantitative measurement of soluble Cd 2+ in the supernatant. Cocoa exhibited a high affinity for Cd 2+ in solution. The amount of bound Cd 2+ rose with increasing metal concentration and pH. TDF was the major fraction responsible for binding of Cd 2+ by cocoa. Phytate was probably another important cause of the decrease of Cd 2+ solubility. The addition of various concentrations of Cd 2+ to cocoa and TDF was shown to affect the solubility of endogenous minerals. When Cd 2+ was bound by TDF there was a marked increase in the availability of endogenous Fe, Zn, Ca and Mg, specially at duodenal pH conditions.

Onion (Allium cepa L.) by-products as source of dietary fiber: physicochemical properties and effect on serum lipid levels in high-fat fed rats

The effect of industrial processes used to obtain onion by-products was evaluated. Fiber composition and physicochemical properties were assessed in order to choose the best process to obtain high-fiber ingredients. Moreover, the effect of the inclusion of the dietary fiber-rich onion by-products in a high-fat diet on serum lipids of rats was also evaluated. Bagasse was the best by-product since it showed the highest fiber content with a balanced soluble-to-insoluble fiber ratio and the best physicochemical properties. This fact is related to its high fiber content and also due to its composition, rich in uronic acids and polysaccharides, which explains its high cation exchange capacity, water-holding capacity and swelling capacity. In addition, the inclusion of Bagasse in a high-fat diet produced a reduction in the serum lipid and total cholesterol increases induced by high-fat diet. This effect could be related to the high cation exchange and swelling capacities that Bagasse showed, since these properties can create a concerted effect in reducing the number of intact micelles available, the transit time, and consequently the total time available for cholesterol and lipid absorption in the small intestine.

Changes in the chemical composition of eggplant fruits during storage

Abstract Changes in the chemical composition of eggplant fruits (Solanum melongena L., cultivar ‘Redonda negra lisa’) were studied during 21 days of storage at 5, 10 or 20°C. Titratable acidity increased after 10 days of storage, the greatest increase occurring at 20°C. Reducing and total sugars increased from 4 to 14 days of storage at 10 or 20°C, but decreased at 5°C. Ascorbic acid content after 18 days at 10 or 20°C decreased by ∼ 75%. Total polyphenol content initially increased, followed by a gradual decrease. The optimum storage temperature ranged from 5 to 10°C, the storage period being extended up to 15 days.