Modelling of the hydrolysis of sorghum straw at atmospheric pressure

Sorghum straw is a renewable, cheap and widespread resource. The acid hydrolysis of sorghum straw to obtain xylose solutions could be a good alternative for this abundant resource. The H₂SO₄ hydrolysis of sorghum straw at two different temperatures (80 and 100 °C) and three H₂SO₄ concentrations (2, 4 and 6%) using a solid/liquid ratio of 1:10 (w/w) was studied. Kinetic parameters of mathematical models for predicting the concentrations of xylose, glucose, acetic acid and furfural were determined. The activation energy of the release reaction was 183.3 kJ mol^?1 for xylose and 185.8 kJ mol^?1 for glucose. The optimal conditions found were 6% H₂SO₄ at 100 °C for 60 min, which allow one to obtain a solution with 18.27 g xylose l^?1, 6.78 g glucose l^?1, 0.7 g furfural l^?1 and 1.35 g acetic acid l^?1. It is concluded that this process has potential for utilisation of this renewable lignocellulosic resource. © 2002 Society of Chemical Industry     

Production of fermentable media from vine‐trimming wastes and bioconversion into lactic acid by Lactobacillus pentosus

Trimmings of vineshoots, an agricultural waste with little use, were hydrolysed with dilute sulphuric acid (1–5%) in order to obtain sugar solutions suitable as fermentation media. The operational conditions for hydrolysis were selected on the basis of both the generation of hemicellulosic sugars (mainly xylose) and glucose and the concentrations of reaction byproducts affecting fermentation (furfural, hydroxymethylfurfural and acetic acid). Hemicellulosic hydrolysates were supplemented with nutrients and fermented with Lactobacillus pentosus, without any previous detoxification stage, to produce lactic acid. Under the best operational conditions assayed (3% H₂SO₄ and 15 min), 21.8 g lactic acid l^?1 was produced (Q_P = 0.844 g l^?1 h^?1, Y_P/S = 0.77 g g^?1), which represents a theoretical yield of 99.6%. Acetic acid was the primary byproduct formed from xylose, at about 25% of the lactic acid level. Copyright © 2004 Society of Chemical Industry     

Lipolysis,lipid peroxidation and texture of Serrano ham processed under different ripening temperature conditions

Lipolysis, lipid peroxidation, texture and rancid taste were investigated in Serrano hams processed under low, medium and high ripening temperature conditions (RTC) for 15 months. Medium RTC hams showed the highest contents of saturated and monounsaturated free fatty acids (FFAs) from month 5 to 15 and of polyunsaturated FFAs from month 7 to 12. The primary peroxidation index decreased during ripening in all hams, with higher levels for low RTC hams from month 5 onwards. Contrarily, the secondary peroxidation index increased during ripening in all hams, with higher levels for medium RTC hams from month 7 onwards. Texture parameters varied significantly among ham muscles. Shear force increased during ripening in all hams, with higher values for medium RTC hams, whereas cutting force was not influenced by RTC or ripening time. Rancid taste scarcely developed during ripening and was not affected by RTC.     

Antioxidant properties,radical scavenging activity and biomolecule protection capacity of flavonoid naringenin and its glycoside naringin: a comparative study

BACKGROUND: This study was designed to evaluate and compare antioxidant capacity and radical scavenging activity of naringin and its aglycone by different in vitro assays. The effects of flavanones on lipid peroxidation, glutathione (GSH) oxidation and DNA cleavage were also assessed. RESULTS: The results showed that naringenin exhibited higher antioxidant capacity and hydroxyl and superoxide radical scavenger efficiency than naringin. Our results evidenced that glycosylation attenuated the efficiency in inhibiting the enzyme xanthine oxidase and the aglycone could act like a more active chelator of metallic ions than the glycoside. Additionally, naringenin showed a greater effectiveness in the protection against oxidative damage to lipids in a dose‐dependent manner. Both flavanones were equally effective in reducing DNA damage. However, they show no protective effect on oxidation of GSH. CONCLUSION: The data obtained support the importance of characterizing the ratio naringin/naringenin in foods when they are evaluated for their health benefits. Copyright © 2010 Society of Chemical Industry     

Timing of the inhibitory effect of fruit on return bloom of ‘Valencia’ sweet orange (Citrus sinensis (L.) Osbeck)

BACKGROUND: In Citrus the inhibitory effect of fruit on flower formation is the main cause of alternate bearing. Although there are some studies reporting the effect on flowering of the time of fruit removal in a well‐defined stage of fruit development, few have investigated the effect throughout the entire fruit growth stage from early fruitlet growth to fruit maturity. The objective of this study was to determine the phenological fruit developmental stage at which the fruit begins its inhibitory effect on flowering in sweet orange by manual removal of fruits, and the role of carbohydrates and nitrogen in the process. RESULTS: Fruit exerted its inhibitory effect from the time it was close to reaching its maximum weight, namely 90% of its final size (November) in the present experiments, to bud sprouting (April). The reduction in flowering paralleled the reduction in bud sprouting. This reduction was due to a decrease in the number of generative sprouted buds, whereas mixed‐typed shoots were largely independent of the time of fruit removal, and vegetative shoots increased in frequency. The number of leaves and/or flowers per sprouted shoot was not significantly modified by fruit load. CONCLUSION: In ‘Valencia’ sweet orange, fruit inhibits flowering from the time it completes its growth. Neither soluble sugar content nor starch accumulation in leaves due to fruit removal was related to flowering intensity, but some kind of imbalance in nitrogen metabolism was observed in trees tending to flower scarcely. Copyright © 2010 Society of Chemical Industry     

Temperature and pH as factors influencing droplet size distribution and linear viscoelasticity of O/W emulsions stabilised by soy and gluten proteins

The influence of pH and two post-emulsification treatments (pH modification and thermal cycles) over linear dynamic viscoelasticity and droplet size distribution, DSD, of O/W emulsions (75% oil) stabilized either by soy protein isolate, SPI, or wheat gluten, WG were studied in the present work. Rheological properties and droplet size of fresh emulsions showed an important dependence on pH as a consequence of the role of electrostatic interactions, not being possible to obtain a stable emulsion for pH values close to the protein isoelectric point, pI, (4–5 for SPI and 6 for WG). In order to overcome this inconvenient, an alternative emulsification procedure, basically consisting in a modification of pH after emulsification (indirect emulsification), was successfully developed. Emulsions obtained after this post-emulsification treatment, showed higher elastic (G′) and loss (G″) moduli and also larger oil droplets than fresh emulsions prepared at the same pH. Moreover, the application of upward/downward temperature cycles from 20 to 70 °C to emulsions directly prepared at a pH yielded to significantly higher values of the rheological functions when compared to those found for fresh emulsions. Accordingly, both post-emulsification treatments lead to apparent enhancements in emulsion rheology and microstructure, which is indicative of a good potential to improve long-term emulsion stability.     

Triterpenic acids in table olives

An experimental investigation was carried out for the first time on the triterpenic acids in table olives. Maslinic acid was found in a higher concentration than oleanolic acid in the flesh of 17, unprocessed olive varieties, with the Picual and the Manzanilla varieties showing the highest and almost the lowest contents, respectively. The level of triterpenic acids in several types of commercial black and green olives ranged from 460 to 1470 mg/kg fruit, which represents a much higher value than reported for virgin olive oils. In fact, the NaOH treatment employed to debitter black and green olives reduced the concentrations of these substances in the flesh because of their solubilisation into alkaline solutions. Thus, natural black olives, which are not treated with NaOH, showed a higher concentration than 2000 mg/kg in the olive flesh. These results will contribute to the reevaluation of table olives from a nutritional and functional point of view because of the promising bioactivity properties attributed to olive triterpenic acids.     

Effect of calcium pidolate on the rheological characteristics of jams and gelatins

Calcium pidolate is a calcium containing molecule that has the essential advantage of being absorbed more easily and in a greater proportion than any other calcium compound. The combination between a low methoxyl pectin and calcium allows forming food gels with a small amount of sugar. In this work, the use of calcium pidolate in the composition of two of these products (jams and gelatins) has been assayed, testing its rheological properties. An optimum content of calcium pidolate has been found for each product and sugar proportion. Both in jams and gelatins, the results obtained with calcium pidolate were better than the ones obtained with calcium chloride.