José A. Ramírez

Kinetic study of the acid hydrolysis of sugar cane bagasse

Economic interest in xylitol production can be enhanced if the needed xylose solutions can be obtained from the hydrolysis of low-cost lignocellulosic wastes. Sugar cane bagasse is a renewable, cheap and widely available waste in tropical countries. The hydrolysis of sugar cane bagasse to obtain xylose solutions has a double consequence, the elimination of a waste and the generation of a value-added product. The objective of this work was to study the xylose production from sugar cane bagasse by sulphuric acid hydrolysis at several temperatures (100, 122 and 128 C) and concentrations of acid (2%, 4% and 6%). Kinetic models were developed to explain the variation with time of xylose, glucose, acetic acid and furfural generated in the hydrolysis. Optimal conditions found were 2% H2SO4 at 122 C for 24 min, which yielded a solution with 21.6 g xylose/l, 3 g glucose/l, 0.5 g furfural/l and 3.65 g acetic acid/l. In these conditions, � 90% of the hemicelluloses was hydrolysed. 2002 Elsevier Science Ltd. All rights reserved.

Hydrolysis of sugar cane bagasse using nitric acid: a kinetic assessment

Abstract Sugar cane bagasse was hydrolysed using nitric acid at variable concentration (2–6%), reaction time (0–300 min) and temperature (100–128 °C). The concentration of sugars released (xylose, glucose and arabinose) and degradation products (acetic acid and furfural) were determined and the kinetic parameters of mathematical models for predicting them in the hydrolysates were obtained. The influence of temperature was also studied using the Arrhenius equation. Applying the kinetic models obtained, the optimal conditions selected were: 122 °C, 6% HNO3 and 9.3 min. Using these conditions, 18.6 g xylose/l; 2.04 g arabinose/l; 2.87 g glucose/l; 0.9 g acetic acid/l and 1.32 g furfural/l were obtained. Comparison of these results with those obtained using sulphuric and hydrochloric acids demonstrated that the nitric acid was the most efficient catalyst for hydrolysis.

Mathematical modelling of hemicellulosic sugar production from sorghum straw

Abstract Xylose is a hemicellulosic sugar that can be used as a carbon and energy source for the growth of microorganisms. The main use of xylose is its bioconversion to xylitol. Sorghum straw is a raw material for xylose production that has not yet been studied. The objective of this work was to study xylose production by hydrolysis of sorghum straw at 122°C, using three concentrations of sulphuric acid (2%, 4% and 6%). Kinetic parameters of mathematical models for predicting the concentration of xylose, glucose, acetic acid and furfural were found and optimal conditions selected. These were 2% H2SO4 at 122°C for 71 min, which yielded a solution with 18.17 g xylose/l, 6.73 g glucose/l, 0.9 g furfural/l and 1.51 g acetic acid/l.

Effect of the hydrochloric acid concentration on the hydrolysis of sorghum straw at atmospheric pressure

Abstract Sorghum straw is a raw material useful for the xylose production by hydrolysis. The main application of xylose is its bioconversion to xylitol, a functional sweetener with important technological properties. The objective of this work was to study the hydrolysis of sorghum straw with hydrochloric acid at 100 °C. Several concentrations of HCl (2–6%) and reaction time (0–300 min) were evaluated. Kinetic parameters of mathematical models for predicting the concentration of xylose, glucose, acetic acid and furfural in the hydrolysates were found and used to optimise the process and compared with results reported in the literature using other conditions and acids. Optimal conditions found for hydrolysis were 6% HCl at 100 °C for 83 min, which yielded a solution with 21.3 g xylose/l, 4.7 g glucose/l, 0.8 g furfural/l and 2.8 g acetic acid/l.

Effect of pectins on the gelling properties of surimi from silver carp

Abstract Protein–carbohydrate interactions affect the functional properties in foods where proteins are the major ingredients, such as meat and fish processed products. The objective of this work was to evaluate the effect of pectin gum with different degree of methoxylation and calcium chloride on the mechanical properties of surimi gels. Surimi from silver carp was supplemented with pectin gum at 1% (w/w). Four high methoxyl pectins and two low methoxyl pectins were evaluated. Calcium chloride was added at 0.2%. Changes on shear stress, shear strain at failure, texture profile analysis and water holding capacity were evaluated. LM35, an amidated low methoxyl pectin, improved shear stress, hardness, and water holding capacity, while the four high methoxyl pectin and the no amidated low methoxyl pectin did not improved the mechanical properties of surimi gels as compared with the control.

Surimi gels from striped mullet (Mugil cephalus) employing microbial transglutaminase

Striped mullet (Mugil cephalus) is an abundant marine coastal fish of tropical waters and has a low commercial value. This work deals with the assessment of striped mullet as a resource for surimi gels. To improve the gels obtained, the addition of microbial transglutaminase was evaluated. Optimal conditions for setting were determined using mathematical models. Concentration of microbial transglutaminase (MTGase), temperature and time were studied to improve the mechanical properties of surimi gels from striped mullet. Shear stress was strongly affected by the variables studied while shear strain was moderately affected. Maximum shear stress (156 kPa) was obtained by employing the following setting conditions: a concentration of MTGase of 9.3 g/kg of surimi, a temperature of 37°C and a time of 3.9 h. Under these conditions the shear strain was 1.34. Maximum shear strain (1.57) was obtained by employing the following conditions: a concentration of MTGase of 5 g/kg of surimi, a temperature of 34.5°C and a time of 1 h. Under these conditions the shear stress was 123 kPa.

Modeling of the hydrolysis of sugar cane bagasse with hydrochloric acid

Sugar cane bagasse was hydrolyzed under different concentrations of hydrochloric acid (2–6%), reaction times (0–300 min), and temperatures (100–128°C). Sugars obtained (xylose, glucose, arabinose, and glucose) and deg-radation products (furfural and acetic acid) were determined. Based on the Saeman model and the two-fraction model, kinetic parameters for predicting these compounds in the hydrolysates were developed. The influence of temperature was studied using the Arrhenius equation. The optimal conditions selected were 128°C, 2% HCl, and 51.1 min. Using these conditions, 22.6g xylose/L, 3.31 garabinose/L, 3.77 g glucose/L, 3.59 g acetic acid/L, and 1.54 g furfural/L were obtained.

Surimi of fish species from the Gulf of Mexico: evaluation of the setting phenomenon

Abstract Atlantic croaker ( Micropogon undulatus ), Mexican flounder ( Cyclopsetta chittendeni ) and Northern kingfish ( Menticirrhus saxatilis ) are warm water species abundant in the Gulf of Mexico, usually obtained as shrimp by-catch. Gels from these species were obtained by several treatments: (1) setting at 25°C/3 h followed by cooking at 90°C/15 min; (2) setting at 40°C/30 min and 90°C/15 min; (3) 90°C/15 min (control). Three different additives were studied: 0.66% ammonium chloride, 0.2% EDTA and 0.2% calcium chloride. The setting phenomenon was induced at 40°C in the three species. 0.2% calcium chloride improved shear stress and shear strain in surimi gels from Atlantic croaker and Northern kingfish. 87.98 and 98.49 kPa for shear stress, and 2.23 and 2.15 for shear strain were achieved, respectively.

Effect of xanthan and locust bean gums on the gelling properties of myofibrillar protein

Abstract Protein-hydrocolloids interactions play an important role on textural and mechanical properties of foods. The objective of this work was to evaluate the effect of xanthan and locust bean gums on the gelling ability of myofibrillar proteins at different levels of calcium addition. Surimi was supplemented with xanthan (X) and locust bean (LB) gums at different X/LB ratios: 0.00/1.00, 0.25/0.75, 0.50/0.50, 0.75/0.25, 1.00/0.00. Calcium chloride was added at 0.2 or 0.4%. Changes on shear stress and shear strain at the failure of surimi gels were evaluated. Addition of 0.4% of calcium chloride improved the mechanical properties. Locust bean added alone negatively affected the shear stress of gels. Xanthan at levels of 0.75 and 1.00 had a disruptive effect on the gelling forming ability. This negative effect was partially inhibited with addition of 0.4% of calcium chloride. A profitable effect was found when a X/LB ratio of 0.25/0.75 was added, with an increase on the mechanical properties of surimi gels. Xanthan and locust bean gums could be employed to elaborate surimi gels when added at a X/LB ratio of 0.25/0.75.

Negative effect of combining microbial transglutaminase with low methoxyl pectins on the mechanical properties and colour attributes of fish gels

Abstract The objective of this work was to determine the effect of combining different concentrations of microbial transglutaminase (MTGase) and types of low methoxyl (LM) pectin on the mechanical properties (textural profile analysis, puncture test) and the colour attributes of fish restructured products. A disruptive effect was observed when LM pectin and MTGase were added to fish gels. Adding 1% MTGase with LM32 pectin significantly decreased the hardness (3.85 kg), springiness (0.631) and chewiness (0.434 kg). When LM32 pectin and 0.1% MTGase were added together, significant decreases of the three puncture test parameters were observed. The chroma of fish gels decreased significantly when 0.3% MTGase was added. Fish gels containing the LM35 pectin had higher chroma values than all other fish gels with the same level of MTGase. Hue value was increased in all fish gels after increasing the MTGase level. The results obtained showed that LM pectin is not suitable for use in products containing MTGase.