A lumped model of the lipase catalyzed hydrolysis of sardine oil to maximize polyunsaturated fatty acids content in acylglycerols.

The aim of this work was to produce diacylglycerols (DAG) and monoacylglycerols (MAG) with a high content of polyunsaturated fatty acids (PUFA). Rhizomucor miehei lipase mediated-hydrolysis of sardine oil was conducted at several water activities. The system was mechanistically modeled to predict the time evolution of the concentration of triacylglycerols, DAG, MAG and free fatty acids (FFA) and the concentration of saturated, mono- and polyunsaturated fatty acids. The release of the first fatty acid from the triacylglycerol was independent on the unsaturation degree. Contrary, the hydrolysis of the second one was highly affected by the degree of unsaturation, PUFA being the fatty acids that showed the highest resistance to hydrolysis. MAG percentage was maximum (7mol%) at lower water activities, while DAG content was favored at higher water activities (35mol%), achieving a 2-fold concentration of DHA.

Development of an up-grading process to produce MLM structured lipids from sardine discards.

The aim of the work was to produce MLM structured lipids with caprylic acid (M) as medium chain fatty acid located at the external bonds of the glycerol backbone and concentrated polyunsaturated fatty acids (L) from sardine discards (Sardine pilchardus) in the central bond of the glycerol. To that end, the following steps were conducted: (i) fish oil extraction, (ii) Omega-3 free fatty acids (FFA) concentration (low temperature winterization), (iii) two-steps enzymatic esterification and (iv) triacylglycerols (TAG) purification (liquid column chromatography). The resultant purified triacylglycerols accomplished with the oxidative state (peroxide and anisidine value, PV and AV) required for refined oils. As enzymatic treatment, Omega-3 concentrate FFA (Omega-3>600mg Omega-3 per g oil) were esterified with dicaprylic glycerol employing Novozyme 435. This process presented high regioselectivity, with ∼80mol% of concentrated fatty acids esterified at the sn-2 position.

Modelling of the production of ACE inhibitory hydrolysates of horse mackerel using proteases mixtures.

Fish protein hydrolysates from Mediterranean horse mackerel were produced by using a mixture of two commercial endoproteases (i.e. subtilisin and trypsin) at different levels of substrate concentration (2.5 g L(-1), 5 g L(-1), and 7.5 g L(-1) of protein), temperature (40 °C, 47.5 °C, and 55 °C) and percentage of subtilisin in the enzyme mixture (0%, 25%, 50%, 75% and 100%). A crossed mixture process model was employed to predict the degree of hydrolysis (DH) and the ACE inhibitory activity of the final hydrolysates as a function of the experimental factors. Both models were optimized for a maximum DH and ACE inhibition. A maximum DH (17.1%) was predicted at 2.54 g L(-1) of substrate concentration, 40 °C and an enzyme mixture comprising 38.3% of subtilisin and 61.7% of trypsin. Although its proteolytic activity is limited, the presence of trypsin in the enzyme mixture allowed obtaining higher degrees of hydrolysis at low temperatures, which is desirable to minimize thermal deactivation of the proteins. Similarly, a percentage of ACE inhibition above 48% was attained at 2.5 g L(-1) of protein, 40 °C and a 1 : 1 mixture of both proteases. Higher values of ACE inhibition could be attained by increasing both the temperature and the amount of trypsin in the enzyme mixture (e.g. 50% ACE inhibition at 55 °C and 81.5% of trypsin). Finally, those hydrolysates exhibiting the highest levels of ACE inhibition were subjected to simulated gastrointestinal digestion. These assays confirmed the resistance of active fractions against their degradation by digestive enzymes.

Functional and antioxidant properties of hydrolysates of sardine (S. pilchardus) and horse mackerel (T. mediterraneus) for the microencapsulation of fish oil by spray-drying.

The functionality of fish protein hydrolysates (FPH) for the microencapsulation of fish oil was investigated. Muscle protein from sardine (Sardina pilchardus) and horse mackerel (Trachurus mediterraneus) was hydrolysed using Alcalase or trypsin. Physically stable emulsions suitable for spray-drying were obtained when using FPH with a degree of hydrolysis of 5%. Microencapsulation efficiency amounted to 98±0.1% and oxidative stability of the encapsulated oil over a period of twelve weeks was in a similar range as it is reported for other matrix systems. Therefore, the suitability of FPH for use in spray-dried emulsions has been shown for the first time. Since no clear correlation between the antioxidative activity of the FPH and the course of lipid oxidation could be established future research is required to more specifically characterise the molecular structure of the peptides and its impact on protein alteration and role in lipid oxidation.

Seasonal variations in the regiodistribution of oil extracted from small-spotted catshark and bogue.

The aim of this work was to seasonally characterize the nutritional quality of oil extracted from small-spotted catshark (Scyliorhinus canicula) and bogue (Boops boops). The proximate composition, lipid profile and regiodistribution of the fatty acid in the glycerol backbone were analyzed. In addition, three nutritional indexes were calculated (atherogenicity and thrombogenicity indexes and the hypocholesterolaemic/hypercholesterolaemic ratio). Both species presented PUFA as the predominant fraction, the most abundant being DHA. Healthy values of the aforementioned indexes were maintained throughout the year. Moreover, the relative composition of omega 3 fatty acids at the sn-2 position ranged from 47.3 to 66.8 mol%, attracting interest in the employment of these oils as the raw source for the production of 2-monoacylglycerols. Regarding the individual behavior of each fatty acid, DHA presented a high tendency to occupy the sn-2 bond, whereas EPA presented the opposite behavior.

Correlation of base consumption with the degree of hydrolysis in enzymic protein hydrolysis.

It is fairly easy to control the enzymic hydrolysis of proteins in alkaline conditions by measuring the base consumption required to keep the pH constant in the reactor. Unfortunately, however, base consumption is not related in any simple way to the degree of hydrolysis reached at any given moment and to establish this relationship it is essential to find out the mean pK of the alpha-amino groups released during the hydrolytic process. We have shown here that the correct mean pK value varies according to the pH of the working conditions and that the relationship between these values may depend upon the kind of protein and protease used. We have put forward a method for determining this relationship experimentally by using a given protein-protease system, consisting of an alkaline titration of the raw protein and when partially hydrolysed. We have tested the results predicted by our theoretical model by applying it to the hydrolysis of whey proteins with a bacterial protease from Bacillus licheniformis at 50 degrees C, pH 8.0. This model can easily be applied to any hydrolytic process involving the appearance of functional groups that are partially protonizable under the working conditions in question in order to follow the kinetics of the reaction via the consumption of the neutralizing agent required to keep pH constant.

Serum amino acid concentrations in growing rats fed intact protein versus enzymatic protein hydrolysate-based diets.

The aim of this study was to evaluate the effect of the molecular form of dietary protein (native or enzymatically hydrolyzed) on the total serum protein concentrations and the serum amino acid profile of growing rats at weaning. Wistar male rats at weaning were randomly assigned to one of the four isocaloric and isonitrogenous (12% protein equivalent content) diets and fed for 7 days. The protein sources of the diets were: whey protein, casein and their respective hydrolysates. Differences in the serum amino acid profiles exclusively related to the amino acid composition of the protein (casein or whey proteins) were observed, but differences due to their molecular form were not observed. It is concluded that the use of enzymatic hydrolysates of whey proteins and casein has the same effects as their native proteins on nitrogen intake, body weight gain and serum amino acid profile of growing rats at weaning.

Enzymatic hydrolysis of whey proteins: I. Kinetic models.

We have studied the enzymatic hydrolysis of whey proteins at pH 8 and50 degrees C with two proteases of bacterial origin, MKC Protease 660 L, and one of animal origin, PEM 2500 S. Our results show that a greater degree of hydrolysis is achieved under the same experimental conditions with the bacterial proteases than with the animal one. In our interpretation of the results we propose a mechanism in which the hydrolytic reaction is a zero-order one for the substrate, and the enzyme denaturalizes simultaneously via a second-order kinetic process due to free enzyme attacking enzyme bound to the substrate. Our results also indicate that there is an irreversible serine-protease inhibitor in whey proteins. (c) 1994 John Wiley & Sons, Inc.

Enzymatic hydrolysis of whey proteins. II. Molecular-weight range.

Using high-pressure liquid chromatography we studied the distribution of molecular weights in whey-protein hydrolysates using the following commercially obtained proteases: Alcalasa 0.6 L and Protease 660 L, both bacterial in origin, and PEM 2500 S, of animal origin. In each of the systems, the range of molecular weights in the hydrolysate depended solely on the degree of hydrolysis (DH) achieved. For DH >/= 20, between 65% and 95% of the hydrolysate is made up of peptides with a molecular weight of less than 1,000 Da. (c) 1994 John Wiley & Sons, Inc.

Laplace's law of the heart and left ventricular wall thickness

A lei de Laplace aplicada ao coraçäo prevê uma parede mais espessa em direçäo à base do ventrículo esquerdo do que ao ápice. Inspeçäo visual de dissecaçöes anatonômicas näo demonstra esta diferença, principalmente por causa de irregularidades geométricas do endocárdio. O objetivo deste estudo foi de encontrar um padräo de distribuiçäo da espessura da parede ao longo do eixo base-ápice para demonstrar (ou rejeitar) a previsäo. Com mediçöes realizadas em coraçöes de oito pessoas normais os resultados foram ajustados por uma parábola do tipo hr = Bo + B1 1r + B2 1r onde os coeficientes B säo iguais, respectivamente, a 76.32, o.77 e 6.64x10, hr é espessura relativa e 1r é o comprimento relativo base-ápice. O máximo das médias de espessura foi localizado em 61% do comprimento do ventrículo (a partir do ápice) com uma regiäo de "parede mais espessa" que variou de 27.7% a 93.1% (aproximadamente 30% a 90%) daquele comprimento. Estes resultados, confirmam a previsäo da lei. Além disto, foi encontrado que isto é verdade somente, (1) para coraçöes em sístole, e (2) quando os músculos papilares fossem incluídos como parte da espessura da parede