Rafael Gómez

Effect of starter cultures on the physico‐chemical and biochemical features in ewe cheese made with extracts from flowers of Cynara cardunculus L

The effect of starter cultures on the physico-chemical and biochemical features of Los Pedroches cheese made by using Cynara Cardunculus L extracts as vegetable coagulant was assessed. Specimens of cheese containing no starter (vats A and C) and others to which a lactic acid starter was added (vats B and D) were stored either under typical farmhouse ripening conditions (vats A and B) or in a controlled chamber at 14°C and 80% relative humidity (vats C and D) for 90 days. The addition of starter cultures and the ripening conditions where found to have no appreciable effect on the moisture, fat, protein, ash, NaCl, Ca and P contents of the cheese, nor on its water activity; however, it resulted in increased lactic acid contents and lower pH values relative to control specimens throughout ripening. The protein breakdown of the cheeses was assessed in terms of soluble nitrogen, non-protein nitrogen, aminoacid nitrogen, ammonia nitrogen, soluble tyrosine and tryptophan, and urea-PAGE. Proteolysis was generally more marked and rapid in cheese containing the lactic starter, the NPN, NH 3 -N and soluble Tyr and Trp contents of which were significantly higher than those of the cheese obtained with no starter. The PAGE technique revealed no appreciable differences between the four cheese batches studied; however, it showed the cheese to be more resistant to β-CN hydrolysis than to α s -CN hydrolysis. In general, the flavour and aroma scores were higher in batches obtained with starter cultures and ripened under controlled conditions.

Water activity of Spanish intermediate-moisture meat products

On the basis of considering foods with water activity from 0·600 to 0·910 to be intermediate-moisture foods (IMF), we determined the water activity, pH, and some chemical parameters for 70 samples from 17 different selected types of Spanish intermediate-moisture meat products. Even though the salt content is the main water-activity depressor, the sodium chloride molality in the overall amount of water of the product cannot be used to calculate the a(w) value of these types of meat products of intermediate moisture.

Calculation of water activity in surface mould-ripened soft cheeses from their chemical composition

Abstract The water activity (Aw) of 24 samples of 12 different brands of Brie cheese and another 12 of Camembert cheese was measured at 20°C by four methods (psychrometric, cryoscopic, dew-point hygrometric and isopiestic equilibration). The cheeses were also analysed chemically for their moisture, salt (NaCl), ash and non-protein nitrogen (NPN) contents. A linear regression analysis of data pairs of the variables [NaCl], [Ash] or [NPN] (in g/100 g moisture) and Aw (average values of the four methods) yielded the following relations A w =0·9813−0·0045 [NaCl] A w =0·9769−0·0019 [Ash] A w =0·9793−0·0101 [NPN] On the other hand, a multiple linear regression analysis of sets of g ash/100 g moisture, g NPN/100 g moisture and average Aw at 20°C led to the equation A w =0·996−0·0029 [Ash] − 0·0106 [NPN] All four equations can be used alone or in conjunction to predict the water activity of surface mould-ripened soft cheeses. The differences between the calculated and measured (average) Aw values were similar to those yielded by the four measurement methods used.

DistribuciÓn ecolÓgica en funciÓn del pH de varias especies leñosas mediterráneas en Sierra Morena (España)

Se ha estudiado el comportamieto ecologico de 17 especies lenosas mediterraneas ( Arbutus unedo Cistus albidus, C. ladanifer, C. monspeliensis, C. salvifolius, Erica arborea, E. australis, Genista hirsuta, Lavandula stoechas, Phyllirea angustifolia, Phlomis purpurea, Pistacia lentiscus, Querqus rotundifolia, Q. suber, Q. coccifera, Q. faginea, Rosmarinus officinalis ) con respecto al pH del suelo en la region de Sierra Morena. Para ello han sido considerados tanto el valor optimo y la amplitud ecologicos de cada especie en base a sus medias aritmeticas y desviaciones estandar, respectivamente. Como resultado de este analisis se han detectado distribuciones netamente acidofilas como las de A. unedo, C. ladanifer, E. arborea, E. australis y L. stoechas (valores medios inferiores a 5,6) frente a otras de tendencia neutrofila-basofila como C. albidus y Ph. purpurea (valores medios de 6,8), ademas de ostras claramente indiferentes a la reaccion del suelo como Q. coccifera, R. officinalis, P. lentiscus y Q. rotundifolia (rangos superiores a 4,0)

Water activity and chemical composition of some food emulsions

Abstract The water activity, pH and other compositional parameters such as the moisture, fat and NaCl contents of various food emulsions were determined: butters, margarine (W/O) and mayonnaises (O/W). Water activity was determined by a gravimetric method (PEC procedure) and an instrumental method (dew-point hygrometer). The mean a w values obtained for the samples assayed were 0.904 ± 0.050 (butters), 0.914 ± 0.028 (margarines) and 0.947 ± 0.013 (mayonnaises). The a w of the butter and margarine samples could be predicted with an error less than 0.02 units from the NaCl content of their aqueous phase ( m ) by using the following simple linear regression equation: a w =0·954 − 0·036m This equation could not be used to predict the a w of the mayonnaises, which, however, were obtained by using the Chen equation for mixtures of solutes.