IDENTIFICACIÓN DE LAS VARIANTES GENÉTICAS DE LAS PROTEÍNAS DE LA LECHE

Se realizó la identificación de las variantes genéticas de las seroproteínas de la leche: α-lactoalbúmina y β-globulina y de las fracciones caseínicas: α-caseína, β-caseína y κ-caseína, de 18 muestras provenientes de un rebaño de 400 vacas en diferentes estadios de lactación de la Provincia de Reggio-Emilia, Italia (Jersey Danesa, Jersey Americana y Jersey Inglesa), con una producción promedio de 4.008 kg/lactación, destinada para la fabricación de queso Parmigiano Reggiano. Se aplicaron las técnicas: Electroforesis en Gel de Urea-Almidón (Urea-SGE) a pH 8,6 y Urea-SGE a pH 1,7. Electroforesis mediante Focalización Isoeléctrica sobre gel de poliacrilamida (IEF). Electroforesis Capilar Zonal en ambiente ácido (CZE). Cromatografía líquida de alta presión con columna de fase reversa (RPHPLC), utilizándose patrones de referencias de la Universidad de Milano y del “Istituto Lattiero Caseario”, Lodi, Italia. De las técnicas analizadas la RPHPLC, demostró ser la más precisa, seguida por las técnicas CZE, la IEF y la Urea-SGE. Por los requerimientos técnicos de la RP-HPLC, de la CZE y de la IEF, se recomiendan como pruebas alternativas para identificar nuevas variantes y/o cuando se requiera cuantificar las variantes genéticas. La técnica Urea- SGE (pH 8,6 y 1,7) permitió identificar todos los genotipos de las fracciones caseínicas y seroprotéicas, su fácil manejo y poca exigencia en el tratamiento de la muestra y en equipos, la hace recomendable como técnica de rutina para la identificación de variantes genéticas en países en donde se realicen actividades de mejoramiento genético del ganado lechero asistida por marcadores genéticos.Identification of the Genetic Variants for Milk ProteinsAbstractA study to identified genetic variants of milk proteins was conducted. Whey proteins (α-lacto-albumin and β-lactoglobulin) and casein fractions (α, β and κ) were assessed from 18 samples of milk used to produce Parmigiano- Reggiano cheese. Data were from 400 Jersey cows of different origin (Danish, American and English) producing on average 4,008 kg/lactation in the Emilia- Region of Italy. Cows were at different lactation stages. Electrophoresis techniques: Urea-Starch Gel (Urea-SGE) pH 8.6 and 1.7; Iso-electric Focusing on polyacrylamide gel (IEF) and Capillary Zonal in acid environment (CZE), and Reversed-Phase high pressure Liquid Chromatography (RPHPLC) were used with reference materials from the Milan University and the “Istituto Lattiero Caseario”, Lodi, Italy. RP-HPLC was identified as having the highest resolution performance followed by IEF, CZE and Urea-SGE. RP-HPLC, CZE and IEF, are the recommended techniques to identify and quantify new milk-protein variants, due to their complex technical requirements. Urea-SGE (ph 8.6 and 1.7) allowed to identify all the genotypes of casein and whey-proteins fractions. Its easy handling and low sample treatment requirements and equipment needs, make it as the recommended rutinar y technique to identified genetic variants in countries identified intending to include milk protein markers

The Influence of Beta-Lactoglobulin Genetic Polymorphism on Protein Distribution and Coagulation Properties in Milk of Massese Breed Ewes

The genotypic frequencies at the beta-lactoglobulin locus were examined on 128 individual ovine milk samples from Massese breed. Chemical composition, casein and whey protein fractions and tromboelastographic parameters were determined on all individual milk samples. Statistical interrelations were calculated using JMP software 3.02 of SAS Institute. The genotypic frequencies at the beta-lactoglobulin locus were: 0.36 AA; 0.54 AB; 0.10 BB. The BB variant of beta-lactoglobulin could be related to a higher milk production with a lower casein content and a greater overall amount in whey proteins, particularly alpha-La and BSA. The AA and AB genotypes showed higher beta-lactoglobulin and total casein contents, and were related to a better quality of milk either in composition or in rennetability

Detection of buttermilk solids in skimmilk powder by HPLC quantification of aminophospholipids

In considerazione delle sovvenzioni previste dalla Comunit\ue0 Economica Europea a sostegno del latte scremato in polvere (SMP) destinato all\u2019ammasso pubblico, l\u2019aggiunta illecita a questo prodotto di latticello in polvere (BMP), disponibile in abbondanza ed a basso costo negli Stati Membri, si presenta economicamente vantaggiosa ed \ue8 incentivata dalla mancanza di metodi analitici in grado di evidenziarla. Viene proposto un metodo per riconoscere la presenza di BMP nel SMP mediante dosaggio per HPLC della fosfatidilserina (PS) e della fosfatidiletanolammina (PE). L\u2019analisi prevede l\u2019estrazione degli amminofosfolipidi con metanolo, la derivatizzazione automatica con OPA (o-phtalaldeide), la separazione per HPLC in fase inversa su colonna C18 con una corsa di 28minuti e la rilevazione in fluorescenza. Sulla base dell\u2019analisi di numerosi campioni di SMP genuino vengono indicati valori soglia per il contenuto di PS+PE che consentono di riconoscere la presenza \u201csospetta\u201d (P<0.05) o \u201ccerta\u201d (P<0.01) di BMP. Il limite di rilevabilit\ue0 del BMP nel SMP risulta mediamente del 2-3% indipendentemente dalle condizioni di miscelazione utilizzate, solido+solido o liquido+liquido, prima della spraizzazione. Tuttavia causa la variabilit\ue0 del contenuto in amminofosfolipidi, la quantit\ue0 minima rilevabile di BMP pu\uf2 oscillare dall\u20191% al 10% un funzione di origine, condizioni di lavorazione ed et\ue0 dei prodotti utilizzati.Due to the high production of buttermilk in EEC Member States and the aids supported by Community for skimmilk powder (SMP), mixing of buttermilk powders (BMP) with SMP of public storage is economically advantageous and attractive, considering that no analytical methods are available to perform suitable control. A method to recognize buttermilk solids in SMP by quantification of phosphatidylserine (PS) and phosphatidylethanolamine (PE) with HPLC is described. The analysis includes extraction of aminophospholipids with methanol, automatic derivatization with OPA (o-Phtalaldehyde), reverse-phase HPLC on C18 column in a 28 min. run time and fluorescence detection. On the basis of several analyses of pure SMP samples, threshold values for PS + PE content of SMP, allowing to recognize \u201csuspected\u201d (P<0.05) or \u201ccertain\u201d (P<0.01) presence of buttermilk solids are reported. Usually a 2-3% of BMP in SMP is detected in powder samples obtained mixing both solid with solid and liquid with liquid material before drying. However, due to the variability of aminophospholipid content, the minimum detectable amount of buttermilk solids in SMP may range from 1% to 10% according to origin, processing conditions and age of raw material

Studio preliminare sulle caratteristiche di impiego di una biochimosina nella produzione di formaggi molli

La ricerca \ue8 stata condotta con lo scopo di verificare le caratteristiche di una biochimosina sostitutiva del caglio tradizionale di vitello, in caseificazioni sperimentali per la produzione di formaggi molli quali Mozzarella, Crescenza ed Italico. Nelle condizioni adottate il comportamento tecnologico del coagulante sperimentale Maxiren appare del tutto simile a quello del caglio di vitello. L\u2019impiego della biochimosina non determina nel formaggio particolari modificazioni della struttura, nel colore e nel gusto. Anche le rese di produzione non si discostano rispetto alla norma. Alcune lievi differenze riscontrate nella composizione centesimale ed in particolare nel contenuto in amminoacidi liberi dei formaggi possono essere attribuite solo alla variabilit\ue0 determinata da una produzione in scala pilota e non all\u2019azione del coagulante di diversa origine.Cheese production is traditionally based on milk clotting by rennet enzymes, such as chymosin and pepsin, extracted from the calves\u2019 abomasum. Recently, the traditional calf rennet is less and less available because the stomachs mainly come from older animals, and the commercial rennet appears to contain ever-increasing amounts of bovine pepsin. For these reasons, new calf rennet substitutes are being promoted as interesting alternative concerning their lower prices and technological properties. The aim of this work is to test the technological suitability of a new biochymosin in comparison with calf rennet in experimental soft cheese production. The features of the new Gist Brocades chymosin Maxiren (GB) have been evaluated in experimental cheesemaking tests and compared with a calf rennet (HA) as reference. A third rennet (MIX) with the same enzymatic composition of the calf rennet reference, but obtained by mixing opportunely GB chymosin and a bovine rennet, has also been tested to compare the effect of different chymosin origin. Parallel tests have been carried out for Mozzarella, Crescenza and Italico cheese on a pilot-scale production (about 100 lt milk each test). At different times during cheese-ripening the chemical-physical parameters and the free amino acid content have been detected. Moreover sensory tests and colour analysis of cheeses have been carried out. The experimental chymosin in normal practice doesn\u2019t cause different states during cheesemaking steps; its technological behavior is quite similar to the traditional rennet. No particular modifications in texture, colour and taste of cheeses appear by using the new biochymosin. Slight differences with regards to cheese composition and organoleptic characters are probably due to the variability of pilot-scale productions. Regarding the free amino acid composition, only for Italico cheese the GB chymosin seems to have a lower proteolytic activity than rennets containing bovine pepsin