Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique
Identifieur interne : 000685 ( Istex/Corpus ); précédent : 000684; suivant : 000686Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique
Auteurs : N. Taifi ; F. Bakkali ; B. Faiz ; A. Moudden ; G. Maze ; D. DcultotSource :
- Measurement Science and Technology [ 0957-0233 ] ; 2006.
Abstract
A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (V). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.
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DOI: 10.1088/0957-0233/17/2/008
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Bakkali</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Faiz, B" sort="Faiz, B" uniqKey="Faiz B" first="B" last="Faiz">B. Faiz</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Moudden, A" sort="Moudden, A" uniqKey="Moudden A" first="A" last="Moudden">A. Moudden</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation><affiliation><mods:affiliation>Ecole Suprieure de Technologie, University Ibn Zohr of Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Maze, G" sort="Maze, G" uniqKey="Maze G" first="G" last="Maze">G. Maze</name><affiliation><mods:affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</mods:affiliation></affiliation></author><author><name sortKey="Dcultot, D" sort="Dcultot, D" uniqKey="Dcultot D" first="D" last="Dcultot">D. 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Taifi</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation><affiliation><mods:affiliation>E-mail: taifi.naima@caramail.com</mods:affiliation></affiliation></author><author><name sortKey="Bakkali, F" sort="Bakkali, F" uniqKey="Bakkali F" first="F" last="Bakkali">F. Bakkali</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Faiz, B" sort="Faiz, B" uniqKey="Faiz B" first="B" last="Faiz">B. Faiz</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Moudden, A" sort="Moudden, A" uniqKey="Moudden A" first="A" last="Moudden">A. Moudden</name><affiliation><mods:affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</mods:affiliation></affiliation><affiliation><mods:affiliation>Ecole Suprieure de Technologie, University Ibn Zohr of Agadir, Morocco</mods:affiliation></affiliation></author><author><name sortKey="Maze, G" sort="Maze, G" uniqKey="Maze G" first="G" last="Maze">G. Maze</name><affiliation><mods:affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</mods:affiliation></affiliation></author><author><name sortKey="Dcultot, D" sort="Dcultot, D" uniqKey="Dcultot D" first="D" last="Dcultot">D. Dcultot</name><affiliation><mods:affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</mods:affiliation></affiliation></author></analytic><monogr></monogr><series><title level="j">Measurement Science and Technology</title><title level="j" type="abbrev">Meas. Sci. 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The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (V). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.</div></front></TEI><istex><corpusName>iop</corpusName><author><json:item><name>N Taifi</name><affiliations><json:string>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</json:string><json:string>E-mail: taifi.naima@caramail.com</json:string></affiliations></json:item><json:item><name>F Bakkali</name><affiliations><json:string>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</json:string></affiliations></json:item><json:item><name>B Faiz</name><affiliations><json:string>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</json:string></affiliations></json:item><json:item><name>A Moudden</name><affiliations><json:string>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</json:string><json:string>Ecole Suprieure de Technologie, University Ibn Zohr of Agadir, Morocco</json:string></affiliations></json:item><json:item><name>G Maze</name><affiliations><json:string>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</json:string></affiliations></json:item><json:item><name>D Dcultot</name><affiliations><json:string>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</json:string></affiliations></json:item></author><subject><json:item><lang><json:string>eng</json:string></lang><value>ultrasonic</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>syneresis</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>firmness</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>milk gel</value></json:item><json:item><lang><json:string>eng</json:string></lang><value>rennet coagulation</value></json:item></subject><language><json:string>eng</json:string></language><originalGenre><json:string>paper</json:string></originalGenre><abstract>A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (V). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.</abstract><qualityIndicators><score>4.254</score><pdfVersion>1.4</pdfVersion><pdfPageSize>595 x 842 pts (A4)</pdfPageSize><refBibsNative>true</refBibsNative><keywordCount>5</keywordCount><abstractCharCount>470</abstractCharCount><pdfWordCount>2854</pdfWordCount><pdfCharCount>17360</pdfCharCount><pdfPageCount>7</pdfPageCount><abstractWordCount>75</abstractWordCount></qualityIndicators><title>Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title><pii><json:string>S0957-0233(06)94844-9</json:string></pii><genre><json:string>research-article</json:string></genre><host><volume>17</volume><publisherId><json:string>mst</json:string></publisherId><pages><total>7</total><last>287</last><first>281</first></pages><issn><json:string>0957-0233</json:string></issn><issue>2</issue><genre><json:string>journal</json:string></genre><language><json:string>unknown</json:string></language><eissn><json:string>1361-6501</json:string></eissn><title>Measurement Science and Technology</title></host><publicationDate>2006</publicationDate><copyrightDate>2006</copyrightDate><doi><json:string>10.1088/0957-0233/17/2/008</json:string></doi><id>FDABA043A182550EBB36339F3E65F6648AF08104</id><score>0.31837195</score><fulltext><json:item><original>true</original><mimetype>application/pdf</mimetype><extension>pdf</extension><uri>https://api.istex.fr/document/FDABA043A182550EBB36339F3E65F6648AF08104/fulltext/pdf</uri></json:item><json:item><original>false</original><mimetype>application/zip</mimetype><extension>zip</extension><uri>https://api.istex.fr/document/FDABA043A182550EBB36339F3E65F6648AF08104/fulltext/zip</uri></json:item><istex:fulltextTEI uri="https://api.istex.fr/document/FDABA043A182550EBB36339F3E65F6648AF08104/fulltext/tei"><teiHeader><fileDesc><titleStmt><title level="a" type="main" xml:lang="en">Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title></titleStmt><publicationStmt><authority>ISTEX</authority><publisher>Institute of Physics Publishing</publisher><availability><p>2006 IOP Publishing Ltd</p></availability><date>2006</date></publicationStmt><sourceDesc><biblStruct type="inbook"><analytic><title level="a" type="main" xml:lang="en">Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title><author xml:id="author-1"><persName><forename type="first">N</forename><surname>Taifi</surname></persName><email>taifi.naima@caramail.com</email><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation></author><author xml:id="author-2"><persName><forename type="first">F</forename><surname>Bakkali</surname></persName><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation></author><author xml:id="author-3"><persName><forename type="first">B</forename><surname>Faiz</surname></persName><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation></author><author xml:id="author-4"><persName><forename type="first">A</forename><surname>Moudden</surname></persName><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation><affiliation>Ecole Suprieure de Technologie, University Ibn Zohr of Agadir, Morocco</affiliation></author><author xml:id="author-5"><persName><forename type="first">G</forename><surname>Maze</surname></persName><affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</affiliation></author><author xml:id="author-6"><persName><forename type="first">D</forename><surname>Dcultot</surname></persName><affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</affiliation></author></analytic><monogr><title level="j">Measurement Science and Technology</title><title level="j" type="abbrev">Meas. 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Technol.</title><idno type="pISSN">0957-0233</idno><idno type="eISSN">1361-6501</idno><imprint><publisher>Institute of Physics Publishing</publisher><date type="published" when="2006"></date><biblScope unit="volume">17</biblScope><biblScope unit="issue">2</biblScope><biblScope unit="page" from="281">281</biblScope><biblScope unit="page" to="287">287</biblScope><biblScope unit="production">Printed in the UK</biblScope></imprint></monogr><idno type="istex">FDABA043A182550EBB36339F3E65F6648AF08104</idno><idno type="DOI">10.1088/0957-0233/17/2/008</idno><idno type="PII">S0957-0233(06)94844-9</idno><idno type="articleID">194844</idno><idno type="articleNumber">008</idno></biblStruct></sourceDesc></fileDesc><profileDesc><creation><date>2006</date></creation><langUsage><language ident="en">en</language></langUsage><abstract><p>A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (V). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.</p></abstract><textClass><keywords scheme="keyword"><list><head>keywords</head><item><term>ultrasonic</term></item><item><term>syneresis</term></item><item><term>firmness</term></item><item><term>milk gel</term></item><item><term>rennet coagulation</term></item></list></keywords></textClass></profileDesc><revisionDesc><change when="2006">Published</change></revisionDesc></teiHeader></istex:fulltextTEI><json:item><original>false</original><mimetype>text/plain</mimetype><extension>txt</extension><uri>https://api.istex.fr/document/FDABA043A182550EBB36339F3E65F6648AF08104/fulltext/txt</uri></json:item></fulltext><metadata><istex:metadataXml wicri:clean="corpus iop not found" wicri:toSee="no header"><istex:xmlDeclaration>version="1.0" encoding="ISO-8859-1"</istex:xmlDeclaration><istex:docType SYSTEM="http://ej.iop.org/dtd/iopv1_5_1.dtd" name="istex:docType"></istex:docType><istex:document><article artid="mst194844"><article-metadata><jnl-data jnlid="mst"><jnl-fullname>Measurement Science and Technology</jnl-fullname><jnl-abbreviation>Meas. Sci. Technol.</jnl-abbreviation><jnl-shortname>MST</jnl-shortname><jnl-issn>0957-0233</jnl-issn><jnl-coden>MSTCEP</jnl-coden><jnl-imprint>Institute of Physics Publishing</jnl-imprint><jnl-web-address>stacks.iop.org/MST</jnl-web-address></jnl-data><volume-data><year-publication>2006</year-publication><volume-number>17</volume-number></volume-data><issue-data><issue-number>2</issue-number><coverdate>February 2006</coverdate></issue-data><article-data><article-type type="paper" sort="regular"></article-type><type-number type="paper" artnum="008">8</type-number><article-number>194844</article-number><first-page>281</first-page><last-page>287</last-page><length>7</length><pii>S0957-0233(06)94844-9</pii><doi>10.1088/0957-0233/17/2/008</doi><copyright>2006 IOP Publishing Ltd</copyright><ccc>0957-0233/06/020281+07$30.00</ccc><printed>Printed in the UK</printed><features colour="none" mmedia="no" suppdata="no"></features></article-data></article-metadata><header><title-group><title>Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title><short-title>Characterization of milk gel by ultrasound</short-title><ej-title>Characterization of milk gel by ultrasound</ej-title></title-group><author-group><author address="mst194844ad1" email="mst194844ea1"><first-names>N</first-names><second-name>Taifi</second-name></author><author address="mst194844ad1"><first-names>F</first-names><second-name>Bakkali</second-name></author><author address="mst194844ad1"><first-names>B</first-names><second-name>Faiz</second-name></author><author address="mst194844ad1 mst194844ad2"><first-names>A</first-names><second-name>Moudden</second-name></author><author address="mst194844ad3"><first-names>G</first-names><second-name>Maze</second-name></author><author address="mst194844ad3"><first-names>D</first-names><second-name>Décultot</second-name></author></author-group><address-group><address id="mst194844ad1"><orgname>Laboratoire d'Instrumentation et de Mesures, Département de Physique, Université Ibn Zohr Faculté des Sciences</orgname>, BP 8106, Agadir, <country>Morocco</country></address><address id="mst194844ad2"><orgname>Ecole Supérieure de Technologie, University Ibn Zohr of Agadir</orgname>, <country>Morocco</country></address><address id="mst194844ad3"><orgname>Laboratoire d'Acoustique Ultrasonore et d'Electronique</orgname>, LAUE UMR CNRS 6068, Université du Havre, 76610 le Havre, <country>France</country></address><e-address id="mst194844ea1"><email mailto="taifi.naima@caramail.com">taifi.naima@caramail.com</email></e-address></address-group><history received="3 February 2005" finalform="4 August 2005" online="23 December 2005"></history><abstract-group><abstract><heading>Abstract</heading><p indent="no">A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (Δ<italic>V</italic>). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.</p></abstract></abstract-group><classifications><keywords><keyword>ultrasonic</keyword><keyword>syneresis</keyword><keyword>firmness</keyword><keyword>milk gel</keyword><keyword>rennet coagulation</keyword></keywords></classifications></header><body numbering="bysection"><sec-level1 id="mst194844s1" label="1"><heading>Introduction</heading><p indent="no">Rennet coagulation involved in cheesemaking generally occurs in two stages: the enzymatic hydrolysis, followed by the non-enzymatic stage, i.e. aggregation and gelation. In a previous work the first stage was studied [<cite linkend="mst194844bib01">1</cite>], allowing one to determine the coagulation time (i.e. beginning of the aggregation). The aggregation and gelation phases are characterized by changes occurring in the physical properties of milk gel. The study of this stage is vitally important in the ability to control syneresis, whereby the whey component of milk is expelled following curd formation [<cite linkend="mst194844bib02">2</cite>].</p><p>Syneresis is an essential step in cheese manufacture that affects the moisture content and cheese texture and ultimately the quality of the final product [<cite linkend="mst194844bib03" range="mst194844bib03,mst194844bib04,mst194844bib05,mst194844bib06,mst194844bib07">3–7</cite>]. So it is useful to understand and quantitatively describe syneresis.</p><p>In recent decades, the monitoring of the syneresis was achieved by different methods: a separation method [<cite linkend="mst194844bib08" range="mst194844bib08,mst194844bib09,mst194844bib10">8–10</cite>]; measurements made in the vat while curd is still in the whey through the use of an added tracer [<cite linkend="mst194844bib11">11</cite>]; non-destructive and non-invasive methods [<cite linkend="mst194844bib01">1</cite>, <cite linkend="mst194844bib12" range="mst194844bib12,mst194844bib13,mst194844bib14,mst194844bib15,mst194844bib16,mst194844bib17,mst194844bib18,mst194844bib19,mst194844bib20">12–20</cite>], which appear to be very attractive.</p><p>In this paper, in order to monitor the syneresis, we extended to ten hours the recording of milk coagulation with the ultrasonic method used previously [<cite linkend="mst194844bib01">1</cite>]. Ultrasound has advantages over many traditional analytical techniques because measurements are rapid, non-invasive, fully automated and can be made in a laboratory or in-line.</p></sec-level1><sec-level1 id="mst194844s2" label="2"><heading>Materials and methods</heading><sec-level2 id="mst194844s2-1" label="2.1"><heading>Samples</heading><p indent="no">Milk samples were prepared by dissolving 13 g of commercial powder in 90 g of warm water. Two different commercial rennets (Marzyne 0.04 g l<sup>−1</sup>, 7% chymosin with a strength of 1:15000) were used. The milk was heated to the temperature of coagulation (32 °C, 37 °C, 42 °C), poured into the milk vessel and placed in the water bath set at the same temperature of coagulation for 30 min. Data acquisition was initiated upon addition of rennet. Since temperature, rennet concentration and calcium chloride concentration are the primary factors affecting the coagulation of milk [<cite linkend="mst194844bib03">3</cite>, <cite linkend="mst194844bib15">15</cite>], three levels of each were considered for the experiments. Addition of calcium chloride (CaCl<sub>2</sub>) to the reconstituted milk is made before renneting milk. The standard concentration of CaCl<sub>2</sub> used is 0.1 g/1 l of milk.</p></sec-level2><sec-level2 id="mst194844s2-2" label="2.2"><heading>Ultrasonic method</heading><p indent="no">The experimental set-up (figure <figref linkend="mst194844fig01" override="yes">1(<italic>a</italic>)</figref>) consists of a Plexiglas parallelepiped vessel (10 × 10 × 6 cm<sup>3</sup>) immersed with the transducer in a thermostated water bath based on an electronically controlled liquid circulation that allows a temperature stability of about 2 × 10<sup>−2</sup> °C. The broadband transducer placed under the vessel is used as an emitter and receiver and is excited by an impulse generator (5073 PR Model, Panametrics, Sofranel, France). Two Panametrics broadband transducers of 5 MHz and 50 MHz central frequencies (V309 and V358-SU models, 10 mm crystal diameter) are successively used for the experiments. The 50 MHz transducer incorporates a delay line of 4.25 µs.
<figure id="mst194844fig01" width="page"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig01.eps" width="31pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig01.jpg"></graphic-file></graphic><caption id="mst194844fc01" label="Figure 1"><p indent="no">(<italic>a</italic>) Experimental set-up. (<italic>b</italic>) Schematic of echoes reflected by the sample (<italic>A</italic><sub>1</sub> to <italic>A</italic><sub>6</sub> are observed echoes reflected from the interfaces between media M<sub><italic>i</italic></sub>).</p></caption></figure></p><p>The ultrasonic impulse is propagated in water and crosses the coagulating milk contained in the vessel before reflecting on a glass surface (figure <figref linkend="mst194844fig01" override="yes">1(<italic>b</italic>)</figref>). The signal detected by the same transducer is amplified and digitized by a Lecroy oscilloscope (300 MHz bandwidth, 9310 M model). This temporal signal is transmitted through an IEEE 488 interface to a microcomputer where the viscoelstic parameters (velocity and attenuation) are calculated at each time. In order to avoid superposition of different echoes, the thickness <italic>d</italic>, <italic>L</italic> and <italic>d</italic>′ respectively of plate 1, coagulating milk and plate 2 are chosen as indicated in table <tabref linkend="mst194844tab01">1</tabref>.
<table id="mst194844tab01" frame="topbot"><caption id="mst194844tc01" label="Table 1"><p indent="no">Thickness of plate 1, coagulating milk and plate 2.</p></caption><tgroup cols="4"><colspec colnum="1" colname="col1" align="left"></colspec><colspec colnum="2" colname="col2" align="left"></colspec><colspec colnum="3" colname="col3" align="left"></colspec><colspec colnum="4" colname="col4" align="left"></colspec><thead><row><entry></entry><entry><italic>d</italic> (Plexiglas)</entry><entry><italic>L</italic> (milk)</entry><entry><italic>d</italic>′ (glass)</entry></row></thead><tbody><row><entry>Experiments with</entry><entry>4 mm</entry><entry>10 mm</entry><entry>5 mm</entry></row><row><entry>5 MHz transducer</entry><entry></entry><entry></entry><entry></entry></row><row><entry>Experiments with</entry><entry>2 mm</entry><entry>1 mm</entry><entry>5 mm</entry></row><row><entry>50 MHz transducer</entry><entry></entry><entry></entry><entry></entry></row></tbody></tgroup></table></p><p>Figure <figref linkend="mst194844fig02">2</figref> shows the experimental signal composed of echoes <italic>A</italic><sub>1</sub> to <italic>A</italic><sub>6</sub> reflected by the vessel enclosing the coagulating milk when using the 5 MHz central frequency transducer.
<itemized-list id="mst194844il1"><list-item id="mst194844il1.1" marker="•"><p indent="no"><italic>A</italic><sub>1</sub> is the specular echo reflected on the bottom surface of plate 1,</p></list-item><list-item id="mst194844il1.2" marker="•"><p indent="no"><italic>A</italic><sub>2</sub> is the reflection echo on the boundary between the top surface of plate 1 and coagulating milk,</p></list-item><list-item id="mst194844il1.3" marker="•"><p indent="no"><italic>A</italic><sub>3</sub> corresponds to the second back-and-forth propagation in plate 1,</p></list-item><list-item id="mst194844il1.4" marker="•"><p indent="no"><italic>A</italic><sub>4</sub> corresponds to the reflection on the bottom surface of plate 2,</p></list-item><list-item id="mst194844il1.5" marker="•"><p indent="no"><italic>A</italic><sub>5</sub> is the reflection echo at the interface between the top of plate 2 and the coagulating milk,</p></list-item><list-item id="mst194844il1.6" marker="•"><p indent="no"><italic>A</italic><sub>6</sub> is the superposition of two echoes reflected on the top surface of plate 2 with a second back-and-forth propagation either in plate 2 or in plate 1.</p></list-item></itemized-list>
The corresponding echoes in the case of 50 MHz central frequency transducer are presented in figure <figref linkend="mst194844fig03">3</figref>. This figure also shows the echoes produced by the delay line of this transducer:
<itemized-list id="mst194844il2"><list-item id="mst194844il2.1" marker="•"><p indent="no"><italic>A</italic><sub>1</sub> is the reflection echo on the bottom surface of plate 1,</p></list-item><list-item id="mst194844il2.2" marker="•"><p indent="no"><italic>A</italic>′<sub valign="yes">1</sub> corresponds to the second back-and-forth propagation in the water between the transducer and plate 1,</p></list-item><list-item id="mst194844il2.3" marker="•"><p indent="no"><italic>A</italic><sub>2</sub> is the reflection echo on the boundary between the top surface of plate 1 and coagulating milk,</p></list-item><list-item id="mst194844il2.4" marker="•"><p indent="no"><italic>A</italic>′<sub valign="yes"><italic>dl</italic></sub> is the second delay line echo,</p></list-item><list-item id="mst194844il2.5" marker="•"><p indent="no"><italic>A</italic>″<sub valign="yes">1</sub> is the third back-and-forth propagation in the water,</p></list-item><list-item id="mst194844il2.6" marker="•"><p indent="no"><italic>A</italic><sub>4</sub> corresponds to the reflection on the bottom surface of plate 2.</p></list-item></itemized-list>
For the measurement of the phase velocity and attenuation in the coagulating milk, the echoes <italic>A</italic><sub>2</sub> and <italic>A</italic><sub>4</sub> are used.
<figure id="mst194844fig02"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig02.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig02.jpg"></graphic-file></graphic><caption id="mst194844fc02" label="Figure 2"><p indent="no">Typical waveform of the reflected ultrasonic signal with the 5 MHz transducer.</p></caption></figure><figure id="mst194844fig03"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig03.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig03.jpg"></graphic-file></graphic><caption id="mst194844fc03" label="Figure 3"><p indent="no">Typical waveform of the reflected ultrasonic signal with the 50 MHz transducer.</p></caption></figure></p><sec-level3 id="mst194844s2-2-1" label="2.2.1"><heading>Attenuation</heading><p indent="no">The value of the attenuation coefficient α<sub>milk</sub>(υ) for the frequency υ corresponding to the maximum of amplitude spectra can be written as [<cite linkend="mst194844bib21">21</cite>, <cite linkend="mst194844bib22">22</cite>]:
<display-eqn id="mst194844ueqn01" number="no" eqnalign="center"></display-eqn>with
<display-eqn id="mst194844ueqn02" number="no" eqnalign="center"></display-eqn>The echoes <italic>A</italic><sub>2</sub> and <italic>A</italic><sub>4</sub> are isolated separately through a time-based filtering programme established in the personal computer. Their corresponding amplitude spectra are denoted A<sub>2</sub>(υ) and A<sub>4</sub>(υ). <italic>Z</italic><sub>milk</sub>, <italic>Z</italic><sub>glass</sub> and <italic>Z</italic><sub>plex</sub> are the acoustic impedances in milk, glass and Plexiglas respectively.</p></sec-level3><sec-level3 id="mst194844s2-2-2" label="2.2.2"><heading>Phase velocity</heading><p indent="no">The phase velocity [<cite linkend="mst194844bib01">1</cite>, <cite linkend="mst194844bib23">23</cite>] can be written as
<display-eqn id="mst194844ueqn03" number="no" eqnalign="center"></display-eqn>To obtain the phase experimentally, the FFT of signals <italic>A</italic><sub>2</sub> and <italic>A</italic><sub>4</sub> are calculated. These phases are written as follows:
<display-eqn id="mst194844ueqn04" number="no" eqnalign="center"></display-eqn><italic>R</italic><sub>2</sub> and <italic>R</italic><sub>4</sub> are the real parts and <italic>I</italic><sub>2</sub> and <italic>I</italic><sub>4</sub> are the imaginary parts respectively of echo <italic>A</italic><sub>2</sub> and echo <italic>A</italic><sub>4</sub>. These phases vary between −π/2 and +π/2. To use these phases it is necessary to have continuous phases; an algorithm is developed to obtain this result. It is possible to calculate the phase velocity as a function of the frequency υ at different times during the coagulation.</p></sec-level3></sec-level2></sec-level1><sec-level1 id="mst194844s3" label="3"><heading>Results and discussions</heading><sec-level2 id="mst194844s3-1" label="3.1"><heading>Experiment with the 5 MHz transducer</heading><p indent="no">The recordings from zero to 420 min of the ultrasonic velocity and attenuation are reported in figures <figref linkend="mst194844fig04">4</figref> and <figref linkend="mst194844fig05">5</figref> for standard conditions of temperature (ST), of rennet (SR) and of calcium chloride (SCaCl<sub>2</sub>). These recordings allow us to single out the phases of milk coagulation: the enzymatic phase corresponding to a decrease in the attenuation and an increase in the phase velocity, and the physico-chemical phase characterized by a stationary evolution of these parameters. During this phase, which can last several hours, the firmness of the milk gel is obtained.
<figure id="mst194844fig04"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig04.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig04.jpg"></graphic-file></graphic><caption id="mst194844fc04" label="Figure 4"><p indent="no">Evolution of the phase velocity during the coagulation and syneresis at standard conditions obtained with the 5 MHz transducer.</p></caption></figure><figure id="mst194844fig05"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig05.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig05.jpg"></graphic-file></graphic><caption id="mst194844fc05" label="Figure 5"><p indent="no">Evolution of the ultrasonic attenuation during the coagulation and syneresis at standard conditions obtained with the 5 MHz transducer.</p></caption></figure></p><p>The end of the gelation phase is characterized by an increase in the phase velocity in two stages: a first stage of about 80 min in which the velocity exhibits a slow variation, followed by a second stage corresponding to a drastic increase of this velocity. Comparison between figures <figref linkend="mst194844fig04">4</figref> and <figref linkend="mst194844fig05">5</figref> shows that the beginning of this second stage is accompanied by a strong increase in the attenuation. These two stages correspond to an increase of tension in the gel network, in which the aqueous phase is retained.</p><p>The tension continues to increase until the contraction of the gel that produces the total expulsion of the lactoserum towards its surface. This last phenomenon is identified in the evolution curves by a high value of attenuation, and thereafter by the disappearance of the ultrasonic signal due to its strong diffusion by the curd grain that bathes in the serum. The onset of syneresis corresponds to the beginning of the increase in the attenuation.</p></sec-level2><sec-level2 id="mst194844s3-2" label="3.2"><heading>Experiments with the 50 MHz transducer</heading><p indent="no">All the experiments carried out at 5 MHz were repeated with the 50 MHz transducer in order to get the best resolution that would allow detection of microsyneresis. The evolutions obtained with this transducer, in standard conditions, are reported in figures <figref linkend="mst194844fig06">6</figref> and <figref linkend="mst194844fig07">7</figref>.
<figure id="mst194844fig06"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig06.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig06.jpg"></graphic-file></graphic><caption id="mst194844fc06" label="Figure 6"><p indent="no">Evolution of the phase velocity during the coagulation and syneresis at standard conditions obtained with the 50 MHz transducer.</p></caption></figure><figure id="mst194844fig07"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig07.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig07.jpg"></graphic-file></graphic><caption id="mst194844fc07" label="Figure 7"><p indent="no">Evolution of the ultrasonic attenuation during the coagulation and syneresis at standard conditions obtained with the 50 MHz transducer.</p></caption></figure></p><p>In comparison with the evolutions obtained at 5 MHz, we observe that:
<itemized-list id="mst194844il3"><list-item id="mst194844il3.1" marker="•"><p indent="no">The phase velocity exhibits at 50 MHz a slow increase during the physico-chemical phase.</p></list-item><list-item id="mst194844il3.2" marker="•"><p indent="no">The onset of syneresis is detected earlier with the 50 MHz transducer.</p></list-item></itemized-list>
These differences are linked to the weakness of the change occurring in the milk gel network during the physico-chemical phase, which cannot be detected at 5 MHz.</p><p>Furthermore, in the two measurements at 5 MHz and 50 MHz, we observe that the onset of syneresis is always preceded by an increase in the phase velocity, which shows that the phase velocity is a good indicator of the occurrence of syneresis.</p><sec-level3 id="mst194844s3-2-1" label="3.2.1"><heading>Effect of rennet concentration</heading><p indent="no">Figure <figref linkend="mst194844fig08">8</figref> shows the evolution of the phase velocity for different concentrations in rennet around the standard concentration. The temperature and the CaCl<sub>2</sub> concentration are kept at the standard values. These evolutions show that the velocity variation Δ<italic>V</italic> reached by the milk gel at the end of the physico-chemical phase is enhanced by an increase in rennet concentration.
<figure id="mst194844fig08"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig08.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig08.jpg"></graphic-file></graphic><caption id="mst194844fc08" label="Figure 8"><p indent="no">Variation of the phase velocity during coagulation and syneresis at different rennet concentrations with the 50 MHz transducer (LR: low concentration, HR: high concentration).</p></caption></figure></p><p>Furthermore, the physical analysis of the milk gel indicates that its firmness is increased with the rennet concentration, indicating a strong correlation between the milk gel firmness and Δ<italic>V</italic>.</p><p>At a very high rennet concentration, the syneresis does not occur and the milk gel continues to gain more elasticity, which is expressed in the evolution curves by a stationary weak attenuation and an increase in the velocity (figures <figref linkend="mst194844fig09">9</figref> and <figref linkend="mst194844fig10">10</figref>). This is well explained by the fact that a high rennet concentration produces the maximum rate of micelle proteolysis, leading to a milk gel network formed by nodes of micelles that give it an important compactness. Due to this rigidity, chains become difficult to break and therefore the expulsion of the lactoserum towards the surface is made impossible.
<figure id="mst194844fig09"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig09.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig09.jpg"></graphic-file></graphic><caption id="mst194844fc09" label="Figure 9"><p indent="no">Evolution of the phase velocity obtained with the 5 MHz transducer at high rennet concentration and standard temperature and CaCl<sub>2</sub>.</p></caption></figure><figure id="mst194844fig10"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig10.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig10.jpg"></graphic-file></graphic><caption id="mst194844fc10" label="Figure 10"><p indent="no">Evolution of the attenuation obtained with the 5 MHz transducer at high rennet concentration and standard temperature and CaCl<sub>2</sub>.</p></caption></figure></p></sec-level3><sec-level3 id="mst194844s3-2-2" label="3.2.2"><heading>Effect of temperature</heading><p indent="no">Figure <figref linkend="mst194844fig11">11</figref> gives the evolution of the viscoelastic parameters for different temperatures and for standard rennet and calcium chloride concentrations. The comparison between these evolutions shows that:
<itemized-list id="mst194844il4"><list-item id="mst194844il4.1" marker="•"><p indent="no">The decrease of the coagulation temperature slows down the aggregation and delays the syneresis, which is reached only after 600 min. This is in agreement with the fact that the hydrophobic linking of casein and the fixing of calcium ions by the casein are very dependent on temperature [<cite linkend="mst194844bib24">24</cite>].</p></list-item><list-item id="mst194844il4.2" marker="•"><p indent="no">The gel firmness increases with the temperature. But the maximal final firmness reached by the gel remains relatively weak. The gel obtained at very high temperature presents a ‘rubberized’ texture and does not give rise to syneresis (figures <figref linkend="mst194844fig12">12</figref> and <figref linkend="mst194844fig13">13</figref>). This is in agreement with the fact that, at high temperature, the speed of link formation between micelles increases, making the system rigid quickly. The endogenous pressure of syneresis is then decreased [<cite linkend="mst194844bib03">3</cite>].</p></list-item></itemized-list><figure id="mst194844fig11"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig11.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig11.jpg"></graphic-file></graphic><caption id="mst194844fc11" label="Figure 11"><p indent="no">Evolution of the phase velocity obtained with the 50 MHz at different temperatures (HT: high temperature, LT: low temperature).</p></caption></figure><figure id="mst194844fig12"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig12.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig12.jpg"></graphic-file></graphic><caption id="mst194844fc12" label="Figure 12"><p indent="no">Evolution of the phase velocity with the 5 MHz transducer at high temperature and standard rennet and CaCl<sub>2</sub>.</p></caption></figure><figure id="mst194844fig13"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig13.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig13.jpg"></graphic-file></graphic><caption id="mst194844fc13" label="Figure 13"><p indent="no">Evolution of the attenuation with the 5 MHz transducer at high temperature and standard rennet and CaCl<sub>2</sub>.</p></caption></figure></p></sec-level3><sec-level3 id="mst194844s3-2-3" label="3.2.3"><heading>Effect of calcium chloride concentration</heading><p indent="no">The calcium chloride effect is illustrated by the evolutions of the phase velocity and the attenuation reported in figures <figref linkend="mst194844fig14">14</figref> and <figref linkend="mst194844fig15">15</figref>. These evolutions show that the increase in the CaCl<sub>2</sub> concentration produces an increase in the firmness of the milk gel and also accelerate the occurrence of syneresis.
<figure id="mst194844fig14"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig14.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig14.jpg"></graphic-file></graphic><caption id="mst194844fc14" label="Figure 14"><p indent="no">Evolution of the phase velocity with the 50 MHz at different concentrations of CaCl<sub>2</sub> and standard temperature and rennet.</p></caption></figure><figure id="mst194844fig15"><graphic><graphic-file version="print" format="EPS" filename="images/mst194844fig15.eps" width="20.5pc"></graphic-file><graphic-file version="ej" format="JPEG" filename="images/mst194844fig15.jpg"></graphic-file></graphic><caption id="mst194844fc15" label="Figure 15"><p indent="no">Evolution of the attenuation with the 50 MHz at different concentrations of CaCl<sub>2</sub> and standard temperature and rennet.</p></caption></figure></p></sec-level3></sec-level2></sec-level1><sec-level1 id="mst194844s4" label="4"><heading>Conclusion</heading><p indent="no">This study has shown that the ultrasonic method is a suitable tool for continuously monitoring milk coagulation and syneresis. The Δ<italic>V</italic> velocity variation appears to be a good indicator of the firmness of the milk gel. The velocity evolution obtained at high frequency also appears to be an indicator of the occurrence of syneresis. The syneresis is clearly characterized by a large increase in the attenuation. This method has shown the effect of temperature, of rennet concentration and of CaCl<sub>2</sub> on the gel firmness and on syneresis.</p></sec-level1><acknowledgment><heading>Acknowledgments</heading><p indent="no">The authors would like to acknowledge the Moroccan and French National Centre of Research CNRST and CNRS that supported this work through a PICS and PROTARS programs.</p></acknowledgment></body><back><references><heading>References</heading><reference-list type="numeric"><journal-ref id="mst194844bib01"><authors><au><second-name>Bakkali</second-name><first-names>F</first-names></au><au><second-name>Moudden</second-name><first-names>A</first-names></au><au><second-name>Faiz</second-name><first-names>B</first-names></au><au><second-name>Amghar</second-name><first-names>A</first-names></au><au><second-name>Maze</second-name><first-names>G</first-names></au><au><second-name>Montero de Espinosa</second-name><first-names>F</first-names></au><au><second-name>Akhnak</second-name><first-names>M</first-names></au></authors><year>2001</year><art-title>Ultrasonic measurement of milk coagulation time</art-title><jnl-title>Meas. 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Dairy Res.</jnl-title><volume>57</volume><pages>101–8</pages></journal-ref></reference-list></references></back></article></istex:document></istex:metadataXml><mods version="3.6"><titleInfo lang="eng"><title>Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title></titleInfo><titleInfo type="abbreviated"><title>Characterization of milk gel by ultrasound</title></titleInfo><titleInfo type="alternative" lang="eng"><title>Characterization of the syneresis and the firmness of the milk gel using an ultrasonic technique</title></titleInfo><name type="personal"><namePart type="given">N</namePart><namePart type="family">Taifi</namePart><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation><affiliation>E-mail: taifi.naima@caramail.com</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">F</namePart><namePart type="family">Bakkali</namePart><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">B</namePart><namePart type="family">Faiz</namePart><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">A</namePart><namePart type="family">Moudden</namePart><affiliation>Laboratoire d'Instrumentation et de Mesures, Dpartement de Physique, Universit Ibn Zohr Facult des Sciences, BP 8106, Agadir, Morocco</affiliation><affiliation>Ecole Suprieure de Technologie, University Ibn Zohr of Agadir, Morocco</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">G</namePart><namePart type="family">Maze</namePart><affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</affiliation><role><roleTerm type="text">author</roleTerm></role></name><name type="personal"><namePart type="given">D</namePart><namePart type="family">Dcultot</namePart><affiliation>Laboratoire d'Acoustique Ultrasonore et d'Electronique, LAUE UMR CNRS 6068, Universit du Havre, 76610 le Havre, France</affiliation><role><roleTerm type="text">author</roleTerm></role></name><typeOfResource>text</typeOfResource><genre type="research-article" displayLabel="paper">paper</genre><originInfo><publisher>Institute of Physics Publishing</publisher><dateIssued encoding="w3cdtf">2006</dateIssued><copyrightDate encoding="w3cdtf">2006</copyrightDate></originInfo><language><languageTerm type="code" authority="iso639-2b">eng</languageTerm><languageTerm type="code" authority="rfc3066">en</languageTerm></language><physicalDescription><internetMediaType>text/html</internetMediaType><note type="production">Printed in the UK</note></physicalDescription><abstract>A non-invasive ultrasonic method was used to control the change in physical properties of milk gel and the syneresis, which is an essential step in the manufacture of cheese. The velocity and the attenuation were recorded for ten hours. They provide a good indicator of syneresis occurring. The firmness of the milk gel increases with the variation in velocity (V). The effects of the temperature, calcium chloride and rennet concentration on the syneresis were studied.</abstract><subject><genre>keywords</genre><topic>ultrasonic</topic><topic>syneresis</topic><topic>firmness</topic><topic>milk gel</topic><topic>rennet coagulation</topic></subject><relatedItem type="host"><titleInfo><title>Measurement Science and Technology</title></titleInfo><titleInfo type="abbreviated"><title>Meas. Sci. Technol.</title></titleInfo><genre type="journal">journal</genre><identifier type="ISSN">0957-0233</identifier><identifier type="eISSN">1361-6501</identifier><identifier type="PublisherID">mst</identifier><identifier type="CODEN">MSTCEP</identifier><identifier type="URL">stacks.iop.org/MST</identifier><part><date>2006</date><detail type="volume"><caption>vol.</caption><number>17</number></detail><detail type="issue"><caption>no.</caption><number>2</number></detail><extent unit="pages"><start>281</start><end>287</end><total>7</total></extent></part></relatedItem><identifier type="istex">FDABA043A182550EBB36339F3E65F6648AF08104</identifier><identifier type="DOI">10.1088/0957-0233/17/2/008</identifier><identifier type="PII">S0957-0233(06)94844-9</identifier><identifier type="articleID">194844</identifier><identifier type="articleNumber">008</identifier><accessCondition type="use and reproduction" contentType="copyright">2006 IOP Publishing Ltd</accessCondition><recordInfo><recordContentSource>IOP</recordContentSource><recordOrigin>2006 IOP Publishing Ltd</recordOrigin></recordInfo></mods></metadata><enrichments><json:item><type>multicat</type><uri>https://api.istex.fr/document/FDABA043A182550EBB36339F3E65F6648AF08104/enrichments/multicat</uri></json:item></enrichments><serie></serie></istex></record>Pour manipuler ce document sous Unix (Dilib)
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