DryingTec-2007

Prévia do material em texto

<p>See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/233007680</p><p>Metabolic Activity of the Dehydrated Yeast by Spray Drying</p><p>Article  in  Drying Technology · July 2007</p><p>DOI: 10.1080/07373930701438824</p><p>CITATIONS</p><p>5</p><p>READS</p><p>408</p><p>4 authors, including:</p><p>V. J. Robles-Olvera</p><p>Instituto Tecnológico de Veracruz</p><p>49 PUBLICATIONS   1,031 CITATIONS</p><p>SEE PROFILE</p><p>Guadalupe Luna-Solano</p><p>Instituto Tecnológico de Orizaba</p><p>85 PUBLICATIONS   712 CITATIONS</p><p>SEE PROFILE</p><p>M. A. Salgado-Cervantes</p><p>Instituto Tecnológico de Veracruz</p><p>71 PUBLICATIONS   1,250 CITATIONS</p><p>SEE PROFILE</p><p>All content following this page was uploaded by Guadalupe Luna-Solano on 24 March 2015.</p><p>The user has requested enhancement of the downloaded file.</p><p>https://www.researchgate.net/publication/233007680_Metabolic_Activity_of_the_Dehydrated_Yeast_by_Spray_Drying?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_2&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/publication/233007680_Metabolic_Activity_of_the_Dehydrated_Yeast_by_Spray_Drying?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_3&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_1&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/V-Robles-Olvera?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_4&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/V-Robles-Olvera?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_5&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/institution/Instituto-Tecnologico-de-Veracruz?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_6&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/V-Robles-Olvera?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_7&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/Guadalupe-Luna-Solano?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_4&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/Guadalupe-Luna-Solano?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_5&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/institution/Instituto-Tecnologico-de-Orizaba?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_6&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/Guadalupe-Luna-Solano?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_7&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/M-Salgado-Cervantes?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_4&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/M-Salgado-Cervantes?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_5&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/institution/Instituto-Tecnologico-de-Veracruz?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_6&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/M-Salgado-Cervantes?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_7&_esc=publicationCoverPdf</p><p>https://www.researchgate.net/profile/Guadalupe-Luna-Solano?enrichId=rgreq-be9e10db1ede19cad97c9d800acd885a-XXX&enrichSource=Y292ZXJQYWdlOzIzMzAwNzY4MDtBUzoyMTA2MTE2OTU4MjA4MDBAMTQyNzIyNTE0OTI4OQ%3D%3D&el=1_x_10&_esc=publicationCoverPdf</p><p>This article was downloaded by:[Luna-Solano, G.]</p><p>On: 20 August 2007</p><p>Access Details: [subscription number 780959473]</p><p>Publisher: Taylor & Francis</p><p>Informa Ltd Registered in England and Wales Registered Number: 1072954</p><p>Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK</p><p>Drying Technology</p><p>An International Journal</p><p>Publication details, including instructions for authors and subscription information:</p><p>http://www.informaworld.com/smpp/title~content=t713597247</p><p>Metabolic Activity of the Dehydrated Yeast by Spray</p><p>Drying</p><p>Online Publication Date: 01 July 2007</p><p>To cite this Article: Márquez-Montes, R., Robles-Olvera, V., Luna-Solano, G. and</p><p>Salgado-Cervantes, M. A. (2007) 'Metabolic Activity of the Dehydrated Yeast by</p><p>Spray Drying', Drying Technology, 25:7, 1281 - 1285</p><p>To link to this article: DOI: 10.1080/07373930701438824</p><p>URL: http://dx.doi.org/10.1080/07373930701438824</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf</p><p>This article maybe used for research, teaching and private study purposes. Any substantial or systematic reproduction,</p><p>re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly</p><p>forbidden.</p><p>The publisher does not give any warranty express or implied or make any representation that the contents will be</p><p>complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be</p><p>independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings,</p><p>demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or</p><p>arising out of the use of this material.</p><p>© Taylor and Francis 2007</p><p>http://www.informaworld.com/smpp/title~content=t713597247</p><p>http://dx.doi.org/10.1080/07373930701438824</p><p>http://www.informaworld.com/terms-and-conditions-of-access.pdf</p><p>D</p><p>ow</p><p>nl</p><p>oa</p><p>de</p><p>d</p><p>B</p><p>y:</p><p>[L</p><p>un</p><p>a-</p><p>S</p><p>ol</p><p>an</p><p>o,</p><p>G</p><p>.]</p><p>A</p><p>t:</p><p>15</p><p>:4</p><p>9</p><p>20</p><p>A</p><p>ug</p><p>us</p><p>t 2</p><p>00</p><p>7</p><p>Metabolic Activity of the Dehydrated Yeast by Spray Drying</p><p>R. M�aarquez-Montes1, V. Robles-Olvera1, G. Luna-Solano2,</p><p>and M. A. Salgado-Cervantes1</p><p>1Instituto Tecnol�oogico de Veracruz, Unidad de Investigaci�oon y Desarrollo en Alimentos. Veracruz,</p><p>Ver. México</p><p>2Instituto Tecnol�oogico de Orizaba, Divisi�oon de Estudios de Posgrado e Investigaci�oon. Orizaba,</p><p>Veracruz, México</p><p>In this investigation, the reactivation of the Mexican brewer’s</p><p>yeast dehydrated by spray drying as a way of generating cells with</p><p>metabolic activity similar to the fresh yeast was studied. Fresh yeast,</p><p>dehydrated-reactivated yeast, and unreactivated-dehydrated yeast</p><p>were used. During the fermentation, fresh and dehydrated-</p><p>reactivated yeast presented a greater growth rate than dehydrated</p><p>yeast. Slow rehydration allowed an increase in alcohol production</p><p>than that observed in a rapid rehydration. The sugars were metabo-</p><p>lized faster by fresh than by dehydrated-reactivated, but this was</p><p>faster than unreactivated-dehydrated yeast. The pH evolution did</p><p>not show significant differences (a ¼ 0.05) among yeasts. The</p><p>reactivation was important for the yeast metabolic activity.</p><p>Keywords Brewery yeast; Fermentation; Metabolic activity; Spray</p><p>drying</p><p>INTRODUCTION</p><p>A number of works related with the preservation of</p><p>baker’s yeast have been published.[1–4] Bakers</p><p>routinely</p><p>use dried yeast because it is easier to handle than fresh</p><p>yeast. It has been estimated that 75% of the wine producers</p><p>use dried yeast.[5] However, there are not many reports on</p><p>dehydrated brewer’s yeast.</p><p>The Mexican beer industry produces great quantities of</p><p>fresh yeast that is used to supply inoculum to breweries in</p><p>distant locations. The main problems associated with the</p><p>fresh yeast transport are: conservation time, risk of contami-</p><p>nation, transportation and storage costs under refrigeration.</p><p>Drying studies have shown that spray drying is a preser-</p><p>vation method for diverse yeast and other microorganism.[6–9]</p><p>Specifically Luna-Solano et al.[8,9] reported the effect of</p><p>spray drying and processing variables on improving of the</p><p>dried brewer’s yeast viability. Some authors have found that</p><p>yeast viability can decrease during the spray drying at</p><p>specific process conditions.[6–9] The decrease of the cell</p><p>viability during the drying process can bring other changes</p><p>such as the decrease of the metabolic activity during its rehy-</p><p>dration and reactivation. The processes of drying and rehy-</p><p>dration essentially affect the structural and metabolism of</p><p>microbial cells. Rehydration is a purely physical process</p><p>when cell saturation with water takes place.[3]</p><p>Some studies have shown the importance of the rehydra-</p><p>tion temperature on cell viability and that the time required</p><p>for the return of water into cells is not long. The viability</p><p>rate of spray-dried microorganism increased linearly as</p><p>the temperature of rehydration increased.[3,10,11] However</p><p>these studies didn’t show the reactivation effect on the</p><p>yeast metabolic activity during fermentation. The duration</p><p>of reactivation period depends on the character and level</p><p>of intracellular damages. Yeast metabolic condition is</p><p>determined by measuring the metabolic function. Several</p><p>studies have also shown the importance of the sugar con-</p><p>sumption, ethanol production and cell growth during the</p><p>fermentation.[5,12,13] Depending on the character and level</p><p>of damages, the specific growth rate of dried yeast cells</p><p>may be lower than that of the initial fresh ones.[3]</p><p>The utilization of dried yeast is a new alternative for</p><p>Mexican breweries. Currently only freshly-propagated yeast</p><p>is used for the brewing process. The dehydrated yeast pre-</p><p>sents more stability, lower cost during the storage, easier to</p><p>handle and lower risk of contamination during the transpor-</p><p>tation than the fresh yeast used currently. It is known that</p><p>during the drying the cellular metabolism can fall. Therefore</p><p>in the present work the reactivation of the brewer’s yeast</p><p>dehydrated by spray drying as a way of generating cells with</p><p>metabolic activity similar to the fresh yeast was studied.</p><p>MATERIALS AND METHODS</p><p>Fresh yeast (Saccharomyces ssp.) with a cell count of</p><p>1.2� 109 cel mL�1 was obtained from the Brewery in</p><p>Correspondence: G. Luna-Solano, Divsi�oon de Estudios</p><p>de Posgradoe Investigaci�oon, Instituto Tecnol�oogico de</p><p>Orizaba, Av. Oriente 9 no. 852, Orizaba, Veracruz, México;</p><p>E-mail: gluna@itorizaba.edu.mx</p><p>Drying Technology, 25: 1281–1285, 2007</p><p>Copyright # 2007 Taylor & Francis Group, LLC</p><p>ISSN: 0737-3937 print/1532-2300 online</p><p>DOI: 10.1080/07373930701438824</p><p>1281</p><p>D</p><p>ow</p><p>nl</p><p>oa</p><p>de</p><p>d</p><p>B</p><p>y:</p><p>[L</p><p>un</p><p>a-</p><p>S</p><p>ol</p><p>an</p><p>o,</p><p>G</p><p>.]</p><p>A</p><p>t:</p><p>15</p><p>:4</p><p>9</p><p>20</p><p>A</p><p>ug</p><p>us</p><p>t 2</p><p>00</p><p>7</p><p>México. This yeast was dried in a spray dryer using the</p><p>optimal variables (out air temperature 60�C, 1 g gris=g</p><p>yeast solids and spray velocity 319 s�1) reported like those</p><p>in which viability loss was minimal.[14] This way, fresh</p><p>yeast (FY), dehydrated and reactivated yeast (RDY) and</p><p>unreactivated dehydrated yeast (DY) were used. Evalu-</p><p>ation of the dried yeast reactivation was carried out with</p><p>wort of Mexican brewery at 9�C, 20�C and 25 �C.</p><p>A 2-L capacity bioreactor (Fig. 1) with strict tempera-</p><p>ture controls was used to ferment the Mexican brewery’s</p><p>wort. Before inoculation, the bioreactor was sterilized</p><p>and wort (1500 mL) was pasteurized at 80� 1�C for</p><p>30 min.[13]</p><p>The wort was placed in the bioreactor and the inoculum</p><p>was added to the system as required to provide 1.25� 107</p><p>yeast cell per milliliter. This cells content is necessary to</p><p>begin the fermentation.[13,15,16] Initial time (0 h) was con-</p><p>sidered when the wort reached 10�C. Every 24 h, the tem-</p><p>perature increased 1�C until reaching 15�C for a total of</p><p>120 h. Wort was kept at 15�C until total fermentation time</p><p>of 168 h. Samples of 25 mL of the fermenting wort were</p><p>taken every 12 h for the analysis. The Mexican brewery</p><p>uses a specific temperature profile (which is confidential)</p><p>to carry out the fermentation process.</p><p>Kinetics of growth were obtained during wort fermen-</p><p>tation. Cells count was evaluated by growth in inverted</p><p>plate. A nutritive medium for yeast was used, containing</p><p>2.5 g bactopeptone, 2.5 yeast extract, 5 g glucose and</p><p>250 mL distilled water, was used. The counts were made</p><p>after 72 h of incubation at 25�C. Viable planting is regarded</p><p>as the reference method for determining yeast viability</p><p>based on the theory that, each viable cell will give rise to</p><p>a single colony.[6,12]</p><p>The cellular concentration expressed as cells mL�1, at</p><p>any time, was fit by nonlinear regression to the logistic</p><p>model,</p><p>dX</p><p>dt</p><p>¼ mmax X</p><p>1�X</p><p>Xmax</p><p>� �</p><p>ð1Þ</p><p>where: X is cellular concentration in a given time, t is time</p><p>(h), mmax is maximum specific growth rate and Xmax is</p><p>maximum cell concentration attainable.</p><p>The evolution of ethanol production, consumed sugars</p><p>and pH was evaluated during the fermentation. Ethanol</p><p>and sugars were quantified in a liquid chromatograph</p><p>(Waters) with flame ionization detector and column (ami-</p><p>nex HPX-87H). Measurements of pH were performed</p><p>using a potentiometer (Orion) calibrated with pH 4 and 7</p><p>buffer standards.</p><p>The analysis of variance (ANOVA) was used to analyze</p><p>the experimental data of alcohol, sugars and pH. Duncan’s</p><p>multiple range tests was used to determine significant</p><p>differences among the three types of yeast (FY, RDY</p><p>and DY).</p><p>RESULTS AND DISCUSSION</p><p>The dried yeast obtained for spray drying at optimal</p><p>conditions reported for Luna-Solano et al.[14] presented a</p><p>viability of 5.4� 107 cell g�1, moisture content of 0.066 g</p><p>H2O=g d.s. and water activity (aw) of 0.415.</p><p>The influence of reactivation temperature on recovery of</p><p>yeast after drying was investigated. Survival rate increased</p><p>with temperatures between 9�C and 25�C. Similar results</p><p>were obtained by Poirier et al.[11] to Saccharomyces cerevi-</p><p>siae rehydration. In addition, the maximum growth rate</p><p>(0.16 h�1) was reached to 25�C, for this reason, this tem-</p><p>perature was chosen to obtain the inocula of the fermen-</p><p>tation studies.</p><p>Figure 2 shows the reproduction of yeast cells during the</p><p>reactivation at 25�C, 20�C and 9�C after of 18 h. It was</p><p>observed that budding of yeast shows the same shape in</p><p>the different treatments during the microscopic analysis.</p><p>Mother and daughter cells are produced through of an</p><p>asymmetric division in which each cell can be distinguished</p><p>(Fig. 2). It is well-known that the senescence is reached</p><p>when the final division of the cells has been achieved.[17]</p><p>Figure 3 shows the percentage obtained of mother and</p><p>daughter cells during the reactivation at 25�C, 20�C and</p><p>9�C. Reactivation done by 18 hours allowed preservation</p><p>of cells as follows: 85.6% at 25�C, 45.3% at 20�C and</p><p>5% at 9�C.</p><p>FIG. 1. The 2-L capacity laboratory bioreactor (2-L capacity) utilized</p><p>to carry up the fermentations.</p><p>1282 MÁRQUEZ-MONTES ET AL.</p><p>D</p><p>ow</p><p>nl</p><p>oa</p><p>de</p><p>d</p><p>B</p><p>y:</p><p>[L</p><p>un</p><p>a-</p><p>S</p><p>ol</p><p>an</p><p>o,</p><p>G</p><p>.]</p><p>A</p><p>t:</p><p>15</p><p>:4</p><p>9</p><p>20</p><p>A</p><p>ug</p><p>us</p><p>t 2</p><p>00</p><p>7</p><p>The results obtained by RDY during wort fermentation,</p><p>were compared with both FY and DY.</p><p>It can be observed in Fig. 4 the experimental and fitted</p><p>points for growth kinetics. The correlation coefficient</p><p>obtained to FY and RDY were greater of 0.90. The logistic</p><p>model was inappropriate to describe the DY.</p><p>When RDY and FY reach their maximum concen-</p><p>tration 6.82� 107 and 1.44� 108 cell mL�1 respectively, a</p><p>stationary phase appears and cells number</p><p>remain con-</p><p>stant. The yeast type has an evident effect on the growth</p><p>rate as shown in Fig. 4.</p><p>Growth rate measured for RDY and FY showed</p><p>enough evidence to be different with respect to DY.</p><p>FIG. 2. Micrographs taken using an optical microscopee (40X),</p><p>illustrating the reproduction of reactivated yeast cells: a) 25�C, b) 20�C</p><p>and c) 9�C.</p><p>FIG. 3. Reproduction of mother and daughter yeast cells during the</p><p>reactivation: a) 25�C, b) 20�C and c) 9�C.</p><p>METABOLIC ACTIVITY OF THE DEHYDRATED YEAST 1283</p><p>D</p><p>ow</p><p>nl</p><p>oa</p><p>de</p><p>d</p><p>B</p><p>y:</p><p>[L</p><p>un</p><p>a-</p><p>S</p><p>ol</p><p>an</p><p>o,</p><p>G</p><p>.]</p><p>A</p><p>t:</p><p>15</p><p>:4</p><p>9</p><p>20</p><p>A</p><p>ug</p><p>us</p><p>t 2</p><p>00</p><p>7</p><p>DY presented a smaller growth rate (0.021 h�1) than RDY</p><p>(0.048 h�1) and FY (0.095 h�1). Beker and Rapport[3] men-</p><p>tioned that depending on the character and level of</p><p>damages, the specific growth rate of dried yeast cells may</p><p>be lower than that of the initial fresh ones. There was no</p><p>evidence that the RDY and FY manifested a lag phase.</p><p>The first sample for monitoring the yeast growth was per-</p><p>formed at 6 hours. The results agree with Henschke[12],</p><p>who reported that many yeast exhibited a short lag phase</p><p>(</p>