Effects of Fermentation in Saltine Cracker Production

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Effects of Fermentation in Saltine Cracker Production' D. E. ROGERS and R. C. HOSENEY 2 ABSTRACT Yeast was found to be necessary in cracker sponges. Stack weight decreased with increased yeast fermentation because of the decreased dough density. In addition, the cracker cell structure was finer and more uniform. The starter slurry inoculated the system with bacteria and was required to decrease the pH. The lower pH allowed the flour proteases to modify the flour proteins. Stack height decreased
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  Effects ofFermentation in SaltineCracker Production' D. E. ROGERSand R. C. HOSENEY 2 ABSTRACT CerealChem. 66(l):6- 10 Yeastwas found to be necessary in cracker sponges. Stack weight During the 18-hr sponge fermentation, gas was produced, the pH declined, decreased withincreasedyeast fermentation because of thedecreased and the flourproteins were enzymatically modified. With the total starterdough density. In addition, the cracker cell structure was finer andmore system, crackerstackheightand stack weight decreased as sponge uniform. The starterslurryinoculated thesystemwith bacteriaand was fermentation time increased. At the same time,the textureof the crackersrequired todecrease the pH. The lower pH allowedthe flourproteasesto changed fromextremelytenderand fragile tostrong with increasing sponge modify the flourproteins.Stack height decreasedwhen slurry was included fermentation time.The 4-hr rest period following dough-up was essentially in the crackerformula,but the texturalstrength of the cracker increased. a proof periodand allowed equilibrationofmoisture. Saltine crackers are produced with a procedure that requires a total of approximately 24 hroffermentation.Pizzinatto and Hoseney (1980a) showed that as fermentation timeincreased,the strength andthe pHof the crackerspongesdecreased. The role of a starter system, as developed for laboratoryproduction ofsaltinecrackers by Doescherand Hoseney (1985), isgenerallyignored in the literature.Piepner (1971) mentioned the use of a buffer or sponge, which could be addedto cracker sponges toenhance fermentation. Most authors, however,simply mention the variability in sponge pH andcracker quality that arises from the fluctuation in materialadheringto the troughs (Johnson and Bailey 1924; Micka 1955; Heppner 1959; Matz 1968,1984; Smith 1972). The assumption can be made that adventitiousbacteria play an important role in the fermentation process (Sugihara 1978). Pizzinattoand Hoseney (1980a) alsosuggested that the reduction of pHduring fermentation brings the sponge to the pH optimum (approximately 4.1) of thenative proteolytic enzymesof flour. Wu (1987) showed that the resulting enzymatic action isresponsible for therheological changes in cracker sponges.Salgo (1981) studied wheat proteasesandfound twoenzymes with similarpH optima, 3.8 and 4.2, whichwere stable in the pH2.5-5.0 range. Saltinecrackers are uniquebaked products with a peculiar 'Contribution no.88-163-J. Kansas Agricultural ExperimentStation. Presented in part atthe AACC 72ndMeeting,Nashville,TN, November 1987. 'Research assistant andprofessor, respectively, Departmentof Grain Science andIndustry, Kansas State University, Manhattan 66506. This manuscript was prepared for electronic processing. ©1989 AmericanAssociation of CerealChemists, Inc. 6 CEREAL CHEMISTRY texture. This texture, although readilyrecognizable toconsumers, is difficultto describe or defineobjectively. Mostreportedinstrumental texture evaluationsof crackers,biscuits, orotherpastryproducts use methods basedon breakingstrength. Samples aresuspendedacross a bridge, and theforce required tosnapthe test specimen is recorded(Swartz 1943, Stinson and Huck 1969, Bruns and Bourne 1975, Zabik et al 1979, Katz andLabuza 1981). Katz andLabuza (1981) examinedcrispnessof four differentsnackfoods,includingsaltinecrackers.Samples were equilibrated at one of 10 relative humidities for three weeks beforetesting. A critical water activity, above which the product was unacceptable, was determined usingsensory techniques. A snap test was used to measure crackertexture, with the initial slope of theforce deformation curve takento indicate crispness (a technique alsousedby Bruns andBourne 1975). Theobjectives ofthis study were todetermine the effects of yeast and starter on crackerqualityandtodeterminewhat changes occurin the system during phases offermentation. MATERIALSAND METHODS Materials Two commercialcrackerfloursprovided by Lance Inc. and Dixie-PortlandFlour MillsInc., and one flour milled fromsoftwheatat Kansas StateUniversity were used in this study (Table I). These flours were selected to represent the rangeofproteins and flour qualitiesavailable from several commercial sources. Compressed yeast (Anheuser-Busch, St. Louis, MO, or Red Star, Universal Foods, Milwaukee, WI)was agedtwo tofour weeks at 4°C beforebeingused. Minordryingredients were supplied by NabiscoBrands, Inc. Hydrogenated vegetable shortening (Crisco, Proctor & Gamble, Cincinnati, OH) wasusedin the cracker baking.  Absorption Determination Optimum absorption was determined by the mixographprocedure described by Rogers and Hoseney (1987). CrackerBaking Crackers were baked using a procedure slightly modified (Rogersand Hoseney 1987) from that developed by Pizzinatto andHoseney (1 980b) and Doescherand Hoseney (1985). For the study on ingredient effects, the fermentation time remained constant. Sponges wereset with flour and water plusyeast alone, yeast plus slurry(control), slurry alone, or no starter at all (flour and water).When mock systems were made, 5 ml of the water was heldback and sponges were mixed for only 2 min. After the desired yeast fermentation, which varied from 1 to 8 hr, approximately 1.3 ml 85% lactic acid (quantity of acid neededvaried slightlybetween flours) was diluted to 5 ml and mixed into the sponge for 1 min.This was followed by fermentation times varying from 8 to 14 hr. In otherexperiments, sponge dough-up fermentation times or dough- up resttimes were varied, holding ingredientsand the other fermentation time constant. Gassing Power Samples of cracker sponge and dough were prepared as for baking. A 10-g sample of sponge or a 50-g sample of dough was placed into a half-pint reaction bottle ina gasograph (Coghill Corp., Hayden Lake, ID) (Rubenthaler et al 1980). Cracker TextureAnalysis To adjust the water activity before texture analysis,crackers were placedonscreens suspended over trays of sulfuric acid solutions diluted with waterto produce an equilibrium relative humidityof 20%. The chambers were sealed and crackers were equilibrated for a minimumof five days. Water activity of the samples was measured with a thermocouple psychrometer (Decagon Devices Inc., Pullman, WA). The universal testing machine (UTM) (Instron model 1132) was used in the compression mode for instrumental texture analyses. For breaking strength determinations, the 2-kg load cell wasused with a crosshead speed of 5 cm/min and a chart speed of 25 cm/ min. An individual cracker, top side down, was placed over a 2.5-cm bridge. A blunt chisel probe, placed parallel to the directionof the last sheeting, was lowered until the cracker broke. The peak force, or force required to break the cracker, was recorded. This test was designed to simulate the initial force requiredto bite, or break, a cracker.The 50-kg compression load cell was used for the crushing test,with a crosshead speed of 2.5 cm/min and a chart speed of 50 cm/min. A 1.27-cm diameter, flat, circular probe was centered over the middle docker hole of an individual cracker placed top side down on a flat plate. The cracker was measured for thickness and then compressed to 50% of its srcinal thickness. The curves generated were examined fortheir general shape, includingthe angle to the first break, the degree of failure,the average forceof the curve, and the final force. This test was designed to simulatethe shatteringof the cracker in the mouthduring chewing with the molars. Organoleptic analysis was also carried out on most samples. RESULTSAND DISCUSSION Cracker Texture Analysis An untrainedorganoleptic panel was used tosurvey five brands TABLE I Analytical Data for Flours Used for Cracker Baking Flour % Protein % Ash of commercial crackers.Panel results revealed distinct differences in cracker texture. The first bite of cracker, with the incisors, indicated the hardness/tenderness of the cracker. Continuedmastication with the molarsindicated the friability of the cracker. To account for those differences,two separatebut relatedcracker texture tests were performed. TypicalUTM crushing curvesare depicted in Figure1. A tender, friable cracker (Fig. IA) requires a moderate amount of force to causethe first failure, yet the angle to thefirst break is steep.After the first failure, the cracker has many minor and major failures.The resistance to force remains fairly constant throughout the test period. A crackerjudged to be tough and pasty, shown in FigureIB, has a lower slope to the first breakandcontinues to buildresistance to force throughout the entiretesting period. Few, if any,major failuresare noted. Effect of Sponge (Starter) Ingredients The sponges made withno yeast or slurryproduced doughsthat were nonuniformormottled in appearanceand crackers that had uneven puffing. Because of the unevenpuffing, the measured stack height (Table II) was not a good guide to the inner structure of the crackers. These crackers had excessive shelling (separation of external layers), poor lamination,poor cell structure, and werevery tender. The extremetenderness made it very difficultto obtain 10 unbroken cells from the sheet of 21 cells. When tested organoleptically, the initial bite was overly tender. However, there was a pastiness that remained around the molars during several compressions. The UTM compressionprocedure showed a building of resistance,with large variability within the treatment. The crackers bakedfrom sponges containing flour, water, andyeast showed a slight decrease in stack height and a decrease instack weight when compared with crackers made from sponges containing only flour and water (Table II). Increased gas production and/or increased gas retention would changethe TABLE II Effect of Varying Starter onBaking PerformanceaSpongeStack Htbc Stack Wtbcd Ht/Wt Starter pH (mm) (g) Ratio None 5.41 72.55 a 35.36 a 2.05 Yeast 4.88 71.51 a 33.36 ab 2.14 Slurry 3.63 63.88 b 36.49 a 1.75 Yeast + slurry 3.77 68.40 ab 31.63 b 2.16 aBaked using flour 1; average of four replicates.bStack of 10 crackers. c Different letters denote significant differences at the 0.05 level. dDry basis. A 00 oV- 2 - ~~~~~~2- 0 o2 020 L)~~~~ 0)~~~~~ LuL 0 .15 .25 .1 5 .25 COMPRESSION (cm) COMPRESSION (cm) Fig. 1. Universal testing machine compression curves of crackers, using a 1.27-cm diameter flat circular probe. A, tender, friable cracker; B, tough and pasty cracker. Vol. 66, No. 1, 1989 7 Sample (14% mb) (14% mb) 1 9.370.45 2 7.82 0.42 3 10.08 0.48  density of the dough,resulting in a reducedweight for the constant volume being examined. The crackers also had a more uniform cell structurethan crackersmade with no yeast or slurry, although the actual stackheight was less. The crackers were noticeablypaler in topcolor than the crackersfrom the othertreatments,indicating the depletionoffermentablecarbohydrates (reducing sugars needed for browning) by the yeast. Organoleptically, the crackers made from the yeasted sponge were tender, although not as fragile as the crackers made without starter. The pastysensation lingering around the molars duringmastication wasstill evident. TheUTM compression curvesshowed a continual building of resistance throughout thecompression, with one or two majorbreaks in the compression curve. After 18 hr of fermentation (Table II), the pH ofthesponge set with flour, water, and yeast, although lower thanthat of the flour and water sponge, was still higher than the optimum pHs (3.8 and 4.2) ofthe proteolytic enzymes reported in flour (Salgo 1981). The major changes, thus, could not be attributed to increased proteinmodificationoccurring in thesponge. Therefore, it appeared that the yeast was necessary for gas production. The gas produced by yeast lowers the dough density.Thus,for a given area (docker cell), fermentation would lower the dough weight and subsequentcracker weight. In addition, bubblenucleation is required for uniform puffing betweenthe lamellae of the finished product. The large bubbles are subdividedduringdough mixing and during sheeting. Those smaller, finer air cells create the even, flakypuffing preferred in saltine crackers.Sponges containing the slurry, flour, and waterproducedcrackers with stack weightsslightly greater than thoseof the flourandwater sponges but with greatly reducedstack height (Table II). U) z z U) U) 41- 365 31 265 21- 16- 1 1- 6- 1- 1 3 57 9 11 1315 17 19 T ME (HR) Fig. 2. Gasograph curve of fermenting sponges. Sponge containingslurry (-x-), sponge containing yeast (-+-), sponge containingslurry andyeast (control) (-o-). I 5. 6- 5. 2 4. 8i 4. 41 4.0-~ 1 5913 17 T ME (HR) Fig. 3. Change in sponge pH as a function of fermentation time. 8 CEREAL CHEMISTRY The dough was both more extensible and more developed (more cohesive) than normal. The improvedpuffing between laminations ofthose crackers compared to the flourand water crackers indicated that some gas was produced, even in the absence of added yeast. The texture of the crackers made with slurry, determinedorganoleptically, was similar to that of the control crackers. The crackers were strong yet nottough and did not build up around themolarsduringmastication. The UTM compression curves were fairly level in force,with mainly minor failures. A sponge set withyeast and slurry (the standard or control cracker) appearedto have a combination of the individual effects of yeast and slurry (Table II).The control sponge yielded crackers that were reduced in both stack heightandstack weight when compared to the flourand water spongecrackers. The texture was strongwithout being pasty. The UTM compression curves showed fairly constant resistance during the compression. Theyshowedtwo to three major failures, along with several minorbreaks. Based on these data, we concluded that the yeast was necessary for gas production, and the starter was requiredto lower the pH sufficiently for the proteolytic enzymes inherent in the flour to becomeactive, as shown byWu (1987). To test the relationship between gas production during sponge fermentationand crackerquality,thegasograph was used. Spongesmadewith flour,water, yeast, and slurry (control, Fig. 2) had a rapidinitialrate of gas productionthat leveled off after approximately 6 hr of fermentation. A plotof sponge pHduring the 18-hr fermentation (Fig.3) indicates that at 6 hr the pH was probablynear pH 5.5, the optimumfor yeast gas production (Pyler 1973, Holmes and Hoseney 1987). Depletionof fermentablecarbohydratesappears to be the most likely reason for the reduction in gas production at 6 hr. To test that assumption, sucrose (3%) was addedto a sponge after 6 hr of fermentation. The rateof gas produced during the next 6 hr was 0.945 gassing units/ hr, whereas that for the control (unfed) sample was0.569 gassing units/hr during the second6-hr period. Gas production ofthe sponges set with flour, water,and yeastwas equal to that of the control (Fig. 2). The sponges made with only flour, water, and slurry produced relativelylittle gas during the 18-hr period. These data supported the hypothesisthatadequate gas production was necessary for goodquality crackers. The bacteria in the slurry lower thesponge pH. If loweringthe pH is the only important functionof the starter, then one should be able to mimic that change by using acid. To produce a mock starter system, a constant 3-hryeast fermentation was arbitrarily selected, followed by a lacticacid reaction time that varied from 8 to 14 hr (Table III). This reaction time was to allowthe flourproteolytic enzymestime towork. Withan 8-hr reaction time, thedough was stiff and strong and did not sheet uniformly. As the acid reaction time was increased, the doughs became moreextensibleand softer to the touch. The crackersproduced with either 8 or 10 hrof acid reaction time gave nonuniform puffing.This indicated an excessively strong sponge.In general, overthe time range studied,increasing acid treatment times resulted in decreased stackheights and slightly decreased stack weights. The 12- and 14-hr treatment crackers had uniform puffing. Because additional timedid not appear to be of TABLEIII Effect of VaryingAcid Reaction Time,Following 3 hr of Yeast Fermentation, on BakingPerformance' AcidTime SpongeStack Htb Stack Wtb,c Ht/Wt (hr) pH (mm) (g) Ratio 8 3.95 73.9733.67 2.20 10 3.8773.09 33.70 2.17 12 3.82 71.39 32.66 2.19 14 3.85 70.3132.11 2.19 'Baked using flour 1; average of three replicates. Mean standard deviation for stackheight = 0.79, for stackweight = 1.09. bStack of 10 crackers. cDry basis. - I :1 *j. I. I * - i i1 i l4 1 1 & i I1 1 iI i ----- II--- . 1 1 i i i i i i  any benefit, a 12-hr lactic acid treatment was selected as optimum. With lactic acid resttime held constant at 12 hr, the length of the initial yeast fermentation was varied (Table IV). In general, stack height increased as thetime of yeast fermentation increased from 1 to 5 hr. No trend was apparent in the stack weight.The height/ weight ratio, an indicationof lift, appeared to plateauat 2 or 3 hr of fermentation. The quality of the cracker cell structurefor all yeast fermentation timeslonger than 1 hr was equal to that of the control crackers, as wasthe texture of thecrackers. Therefore, an adequate mock cracker system had been developed, using a 2-3-hr yeast fermentation followed by a12-hr reaction time at pH 4. Effect of Sponge Fermentation Time As might be expected, the sponge pH decreased, and total titratable acidity (expressed as milliequivalentsof acid per gram of sponge)increased as the fermentation time increased (Table V). Doughs with 0- and 6-hrsponge fermentation times were too crumbly to hold togetherduring sheeting. An additional 2% water was added, but even then the doughs appeareddry in areas and were too crumbly to sheet satisfactorily. The crackers producedfrom both the 0- and 6-hr sponge fermentation samples shattered easily and puffed unevenly.As fermentation time was increased, both the stackheight and stack weight of the crackersdecreased, indicating a continualproteinmodificationand/or increased gas production. This was in agreement with work by Pizzinattoand Hoseney (1980a,b). Increasing fermentation time resulted in doughs that were more pliable and easier to machine. As shownpreviously (Rogers and Hoseney 1987), for any given TABLE IV Effect of Varying Yeast Fermentation, Prior to 12-hr LacticAcid Fermentation, on BakingPerformancea Yeast TimeSpongeStackHtbcStack Wtbd Ht/Wt (hr) pH (mm) (g) Ratio 1 3.88 77.49 bc37.53 1.93 2 3.9573.05 bc 36.022.03 3 3.86 73.54 bc 35.51 2.07 4 3.89 71.72 c 36.70 1.95 5 3.88 75.84 a 38.12 1.996 3.96 74.68 ab 36.56 2.04 7 3.88 73.71 abc 35.832.06 8 3.9273.77 abc 35.71 2.07 aBaked using flour 1; average of five replicates. bStack of 10 crackers. cDifferent letters denote significant differences at the 0.05 level. dDrybasis. TABLE V Effect of Varying Sponge Fermentation Time on BakingPerfromancea Fermentation Sponge TTAb StackHtcd Stack Wtcde Ht/Wt Time pH(meq/g) (mm) (g) Ratio Flour I 0 hr (+2%) 5.35 0.0150 76.72 a38.78 a 1.996 hr (+2%) 4.95 0.0254 73.95 ab 35.67 b 2.07 12 hr 4.61 0.030474.26 ab 36.12 b 2.06 19 hr 4.10 0.043373.04 b 34.18 b 2.14 Flour 2 0 hr (+2%) 5.10 0.0145 70.33a38.99 a 1.80 6 hr(+2%)4.54 0.0251 68.64 b 37.46 ab 1.83 12 hr 3.92 0.0392 67.29 b 35.67 b 1.89 18 hr 3.60 0.0523 63.48 c 35.50 b 1.79 Flour 3 0 hr (+2%) 5.57 0.0152 76.19 a 45.65 a 1.67 6 hr (+2%)4.890.0299 75.18a 44.35 ab 1.70 12 hr 4.15 0.0436 72.08 b 42.16 b 1.71 18 hr 3.82 0.0607 73.05 b 42.26 b 1.73 'Average of four replicates. hTotal titratable acidity. 'Stack of 10 crackers. dDifferent letterswithin flours denote significantdifferences at the 0.05 level. 'Drybasis. treatment, increasingthe water level caused a decrease in stack height and stack weight. Therefore, theeffectof sponge fermentation time on stack height andstack weight is greaterthannoted in Table V and can be used to explain the slightincreaseinstackheight and weightbetweenthe 6- and 12-hr samples for flour 1. The doughs became more extensible as fermentation time increased. The doughsnot only felt different,but, because of increased extensibility, the finalsheeted dough-piece increased in dimensions as fermentation time was increased. That resulted in a change in the weight of an unbakedcracker cell. The net result was thatimportant, time-mediated changes occurred during sponge fermentation that affectedthe final crackerquality. These changes may have been caused by increased flour protease activity, pH- induced conformational changesof the protein,or a combination of those phenomena. The effect of the fermentation time on crackertexture wasalso studied. The UTM breakingstrength increased as fermentation time increased.There was a definite continuum of the organoleptictexturefrom the crackersfermented 0 hr through those fermented 18 hr. Those crackers withno sponge fermentation were overly tenderand easily broken on the first bite. The layers appeared to be very thin,both visually and organoleptically. However, thecrackers seemed to clingto the teeth, asif the fragments remained positioned in the mouth exactly where they broke. The 18 hr fermentation crackersrequired more force to bite initially, yet they broke cleanly in the mouth. UTM compression curves showed a slight building of resistance with few major failures for the samples fermented for 0 and 6 hr. The samples fermentedfor 12 and 18 hr were strongerand had more major failures. It would appear from these data that sponge fermentation time was necessary to transform the textureof thecrackers from exceedingly tender to strong. One explanation for such a transformation would be that in a low water system,the flour particlesremain discrete entities that do notform a continuousmatrixduring mixing or during the sheeting process. After baking, the crackers fracture easily at the particle-particle interfaces, resulting in overly tender crackers. Smallincreases in the baking absorption permit a more continuousdough mass to be formed, although most ofthe protein remains within the particles. Further increases in the bakingabsorptionresult in a disappearanceof all (or most) of the particles. The matrix is strong, yet brittle, and breaks all at once. When a mixtureof particles and matrix is present, as at the medium absorption levels, failures occur first around the particles andthen through thedeveloped matrix. Increasing fermentation time permits more of the flour particles tohydrate and, thereby, form a more continuousmatrix. The more extensivethe matrix, the stronger the cracker. Effect ofDough-Up Rest Time The importance of the dough-up fermentation or rest time was also studied. Itwas assumed that the dough-up rest period was simply a hydration time, allowing the 35% additionalflour to become equilibrated in moisture with the sponge ingredients. Stack heightincreased as dough rest increased from 0 to 4 hr, thendropped (Table VI). The crackers with a 2-hr dough resthad stack weights that were muchheavier than those withthe other rest times. The crackers produced with 0- and 2-hr dough-up rest times TABLE VI Effect of Varying Dough-Up Rest Time onBaking PerformanceaDough RestStack Htb Stack Wtbc Ht/Wt (hr) (mm) (g) Ratio 0 66.4037.29 1.78 2 72.40 39.42 1.84 4 74.6637.00 2.02 6 71.84 37.72 1.90 Baked using flour 1; average of four replicates. Mean standard deviation forstack height = 0.79, forstack weight = 1.07. 5 Stack of 10 crackers. 'Drybasis. Vol. 66, No. 1, 1989 9 I
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