2006牛肉干的干燥特性

The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of ASABE, and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process, therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE Section Meeting paper. EXAMPLE: Author's Last Name, Initials. 2006. Title of Presentation. ASABE Section Meeting Paper No. xxxx. St. Joseph, Mich.: ASABE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASABE at rutter@ or 269-429-0300 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).The Canadian Society forBioengineeringThe Canadian society for engineering in agricultural, food, environmental, and biological systems .A CSBE/ASABE Inter Sectional MeetingPresentation Paper Number: MBSK 06-214Thin - Layer Drying Characteristics of Beef JerkyIgnaci Victoria Thiagarajan, Graduate StudentVenkatesh Meda, Assistant ProfessorSatya Panigrahi, SAFRR Research ChairDepartment of Agricultural and Bioresource EngineeringUniversity of Saskatchewan,57 Campus Drive, Saskatoon, SK, CANADA S7N 5A9Phyllis Shand, Associate ProfessorDepartment of Applied Microbiology and Food ScienceUniversity of Saskatchewan,51 Campus Drive, Saskatoon, SK, CANADA S7N 5A8Written for presentation at the2006 North Central CSBE/ASABE inter sectional MeetingSponsored by CSBE/ASABESaskatoon, SK October 5- 7, 2006Abstract . Jerky is one of the popular North American dried meat products and it presently relies on conventional drying methods for its processing. There is a need to improve the product processing conditions. As drying is the major preservation method used for jerky processing, it is necessary to understand the drying behavior of beef jerky to optimize the process. In this study, drying characteristics of beef jerky in forced air thin layer drying unit was explored. The drying tests were contacted for different relative humidity and air flow rate. In addition to this, effect of pH of the sample formulation was also studied. Physical and chemical characteristics were analyzed. It was found out from the study that pH has a significant influence on drying characteristics such as drying rate and drying time and also it has a significant influence in physical characteristics like color, shrinkage, water activity etc., Relative humidity and airflow rate has a significant effect in drying characteristics of beef jerky. Higher air flow rate and lower relative humidity have stimulated the drying process. Physical properties such as water activity, color and shrinkage was also affected by relative humidity and air flow rate of the air.Keywords. Thin layer drying, beef, drying, pH, relative humidity, airflow rateIntroductionJerky is one of the old traditional North American dried meat product and this self stable food product relies on salting and drying for its shelf life (Faith, N.G. et al. 1998). Low fat content, low calories and high protein are the special features of this ready to eat meat product and is very popular among hikers, hunters, bikers and skiers. Jerky can be added to enhance the flavor and nutrition of soups, stews and casseroles. As per USDA (1996) recommendation, this stable product should have a moisture- protein ratio of ≤ 0.75:1 and water activity of less than 0.85 to ensure the product safety. Martha Archuleta (2004) has analyzed different aspects of jerky processing and reported that there is no safe processing method available for Jerky. It is necessary to understand the drying behavior of beef jerky to improve the quality and market value.As per Leistner (1995), the most important hurdles in food processing industries are temperature, water activity, acidity level, redox potential and preservatives (organic acids, spices). The manipulation of water activity and pH is the less complicated technologies of preservation in terms of equipment, expense and expert personnel needed. Reducing the water activity and pH may retard or impede microbial growth.Drying preserves food by removing sufficient moisture to prevent the growth of spoilage and ill-causing micro-organisms. Drying is a complex operation involving transient transfer of heat and mass along with several rate processes, such as physical and chemical transformations which, in turn may cause changes in product quality as well as the mechanisms of heat and mass transfer. As per Mujumdar & Devahastin (2000), physical changes may include shrinkage, puffing, crystallization, glass transitions and in some desirable or undesirable chemical or biochemical changes may occur leading to changes in color, texture, odor and other properties. Selection of dryer depends on the type of the product to be dried, desired final product quality, the product’s susceptibility to heat and the cost of drying (Cohen,J.S.& Yang,T.C.S.,1995). Calicioglu, M.et al. (2002) reported that texture is affected by drying jerky at high temperatures for extended periods of time. Humphrey, K.J.T (2002) has reported that the protein content of dried meat is higher than fresh meat. Drying at very high temperature will result in improperly dried product due to the case hardening phenomenon of food material. At present only the home dehydrators and smoke housing, which takes quite longer time, 10 hr with 60 °C (AAMP, 2004). So, there is a need of reducing the drying time.For optimizing the process, it is necessary to understand the drying behavior of the food material. As there have been no detailed studies on drying behavior of beef jerky available, in this study we focus on drying characteristics of beef jerky in forced air thin layer drying unit. In convection air drying, air flow rate influences convective mass transport (Hamdy & Barre, 1969).A number of researchers have chosen to neglect the effect of airflow rates in the analysis of thin layer drying data, citing the conclusion of Henderson & Pabis (1962) that resistance to moisture at the surface is negligible compared to internal resistance. The humidity of drying air has a significant impact on the final or equilibrium moisture content that is achieved as a result of drying. In addition, the driving force for convective transport at the surface of the drying material depends on the difference between the partial pressure of water vapor at the surface and that of drying air (Fortes and Okos, 1981). The effect of temperature on drying rate is well documented in the literature (Henderson and Pabis, 1961). Most of the material properties that are relevant to drying, for example, mass diffusivity, thermal conductivity and latent heat of evaporation, are temperature dependent (Singh et al., 1972).There are several works done to evaluate the drying model for different plant based products in thin layer dryer. Researchers have developed numerous thin layer models for various agricultural products. Generally these models are basedon thin layer data characterizing the change in moisture content and temperature under constant drying conditions (Babalis et al.2005). There is no literature on thin layer drying of meat or any meat products till now.Objective of the present study is to study the drying characteristics of beef jerky in thin layer drying and to investigate the effect of pH, relative humidity and air flow rate in thin layer drying of beef jerky.Materials and MethodsSample PreparationFor the present study , biceps femoris muscles were taken and stored at -30°C after the slaughter. The meat has been kept in 4°C environment for 48hrs before sample preparation. The meat was trimmed to remove excess fat as per USDA (1996)’s recommendation to prevent fat being rancid while drying. The meat was first ground using a kidney plate in a meat grinder (Biro, Biro Mfd. Co, Marblehead, OH, USA).Before final grinding, the ground meat has been mixed in a vacuum tumbler (H.Glass, Model-VSM-150, Frankfurt, Germany) for 2 minutes for improving the uniformity. Then, the meat was ground twice in the meat grinder using a 1/8” blade. The other ingredients, given in the table 1, were mixed with the ground meat in lowest speed for 105 sec in an Industrial Blender (Berkel BA-20, Model ARM-02) to make 3 kg formulation. The common industrial acidifier Glucono Delta Lactone to an amount of 0 & 0.5 w/w was added to the formulation to alter the pH from 5.65 to 5.30. The mixture was then stuffed into slices of 6mm thickness in an industrial handfmann Stuffer (Albert Handfmann Mfd. Ltd., model-VF-80, West Germany). The slices were then vacuum packed and stored in -1°C freezer for further processing. Table 1: Formulations for Different Treatments (All units are in grams)Treatment Meat GDL Salt 2 % Sugar2% Praque 0.3%Na Ery* 0.05% Water 3% pH:5.6 2787.92 0 51.58 60 91.5 90 pH: 5.35 2772.92 15 51.58 609 1.5 90* Sodium ErythorbateDryingDrying experiments were carried out in the laboratory scale forced air convection drying unit shown in the figure 1. The drying unit consists of drying chamber with scale mounted trays, air conditioning unit (Bryant manufacturing Model AH-213, BMA Inc., Ayer, MA), vane axial circulating fan and a connecting duct system. The air conditioner has a temperature range of -17 to 200ºC and relative humidity range of 2 to 98% limited by 2ºC dew point, and these parameters are controlled by Watlow microprocessor controller with a temperature accuracy of ±0.25ºC and relative humidity accuracy of ±2%. The conditioned air is re-circulated through the dryer unit by an axial fan (Model VA7D32, American Cool air Corporation, Jacksonville, FL). The fan speed is controlled by a variable electronic transistor inverter (Model VFS7, Toshiba Corporation, Japan). Three drying trays are housed in the duct system which is insulted with 50.8mm thick fiberglass insulation, downstream from a set of straightening vanes. Surrounding the drying trays (5 before and 5 after),10 thermocouples were inserted to measure the airFigure.1 Laboratory scale forced air convection drying unit temperature. One infrared thermometer is also inserted to monitor the product temperature while drying. All the data were logged and downloaded to the computer using Labview 6.0 (National Instruments, Austin, TX). The fresh samples were dried to 33 % db final moisture content for different relative humidity (30 and 40%) and air flow rate (1 and 1.45 m3/s) by keeping the air temperature as 70 º C. The dried samples were then analyzed for different physical, chemical properties.Shrinkage Loss AnalysisInitial and final volume has been measured and shrinkage coefficient was calculated by, Shrinkage Coefficient = [1 – (V f / V i)] x 100Where V f is the final volume and V i is the initial volume of the sample (Trujillo, F.J et al. 2005).Moisture content MeasurementFresh and dried samples were passed through a precision grinder for three times with screen opening size equal to 3mm and the powder was mixed thoroughly after grinding. The 5 grams of these ground samples were taken in covered aluminum dishes and placed in a vacuum at 100°C under 100 mmHg absolute pressures for about 5hours until it reaches a constant weight. Measurements were done in three replicates for each treatment. The loss in weight was measured as moisture content as per ASAE S353 (2003) method.Water Activity MeasurementWater activity, which is the critical parameter used to assure the product safety was measured in Aqua lab water activity meter (Model CX2, Decagon Devices Inc., Washington, USA). The dried sample was crushed into small pieces and placed in water activity measurement cup and the readings were noted. Measurements were taken in three replicates.Color MeasurementColor of the meat before and after drying will be measured to indicate the appearance change. All the color measurements will be done using Hunter lab Color Analyzer- Labscan-2 (Hunter Associates laboratory,Inc. Virginia,USA). The fresh or dried samples were placed in the 1.25 cm of area of view and D65 was used as illuminant source. CIE lab color scale (L*, a* and b*) value were recorded, where ‘L’ coordinate indicates lightness, which represents the grayness ranging from black (L=0) to white (L=100). ‘a’ represents the redness/greenness of the product. Positive of ‘a’ indicates the redness of the product and the coordinate ‘b’ indicates the yellowness (positive) or bluishness (negative). Three replicates were taken for each treatment and six readings were taken. To evaluate the effect of different drying temperature on the overall combined color of dried meat, the index ∆E as given by following equation (Tabil.et al., 2001) was calculated by taking the color of fresh meat as the base value. ()()()2b 2a 2L ∆E ∆+∆+∆=Where ∆L= L - L base , ∆a= a - a base and ∆b= b - b base , and L, a, and b are the color coordinates of the sample and L base , a base , and b base are the color coordinates of the control sample.Statistical AnalysisThe experiment has been designed in Randomized Complete Block Design (RCBD) and all the data were analyzed using factorial ANOVA test in SAS for windows V8 (SAS Institute, Cary, NC) by relative humidity and air flow rate as main factors and physical properties as sub factors. All the experiments were done with three replicates. The means were compared by both LSD and Duncan’s multiple range tests. Type I error rate (α) was set at 0.05 for all statistical tests.Results and DiscussionsEffect of pH on the Drying CharacteristicsThe drying characteristics curve derived from the thin layer drying experiments done with different pH level samples and air temperature 70º C, relative humidity 40 % and airflow rate1.45 m 3/s is shown in figure2. It is observed from the figure 2 that there is a significant effect of pH on the drying characteristics of beef jerky. The drying time was reduced by reducing the pH of the sample. So, it can be concluded that manipulating the sample pH can improve the drying rate which in turn help reduce the drying time. Also it was noticed from the physical properties analysis that pH has a significant effect on shrinkage, water activity and color parameters.Figure 2. Showing the effect of pH on thin layer drying curve for air temperature 70º C, relativehumidity 40 % and airflow rate 1.45 m3/s.Effect of Relative Humidity on the Drying CharacteristicsThe figure 3 is showing the effect of relative humidity on the drying rate curve of the normal pH samples dried in 70º C air temperature and airflow rate 1.45 m3/s. The curves have proved that the effect of relative humidity on beef jerky samples can be compared to those reported for other agricultural materials. Lowering relative humidity increased the drying rate of the beef jerky samples. Also it was noticed from the study that relative humidity has a significant effect of shrinkage loss, water activity and color parameters.Figure 3. Showing the effect of relative humidity on thin layer drying characteristics for airtemperature 70º C and airflow rate 1.45 m3/s.Effect of Airflow Rate on the Drying CharacteristicsThe figure 4 is showing the effect of airflow rate on the drying characteristics of beef jerky dried in a 70º C air temperature and 40 % relative humidity environment. It is found that air flow rate has a significant effect on drying characteristics of beef jerky. Higher airflow rate showed a significant reduction in drying time and improved drying rate. Also it was observed that air flow rate showed a significant effect on shrinkage loss and water activity.Figure 4. Showing the effect of air flow rate on thin layer drying characteristics for airtemperature 70º C and 40 % relative humidity.ConclusionIn this study, drying characteristics of beef jerky in forced air convection drying was investigated. From this present study, it was observed that relative humidity and air flow rate of the heating medium, that is air has a significant effect on drying characteristics of beef jerky. Also, it was found that these air properties have significant effects on other physical-chemical properties such as shrinkage, water activity and color. Sample formulation’s pH also has a significant effect on drying characteristics as well as physical-chemical characteristics of beef jerky in thin layer drying environment. It can be concluded that to improve the drying rate of the process, lowering of sample pH, running drying experiments using air with a low relative humidity and high air flow rate will be helpful in achieving the desired product in reduced time.AcknowledgementsI would like to acknowledge NSERC for financial support and Mr. Crerar and Mr. Wiebe for technical assistance.ReferencesAmerican Association of Meat Processors. 2004. The Jerky Manual.Elizabethtown, PA, USAASAE Standards, 50th ed. 2003. S353: Moisture measurement – Meat and Meat Products. St.Joseph, Mich.: ASAEBabalis,S.J.et al.2006. Evaluation of thin layer drying models for describing drying kinetics of figs (Ficus carica). Journal of Food Engineering. 75. 205-214Calicioglu.M. et al. 2002. Destruction of acid and non-adapted Listeria monocytogenes during drying and storage of beef Jerky. Journal of Food Microbiology. 19.545-559Cunningham, F.E.1980.Influence of microwave radiation on psychrotropic bacteria. Journal of Food Protection.43(8).651-655.Faith, N.G. et al. 1998.Viability of Escherichia coli O157:H7 in ground and formed beef jerky prepared at levels of 5 and 20% fat and dried at 52, 57, 63 or 68ºC in a home-styledehydrator. International Journal of Food Microbiology.41.213-221Hamdy,M.Y. and H.J.Barre,1969.Evaluation film coefficient in single kenel drying. Transactions of the ASAE 12: 205.Hamm.r.(1981). In: Developments in meat science-2.Applied science Publishers, London, 93.Henderson,S.M. and S.Pabis.1961.Grain drying theory:IV. The effect of airflow rate on the drying index. Journal of Agricultural Engineering Research 6:169.Mujumdar, A.S and S.Devahastin. 2000. Mujumdar’s practical Guide to Industrial Drying: Principles, Equipment and New Developments. Chapter I.pp:1-22.Quenzer,N.M & Burns,E.E.1981. Effect of the microwave steam and water blanching on freeze dried spinach. Journal of Food Science.46(2).410Serra.X. et al. 2005.Texture parameters of dry cured ham m.biceps femoris samples dried at different levels as a function of water activity and water content. Journal of MeatScience. 69.249-254.Singh,R.H.J.Barre,M.Y.hamdy.1972.Drying spherical porous bodies. Transactions of the ASAE 15:338Tabil, L.G., M. Kashaninejad and B. Crerar. 2001. Drying characteristics of Purslane (Portulaca oleraceae L.). Department of Agricultural and Bioresource Engineering, University ofSaskatchewan. Saskatoon, SK.Taher,B.J.& Farid,M.M.2001. Cyclic microwave thawing of frozen meat; experimental and theoretical investigation. Journal of Chemical Engineering and processing.40.379-389 Thostenson E.T. & Chou T.W.1999. Microwave processing: Fundamentals and applications.Composites A 30, 1055-1071.Trujillo,F.J et al. 2005. Drying modelling and water diffusivity in beef meat. Journal of Food Engineering. Article in Press.United States department of Agriculture.2003.Consumer Education and Information./OA/ pubs/jerky.html。