M Mehmet Ak

Cheese rheology and texture.

Cheesemaking - An Overview Cheese Types Cheesemaking References Fundamental Rheological Methods Definition of Rheology Basic Concepts Fundamental Methods Uniaxial Compression Shear Rheometry Extensional Rheometry References Uniaxial Testing of Cheese Uniaxial Compression Measurements Structure and Composition Effects Stress-relaxation Measurements Torsion Measurements Tension Measurements Creep Measurements Bending Measurements Vane Measurements Shear Measurements Lubricated Squeezing Flow Measurements References Fracture Properties of Cheese Fracture Mechanics Brittle Fracture Griffith Criterion Determination of KI Fracture Tests on Cheese Cutting, Slicing, and Shredding Cutting with Wire and Blade Eye/slit Formation and Growth References Linear Viscoelasticity of Cheese Mathematical Relations in Linear Viscoelasticity Types of SAOS Measurements Time-Temperature Superposition Application of SAOS in Cheese Rheology Linear Viscoelastic Region of Cheeses Mozzarella: Time-Temperature Superposition Example Cox-Merz Rule References Nonlinear Viscoelasticity of Cheese Pipkin Diagram Sliding Plate Rheometer Large Amplitude Oscillatory Shear Flow Spectral Analysis Discrete Fourier Transform Determining Material Properties Amplitude Spectrum Stress-Shear Rate Loops Effect of Wall Slip Constitutive Model for Cheese Relaxation Modulus Obtained from SAOS Relaxation Modulus Conforming to LAOS References Cheese Texture Texture Development in Cheese Cheese Manufacturing Factors that Affect Texture Measurement of Texture Uniaxial Tests for Cheese Texture Measurement Compression Test Torsion Test and Vane Rheometry Texture Map Dynamic Tests Empirical Tests Crumbliness References Measuring Cheese Melt and Flow Properties Meltability Empirical Tests Objective Tests Steady Shear Viscometry Capillary Rheometry Squeeze-Flow Rheometry UW Meltmeter Viscoelasticity Index for Cheese Meltability Dynamic Shear Rheometry Helical Viscometry Cheese Melt Profile Measurement UW Melt Profiler Determination of Melt Profile Parameters Graphical Method Modeling Melt Profile Constant Temperature Test Conduction Heating References Measuring Cheese Stretchability Empirical Methods Instrumented Methods Vertical Elongation Horizontal Elongation Compression Tests Helical Viscometry Fiber-spinning Technique The Weissenberg Effect References Factors Affecting Functional Properties of Cheese Properties of Milk Cheesemaking Procedures Addition of Starter Culture and Coagulants Cheese Composition Post-Manufacturing Processes Aging/Ripening References

Dynamic oscillatory shear testing of foods - selected applications

Abstract An ideal solid material will respond to an applied load by deforming finitely and recovering that deformation upon removal of the load. Such a response is called “elastic”. Ideal elastic materials obey Hookes law, which describes a direct proportionality between the stress (σ) and strain (γ) via a proportionality constant called modulus (G), i.e., σ=Gγ. An ideal fluid will deform and continue to deform as long as the load is applied. The material will not recover from its deformation when the load is removed. This response is called “viscous”. The flow of simple viscous materials is described by Newtons law, which constitutes a direct proportionality between the shear stress and the shear rate ( γ ), i.e., σ=η γ . The proportionality constant η is called the shear viscosity. From energy considerations, elastic behavior represents complete recovery of energy expended during deformation, whereas viscous flow represents complete loss of energy as all the energy supplied during deformation is dissipated as heat. Ideal elastic and ideal viscous behaviors present two extreme responses of materials to external stresses. As the terms imply, these are only applicable for “ideal” materials. Real materials, however, exhibit a wide array of responses between viscous and elastic. Most materials exhibit some viscous and some elastic behavior simultaneously and are called “viscoelastic”. Almost all foods, both liquid and solid, belong to this group. The viscoelastic properties of materials are determined by transient or dynamic methods. The transient methods include stress relaxation (application of constant and instantaneous strain and measuring decaying stress with respect to time) and creep (application of constant and instantaneous stress and measuring increasing strain with time). Though such methods are fairly easy to perform, there are several limitations. Major among them is that the material response cannot be determined as a function of frequency.

Effects of processing conditions and formulation on spray drying of sour cherry juice concentrate

BACKGROUND Sour cherries are rich in phenolic compounds possessing several health-promoting effects. Processing of sour cherry juice into powder form offers additional advantages such as increased utilization, reduced volume, easier handling and transportation. However, spray drying of fruit juices is difficult owing to their low glass transition temperatures (Tg). The aim of this study was to investigate the effects of inlet temperature (130-150 °C), feed flow rate in terms of pump setting (30-50%), sour cherry content (25-50% of total dry matter) and carrier type (maltodextrin DE6, maltodextrin DE12, gum arabic) on yield, Tg and total phenolic content (TPC) of spray-dried sour cherry powder. RESULTS Feed flow rate, sour cherry content and carrier type significantly affected yield and Tg, whereas TPC was affected by sour cherry content and carrier type. The effect of sour cherry content on yield depended on the carrier type. Although gum arabic provided better protection of phenolic content than maltodextrins, it resulted in lower average yield. CONCLUSION Spray-dried sour cherry powder with high yield (>85%) and high Tg (60 °C) was obtained using the following conditions: 150 °C inlet temperature, 30% pump setting, 25% sour cherry content and maltodextrin DE12 as carrier.

PÜSKÜRTMELİ KURUTMA İŞLEMİNİN MEYVE SUYU KONSANTRELERİNİN FENOLİK MADDE İÇERİĞİNE VE ANTİOKSİDAN AKTİVİTESİNE ETKİSİ

Bu calismada dokuz cesit meyve suyu konsantresi puskurtmeli kurutma (PK) teknigi ile toz haline donusturulerek islemin toplam fenolik madde ve antioksidan aktivitesi uzerindeki etkisi incelenmistir. Ahududu, armut, bogurtlen, cilek, elma, kayisi, kirmizi yaban mersini, portakal ve visne suyu konsantrelerinin toplam fenolik madde (TFM) icerigi ve DPPH ile ABTS radikallerini yakalama aktivitesi kurutma oncesi ve sonrasi olculmustur. Visne, cilek ve kirmizi yaban mersini tozlari yuksek TFM icerigine (19.2–30.1 mg GAE/g meyve k.m.) sahipken; armut ve elma tozlarinin TFM icerigi ise dusuk (3.3-4.7 mg GAE/g meyve k.m.) bulunmustur. Uygulanan deneysel kosullar altinda PK islemi, meyve konsantrelerinin TFM icerigi ve antioksidan aktivitesi uzerinde istatistiksel olarak onemli bir degisiklige yol acmamistir. Meyve tozlarinin DPPH radikalini yakalama aktivitesi 9.2 ila 25.0 mg TE/g meyve k.m. arasinda degisirken; ABTS radikalini yakalama aktivitesi ise 5.1 ila 18.4 mg TE/g meyve k.m. arasinda degismistir. Genel olarak visne, cilek ve kirmizi yaban mersini tozlari yuksek antioksidan aktivite gostermistir. Meyve suyu konsantreleri de TFM icerigi ve antioksidan aktivite acisindan meyve tozlarina benzer egilimler gostermistir.