Aylin Altan

Effect of extrusion cooking on functional properties and in vitro starch digestibility of barley-based extrudates from fruit and vegetable by-products.

Barley flour and barley flour-pomace (tomato, grape) blends were extruded through a co-rotating twin-screw extruder. The aim of the present study was to investigate the effects of die temperature, screw speed, and pomace level on water absorption index (WAI), water solubility index (WSI), degree of starch gelatinization, and in vitro starch digestibility using a response surface methodology. The selected extrudate samples were examined further using differential scanning calorimetry (DSC) and polarized light microscopy, respectively. The WAI of barley-pomace extrudates was affected by increasing pomace level. Temperature had significant effect on all types of extrudate but screw speed had significant linear effect only on barley and barley-grape pomace extrudates on degree of starch gelatinization. Although no gelatinization peak was detected, an endotherm was observed on all selected extrudates. In general, extrusion cooking significantly increased in vitro starch digestibility of extrudates. However, increasing level of both tomato and grape pomace led to reduction in starch digestibility.

Spray Drying and Process Optimization of Unclarified Pomegranate (Punica granatum) Juice

In this study, production of pomegranate juice powder using a spray dryer was investigated. To prevent stickiness, maltodextrin dextrose equivalent 6 (DE6) was used as a drying agent. While feed flow rate, feed temperature, and air flow rate were kept constant, air inlet temperature (110–140°C), percentage maltodextrin (MD; maltodextrin dry solids/100 g feed mixture dry solids; 39.08–64.12%), and feed mixture concentration (19.61–44.11 °Brix) were chosen as the independent variables. Product properties investigated included moisture content, hygroscopicity, anthocyanin content, color change, solubility, bulk density, total phenolics content, antioxidant capacity, and sensory properties. The products were produced with high yield (86%) and high antioxidant activity (77%). MD and drying temperature were found to be the most important variables in production of pomegranate juice powders. Because total color change (ΔE), bulk density, antioxidant capacity, and powder yield were affected strongly by the independent variables, these parameters were used in optimization of the process. The optimum temperature, feed mixture concentration, and percentage maltodextrin were 100°C, 30.8 °Brix, and 53.5% MD, respectively. This study revealed that by applying these optimal conditions, pomegranate juice powder with a 55% dry solids yield, 9.78 total color change, 0.35 g/mL bulk density, and 57.8% antioxidant capacity were produced.

Rheological Behaviour and Time Dependent Characterisation of Gilaboru Juice (Viburnum opulus L.)

The flow curves and time-dependent rheological behaviour of gilaboru (Viburnum opulus L.), a traditional drink in the middle Anatolia region of Turkey, with different solid concentrations (59.7, 56.3, 53.1, 43 and 35°Brix) were studied at different temperatures (5-60°C) using a controlled stress rheometer. Gilaboru samples exhibited thixotropic behaviour for all concentrations, both in the forward and backward measurements were characterised by the power law. A single equation was proposed for the apparent viscosity 1. Temperature played a major role in determining the magnitudes of the apparent viscosity 1. The completely destructed gilaboru samples flow curves were also measured after subjecting the samples to a high shear rate for 2h. After eliminating thixotropy by shearing, samples showed shearthinning properties that fitted well to the power law model. Three models were used to describe the time-dependent behaviour, namely, the second-order structural kinetic, Weltman and first-order stress decay models. Among the models, the first-order stress decay model fitted well compared to the second- order structural kinetic and Weltman models.

Oil Migration in Chocolate and Almond Product Confectionery Systems

UNLABELLED Oil migration from high oil content almond confections into adjacent chocolate causes changes in product quality. The objective of this study was to quantify the oil migration from almond products to dark chocolate. Magnetic resonance imaging (MRI) was used to monitor spatial and temporal changes of liquid lipid content. A multislice spin echo pulse (MSSE) sequence was used to acquire images with a 7.8-ms echo time and a 1000-ms repetition time using a 1.03T Aspect AI MRI spectrometer. Samples were prepared as a 2-layer model system of chocolate and almond confection. Six different almond products and 1 type of dark chocolate were used. Samples were stored at 20, 25, and 30°C for a time frame of several months. Rate and extent of migration were quantified by a kinetic expression based on the linear dependence of oil uptake by chocolate and the square root of the time. Samples showed distinctly different rate and extent of oil migration, as evidenced by quantitative differences in the kinetic rate constants and equilibrium uptake for the different sample types. This work will be helpful to design formulations for almond and almond-based products in confections. PRACTICAL APPLICATION This work will be helpful to design formulations for almond use in confections.

Image Analysis of Microstructural Changes in Almond Cotyledon as a Result of Processing

Release of oil from nuts due to damaged cellular structures can degrade the quality of products incorporating nuts. The aim of this study was to investigate the effects of different processing conditions on microstructure of almond tissue and to quantify these changes using image processing. Spinning disk confocal fluorescence microscopy was used for imaging changes in microstructure of almonds as a function of different thermal processing of almonds. Multiple staining of Nile Red and Calcofluor White was applied to differentiate cell wall structures and oil bodies within individual almond cells without chemical fixation. An algorithm for image processing, included image preprocessing, segmentation, and determination of morphological features of segmented objects, was developed. Oil-roasting processes (140 °C and 150 °C) were found to have a significant impact on microstructure of almonds when compared to the hot air-roasting and blanching processes. Oil-roasted almond at 150 °C had a greater cellular damage due to cell wall and membrane rupture. These changes in microstructure of almonds would make them slightly more susceptible to release oil during storage. The image analysis presented allows quantitative evaluation for the effect of different processing on almond microstructure.

Microwave Assisted Drying of Short-Cut (Ditalini) Macaroni: Cooking Process and Textural Properties

The colour, re-hydration capacity and macaroni cooking quality, related to cooked weight, cooking loss and firmness of drying of short-cut (ditalini) macaroni were evaluated. The textural properties of uncooked and cooked macaroni samples were measured using a TA-XT2i texture analyser. Protein denaturation of dried samples increased significantly with microwave power level. Physical and textural properties of macaroni samples dried with combined hot air/microwave (210 W) were equal to or better than those dried with hot air. Also, hot air/microwave combination drying exhibited superior cooking properties. Firmness of samples increased while cooking loss decreased generally with microwave application after hot air drying, i.e., hot air/microwave combination shortened the drying time and improved many of the physical, textural and cooking properties of macaroni samples.