Instrumental analysis, sensory analysis and consumer acceptance of strained yogurt in frozen desserts
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There is a surging demand from consumers for healthier products that are lower in calories but maintain their original flavor and texture. Many countries around the world have worked to develop new techniques to improve our food supply and food products, including the utilization of functional foods and nutraceuticals. Utilizing Greek style yogurt (GSY) as a functional ingredient in frozen desserts will be a unique approach to enhancing the texture and flavor of frozen yogurts without sacrificing consumer acceptance. The objective of this study was to investigate various formulations of set yogurt and GSY with an ice cream mix in order to assess the physico-chemical effects and organic acid and carbohydrate changes. The second objective was to assess these formulations from a sensory perspective, with a combination of descriptive analysis and consumer acceptance to determine which treatments were preferred in relation to a control ice cream. Another objective was to investigate various statistical techniques that link the Overall Liking attribute among the treatments with the measured sensory and non-sensory based attributes. A one-way ANOVA analysis with orthogonal contrasts found that that despite the lack of significant differences among macronutrients (e.g., protein, fat, and carbohydrates), significant differences could be observed among pH, titratable acidity, hardness, gumminess, chewiness, particle size and flow behavior at small changes in the frozen dessert formulation. Treatments containing higher yogurt concentrations, especially those with Greek yogurt, were significantly different than the treatments with lower concentrations of yogurt. The chemical compounds used to develop various standard curves functioned well for method validation and overall analysis of organic acids and carbohydrates in frozen dessert treatments. The standard curves aided in good separation on both Aminex – 87 HPX columns. The precision study suggested that extraction of all compounds was repeatable, with all compounds falling below 5% RSD, an acceptable level for analysis. The recovery study demonstrated the efficiency of this method regardless of the various food matrix that was utilized. Based on a one-way ANOVA analysis with orthogonal contrasts, citric acid, formic acid, sucrose, lactose, and glucose demonstrated a decrease in their average concentration as more of any yogurt type was applied to the various formulations; on the other hand, the concentration of lactic acid, acetic acid, propionic acid, and butyric acid increased in concentration as more of any yogurt type was applied to the various formulations. The descriptive analysis conducted in this study showed that more than half of the flavor and texture attributes developed had significant differences across the tested products based on a mixed-model ANOVA. The control ice cream and GFYC (80% ice cream; 20% Greek-style yogurt) treatments held the highest intensity for most of the attributes with high significant differences. PCA indicated that the control ice cream had a high intensity in sheen, gooeyness, creaminess, denseness, smoothness, gumminess, mouth coating, fat flavor, sweet flavor, milk flavor, fat aftertaste, sweet aftertaste, and milk aftertaste. The cluster analysis demonstrated that the intensity of sweet flavor, fat flavor, milky flavor, sour flavor, hardness, and iciness attributes was a determinant in dissimilarity of taste among the tested products. It was found that consumers were able to distinguish between provided frozen desserts and that there were significant differences in consumer preference. Among the samples, the control ice cream received the highest hedonic rating of 7.44, and the FYA, FYB and GFYA products were not significantly different from the control. Essentially, products that contain lower concentrations of yogurt were more accepted compared to other products based on their high concentrations of gooeyness, creaminess, smoothness, gumminess, mouth coating, fat flavor, sweet flavor, milk flavor, fat aftertaste, sweet aftertaste, and milky aftertaste. Overall, Greek yogurt as an ingredient within frozen desserts was accepted by panelists when a low concentration was utilized. The statistical methodologies assessed the relationship between Overall Liking and variables from sensory and non-sensory data collected from frozen desserts developed with different types and concentrations of yogurts. The PCA model described Overall Flavor, Milk Flavor, Sweet Flavor, Overall Liking, Fat Flavor, titratable acidity, hardness (descriptive analysis), sour flavor, sour aftertaste, pH, lactic acid, particle size, and protein as significant attributes to explain differences among the treatments. The multiple linear regression demonstrated that Overall Flavor, Milk Flavor, Sweet Flavor were the most significant variables among all of the data that best predict the Overall Liking of treatments, despite the overfit nature of the model. The MFA model demonstrated a unique perspective in assessing the relationship between the Overall Liking among the frozen dessert treatments and the other 57 variables in the dataset. The MFA model found associations among Overall Liking and its categorical group, Preference Analysis, in comparison to other variables and categories representing sensory and non-sensory data. The results indicated that there are relationships among the variables in different sensory and non-sensory categories. This statistical analysis provides evidence that the Overall Liking of frozen dessert treatments within this study can be assessed from both a sensory and non-sensory perspective in the same model. Overall, the addition of Greek-yogurt as a functional ingredient within a frozen dessert system appears to yield an acceptable product by consumers at concentrations at or below 10%. Across the various studies in this dissertation, it was found that there were no or minimal statistical differences between the control ice cream and frozen desserts that contained low concentrations of yogurt (e.g., frozen yogurt with 10-15% yogurt and frozen yogurt with 10% Greek-yogurt).
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Ph. D.