Crispness is one of the most important and desirable textural characteristics that signify freshness and high quality in breaded fried foods. Though many approaches to instrumental measurement of crispness have been made, the best measurements are still inconclusive. There is no reliable method available that can accurately measure and quantify crispness in breaded fried foods. In this study, the mechanical and ultrasonic techniques were used to determine crispness in breaded fried chicken nuggets under different storage conditions. The mechanical measurements have been made, using an Instron universal testing machine. An ultrasonic non-destructive evaluation system was used to measure ultrasonic properties of breaded friend chicken nuggets. A pair of dry-coupling 250-kHz ultrasonic transducers was used to perform the ultrasonic transmission through the breaded fried chicken nugget. The equipment set up was in the through-transmission mode because breaded fried chicken nugget is highly attenuative material. A sensory panel of eight members was trained to evaluate crispness in breaded fried foods. Panelists rated crispness on a nine-point category scale (1 = not crisp/soggy, 9 = very crisp). Sensory crispness values for breaded fried foods under different storage conditions were obtained. Ultrasonic velocity, transmission loss, peak frequencies and its energies, peak force and total energy were determined for each tested product. Correlation between sensory crispness and instrumental parameters suggests that the ultrasonic method can be used to evaluate crispness. The ultrasonic velocity had high correlation with sensory crispness (R2 = 0.83). This indicates that sensory crispness could be reasonably well predicted by the ultrasonic velocity. / Master of Science

Orientador: Celso Costa Lopes / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-18T08:10:10Z (GMT). No. of bitstreams: 1 LaFuenteArias_CarlaIvonne_M.pdf: 1773876 bytes, checksum: 0229ec1ebad94e8b4ebb343f440c2fd6 (MD5) Previous issue date: 2011 / Resumo: Neste trabalho estudou-se a secagem de banana Nanica empregando um pulso inicial a alta temperatura e curto tempo (150°C e 15 minutos), seguido de uma etapa de resfriamento e uma etapa de secagem convencional a ar quente a 70°C. Na primeira parte do trabalho, avaliou-se especificamente a etapa de resfriamento pós-pulso HTST quanto aos atributos de crocância, encolhimento e cor no produto terminado. Analisaramse também as mudanças estruturais através de microscopia ótica. Na segunda parte do trabalho, estudou-se a temperatura de transição vítrea, através de Calorimetria Diferencial de Varredura, em bananas submetidas a este processo de secagem. Os resultados mostraram que, na etapa de resfriamento, a redução gradual de temperatura associada com tempos longos foi importante para que o produto mantivesse a estrutura porosa e crocante, porém também ocasionou produtos com cor escura, com baixos valores de luminosidade. Em contraposição, a redução acelerada de temperatura na etapa de resfriamento ocasionou a perda da estrutura porosa, além de os produtos finais ficarem duros e encolhidos; no entanto, a degradação de cor foi menor. Uma redução gradual da temperatura, com amplitude de 10°C e período de 7,5 minutos, totalizando 75 minutos, mostrou-se adequada para a manutenção da estrutura porosa e crocante, com a menor degradação de cor. A temperatura de transição vítrea decresceu com o aumento do conteúdo de umidade, para todas as amostras, comprovando o efeito plasticizante da água. O início da crocância nas amostras, expressada em número de picos do gráfico força-deformação, foi identificada entre 11% e 6% de umidade (bu) / Abstract: This work studied the drying of banana Nanica employing an initial pulse at high temperature and short time (150°C and 15 minutes); a cooling stage and a final hot air drying at 70°C. In the first part of this work, it was analyzed the post-pulse stage, as attributes of crispness, shrinkage and color. The structural changes also had been analyzed with optical microscopy. In the second part of this work, glass transition temperature of banana, dried with the same process, was studied by Differential Scanning Calorimetry. The results showed that in the cooling stage, the gradual reduction of temperature with longer times, were important for the product retains the porous structure and crispness, but also caused the formation of dark color products with lowest values of brightness. On the other hand, the sudden reduction of temperature, in the cooling stage, caused the loss of the porous structure, and final products became harder and shrunken but with less color degradation. A gradual decrease of temperature with amplitude of 10°C and period of 7.5 minutes summarizing 75 minutes of the cooling stage, proved to be appropriate for the maintenance of porous and crispness structure, with less color degradation. The glass transition temperature decreased with increasing moisture content for all the samples, confirming the water plasticization effect. Crispness in the samples, expressed in peaks number in stress-strain graphs, was initially observed between 11% and 6% of moisture content (wb) / Mestrado / Engenharia de Alimentos / Mestre em Engenharia de Alimentos

Orientador: Roger Darros Barbosa / Resumo: O beiju, produto de cultura indígena milenar, é obtido a partir do aquecimento da fécula de mandioca salgada e hidratada, com cerca de 40 a 45% de umidade, para a formação de um gel rígido e opaco, com baixa umidade (máx. 10%). As características de textura crocante, de cor branca e opaca e de sabor neutro levemente salgado, posicionam o beiju como concorrente de biscoitos crocantes. A pesquisa sobre hábitos de consumo mostrou preferência de compra associada aos atributos sensoriais de sabor, cor e crocância. O produto ofertado ao mercado do Nordeste é de baixa qualidade devido ao processo artesanal e instabilidade da textura. Esta pesquisa investigou os parâmetros do processo que influenciam na qualidade do beiju, entre os quais a razão fécula/água na hidratação, temperatura e tempo de exposição ao calor no processo térmico, para o qual foi desenvolvido um equipamento de bancada específico. A caracterização dos beijus comerciais em termos dos atributos sensoriais e de análises instrumentais de textura e cor, juntamente com informações de produtores artesanais de beiju, auxiliaram na determinação das condições para o processamento do beiju em laboratório. Adicionalmente, foram realizados estudos de estabilidade do beiju durante a estocagem com base nas características de textura e equilíbrio higroscópico. O beiju obtido em todas as condições investigadas apresentou parâmetros de textura instrumental com valores que permitem caracterizá-lo como um produto crocante e moderado g... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Beiju, a product of ancient indigenous culture, is obtained by heating the salted and hydrated cassava starch, with 40 to 45% moisture, to form a rigid and opaque gel, with low moisture (maximum 10 %). The characteristics of crispy texture, white and opaque and with a slightly salty neutral flavor, make beiju as a competitor for crispy crackers or snacks. A survey on consumption habits showed the purchase preference associated with the sensory attributes of flavor, color and crispness. The product offered to the market is of low quality due to the artisanal process and texture instability. This research investigated the process parameters that may influence the quality of beiju, among which the starch/water ratio in hydration, temperature and time of exposure to heat in the thermal process, for which a specific bench equipment was developed. The characterization of commercial beijus in terms of sensory attributes and instrumental analyzes of texture and color, along with artisanal producers processing information, helped in determining process variables range for laboratory processing. Additionally, beiju stability studies were carried out during storage based on texture and hygroscopic equilibrium characteristics. The beiju obtained in all investigated conditions presented instrumental texture parameters with values that allow to characterize it as a crispy product and a moderate degree of hardness. The main responses for the characterization of the crispness were attributed... (Complete abstract click electronic access below) / Mestre

Crispness is one of the most desirable textural characteristics of breaded fried foods. Consumers often judge the quality of breaded fried foods based on the perceived crispness of the product. Furthermore, today's consumers are showing increasing concern over fat intake. As a result, there is great interest in being able to enhance the crispness and reduce the fat uptake in breaded fried foods without sacrificing other quality attributes. To achieve these goals, modifications to both frying equipment and product formulation have been explored in this study. In this study, two edible film coatings, methylcellulose (MC) and whey protein isolate (WPI) were incorporated into the batter and pre-dust to determine their effect on the crispness of breaded fried chicken nuggets held under a heat lamp for varying time intervals. Crispness was evaluated by both objective (ultrasonic non-destructive evaluation system) and subjective methods. An untrained sensory panel was used to obtain subjective measurements of product crispness. Panelists rated product attributes such as crispness, juiciness, oiliness and flavor on a simple intensity scale. Additionally, panelists rated the liking of the products on a nine-point hedonic scale (1=dislike extremely, 9=like extremely). Two pressure sources (nitrogen gas and steam naturally released from the food material) were used to determine their effects on product crispness, texture, pressed juice, moisture content, fat content and color. Products fried with nitrogen gas as the pressurizing medium produced samples that were comparable to or exceeding the quality of products generated by frying with steam, as it relates to product crispness, texture, pressed juice, moisture content, fat content and color. As related to objective crispness, chicken nuggets fried with nitrogen were significantly crispier (p<0.05) than those fried with steam. Coating type and application also had a significant effect on product crispness. Samples coated with MC in the pre-dust were crispier than samples coated with WPI. However, no significant differences were found in product crispness, juiciness, oiliness or flavor, and overall liking among samples tested by the sensory panel. The results of this study demonstrated that applying an edible film coating to the pre-dust and using nitrogen gas as the pressurizing medium can enhance and maintain the crispness of breaded fried foods. / Master of Science