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

The main objective of this study was to evaluate the effects of different flour and protein types on quality of deep-fat fried chicken nuggets. Additionally, the rheological properties of batters were studied and the batter viscosity was correlated with fried product quality. In the first part of the study, the effects of soy and rice flour (5%) addition to the batter formulation on product quality were studied. Coating pick-up of batters, and moisture content, oil content, texture, color, volume, porosity, and cooking yield of nuggets were determined for 3, 6, 9 and 12 minutes of frying times at 180&ordm / C. In the second part of the study, the effects of protein types (soy protein isolate, whey protein isolate and egg albumen) at different concentrations (1 and 3%) on quality attributes were studied. A batter formulation with no flour or protein addition was used as control. In both parts of the study, flow behavior of batters prepared using different flour and protein types were determined. Soy flour and soy protein isolate (SPI) provided the highest apparent viscosity. Batter viscosity was found to be correlated with coating pick-up. All batters were found to show thixotropic behavior. The batters were modeled as power-law fluid and all of them turned out to be shear-thinning except egg albumen added batter, which was shear-thickening. As a result of the study, among the flour and protein types used, 3% whey protein isolate (WPI) was found to be the most effective ingredient on improving quality parameters of deep-fat fried chicken nuggets. 3% WPI added batters provided the hardest and crunchiest product with the darkest color. It also reduced the oil content of fried nuggets significantly. However, low cooking yield values were observed for batters with 3% WPI. On the other hand, soy flour containing batters provided high cooking yield. Therefore, if high cooking yield with low oil content is desired, soy flour can be advised to be used in batter formulations for chicken nuggets.

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

A presente pesquisa teve por objetivo avaliar as fontes de contaminação por Listeria monocytogenes em uma linha de processamento de \"nuggets\" congelados de frango. Linhagens de L. monocytogenes isoladas de diferentes pontos de uma usina de processamento industrial nas diversas etapas do processamento foram avaliadas quanto à sua diversidade genética. A técnica empregada foi o RAPO com metodologia modificada da Organização Mundial da Saúde (OMS/WHO). Os perfis RAPO gerados com os \"primers\" M13 e UBC155 foram agrupados, combinados e analisados quanto à sua similaridade. As cepas foram também sorotipadas e 189 pertenciam ao sorogrupo 1 e 63 ao sorogrupo 4. A correlação entre a diversidade genética e a distribuição do microrganismo na linha de processamento foi estabelecida. As 252 L. monocytogenes estudadas puderam ser divididas em dois grandes \"clusters\" cada qual dividido em dois grupos. Os resultados da análise de \"clusters\" foram relacionados aos da sorologia, determinando sete subtipos. Verificou-se que três subtipos são introduzidos no ambiente de processamento juntamente com a matériaprima. Um deles foi encontrado somente na matéria-prima e os outros dois também foram detectados em superfícies de equipamentos e no ambiente de processamento. Outros subtipos encontrados em superfícies de equipamentos e no ambiente foram encontrados no produto em etapas subseqüentes. A contaminação da matéria-prima por cepas diferentes daquelas encontradas no ambiente de processamento mostra a sua importância como fonte de contaminação. Formas de controle da presença de L. monocytogenes na matéria-prima devem ser buscadas assim como o controle da contaminação ambiente. / This research was carried out in order to evaluate the sources of Listeria monocytogenes contamination in a frozen chicken nugget processing line. Strains of L. monocytogenes from different origins and isolated from different steps of the processing line were analysed for their genetic diversity. RAPO methodology modified from a WHO protocol was used. The RAPO profiles generated by primers UBC155 and M13 were grouped, combined and the similarities analysed. The strains were also serotyped and 189 belonged to serogroup 1 and 63 to serogroup 4. The correlation between genetic diversity and the strain distribution along the processing line was established. The 252 L. monocytogenes strains analysed were divided in two clusters, each of them containing 2 groups. Seven subtypes could be determined when the results of RAPO and serotyping were combined. It could be established that from the three sub-types of L. monocytogenes that belonged to the raw material, two could establish themselves in the processing line. These sub-types were detected latter in the environmental samples (food contact and non-food contact surfaces). On the other hand, other sub-types found initially in environmental samples were detected in the product in subsequent steps. The introduction of L. monocytogenes into the plant by raw material highlights its importance as a contamination source. Measures must be taken to control the presence of L. monocytogenes in the raw material as well as in the processing environment.

A presente pesquisa teve por objetivo avaliar as fontes de contaminação por Listeria monocytogenes em uma linha de processamento de \"nuggets\" congelados de frango. Linhagens de L. monocytogenes isoladas de diferentes pontos de uma usina de processamento industrial nas diversas etapas do processamento foram avaliadas quanto à sua diversidade genética. A técnica empregada foi o RAPO com metodologia modificada da Organização Mundial da Saúde (OMS/WHO). Os perfis RAPO gerados com os \"primers\" M13 e UBC155 foram agrupados, combinados e analisados quanto à sua similaridade. As cepas foram também sorotipadas e 189 pertenciam ao sorogrupo 1 e 63 ao sorogrupo 4. A correlação entre a diversidade genética e a distribuição do microrganismo na linha de processamento foi estabelecida. As 252 L. monocytogenes estudadas puderam ser divididas em dois grandes \"clusters\" cada qual dividido em dois grupos. Os resultados da análise de \"clusters\" foram relacionados aos da sorologia, determinando sete subtipos. Verificou-se que três subtipos são introduzidos no ambiente de processamento juntamente com a matériaprima. Um deles foi encontrado somente na matéria-prima e os outros dois também foram detectados em superfícies de equipamentos e no ambiente de processamento. Outros subtipos encontrados em superfícies de equipamentos e no ambiente foram encontrados no produto em etapas subseqüentes. A contaminação da matéria-prima por cepas diferentes daquelas encontradas no ambiente de processamento mostra a sua importância como fonte de contaminação. Formas de controle da presença de L. monocytogenes na matéria-prima devem ser buscadas assim como o controle da contaminação ambiente. / This research was carried out in order to evaluate the sources of Listeria monocytogenes contamination in a frozen chicken nugget processing line. Strains of L. monocytogenes from different origins and isolated from different steps of the processing line were analysed for their genetic diversity. RAPO methodology modified from a WHO protocol was used. The RAPO profiles generated by primers UBC155 and M13 were grouped, combined and the similarities analysed. The strains were also serotyped and 189 belonged to serogroup 1 and 63 to serogroup 4. The correlation between genetic diversity and the strain distribution along the processing line was established. The 252 L. monocytogenes strains analysed were divided in two clusters, each of them containing 2 groups. Seven subtypes could be determined when the results of RAPO and serotyping were combined. It could be established that from the three sub-types of L. monocytogenes that belonged to the raw material, two could establish themselves in the processing line. These sub-types were detected latter in the environmental samples (food contact and non-food contact surfaces). On the other hand, other sub-types found initially in environmental samples were detected in the product in subsequent steps. The introduction of L. monocytogenes into the plant by raw material highlights its importance as a contamination source. Measures must be taken to control the presence of L. monocytogenes in the raw material as well as in the processing environment.