Thesis (M. Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 208-219).

Objetivou-se com este estudo avaliar a potencialidade dos revestimentos comestíveis à base de Fécula de mandioca e pectina com e sem adição de óleo de buriti para aplicação em melancia e melão minimamente processados, visando a extensão da vida de prateleira destes produtos. A qualidade do óleo de buriti adicionado aos revestimentos comestíveis foi comprovada através do parâmetros físico-químicos; densidade: 1021 kgm-3; índice de acidez: 1,59 % em ácido oleico; índice de peróxido: 6,20 meqKg-1 e viscosidade cinemática: 41,3 mm²s-1. A caracterização dos principais ácidos graxos presentes no óleo de buriti foi realizada por métodos espectroscópicos de Ressonância Magnética Nuclear de Prótons (1H-RMN) e Espectroscopia de Infravermelho com Transformada de Fourier (FTIR). O ácido oleico (78%) foi o componente majoritário na composição do óleo de buriti. Os revestimentos comestíveis foram elaborados com 3% de fécula de mandioca ou 3% de pectina, 1% de glicerol ou 1% óleo de buriti, 2,5% de gelatina, 0,5% de ácido cítrico e 0,5% ácido ascórbico, os frutos minimamente processados foram revestidos utilizando a técnica de imersão. Os frutos revestidos foram analisados em relação ao pH, sólidos solúveis totais, acidez titulável e contagem microbiana ao longo de 10 dias de armazenamento. Os pH dos frutos revestidos variaram entre 5,35-5,76 para o melão e (4,52-5,49) para a melancia ao longo do tempo de armazenamento. Os teores de sólidos solúveis totais da melancia (7,6-9,6 °Brix) e do melão (7,2-8,6 °Brix) minimamente processados se mantiveram constantes para todos os revestimentos testados. A acidez titulável da melancia e do melão variou de 0,11 à 0,20 % e de 0,06 a 0,14 % em ácido cítrico, respectivamente. Os revestimentos comestíveis apresentaram eficiente barreira para permeabilidade de vapor, sendo que película à base de fécula proporcionou menor média de perda de massa da melancia (2,32%) e o revestimento fécula/óleo para o melão (3,39%). A população microbiana aeróbica e mesófila foi crescente ao longo do período de armazenamento em todos os revestimentos e no controle em ambos os frutos. Ao final dos 10 dias de armazenamento, a melancia apresentou crescimento de bactérias cerca de 9,0 log UFCmL-1, sendo o mesmo valor na população de bolores e leveduras. Os revestimentos fécula e pectina/óleo proporcionaram menor população de bactérias, aproximadamente 7,8 log UFCmL-1. O melão apresentou maiores valores de população de bactérias em comparação com a melancia no revestimento fécula e controle; 10,1 e 9,7 log UFCmL-1, v respectivamente. A contagem de bolores e leveduras também foi maior nos revestimentos fécula e fécula/óleo, aproximadamente 9,0 log UFCmL-1. Conclui-se que o óleo de buriti neste trabalho não apresentou atividade antimicrobiana nos revestimentos comestíveis presentes nos frutos. Os revestimentos comestíveis fécula e pectina proporcionaram à melancia condições adequadas para o consumo até o oitavo dia após o processamento. Entretanto no melão, apenas o revestimento pectina e pectina/óleo garantiram estabilidade microbiológica ao consumo até o quarto dia de armazenamento. / The objective of this study was to evaluate the potential of cassava starch and pectin-based edible coatings with and without addition of buriti oil for application in minimally processed watermelon and melon, aiming to extend the shelf life of these products. The quality of the buriti oil added to the edible coatings was confirmed by physicochemical parameters; Density: 1021 kgm-3; Acidity index in oleic acid: 1.59%; Peroxide index: 6.20 meqKg-1 and kinematic viscosity: 41.3 mm²s-1. The characterization of the main fatty acids present in the buriti oil was performed by spectroscopic methods of Proton Nuclear Magnetic Resonance (1H-NMR) and Fourier Transform Infrared Spectroscopy (FTIR). Oleic acid (78%) had the major percent composition in the buriti oil. The edible coatings were prepared with the concentration of 3% cassava starch or 3% pectin, 1% glycerol or 1% buriti oil, 2.5% gelatin, 0.5% citric acid and 0.5% ascorbic acid, the minimally processed fruits were coated using the immersion technique. The coated fruits were analyzed for pH, total soluble solids, titratable acidity and microbial counts over 10 days of storage. The pH of the coated fruits varied between 5.35 and 5.76 for melon and 4.52 and 5.49 for watermelon over the storage time, respectively. The total soluble solids contents of minimally processed watermelon (7.6-9.6 ° Brix) and melon (7.2-8.63 ° Brix) remained constant for all evaluated coatings. The titratable acidity of watermelon and melon ranged from 0.11 to 0.20% and from 0.06 to 0.14% in citric acid. The edible coatings presented an efficient barrier for vapor permeability, being the starch-based film provided a lower average loss of watermelon mass (2.32%) and starch/oil coating for melon (3.39%). The aerobic and mesophilic microbial population was increasing over the storage period in all coatings and control in both fruits. At the end of the 10 days of storage, the watermelon had a bacterial growth of about 9 log UFCmL-1, the same value for mold and yeast population. The starch and pectin/oil coatings provided a lower bacterial population of approximately 7.8 log UFCmL-1. The melon presented higher values of bacterial population in comparison with the watermelon in the starch and control coating; 10.15 and 9.7 log UFCmL-1, respectively. The mold and yeast counts were also higher in the starch and oil coatings, approximately 9 log UFCmL-1. It is concluded that the buriti oil in this work didn’t present antimicrobial activity in the edible coatings present in the fruits. The edible coatings starch and pectin provided the watermelon suitable conditions for consumption until the eighth day after processing. However, for the melon, only pectin and pectin/oil coating ensured microbiological stability for consumption up to the fourth day of storage.

El comercio electrónico ha ido evolucionando alrededor del mundo, cambiando el entorno comercial de las tiendas tradicionales. La competencia ya no se limita a los servicios que brinda una tienda física, sino que se ha vuelto necesario incursionar en el mundo digital. Asimismo, los productos comestibles en línea están en la categoría con mayor evolución en el mundo. Sin embargo, en Perú no se la ha logrado explotar debido al poco estudio de los factores que influyen en la decisión de compra. Partiendo de esta realidad, la presente investigación busca determinar qué factores externos en el comportamiento del consumidor influyen en la decisión de compra de productos comestibles en supermercados en línea. Para ello, se revisó bibliografía sobre la venta de alimentos en supermercados en línea y sobre los factores del comportamiento del consumidor. Además, se obtuvo información cualitativa mediante entrevistas a expertos y tres focus groups, para conocer la percepción acerca de este canal de comercialización. Respecto al análisis cuantitativo, se realizó encuestas con el objetivo de conocer qué factores en el comportamiento del consumidor influyen en la decisión de una compra de productos comestibles en supermercados en línea. Finalmente, se identifican características de la mujer moderna, entre las edades de 26 a 35 años, de la generación Millennial, de los niveles socioeconómicos B y C de Lima Metropolitana. Asimismo, como resultado del análisis, se presentan las conclusiones y recomendaciones en relación a la influencia de los factores externos en la decisión de compra de productos comestibles en un supermercado en línea. / In recent years, e commerce progress has evolved around the world, changing the commercial environment of traditional stores. The competition is no longer limited to the services provided by a physical store but it is necessary to enter the digital world. In that sense, the online food products sector is the category with the greatest evolution in the world. However, in Peru this sector has not been exploited due to the little study of external factors that influence in the purchase decision. Based on this, the present investigation seeks to determine which external factors of consumer behavior influence the decision to buy grocery products in online supermarkets. Therefore, bibliography was reviewed based on the sale of food in online supermarkets and based on the factors of consumer behavior. In addition, qualitative information was obtained through interviews with experts and three focus groups, this to know the perception about this commercialization channel. Regarding the quantitative analysis, surveys were carried out as planned in order to know the factors of consumer behavior that influence the decision to purchase grocery products in online supermarkets. Finally, characteristics of modern women are identified, between the ages of 26 to 35 years, of the Millennial generation of the NSE B and C of Metropolitan Lima. Likewise, as a result of the analysis, the conclusions and recommendations are presented in relation to the influence of external factors in the decision to buy grocery products in an online supermarket. / Tesis

Traditional fabrication methods used to manufacture biosensors for physiological, therapeutics, or health monitoring purposes are complex and rely on costly materials, which has hindered their adoption as single-use medical devices. The development of a new kind of wearable and implantable electronics relying on inexpensive materials for their manufacturing will pave the way towards the ubiquitous adoption of sticker-like health tracking devices.<div>One of growing and most promising applications for biosensors is the continuous health monitoring using mechanically soft, stretchable sensors. While these healthcare devices showed an excellent compatibility with human tissues, they still need highly trained personnel to perform multi-step, prolonged fabrication for several functioning layers of the device. In this dissertation, I propose low-cost, scalable, simple, and rapid manufacturing techniques to fabricate multifunctional epidermal and implantable sensors to monitor a range of biosignals including heart, muscle, or eye activity to characterizing of biofuids such as sweat. I have also used these devices as an implant to provide heat therapy for muscle regeneration and optical stimulation of neurons using optogenetics. These devices have also combined with those of triboelectric<br>nanogenerators to realize self-powered sensors for monitoring imperceptible mechanical biosignals such as respiratory and pulse rate.</div><div>Food health and safety has also emerged as another important frontier to develop biosensors and improve the human health and quality of life. The recent progresses on detecting microbial activity inside foods or their packages rely on development of highly functional materials. The existing materials for fabrication of food sensors, however,<br>are often costly and toxic for human health or the environment. In this dissertation, I proposed biocompatible food sensors using protein/PCL microfibers to reinforce the protein microfibrous structure in humid conditions and exploit their excellent hygroscopic properties to sense biogenic gas, as an indicator for early detection of food spoilage. Finally, my battery-free food sensors are capable of monitoring food safety with no need of extra measurement devices. Collectively, this dissertation proposes cost-effective solutions to solve human health issues, enabled by developing low-cost, functional materials and exploiting simple fabrication techniques.<br></div>