Thesis (Master)--İzmir Institute of Technology, İzmir, 2005. / Keywords: Biopreservatives, antimicrobial enzymes, antioxidant proteins, edible films, functional packaging materials. Includes bibliographical references (leaves.88-101).

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xii, 196 p.; also includes graphics (some col.). Includes bibliographical references (p. 185-192). Available online via OhioLINK's ETD Center

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Simple technologies are required for reducing the post harvest losses of horticultural produce. Edible films are being studied extensively for application on fresh and cut fruits and vegetables. Tomato, being a very nutritious and important food and a highly perishable climacteric fruit, this study was planned to investigate the application of chitosan films. Chitosan is a biodegradable waste product from sea food and is safe for consumption. With a view to broaden its antimicrobial activity it was combined with lysozyme, a lytic enzyme. Since the edible films are sensitive to changes in temperature and humidity, they were studied under ambient and optimal conditions of storage. / This study showed that 1% chitosan was more suitable for tomatoes for storage at both conditions of ambient and low temperature. Respiration study showed that 1% chitosan treatments resulted in more favorable levels of CO 2 production and internal O2. This was reflected in the quality of tomatoes held under these conditions. Two per cent chitosan films were unsuitable due to their high CO2 production and low internal O 2 levels. Spoilage was more apparent in this treatment. Lysozyme addition did not show any additional benefit. / The research in this study has demonstrated that the selection of edible films for horticultural produce needs to be integrated with the requirement of storage conditions of the produce.

Minimally processed fruits and vegetables are increasingly demanded by local consumers and for export purposes. However, the marketing potential of these produce is limited because of physiological ageing, biochemical changes and microbiological spoilage that lead to a short shelf life. The use of polymeric packaging films to control microbial and metabolic processes and edible coatings to control the white blush formation respectively, have shown potential in improving the quality of minimally processed carrots. In combination they may form a double barrier to gases and water vapour that could provide an interaction effect to enhance the shelf life of minimally processed carrots. The aim of the study was to determine the effects of the polymeric packaging films of different permeability and edible coatings at different levels of concentration, alone and in combination on the physiological and biochemical, microbiological, and sensory quality of minimally processed carrots. A factorial experiment of 3 polymeric packaging films x 3 levels of edible coating was conducted. The three polymeric packaging films were P-Plus®, an oriented polypropylene which were fully permeable to gases and water vapour (pi, control), semi permeable (p160) and least permeable (p90) to gases only. The semi permeable and least permeable packaging had similar water vapour permeability. The coating was Nature Seal®, a cellulose based, at 0% (control), 7.5% and 15% w/w. Carrots were minimally processed into slices, dipped in the edible coating, then packed in the polymeric films and stored for 12 days at 10°C. Four packs were analysed for each combination treatment on d4, d8 and d12, and dO was taken as reference point. With time, the head space in the semi permeable packaging (p160) showed a decrease to about 11.5-13.6% oxygen and an increase to about 7.5-9.6% carbon dioxide. The least permeable pack (p90) showed an oxygen decrease to about 9.8-7.6% and a carbon dioxide increase to about 12.3-13.5%. This change showed the creation of a modified atmosphere that will decrease the metabolic activities. As the coating concentration increased, a slight increase in carbon dioxide and a slight decrease in oxygen were recorded in the head space of the packs. This change was unexpected as the coating was supposed to be a gas barrier. Thus, this change questioned the gas permeability properties of the edible coating. The polymeric packaging and the coating interacted to give lower oxygen and higher carbon dioxide levels in the head space atmosphere. However, packaging had a more pronounced effect in the creation of the modified atmospheres than the coating. A lower white blush formation and a higher retention of chroma values was recorded on the lower surfaces of the carrot slices than on the upper surfaces (upper surfaces refer to those that were facing the packaging material, the lower surfaces was the opposite side of the upper surfaces). This showed that the relative humidity gradient was probably not the same between the surfaces. The coating effectively controlled the white discolouration and maintained higher chroma values on both surfaces of the carrot discs, but packaging did not affect the colour changes of the upper surfaces. An interaction effect was also observed between the packaging and coating showing a better control of the white blush formation of the lower surfaces of the carrot discs. Yeast and moulds did not prove to be a problem in minimally processed carrots as they were lower than 103 cfu/g carrots throughout the storage period. When the carrots were visibly spoiled, the lactic acid bacteria were over 106 cfu/g and the psychrotrophs were about 107 to 108 cfu/g. Initially, a high growth rate of psychrotrophic bacteria occurred followed by a high growth rate of the lactic acid bacteria. This showed a dynamic relationship between the two microbes. Visible rot was observed by brown discolouration, tissue softening and exudate production. The packaging controlled the microbiological growth and spoilage as compared with the coating that enhanced it. A decrease in pH from d4 to d12 corresponded to an increase in the lactic acid bacteria and visible spoilage. Combination of edible coatings and polymeric packaging films did not show any synergistic or additive effects to enhance the shelf life of minimally processed carrots despite some interactions between these two variables. This was because the polymeric packaging films primarily prevented microbiological growth and spoilage, whereas edible coatings partly controlled white blush formation. White blush formation was the most important shelf life determinant of minimally processed carrots. Research efforts should therefore be focused on overcoming this defect. / Dissertation (MSc (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

No description available.

Two lipid-based edible coatings, Apex B (AC Humko, Memphis, TN) and Durafresh (Pacrite, Ecoscience Produce Systems, Orlando, Fl) were evaluated for their ability to preserve post harvest quality changes in green bell peppers (Capsicum annum L. cv. King Arthur). Post harvest storage quality conditions tested included respiration rates, weight, color and texture changes, and stability of ascorbic acid (AA) and dehydroascorbic acid (DHA) content. Results indicated that no appreciable changes between days or treatment groups occurred in three of the parameters tested: weight, texture, and hue angle (p>0.05 for all parameters). Significant weekly changes were seen in respiration rates, dehydroascorbic acid content, and chromaticity values. Respiration rates and DHA were significantly higher during the last two weeks of the study (p=0.0001, p=0.0001 respectively). Chromaticity values were significantly lower, indicating a more faded color on the 14th day of the study alone (p=0.0097). Initial AA levels were much lower than expected (average initial content=78.72mg/100g). Significant differences between coated and uncoated pepper groups were seen in AA and DHA levels. AA content was found to be significantly lower in coated peppers (p=0.0279), while DHA levels were significantly higher in coated groups (p=0.0126). Overall, coated groups differed little from uncoated counterparts, except in the area of vitamin content in which the coated peppers showed an increase in vitamin breakdown. Despite the results, modifications of lipid coatings are needed, such as creating bilayer and composite coatings that contain either polysaccharide or protein constituents to enhance coating effectiveness. / Master of Science

Three hydrocolloid-lipid emulsion coatings were developed using Humkote brand partially hydrogenated cottonseed and vegetable oil, and one of three combined hydrocolloid bases: xanthan gum and propylene glycol alginate (xanthan coating), locust bean gum and xanthan gum (locust bean gum coating), and maltodextrin. Sensory testing using a ranking preference test indicated that these coatings had acceptable appearance and palatability. Quality characteristics of green bell peppers (Capsicum annum L. cv. King Arthur) measured during the 5-week storage period included: respiration rates, chlorophyll content, surface color, puncture force, pectin (uronic acid) content, ascorbic acid (AA) and dehydroascorbic acid (DHA) content, and cumulative weight loss. No significant differences between coated and uncoated peppers were noted in tests for respiration, puncture force, hue angle, chlorophyll content, and AA content. Uncoated peppers had significantly inferior moisture retention (p<0.05), which caused them to be unsaleable after 8 days, while coated groups were saleable for an additional 6 to 8 days. Uncoated fruits also had greater uronic acid breakdown (p<0.05) and higher DHA content (p<0.06) than coated peppers. Significant weekly changes (all treatment groups combined) included linear increases in respiration rates (p<0.01) and moisture loss (p<0.01), increasing linear and quadratic trends in uronic acid content (p<0.01 for both trends), increasing quadratic trends for both chlorophyll and AA content (p<0.05, p<0.01, respectively), and decreasing linear and quadratic (p<0.05 for both trends) in DHA content. The only significant difference between coated groups was in chroma value, with maltodextrin coated peppers appearing less vivid than locust bean coated peppers. Overall, all three coatings performed equally well during the storage study. However, coatings with higher lipid content, which included xanthan gum and locust bean gum groups, withstood humidity changes better than the maltodextrin coated peppers. Coating application provided the greatest benefits in terms of texture maintenance through water retention and prevention of pectin breakdown, despite the lack of differences observed in puncture force. Coatings may also have prevented AA oxidation as demonstrated by the higher DHA content in uncoated groups, however AA patterns do not confirm this concept. Future research should be directed toward further minimizing textural changes and maximizing coating durability. / Ph. D.

A principal função das embalagens tradicionais utilizadas pela indústria de alimentos é a proteção dos alimentos de contaminações externas sem interagir com o mesmo. No entanto, a maioria dessas embalagens é produzida a partir de fontes não biodegradáveis e não renováveis. Para atender à crescente demanda em relação à sustentabilidade ambiental, os filmes e coberturas comestíveis têm despertado o interesse e atenção por parte de indústrias e pesquisadores. Além disso, tais filmes ou coberturas podem ser acrescidos de diferentes compostos, para conferir as mesmas um caráter ativo, com interação positiva com os alimentos, para auxiliar a conservação. Dessa forma, este trabalho teve por objetivo (1) desenvolver filmes ativos pela técnica de casting a partir de matrizes biodegradáveis, com atividade antimicrobiana devido a incorporação de nanopartículas de ouro (AuNPs) e óleos essenciais, além de filmes com atividade antioxidante pela adição de nanocápsulas de bixina, (2) avaliar as características mecânicas, físicas e de barreira dos filmes ativos, além da atividade antimicrobiana e antioxidante, e (3) verificar a eficiência na aplicação de coberturas comestíveis na conservação de alimentos. Os filmes com atividade antimicrobiana utilizaram como matérias primas o amido e a farinha integral de grãos quinoa (Chenopodium quinoa W.). Os filmes de amido de quinoa foram preparados com 4 % de matéria prima e 1 % de glicerol como plastificante e incorporados com solução de nanopartículas de ouro nas concentrações de 2,5 % e 5 % (v/v). A presença de AuNPs levou a uma melhoria nas propriedades mecânicas, ópticas e morfológicas dos filmes, sem alterar as propriedades térmicas e de barreira, além de exibirem forte atividade antibacteriana contra agentes patogênicos de origem alimentar, com porcentagens de inibição de 98 % contra E. coli e S. aureus. Nos filmes ativos elaborados com a farinha de quinoa (6 % de matéria prima e 1 % de glicerol como plastificante em 100 g de solução filmogênica), foram adicionados os óleos essenciais (OE) de orégano (Origanum vulgare L.) e tomilho (Thymus vulgaris L.) (0,5 %, 1 % e 2 % p/p). Observou-se que o tipo de OE não interferiu significativamente nos parâmetros físicos e de barreira dos filmes. Já o aumento na concentração dos OEs, produziu filmes mais elásticos e menos resistentes, bem como, menos solúveis em água e com menor permeabilidade aos vapores de água. Os filmes com 1 % e 2 % de OEs exibiram um efeito inibidor sobre o crescimento de S. aureus e E. coli. No entanto, o S. aureus mostrou-se mais sensível a ambos os OEs; e os filmes com orégano foram mais eficazes na inativação de ambos os microrganismos. As embalagens antioxidantes foram elaboradas a partir de amido de mandioca (4 % de matéria prima e 1 % de glicerol como plastificante em 100 g de solução filmogênica) incorporadas com solução de nanocápsulas de bixina (0 %, 2 %, 5%, 8 % e 10 %). Os filmes foram caracterizados em relação as suas propriedades de barreira, mecânicas e físicas e a atividade antioxidante foi avaliada pelo efeito protetor do óleo de girassol exposto a condições de oxidação aceleradas (13 dias a 65 % UR / 35 ºC). Embalagens com maiores concentrações de nanocápsulas demonstraram maior resistência e elasticidade, bem como, uma melhora significativa na proteção contra os raios UV e luz visível. O óleo de girassol embalado nos filmes contendo nanocápsulas de bixina apresentaram índices de peróxidos abaixo dos estipulados pelo Codex Alimentarius (<10 meq. O2 kg-1) para óleos frescos para o período de armazenamento testado. A cobertura comestível foi preparada à base de quitosana (1,5 %) e foi aplicada sobre tomates armazenados por 14 dias (20 ° C), com acompanhamento da perda de peso, sólidos solúveis totais (SST), firmeza e acidez titulável (AT), taxa de respiração, produção de etileno e quantificação de carotenoides e compostos fenólicos por CLAE. Os frutos revestidos demonstraram retardo no processo de amadurecimento com a diminuição da taxa respiratória e produção de etileno, bem como menores perdas de peso, firmeza -caroteno e menor degradação de compostos fenólicos durante o armazenamento, em comparação com frutos controle (não revestidos). Os resultados sugerem que o desenvolvimento de filmes ativos para conservação de alimentos é um campo promissor, pois além do forte apelo ambiental, filmes ativos podem auxiliar na conservação dos alimentos, para retardar a proliferação de microrganismos patogênicos e degradações oxidativas. Em relação a aplicações de coberturas comestíveis, os resultados indicaram ter potencial para uma utilização comercial no auxílio de prolongamento da vida útil de tomates. / The principal function of traditional packaging used by the food industry is the protection of food against external contamination without interacting with it. However, most of these packages are produced from non-biodegradable and non-renewable sources. Films and edible coatings have attracted the interest and attention from industries and researchers due increasing demand on environmental sustainability. In addition, this films and coatings can be added with different compounds to confer an active character, with positive food interaction and increased of preservation. This study aimed to (1) to develop active films by casting technique from biodegradable matrices with antimicrobial activity, incorporated of gold nanoparticles (AuNPs) and essential oils, as well as films with antioxidant activity by addition of nanocapsules of bixin, (2) evaluate the mechanical, physical and barrier characteristics of active films, and capacity antimicrobial and antioxidant, and (3) verify the efficiency in the application of edible coatings in food preservation. The active antimicrobial films it was used as raw material starch and flour quinoa (Chenopodium quinoa, W.). Starch quinoa films were prepared with 4 % raw material and 1% glycerol as plasticizer (100 g filmogenic solution), incorporating gold nanoparticles at concentrations of 2.5% and 5% (v / v). The presence of gold nanoparticles produces improvement in the mechanical, optical and morphological properties, maintaining the thermal and barrier properties unchanged when compared to the standard biofilm. The active biofilms exhibited strong antibacterial activity against food-borne pathogens with inhibition percentages of 99 % against E. coli and 98 % against S. aureus. The active films produced with flour quinoa (6% of raw material and 1% glycerol as a plasticizer in 100 g of filmogenic solution), incorporated with oregano (Origanum vulgare L.) and thyme (Thymus vulgaris L.) essential oils (EO) (0.5%, 1% and 2% p/p). It was observed that the kind of EO was not significant for the physical and barrier parameters of the films, however, the increase in the EOs concentration promote increase in the elongation but decrease in the tensile strength, solubility and water vapor permeability. Films containing 1% and 2 % EOs, inhibit the growth of S. aureus and E. coli. However, S. aureus was more sensitive to both EOs and the oregano oil was more efficient in the inactivation to both microorganisms. The antioxidant packages were prepared from cassava starch (4% raw material and 1% glycerol as plasticizer in 100 g of filmogenic solution), incorporated with solution of different concentrations of bixin nanocapsules (0 %, 2 %, 5%, 8 % e 10 %). Films with higher concentrations of bixin nanocapsules exhibited significant reduction tensile strength and increases in elongation at break, well as, improvement in protection against UV and visible light and decreased water solubility and increased water vapor permeability. The sunflower oil packed in films containing nanocapsules bixin exhibited lower oxidation rates, thus maintaining its freshness according to Codex Alimentarius guidelines (< 10 milliequivalent.kg-1), for the storage time tested (13 days / 65 % RH / 35 ºC). The edible coating was prepared based on chitosan (1.5 %), and it was applied on tomatoes stored for 14 days (20 °C). The analyses carried out on tomato fruit were: weight loss, total soluble solid (TSS), firmness, and titratable acidity (TA), respiration rate, ethylene production and quantification of carotenoids and phenolics by HPLC. Coated fruit delayed the ripening process by decrease of the rate of respiration and ethylene production, as well changes of weight, firmness and TSS concentration and delay peak of lycopene and b-carotene accumulation and degradation of phenolic compounds during storage, compared to uncoated control. The results suggest that the development of active films for food preservation is a promising field, because besides the strong environmental appeal, active films can increase the food preservation, to decrease the proliferation of pathogenic microorganisms and oxidative degradation. Regarding the edible coatings applications, the results indicated that coating is a promising tool for commercial use in helping to prolong the storage of tomatoes.

Graduation date: 2004