Ultra high temperature (UHT) processing can extend shelf life of milk to several months without refrigeration, which is more convenient and energy saving than pasteurized milk. However, the poor acceptance caused by "cooked" flavors limits its marketing growth, especially in United States. Ohmic heating, which has a more uniform and rapid heating than conventional UHT process, may minimized the flavor change during the thermal treatment. Flavor composition between Ohmic heated UHT milk and other traditionally processed UHT milk (direct steam injection and indirect plate heating) during 36 weeks storage were investigated in this study. A total of 20 volatile compounds were analyzed based on their importance to UHT milk as well as their representation to different chemical classes including sulfur-containing compounds, ketones, lactones, aldehydes and others. Dimethyl sulfide (DMS) and methyl ketones were significant different among three types of UHT heated milk. δ-lactones showed higher amount in Ohmic heating after stored for four weeks, which might generate creamy, fruity intermediate aroma. Other compounds showed no significant difference among three heating processes. Aroma recombination test revealed that the overall aroma of the ultra pasteurized (UP) milk could be mimicked by recombining 15 important reference odorants in the same concentrations as they occurred in the UHT milk using commercial pasteurized milk as the matrix. / Graduation date: 2012

Heating milk to high temperatures such as 140 ºC, as used in ultra high temperature (UHT) processing, causes physical and chemical changes in the milk. The production of a cooked flavour is a major change which reduces consumer acceptance of the UHT milk. It has been correlated with the formation of volatile sulphur compounds (VSCs) that result from milk proteins, principally the whey proteins β-lactoglobulin, containing the the sulphur amino acids cystine, cysteine and methionine. The VSCs in milk, whose concentrations are in the parts per billion to parts per million range, are highly reactive, easily oxidised, and sensitive to heat during thermal processing and analysis; this makes them a challenge to analyse. A sensitive method based on gas chromatography with pulsed flame photometric detection coupled with headspace sampling by solid phase microextraction (SPME/GC/PFPD) was developed to detect these compounds in commercial UHT milk and to investigate their production and disappearance during heating and storage. The SPME/GC/PFPD procedure was optimised using different extraction time (15 min, 30 min, & 60 min) – temperature (30 oC, 45 oC & 60 oC) combinations with CAR/PDMS fibre to obtain maximum sensitivity. A short extraction time (15 min) at low temperature (30 oC) was chosen to provide high sensitivity for detecting all VSCs in UHT milk without introducing artefactual VSCs. The extraction method and GC run time (16 min) make this method simple and fast. Nine VSCs were detected in commercial indirectly processed UHT milk, skim and whole. These are hydrogen sulphide (H2S), carbonyl sulphide (COS), methanethiol (MeSH), dimethyl sulphide (DMS), carbon disulphide (CS2), dimethyl disulphide (DMDS), dimethyl sulphoxide (DMSO), dimethyl sulphone (Me2SO2) and dimethyl trisulphide (DMTS). An additional unknown compound was detected but could not be identified by GC/MS because its concentration was below the detection limit of the MS detector. The concentrations of H2S, DMS and DMTS were higher than their threshold values indicating their importance in milk flavour, especially cooked flavour. Several attempts have been made to reduce the cooked flavour in UHT milk. In the current research, the use of hydrogen peroxide (H2O2) to oxidise the VSCs and thereby reduce cooked flavour was investigated. H2O2 is used as a milk preservative and is generally recognised as safe (GRAS) in USA. Several concentrations of H2O2 (0.001%, 0.005%, 0.01%, 0.02% & 0.03%) were added to milk to assess its effects on VSCs and on whey proteins denaturation in UHT milk. H2O2 effectively reduced the concentration of all VSCs, except DMDS which was increased, presumably by oxidation of MeSH. H2S was completely oxidised or reduced below its threshold value. Low concentrations of H2O2 (0.001% & 0.005%) had no effect on, or decreased, the extent of denaturation of β-lactoglobulin when added after or before processing, respectively. Some UHT plants use severe heating conditions, leading to high levels of denaturation of whey proteins, particularly β-Lg, the main source of the VSCs in milk. Correlations between heat severity, β-Lg denaturation and individual VSC generation were investigated in milk batch-heated at 80 oC and 90 oC, and UHT milk processed at 120-150 oC. In accordance with previous reports, β-Lg was more heat-sensitive than α-La. Only five VSCs were detected. The concentrations of H2S and MeSH correlated well with denaturation of β-Lg and α-La. DMS concentration correlated well with β-Lg in UHT milk but not in the batch-heated milk. CS2 did not show a good correlation with heat intensity and appeared to plateau out after a certain level of heating. Conversely, COS and MeSH seemed to require a certain minimum amount of heat before generation commenced; this corresponded to denaturation of β-Lg above 49% and 89% respectively at 80 oC. The higher concentrations of DMS and H2S in UHT milk compared with batch-heated samples having similar degrees of denaturation suggested other possible sources for their production and the importance of the heat severity in generating them. For example, at high heat intensity, S-methylmethionine and thiamine could be sources of DMS and H2S respectively. Furthermore, in whole milk as used in this work, milk fat globule membrane proteins are another source of VSCs. The outcome of this study will help UHT manufacturers to understand the production and disappearance of the VSCs in commercial UHT milk and how to adjust the processing conditions to avoid generation of cooked flavour. Additionally, the promising results of using low concentrations of H2O2 to oxidise the VSCs will provide the industry with another means of reducing cooked flavour. Before H2O2 use is implemented in UHT processing, future studies are required to evaluate all of its effects, including sporicidal effects. Overall, this study makes a contribution to finding a solution to the cooked flavour problem in UHT milk, thereby increasing market share of this milk in countries such as Australia, the UK and North America where cooked flavour is the main barrier to its consumer acceptance.

Orientador: Walkiria Hanada Viotto / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-16T13:43:28Z (GMT). No. of bitstreams: 1 Lisita_MilenaOlivieri_D.pdf: 2002607 bytes, checksum: 1ec6e24923de12f23613383df46f56a3 (MD5) Previous issue date: 2010 / Resumo: Leite cru foi armazenado por tres dias sob tres temperaturas (3, 7 e 10oC) para a utilizacao em processamento de leite longa vida (ou UHT ¿ ultra high temperature) em embalagem flexivel, de polietileno de baixa densidade (PEBD). Tambem foi produzido leite UHT com leite cru da ordenha do dia (amostra controle), totalizando, portanto, 4 tratamentos. Os lotes de leite UHT foram estocados no escuro a temperatura ambiente. O objetivo deste trabalho foi avaliar a influencia da temperatura de armazenamento do leite cru sobre sua qualidade, e a qualidade e vida de prateleira do leite UHT com ele produzido. Foi verificado maior desenvolvimento bacteriano, de mesofilos e psicrotroficos aerobios e Pseudomonas spp., no leite cru armazenado a 10°C/ 3 dias quando comparados aos armazenados a 3 e 7°C pelo mesmo periodo de tempo. Da mesma forma, o leite UHT produzido a partir de leite cru que foi armazenado por 3 dias a 10oC, apresentou maiores extensoes de lipolise, possivelmente pela maior atividade enzimatica das enzimas termorresistentes de psicrotroficos. Não houve aumento de viscosidade. Na oitava semana de estocagem, todos os lotes de leite UHT, inclusive o controle feito com leite fresco, foram rejeitados pelos provadores atraves dos atributos de sabor e impressao global. Concluiu-se que o leite UHT em embalagem flexivel produzido a partir de leite cru refrigerado de boa qualidade e armazenado por tres dias antes do processamento, apresentou vida de prateleira maxima de 7 semanas quando estocado no escuro a temperatura ambiente. Em outro experimento, o leite UHT em embalagem flexivel (PEBD + 1,5% TiO2) foi exposto a luz (1920 ±?100 lux) pelo periodo de 72h com o objetivo de avaliar a qualidade do produto nessas condicoes de estocagem. Os resultados mostraram um aumento da oxidacao lipidica com o tempo e rejeicao dos provadores a partir de 24h de exposicao, mostrando que o leite UHT nesta embalagem necessita de uma barreira complementar a luz / Abstract: Raw milk was stored for three days under three different temperatures (3, 7 and 10oC) for use in UHT milk processing, and then stored in flexible low density polyethylene (LDPE) package. UHT milk was also made from raw milk taken from same day milking (control sample), therefore completing a total of 4 different treatments. The milk was later stored in dark, room temperature conditions. The objective of this work was to evaluate the influence of temperature on the quality of the milk, and on the shelf life and quality of UHT milk made from it. A larger bacterial development, of aerobic mesophilic and psychrotrophic and Pseudomonas spp was verified. In the same way, the UHT Milk made from raw milk stored for three days showed more lipolysis, possibly due to psychrotrophic thermoresistant enzyme action. No increase in viscosity was detected. On the eighth week of storage, all the UHT milk samples, including the control sample, were rejected by the panellists on the attributes of taste and general impression. This lead to the conclusion that when stored in flexible package under dark room temperature conditions, the UHT milk made from good quality raw milk, even when submitted to a three day refrigeration abuse, presents a maximum shelf life of 7 weeks. In another experiment, the flexible package (LDPE + 1,5% TiO2) UHT milk was exposed to light (1,920 ±?100 lux) for a 72 hour period with the objective of evaluating the quality of the product under these conditions. The results showed an increase of lipid oxidation through time, and rejection by panelists after 24 hours, indicating that this package needs another complementary layer working as a light barrier / Doutorado / Doutor em Tecnologia de Alimentos

Orientador: Jose de Assis Fonseca Faria / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-15T08:14:09Z (GMT). No. of bitstreams: 1 Walter_EduardoHenriqueMiranda_D.pdf: 5634901 bytes, checksum: 43f060f6a152462fae06f4a9bd631c70 (MD5) Previous issue date: 2010 / Resumo: Os sistemas assepticos sao uma das tecnologias mais empregadas na conservacao de bebidas a temperatura ambiente, compondo um mercado dinamico e promissor de produtos, embalagens e equipamentos. O objetivo desse trabalho foi avaliar um sistema asseptico projetado para produzir 1.000 L/h de leite longa vida e bebidas de alta acidez (dois tipos de chas e quatro refrescos mistos de maca, pera e pessego), com uma taxa de defeitos de 0,1%. As embalagens consistiram em bolsas flexiveis com termossoldagem tipo almofada de polietileno de baixa densidade pigmentado de branco com dioxido de titanio, tradicionalmente utilizado para leite pasteurizado, e laminado multicamada com propriedades de barreira ao oxigenio e a luz. Foram realizadas 15 producoes de leite longa vida e quatro das bebidas de alta acidez. Os testes foram conduzidos num sistema composto por equipamentos comerciais (tanques, bombas, valvulas, tubulacoes e trocador de calor) e em desenvolvimento (tanque de produto e maquina de embalagem tipo forma, enche e fecha), todos destinados as industrias de pequena escala de producao. O sistema foi avaliado com base em testes de esterilizacao comercial e analises de aceitacao sensorial dos produtos. A taxa de defeitos nas producoes de leite longa vida ficou na ordem de 2%, enquanto para as bebidas de alta acidez de 0,4%. A aceitacao sensorial do leite longa vida nas embalagens de polietileno, estocadas no escuro, variou entre quatro e sete semanas, de acordo com a qualidade da materia-prima, enquanto a aceitacao sensorial do produto exposto a luz foi de alguns dias. Na embalagem laminada, a luz nao afetou a estabilidade do produto, que teve uma vida de prateleira entre 12 e 24 semanas, dependendo da materia-prima. Esses resultados comprovaram a viabilidade das embalagens para a conservacao do produto. Entretanto, o sistema devera passar por melhorias, alcancando desse modo o potencial para aplicacao em industrias de pequena escala de producao. A simplicidade da linha de processamento e embalagem contribuiu para quebrar o paradigma de que os sistemas assepticos tem de ser sofisticados e onerosos / Abstract: Aseptic systems are one of the main technologies employed for shelf stable milk and juices, creating a dynamic and promising market for products, packaging and equipments. The aim of this study was to evaluate an aseptic system designed to produce 1000 L/h long-life milk and high acidity soft drinks (two teas and four soft drinks, mixed with apple, pear and peach), with a defect rate of 0.1 %. The packages were pillow-style pouches of low density polyethylene pigmented white with titanium dioxide, traditionally used for packaging pasteurized milk in Brazil, and multilayer laminate with oxygen and light barrier properties. There were performed 15 trials of long-life milk and four of soft drinks. Tests were conducted in the system composed of commercial equipment (tanks, pumps, valves, piping and heat exchanger), product tank, and form/fill/seal packaging machine, all used to small-scale production. The system evaluation was based on tests for commercial sterility and sensory acceptability testing of the products. The defect rate in the production of long-life milk was around 2%, while in high acidity drinks of 0.4%. The sensory acceptability of long-life milk in polyethylene containers, stored in the dark, ranged from four to seven weeks, according to the quality of raw material, while for the products exposed to light, it was of a few days. In the laminated bag, light did not affect the stability of the product, which had a shelf life ranged from 12 to 24 weeks, depending on the raw material used. These results have proved the feasibility of both packs for the conservation of the product. However, the system must go through improvements, thereby achieving the potential for application in small-scale industries. The simplicity of the processing and packaging system helped to break the paradigm that aseptic systems have to be sophisticated and expensive / Doutorado / Doutor em Tecnologia de Alimentos

Orientador: Mirna Lucia Gigante / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-15T18:42:59Z (GMT). No. of bitstreams: 1 Vianna_PriscilaCristinaBizam_D.pdf: 1512890 bytes, checksum: cfe5342097a5fc9d5f272c136b132b45 (MD5) Previous issue date: 2010 / Resumo: O objetivo deste trabalho foi avaliar o efeito da adição de dióxido de carbono (CO2) sobre a qualidade dos leites cru e UHT. Inicialmente, o leite cru adicionado ou não de CO2 foi armazenado em garrafas de vidro a 4 e 7ºC e amostras foram avaliadas diariamente quanto à contagem padrão em placas, psicrotróficos e Pseudomonas spp. e a cada dois dias quanto à concentração de CO2, proteólise e lipólise, até que a contagem padrão em placas atingisse 7,5x105 ufc/mL. O delineamento experimental utilizado foi o de sub-sub-parcelas divididas e os resultados foram avaliados por análise de variância multivariada, pelo teste de médias de Tukey (p<0,05) e através do modelo matemático de Gompertz. A contagem padrão aumentou ao longo do tempo para todos os tratamentos e o tempo de conservação foi de 14 dias para o leite armazenado a 4ºC adicionado de CO2 e de 5 dias para o armazenado a 7ºC não adicionado de CO2. Independente da temperatura de armazenamento, a adição de CO2 estendeu o tempo de fase lag e de geração dos micro-organismos psicrotróficos e reduziu sua taxa de crescimento. O leite adicionado de CO2 apresentou menor proteólise e lipólise quando comparado ao não adicionado devido ao menor desenvolvimento de psicrotróficos. Com base nesses resultados, definiu-se o armazenamento do leite cru adicionado ou não de CO2 a 4ºC por 6 dias antes do processamento UHT. Nesta etapa, o leite cru adicionado ou não de CO2 foi armazenado em tanques de expansão antes do processamento UHT (140ºC/5 s). O leite cru foi avaliado no dia da recepção e após 6 dias de armazenamento quanto à composição físico-química, proteólise, lipólise e contagens microbianas. Após o processamento, as amostras foram avaliadas durante 120 dias quanto à composição físico-química, lipólise e proteólise. O delineamento experimental utilizado foi o de parcelas subdivididas em blocos com três repetições. Os resultados foram avaliados por análise de variância e teste de médias de Tukey (p<0,05). Após 6 dias de armazenamento a 4 ºC o leite cru adicionado de CO2 manteve sua qualidade físico-química e microbiológica enquanto que o leite não adicionado sofreu perda significativa de qualidade. A taxa de aumento de proteólise foi 1,4 vezes maior no leite UHT produzido a partir de leite cru não adicionado de CO2 quando comparado à amostra produzida com adição de CO2. Em ambas as amostras, a proteólise foi decorrente tanto da ação de plasmina como de proteases microbianas. Entretanto, o leite UHT produzido a partir de leite cru não adicionado de CO2 apresentou maior ação de proteases microbianas, caracterizada pelo aumento de peptídeos menos hidrofóbicos. A lipólise aumentou para as duas amostras durante os 120 dias e foi maior no leite UHT produzido a partir de leite cru não adicionado de CO2. Os resultados mostraram que a adição de CO2 ao leite cru preservou sua qualidade físico-química e microbiológica durante o armazenamento refrigerado e afetou positivamente a manutenção da qualidade do leite UHT durante seu armazenamento / Abstract: The objective of this work was to evaluate the effect of the CO2 addition on the raw and UHT milk quality. First, raw milk with or without CO2 addition was stored in glass bottles at 4ºC and 7ºC and daily analyzed to standard plate count, psychrotrophic bacteria count and Pseudomonas spp. and every other day to CO2 concentration, proteolysis and lipolysis until standard plate count reached 7,5x105 ufc/mL. Split-split-plot design was used and the results were evaluated by multivariate variance analysis, Tukey¿s test (p<0,05) and by Gompertz model. The standard plate count increased throughout the time for all treatments and the preservation time was 14 days for CO2 added raw milk stored at 4ºC and 5 days for raw milk without CO2 addition stored at 7ºC. Independent of the storage temperature, CO2 extended the lag phase, increased the generation time and decreased the growth rate of psychrotrophic bacteria. Milk with CO2 addition presented lower proteolysis and lipolysis, related to the slower psychrotrophic bacteria development. Based on these results, it was defined a storage of raw milk with and without CO2 addition in bulk tanks at 4ºC during 6 days before UHT treatment (140ºC/5 s). Raw milk was evaluated to physical-chemical composition, proteolysis, lipolysis and microbial counts in the day of reception and after 6 days of storage. After processing, samples were evaluated to physical-chemical composition, lipolysis and proteolysis. Split-plot design was used with three replications. The results were evaluated by analysis of variance (ANOVA) and Tukey¿s test (p<0,05). After 6 days of storage at 4ºC, CO2 added raw milk kept its physical-chemical and microbiological quality, while raw milk without CO2 addition had significant losses. Proteolysis increased ratio was 1,4 higher in UHT milk produced with raw milk without CO2 addition when compared to UHT milk produced with CO2. In both samples proteolysis was a consequence of plasmin and microbial proteases action, but the sample produced with raw milk without CO2 addition presented higher microbial proteases action, characterized for the increase of less hydrophobic peptides. Lipolysis increased for both samples during the 120 days of storage and it was higher in UHT milk produced from raw milk without CO2 addition. The results had shown that CO2 addition to raw milk preserved its physical-chemical and microbiological quality during refrigerated storage and positively affected the quality maintenance of UHT milk during its storage / Doutorado / Doutor em Tecnologia de Alimentos

Orientador: Mirna Lúcia Gigante / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-19T11:42:02Z (GMT). No. of bitstreams: 1 Dias_MariaElisabeteFernandesDias_M.pdf: 5400605 bytes, checksum: 00a236017885ffd7ef50a95f530931bb (MD5) Previous issue date: 2011 / Resumo: O objetivo deste trabalho foi avaliar o efeito da adição de CO2 ao leite cru sobre as características do leite UHT obtido por injeção direta de vapor e armazenamento a 25ºC, 35ºC e 45ºC por 180 dias. O leite cru (250 litros) foi dividido em duas porções que foram armazenadas em tanques de expansão a 4?1ºC por seis dias. Uma porção foi adicionada de CO2 grau alimentício até que o pH do leite atingisse 6,20, enquanto a outra serviu de controle. O leite cru foi avaliado quanto ao pH, acidez, prova do álcool, composição físico-química, proteólise, lipólise, cor e concentração de CO2 após a injeção. Para caracterização microbiológica, o leite cru foi avaliado quanto à contagem padrão em placas e de micro-organismos psicrotróficos no dia da recepção e após seis dias de armazenamento refrigerado. As amostras foram submetidas ao tratamento UHT por injeção direta de vapor (143ºC/4s), envasadas em embalagens tetra brik asseptic de 125 ml e armazenadas em BOD a 25, 35 e 45 ºC por 180 dias. No dia seguinte, as amostras foram avaliadas quanto as mesmas características do leite cru, além da prova do álcool, viscosidade, sedimentação, eletroforese, peptídeos por HPLC e esterilidade comercial. Após 1, 30, 60, 90, 120, 150 e 180 dias de armazenamento, as amostras foram avaliadas quanto ao pH, acidez, nitrogênio e frações nitrogenadas, cor, ácidos graxos livres, sedimentação, viscosidade, eletroforese e peptídeos por HPLC. O delineamento experimental foi o de sub-sub-parcelas divididas e o experimento foi repetido três vezes. O efeito do tratamento, da temperatura e do tempo de armazenamento, e a interação destes fatores sobre as características do leite UHT foi avaliado por análise de variância (ANOVA) e teste de Tukey ao nível de 5% de significância. Após seis dias de armazenamento refrigerado, não houve diferença significativa nas características físico-químicas do leite adicionado ou não de CO2, exceto na quantidade de ácido graxos livres que foi maior no leite controle do que no adicionado de CO2. A adição de CO2 inibiu o desenvolvimento de micro-organismos durante o armazenamento refrigerado, uma vez que a contagem total e de psicrotróficos do leite controle foi maior que as contagens do leite adicionado de CO2 . O pH das amostras de leite UHT armazenadas a diferentes temperaturas foi afetado pela temperatura e pelo tempo de armazenamento, apresentando maior decréscimo do pH nas amostras armazenadas a 45 ºC. A cor das amostras a 25°C não apresentou escurecimento durante os 180 dias, enquanto as armazenadas a 35°C e 45°C apresentaram desenvolvimento de cor visível a olho nu e aumento no valor b* ao longo do tempo. A lipólise do leite UHT foi maior nas amostras armazenadas a 45ºC. A proteólise foi maior no leite armazenado a 45°C, cujo aumento não refletiu na viscosidade e sedimentação do leite, que não foram significativamente afetados até o 120° dia de armazenamento, prazo de validade usualmente garantido pelas indústrias de processamento de leite UHT no Brasil / Abstract: The objective of this study was to evaluate the effect of CO2 addition to raw milk on the characteristics of UHT milk obtained by direct steam injection and stored at 25 ° C, 35 ° C and 45 ° C for 180 days. Raw milk (250 liters) was divided in two portions that were stored in bulk tanks at 4 ± 1 ° C for six days. To one portion was added food grade CO2 until the pH of milk was 6.20, while the other portion was the control sample. Raw milk was evaluated for pH, acidity, physicochemical composition, proteolysis, lipolysis, color and concentration of CO2 after injection. Raw milk was evaluated for standard plate count and psychrotrophic micro-organisms on the reception and after six days of cold storage, for microbiological characteristics. The samples were submitted to UHT treatment by direct steam injection (143°C/4s), packed in 125 ml Tetra Brik Asseptic packing and stored in BOD at 25, 35 and 45 ° C for 180 days. One day after processing, the samples were evaluated for the same characteristics of raw milk, plus alcohol stability, viscosity, sedimentation, electrophoresis, peptides by HPLC and commercial sterility. After 1, 30, 60, 90, 120, 150 and 180 days of storage, samples were evaluated for pH, acidity, nitrogen and nitrogen fractions, color, free fatty acids, sedimentation, viscosity, electrophoresis and peptides by HPLC. The experimental design was split-split-plot and the complete experiment was repeated three times. The effect of treatment, temperature and storage period as well as the interaction of these factors on the characteristics of UHT milk was assessed by analysis of variance (ANOVA) and Tukey¿s test at 5% significance level. After six days of cold storage, there was no significant difference in the physicochemical characteristics of raw milk with or without CO2 addition, except for free fatty acid values, which were higher for the milk without CO2 addition. The addition of CO2 inhibited the development of microorganisms during storage, since the standard plate count and psychrotrophic count of milk control was higher than values for the CO2 added milk. The pH of UHT milk samples was affected by temperature and storage time, showing greater decrease in pH for samples stored at 45°C. The color of the samples at 25°C showed no browning during the 180 days, while those stored at 35 ° C and 45 ° C showed brown color visible to the naked eye and an increased b * value over time. Lipolysis of UHT milk samples was higher for samples stored at 45°C. The proteolysis was higher in milk stored at 45°C, whose increase was not reflected in viscosity and sedimentation of the milk, since these parameters were not significantly affected during 120 days-storage, period of shelf life usually guaranteed by the processing industries of UHT milk in Brazil / Mestrado / Tecnologia de Alimentos / Mestre em Tecnologia de Alimentos

Bovine milk contains a variety of endogenous peptides, partially formed by milk proteases that may exert diverse bioactive functions. Milk storage allows further protease activities altering the milk peptidome, while processing, e.g., heat treatment can trigger diverse chemical reactions, such as Maillard reactions and oxidations, leading to different posttranslational modifications (PTMs). The influence of processing on the native and modified peptidome was studied by analyzing peptides extracted from raw milk (RM), ultra-high temperature (UHT) milk, and powdered infant formula (IF) by nano reversed-phase liquid chromatography coupled online to electrospray ionization (ESI) tandem mass spectrometry. Only unmodified peptides proposed by two independent software tools were considered as identified. Thus, 801 identified peptides mainly originated from αS- and β-caseins, but also from milk fat globular membrane proteins, such as glycosylation-dependent cell adhesion molecule 1. RM and UHT milk showed comparable unmodified peptide profiles, whereas IF differed mainly due to a higher number of β-casein peptides. When 26 non-enzymatic posttranslational modifications (PTMs) were targeted in the milk peptidomes, 175 modified peptides were identified, i.e., mostly lactosylated and a few hexosylated or oxidized peptides. Most modified peptides originated from αS-caseins. The numbers of lactosylated peptides increased with harsher processing.

The sensory evaluation of heat treated consumer milk at different temperatures by preference tests was main topic of this thesis. The survey based on questionare is part of this thesis.

The objective of this work was to evaluate the microbiological and physicochemical quality of UHT whole milk commercialized in the State of Rio Grande do Sul, during the winter and spring of 2009. Four samples of 10 marketed marks were collected in each period. Of these, two of each mark was destined for microbiological analyses and the others two for physicochemical analyses. For the microbiological analyses, the samples were incubated in their original packages at 36±1ºC for 7 days before the analyses were carried out. These analyses, that were carried out in duplicate, were: Most likely number of coliforms at 35˚C and 45˚C; moulds and leavenings count; staphylococcus coagulase positive count; Salmonella research; viable strict and facultative aerobic mesophyle microorganisms standard count; viable aerobic mesophyle microorganisms capable of causing alteration in UHT liquid lactic products count; Bacillus sporothermodurans presence; total aerobic thermophyle and Flat-Sour spore count, that evidences the presence of Geobacillus stearothermophilus and Bacillus coagulans. The physicochemical analyses, carried out in triplicates were: fat, acidity, non fat dry extract, protein, density, cryoscopy and fatty acids profile. The results were analyzed using the SPSS program, version 13.0. For the microbiological analyses, the averages and the mean deviations were obtained. The physicochemical analyses were submitted to the analysis of variance (ANOVA) and the differences were analyzed by the Tukey test with a level of 5% of probability. The ten marks of UHT whole milk analyzed were within the standard microbiological values in effect for the microorganisms that were analyzed. The physicochemical parameter were evaluated partially attended the specifications of the Technical Regulation of Identity and Quality of UHT Milk in relation to that in disagreement 60% in winter and 80% in spring. A prevalence of miristic, palmitic, stearic and oleic fatty acids was observed with significant differences between the marks. It can be concluded that, although some physicochemical parameters were not in accordance with the standards of identity and quality, the ten UHT whole milk commercialized in the State of Rio Grande do Sul attends the specifications related to the microbiological quality, indicating that it is a safe product from the sanitary point of view. / Este trabalho teve por objetivo avaliar a qualidade microbiológica e físico-química do leite UHT integral comercializado no Rio Grande do Sul, durante o inverno e primavera de 2009. Foram coletadas quatro amostras de 10 marcas comerciais, em cada período, destas, duas foram destinadas as análises microbiológicas e duas às análises físico-químicas. Para as análises microbiológicas, as amostras foram incubadas em suas embalagens originais a 36±1ºC por 7 dias, antes do início das análises. Estas análises foram realizadas em duplicata, sendo analisado o número mais provável de coliformes a 35˚C e 45˚C, contagem de bolores e leveduras, contagem de estafilococos coagulase positiva, pesquisa de Salmonela, contagem padrão de microrganismos mesófilos aeróbios estritos e facultativos viáveis, contagem de microrganismos mesófilos aeróbios viáveis capazes de causar alteração em produtos lácteos líquidos UHT, presença de Bacillus sporothermodurans e a contagem de esporos de termófilos aeróbios totais e Flat-Sour que evidenciam a presença de Geobacillus stearothermophilus e Bacillus coagulans. As análises físico-químicas de gordura, acidez, extrato seco desengordurado, proteína, densidade, crioscopia e o perfil de ácidos graxos foram realizados em triplicata. Os resultados foram analisados utilizando o programa SPSS versão 13.0, para as análises microbiológicas foram calculadas as médias e o desvio padrão e as análises físico-químicas foram submetidas à análise de variância (ANOVA) e a diferença analisada pelo teste de Tukey, nível de 5% de probabilidade. As dez marcas de leites UHT integral analisadas apresentaram-se dentro dos padrões microbiológicos vigentes, para os microrganismos estudados. Os parâmetros físico-químicos avaliados atenderam parcialmente as especificações do Regulamento Técnico de Identidade e Qualidade do Leite UHT, apresentando 60% e 80% dos resultados em desacordo no inverno e na primavera, respectivamente. Houve prevalência dos ácidos graxos mirístico, palmítico, esteárico e oléico com diferenças significativas entre as marcas. Pode-se concluir que, apesar de alguns parâmetros físico-químicos não terem atendido aos padrões de identidade e qualidade, as dez marcas de leite UHT integral comercializado no Rio Grande do Sul atendem as especificações quanto à qualidade microbiológica, demonstrando ser um produto seguro do ponto de vista sanitário.

Extraction is required to separate and concentrate trace level analytes from the sample matrix prior to gas chromatography (GC). Classical extraction procedures utilise large amounts of hazardous solvents, generate waste, and sensitivity limitations are associated with the injection of microlitre amounts of the final solvent extract. In response to real world challenges, and to overcome the problems associated with solvent extraction, novel silicone rubber (polydimethylsiloxane (PDMS)) samplers were developed for solvent free enrichment of trace level analytes from indoor air, contaminated soil, desert soil, ultra high temperature (UHT) milk and Pinotage wine. Versatile PDMS samplers as a loop, a multichannel trap, or a denuder for trace environmental forensics, geochemical and aroma investigations are presented. A unique off-line multidimensional GC approach involving heart-cut gas chromatographic fraction collection is described, as is off-line olfactory assessment of recombined heart-cuts for synergistic odour effects. PDMS loop samplers were used for the extraction of DDT (1,1,1- trichloro-2,2-bis(p-chlorophenyl)ethane) and its associated environmental pollutants from soil samples. Miniature denuder samplers accomplished separate concentration of vapour phase and of particulate phase fractions of DDT and its associated environmental pollutants from indoor air, in a single step. Ratios of airborne p,p’-DDD/p,p’-DDT and of o,p’-DDT/p,p’-DDT are unusual and do not match the ideal certified ingredient composition required of commercial DDT. Results suggest that commercial DDT used for indoor residual spraying may have been compromised with regards to insecticidal efficacy, demonstrating the power of this new environmental forensics tool. Multichannel PDMS trap samplers were used in a unique heart-cut multidimensional GC approach for off-line enantiomeric separation of o,p’-DDT and o,p’-DDD in air and soil. This alternative multidimensional method is compared to the complementary technique of comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detection (GCxGC-TOFMS). PDMS loop samplers were also employed for the solvent free extraction of hydrocarbons from desert soil to investigate, for the first time, a possible geochemical origin of the enigmatic fairy circles of Namibia. It is proposed that microseepages of natural gas and low volatility hydrocarbons are expressed at the surface as a geobotanical anomaly of barren circles and circles of altered vegetation. Multichannel PDMS trap samplers were utilised for sampling of the headspace of UHT milk and of Pinotage wine, and to study off-line, using a portable olfactometer, synergistic effects between recombined heart-cut aroma compounds. Olfactory results show that a synergistic combination of 2- heptanone and 2-nonanone was responsible for a pungent cheese-like odour in UHT milk, while a synergistic combination of furfural and 2-furanmethanol was responsible for a roast coffee bean-like odour in coffee style Pinotage wine. The small, low cost samplers are quick and easy to assemble and they fit commercial thermal desorber systems. The PDMS samplers are reusable. Solvent extraction of the sampling materials, extract clean-up and pre-concentration are not required. Thus, potential loss of analyte, introduction of contaminants and waste disposal are minimised. Solvent free thermal desorption permits transfer of the entire sample mass to the cooled injection system (CIS) inlet of a GC resulting in greater sensitivity when compared to injection of microlitre amounts of a solvent extract. This allowed for sampling of smaller sized soil samples, shorter air sampling times and lower air sampling flow rates when compared to solvent based methods. / Thesis (PhD)--University of Pretoria, 2013. / Chemistry / unrestricted