Fingerprint Volatile Organic Compounds (VOC) analysis in Goat’s Milk and Halloumi Cheese as Marker for Authentication of Region of Origin

Goats’ milk is responsible for unique traditional products such as Halloumi cheese. The characteristics of Halloumi depend on the original features of the milk and on the conditions under which the milk has been produced such as feeding regime of the animals or region of production. Using a range of milk (33) and Halloumi (33) samples collected over a year from three different locations in Cyprus (A, Anogyra; K, Kofinou; P, Paphos), the potential for fingerprint VOC analysis as marker to authenticate Halloumi was investigated. This unique set up consists of an in-injector thermo desorption (VOCtrap needle) and a chromatofocusing system based on mass spectrometry (VOCscanner). The mass spectra of all the analyzed samples are treated by multivariate analysis (Principle component analysis and Discriminant functions analysis). Results showed that the highland area of product (P) is clearly identified in milks produced (discriminant score 67%). It is interesting to note that the higher similitude found on milks from regions “A” and “K” (with P being distractive; discriminant score 80%) are not ‘carried over’ on the cheeses (higher similitude between regions “A” and “P”, with “K” distinctive). Data have been broken down into three seasons. Similarly, the seasonality differences observed in different milks are not necessarily reported on the produced cheeses. This is expected due to the different VOC signatures developed in cheeses as part of the numerous biochemical changes during its elaboration compared to milk. VOC however it is an additional analytical tool that can aid in the identification of region origin in dairy products.

Changes in quality and safety attributes throughout long term storage of tomato juice processed by high pressure.

Tomato is the second most widely grown vegetable crop across the globe and it is one of widely cultivated crops in Sri Lanka. However, tomato industry in Sri Lanka facing a problem of high postharvest loss (54%) during the glut coupled with heavy revenue loss to the country by importing processed products. The aim of this work is to develop shelf-stable tomato product with maximum quality characteristics using high pressure processing (HPP). Tomato juice with altered and unaltered pH was processed using HPP at 600 MPa for 1 min after blanching (90 oC/2 min). As a control tomato juice was subjected to thermal processing (TP) at 95 oC /20 min. Processed samples were stored under 20oC and 28oC for 9 month period and analysed for total viable count (TVC) and instrumental colour (L, a, b) value at 0,1,2 3, and 4 week and 2, 3, 6 and 9 months interval. The raw juice sample had initial 6.69 log10 CFU/ml and both TP and HPP caused a more than 4.69 log10 reduction in the TVC of juice and microbial numbers remained low throughout the storage period even at 3 months after storage irrespective of the storage temperature. Both TP and HPP treated samples had the redness ⤘a value’ of 14.44-17.15 just after processing and showed non-significant reduction with storage in all the treatments after 3 months. The storage study results and discussed in relation to the end goal and compared with the literature.

Secular trends in reported portion size of food and beverages consumed by Irish adults

The present analysis aimed to investigate the changes in the reported portion sizes (PS) of foods and beverages commonly consumed by Irish adults (18-64 years) from the North South Ireland Food Consumption Survey (NSIFCS) (1997-2001) and the National Adult Nutrition Survey (NANS) (2008-10). Food PS, which are defined as the weight of food (g) consumed per eating occasion, were calculated for comparable foods and beverages in two nationally representative cross-sectional Irish food consumption surveys and were published in NSIFCS and NANS. Repeated measure mixed model analysis compared reported food PS at the total population level as well as subdivided by sex, age, BMI and social class. A total of thirteen commonly consumed foods were examined. The analysis demonstrated that PS significantly increased for five foods ('white sliced bread', 'brown/wholemeal breads', 'all meat, cooked', 'poultry, roasted' and 'milk'), significantly decreased for three ('potatoes', 'chips/wedges' and 'ham, sliced') and did not significantly change for five foods ('processed potato products', 'bacon/ham', 'cheese', 'yogurt' and 'butter/spreads') between the NSIFCS and the NANS. The present study demonstrates that there was considerable variation in the trends in reported food PS over this period.

Characterisation of melt processed nanocomposites of Polyamide 6 subjected to uniaxial-drawing

In this paper, the processing and characterization of Polyamide 6 (PA6) nanocomposites containing graphite nanoplatelets (GNPs) is reported. PA6 nanocomposites were prepared by melt-mixing using an industrial, co-rotating, intermeshing, twin-screw extruder. A bespoke screw configuration was used that was designed in-house to enhance nanoparticle dispersion into a polymer matrix. The effects of nano-filler type (xGnPTM M-5 and xGnPTM C-500), nano-filler content, and extruder screw speed on the bulk properties of the PA6 nanocomposites were investigated. The crystalline structures of PA6 nanocomposites are related to thermal treatment, stress history and the presence of moisture and nanofillers. DSC, Raman and XRD studies show an increase in crystallinity with increasing GNP content and a phase transformation between α-form to γ-form crystals as a result of the heterophase nucleation effect. The effect of uniaxial stretching on PA6 nanocomposites was investigated by drawing specimens heated at temperatures below the melting temperature. DSC and Raman studies on the drawn samples show an increase in yield stress as the GNP content increases due to the strain induced crystallization and γ—β transition during stretching. The rheological response of the nanocomposites resemble that of a ‘pseudo-solid’, rather than a molten liquid, and analysis of the rheological data indicates that a percolation threshold was reached at GNP contents of between 10–15wt%. An increase in tensile modulus of as much as 412% was observed for PA6/C-500 xGnPTM composites, at a filler content of 20wt%. The enhancement of Young’s modulus and yield stress can be attributed to the reinforcing effect of GNPs and their uniform dispersion in the PA6 matrix. The electrical conductivity of the composite also increased with increasing GNP content, with an addition of 15wt% GNP resulting in a 6 order-of-magnitude increase in conductivity. The effects of uniaxial-drawing and the inclusion of multiple nano-filler varieties on the electrical and mechanical properties are currently under investigation.

Processability, structural evolution and properties of melt processed biaxially stretched HDPE/MWCNT nanocomposites

Biaxial stretching of melt mixed high density polyethylene (HDPE)/multiwalled carbon nanotube (MWCNT) nanocomposites was conducted in the melt state at different stretching ratios (SRs). The addition of MWCNTs leads to significant strain hardening in the HDPE, greatly improving the stability and thus processability of the stretching process. Scanning electron microscopy shows that the MWCNTs in the polymer matrix are gradually disentangled and randomly oriented in the stretching plane with increasing SRs. All the stretched samples exhibit an increase in crystallinity (about 10%) due to strain induced crystallization and a broadened distribution of crystallite size according to the XRD and DSC results. The mechanical properties of the composites improve with increasing SRs, while they drop off after a SR of 2.5 for the neat HDPE which is likely to be due to the relaxation of polymer chains prior to solidification. The presence of the MWCNTs appears to inhibit this relaxation thus helping to maintain the orientation and mechanical properties at high SRs. The modulus, yield strength and breaking strength of stretched composites with 8 wt% MWCNTs increase by approximately 54%, 85% and 193% respectively compared with the neat HDPE at a SR of 3. The electrical percolation threshold for the unstretched material occurs at 1.9 wt% MWCNTs. As SR increases, the values of critical concentration increase from 1.9 wt% to 4.9 wt% implying the destruction of conductive networks due to an increased inter-particle distance. A loading of 6 wt% MWCNTs is sufficient to ensure that the sheet conductivity is robust to changes in the SR. Decreased values of critical exponent from 1.9 to 1.1 and morphological investigation reveal a transformation of the system structure from three dimensional to two dimensional as SR increases.

Structure, mechanical, and electrical properties of high-density polyethylene/multi-walled carbon nanotube composites processed by compression molding and blown film extrusion

The structure and properties of melt mixed high-density polyethylene/multi-walled carbon nanotube (HDPE/MWCNT) composites processed by compression molding and blown film extrusion were investigated to assess the influence of processing route on properties. The addition of MWCNTs leads to a more elastic response during deformations that result in a more uniform thick-ness distribution in the blown films. Blown film composites exhibit better mechanical properties due to the enhanced orientation and disentanglement of MWCNTs. At a blow up ratio (BUR) of 3 the breaking strength and elongation in the machine direction of the film with 4 wt % MWCNTs are 239% and 1054% higher than those of compression molded (CM) samples. Resistivity of the composite films increases significantly with increasing BURs due to the destruction of conductive pathways. These pathways can be recovered partially using an appropriate annealing process. At 8 wt % MWCNTs, there is a sufficient density of nanotubes to maintain a robust network even at high BURs.

Major and trace elements in milk and Halloumi cheese as markers for authentication of goat feeding regimes and geographical origin

Sixty samples of milk, Halloumi cheese and local grazing plants (i.e. shrubs) were collected over a year from dairy farms located on three different locations of Cyprus. Major and trace elements were quantified using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Milk and Halloumi cheese produced in different geographical locations presented significant differences in the concentration of some of the elements analysed. Principal component analysis showed grouping of samples according to the region of production for both milk and cheese samples. These findings show that the assay of elements can provide useful fingerprints for the characterisation of dairy products.

Impact of long-term storage at ambient temperatures on the total quality and stability of high-pressure processed tomato juice

High-pressure processing (HPP) can produce tomato juice of high quality and safety with a short shelf life under refrigeration temperatures. Long-term higher temperature storage studies are rare and temperature tolerant products are challenging to develop. The effect of high-pressure processing (HPP) on the total quality (colour, microbial counts, phytochemical levels, antioxidant and enzymatic activities) and stability (retention over time) of tomato juice during long-term storage was investigated. Thermal processing (TP) was used as a control treatment, and overall, two different ambient conditions (20 °C and 28 °C) were tested. Immediately after processing, HPP products proved superior to TP ones (enhanced redness, total carotenoids and lycopene, stable total phenols and inactivation of pectin methyl esterase). During initial storage (30 d) most quality attributes of HPP juice remained stable. Prolonged storage, however, led to losses of most quality attributes, although HPP (20 °C) showed lower quality degradation rate constants comparison to TP and HPP (28 °C). Industrial Relevance: There is a demand for ambient stable tomato products, especially in some parts of the world, and current industrial practices (canning, pasteurisation) either compromise in product quality or require refrigeration conditions. High-pressure processing has been investigated as milder technology, with a potential to deliver superior quality. The drawback is that is also requires chill storage. The results of this study show how quality parameters behave in a high-pressured tomato product and pave the way for further development that could optimise this technology. This could be of economic importance for the tomato juice industry to develop new products stable in ambient temperatures and perhaps beneficial for cutting down the refrigeration costs under specific conditions.

Microplasma Processed Ultrathin Boron Nitride Nanosheets for Polymer Nanocomposites with Enhanced Thermal Transport Performance

This paper reports on the enhancement of the thermal transport properties of nanocomposite materials containing hexagonal boron nitride in poly (vinyl alcohol)through room-temperature atmospheric pressure direct-current microplasma processing. Results show that the microplasma treatment leads to exfoliation of the hexagonal boron nitride in isopropyl alcohol, reducing the number of stacks from >30to a few or single layers. The thermal diffusivity of the resulting nanocomposites reaches 8.5 mm2 s-1, 50 times greater than blank poly (vinyl alcohol) and twice that ofnanocomposites containing non-plasma treated boron nitride nanosheets. From TEM analysis, we observe much less aggregation of the nanosheets after plasma processing along with indications of an amorphous carbon interfacial layer which may contribute to stable dispersion of boron nitride nanosheets in the resulting plasma treated colloids.

Development of sialons colloidally processed in aqueous medium

Desenvolveu-se um novo método de processamento coloidal em meio aquoso para consolidar cerâmicos de α-Y-SiAlON, os quais foram sinterizados por prensagem isostática a quente (HIP) e por spark plasma sintering (SPS). Preparou-se com sucesso uma suspensão aquosa de pós precursores de YSiAlON (Si3N4, Al2O3, Y2O3 e AlN), temporariamente estável, usando Dolapix PC21 como dispersante, permitindo a fabricação de pós granulados pela técnica de aspersão-congelamento-liofilização e a consolidação de corpos em verde por enchimento por barbotina. Avaliou-se o efeito do excesso de oxigénio introduzido pelo processamento aquoso no desenvolvimento microestrutural e nas propriedades mecânicas. Os corpos de Y-SiAlON consolidados por enchimento por barbotina e sinterizados por HIP a 1800ºC apresentaram microestruturas e propriedades mecânicas similares a corpos consolidados por prensagem a seco. Estes materiais exibiram densificação completa, dureza Vickers máxima de 2003 e tenacidade à fractura (método SEVNB) máxima de 5.20 MPam1/2. Foi ainda possível estabelecer uma relação estreita entre o aumento do conteúdo em oxigénio das amostras sinterizadas e a diminuição da tenacidade à fractura. Na tentativa de melhorar a tenacidade à fractura dos materiais, procedeu-se à incorporação nas suspensões de sementes de Ca-α-SiAlON de geometria alongada produzidas por síntese por combustão, adicionadas como agentes de reforço. A síntese por combustão realizada em larga escala (cargas até 1 kg) não produziu efeitos negativos óbvios nos produtos da reacção. Investigara-se os efeitos da adição de 5 % em peso de sementes nas propriedades mecânicas e no desenvolvimento microestrutural de amostras densificadas por HIP. Em comparação com os materiais sem sementes, a tenacidade à fractura (método SEVNB) aumentou 13%, mas a dureza Vickers resultou 14,5% inferior. A sinterização por SPS permitiu obter densificação completa a temperaturas tão baixas como 1600ºC a partir dos pós granulados de Y-SiAlON sem a adição extra de Y2O3 para aumentar o teor de fase líquida. Os materiais sinterizados a 1700ºC e 1600ºC mostraram valores máximos de tenacidade à fractura de 4.36 e 4.20 MPam1/2 (método SEVNB), e de dureza Vickers de 2089 e 2084, respectivamente. Esta técnica de sinterização permitiu ainda obter corpos sinterizados translúcidos com uma transmitância máxima de 61% numa amostra de 2mm de espessura. Os corpos translúcidos apresentaram dureza Vickers de 2154 e tenacidade à fractura 3.74 MPam1/2 (método SEVNB).

Production of laminar extrudates containing particles of a model drug processed by supercritical fluids

Tese de doutoramento, Farmácia (Tecnologia Farmacêutica), Universidade de Lisboa, Faculdade de Farmácia, 2015

Optimization of bioplastics production from cheese whey

Dissertation presented in partial fulfillment of the requirements for the degree of Master in Biotechnology

Production of polyhydroxyalkanoates from cheese whey - pH effect on the acidogenic fermentation stage and nutrient needs of the culture selection stage

Dissertação para obtenção do Grau de Mestre em Biotecnologia

Bioconversion of cheese whey into polyhydroxyalkanoates

Dissertação para obtenção do Grau de Doutor em Engenharia Química e Bioquímica