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RESULTS AND DISCUSSION
Scanning Electron Microscopy showed that -carrageenan containing samples had a less homogeneous aqueous phase distribution than the control. This was to be expected as -carrageenan increased the viscosity and most likely, induced gelation and increased the size of the aqueous droplets during spread manufacture. Texture evaluation showed that the firmness of reduced-fat W/O spreads increased with storage period. For instance, the control showed an increase in firmness from 11.1 to 17.6 N after 90 days, resulting in a more structured crystal association due to post-crystallisation processes. Addition of Copper did not have a significant effect on the texture of spreads measured at 4.5C. Small-scale rheological assessment (non-destructive to sample) showed that the storage modulus (G) of the control increased from 127 to 220 kPa during storage time, whereas the G of the sample containing 7.5 g.kg-1 increased from 99.5 to 175 kPa. Although the melting temperature increased with storage, addition of -carrageenan reduced the melting temperature from 64.5 to 57C after 15 days, probably due to the variation in the emulsion properties, with -carrageenan having a destabilising effect. Peroxide values of all samples increased noticeably during storage period. Samples containing Copper (1-10 mM) reached an unacceptable level of oxidation (2.27 and 3.62 mEq O/kg, respectively) after one day of storage.
The rheology and microstructure of W/O spreads was modified by -carrageenan. The addition of -carrageenan improved the melting properties of the spreads, but it did not inhibit oxidation of the fat. More complex microgel-containing systems are necessary for the fortification of dairy spreads with metallic cations.
The authors acknowledge the Department of Agriculture and Food under the Food Institutional Research Measure (National Development Plan) and National Food Imaging Centre.
1Benichou, A., Aserin, A. and Garti, N. (2002). J. Dispersion Sci. & Technol. 23: 93-123
2Berger, K. G., Jewell, G. G. and Pollitt, R. J. M. (1979). In Vaughan, J. G. (Ed.) Food Microscopy (p.445-497). London, Academic Press
3Bot, A. and Vervoort, S. (2006). In Williams, P. A. and Phillips, G. O. (Eds.) Gums and Stabilisers for the food industry 13 (p. 381-394). Cambridge, RSC Publishing
4Chronakis, I. S. and Kasapis, S. (1995). Lebensm.-Wiss.-Technol. 28: 488-494
5Mounsey, J. S., Stathopoulos, C. E., Chockchaisawasdee, S., O’Kennedy, B. T., Gee, V., & Doyle, J. (2008). European Food Research and Technology, 227, 675-681.
POPULATION BALANCE MODELLING OF GRANOLA BREAKAGE DURING PNEUMATIC CONVEYING SYSTEMS
N. Baş, P.B. Pathare, E.P. Byrne
Department of Process and Chemical Engineering, University College, Cork
In the food and process industries, population balances can be applied to describe the size distribution of dispersed phase systems. Systems such as aggregation and breakage processes contain particles which are continually being created and destroyed. Granola is an aggregated food product which serves as a breakfast cereal or snack consisting of oats, cereals, rice and honey. Particle breakage of granola can occur during pneumatic conveying as product is transferred as part of the production process on its way to packaging. Such breakage occurs as a result of particle-particle and particle-wall collisions. In this work, a population balance for the breakage of granola that is conveyed through a pipeline conveying rig is introduced by defining certain parameters associated with aggregate formation such as granulator mixing speed and time, conveying pressure and pipeline geometry. When initial particle size distribution is known and appropriate parameters are defined population balance modelling can be a useful predictive tool in determining particle size distribution over time during the breakage of granola and indeed other aggregate food products subjected to breakage forces.
In the food and process industries population balances can be applied to describe the size distribution of dispersed phase systems. In particle technology, the most common particle property is particle size and population balances can be applied to model changes in the particle size distribution (PSD) during the process. The PSD that allows comparisons of populations is properly defined by means of a density function1. Systems such as aggregation and breakage processes contain particles which are continually being created and destroyed. Granola is an aggregated food product which serves as a breakfast cereal or snack consisting of oats, cereals, rice and honey. Particle breakage of granola can occur during pneumatic conveying as product is transferred as part of the production process on its way to packaging. Such breakage occurs as a result of particle-particle and particle-wall collisions.
MATERIALS AND METHODS
Modelling the breakage of granola in a conveying system can be achieved by constructing a population balance equation (PBE) in the form of mass balance on particles2. The model includes the influence of conveying pressure, exposure time and pipeline geometry, and is also related to parameters associated with aggregate formation such as granulator mixing speed and time. The aggregates were formed in a high shear mixer subject to impeller agitation at 200rpm, 300rpm and 400rpm for 9 minutes and were then baked in an oven for 10 minutes. The resultant granola was propelled through a pipeline at a number of different flow rates. Trials were carried out by applying compressed air pressures. PBE for the breakage process can be defined as3;
where t is time, x, y are particle sizes, b(x) is the breakage frequency, p(x, y) is the fragment size distribution and f(x, y) is mass density function.
Results and Discussion
Parameters that have significant roles on the breakage of granola during pneumatic conveying systems were found to be; compressed air pressure, flow geometry, velocity, agitation intensity during formation of granules and binder content. It was observed that increasing agitation impeller speed resulted in a decreased level of breakage of the granola propelled through the conveying rig. However, high agitation speed causes denser granola particles. On the other hand it was seen that the breakage is more frequent in a pipeline with a 90o bend than a straight pipeline.
In this work population balance modeling (PBM) is applied to the breakage of granola during pneumatic conveying systems. PBM is used to describe changes in particles which have one or more different properties. The solution of the PBEs was carried out by means of a discretization. When the size range of the system was divided into a reasonable number of states, the population balance modelling exhibited a good approximation for predicting evolution of the particle size distribution (PSD) over time during the breakage of the granola aggregate food product.
The authors would like to acknowledge the National Development Plan, through the Food Institutional Research Measure, administered by the Department of Agriculture, Fisheries & Food, Ireland for providing funding for this work.
1 Litster, J., Ennis, B., 2004. The Science and Engineering of Granulation Processes. Kluwer Academic Publishers, Netherlands.
2 Randolph, A., Larson, M., 1964. A population balance for countable entities. Canadian Journal of Chemical Engineering 42, 280–281.
3 Ramkrishna, D. (2000). Population Balances Theory and applications to Particulate Systems in Engineering. Academic Press, USA.
THE EFFECT OF NOVEL PROTEIN-CARBOHYDRATE FOOD COMPLEXES ON GLUCAGON-LIKE PEPTIDE 1 SIGNALLING IN VITRO
C. Bruen, 1, 2 F. O’Halloran1, M. Fenelon 1, K. Cashman2 and L. Giblin1
1Teagasc, Moorepark Food Research Centre, Fermoy, Co. Cork Ireland
2Department of Food and Nutritional Science, University College Cork, Ireland
Glycaemia is defined as the concentration of glucose in the bloodstream. Studies have shown that ingestion of carbohydrates in combination with proteins can result in a lower glycaemic response than ingestion of carbohydrates alone. A lower glycaemic response is favourable as it results in a steady release of glucose into the bloodstream. This study investigates the response of the incretin peptide glucagon-like peptide 1, GLP-1, to novel protein carbohydrate complexes. The enteroendocrine cell line NCI-H716 was incubated for18hours with various food complexes. In agreement with previous studies, levels of secreted GLP-1 peptide, increased upon exposure of the cells to essential amino acids. However expression of the proglucagon gene, of which exon 4 codes for GLP-1, remained unaffected as determined by Real time-PCR with absolute quantification. In addition, the level of proglucagon gene expression was unaffected by cell exposure to any of the four β-lactoglobulin/starch hydrolysates tested.
Glucose homeostasis is finely controlled through the production and secretion of insulin. Blood glucose levels are usually maintained between 4-5.5 mmol/L. The incretin hormones glucagon-like peptide 1 (GLP-1) and glucose-dependant insulinotropic polypeptide (GIP) are produced by the intestinal mucosa in response to nutrient ingestion.1 These hormones travel to the pancreas where they stimulate insulin release. This release combats the rise in glucose levels to between 8-10 mmol/L within 30 minutes of ingesting a carbohydrate-rich meal2. GLP-1 is secreted from intestinal L-cells localised primarily in the ileum and colon3. NCI-H716 is an enteroendocrine colonic cell line which secretes GLP-1 in response to nutrients4. The objective of this study was to examine the effects of various food components on gene expression and peptide levels of GLP-1 in vitro.
MATERIALS AND METHODS
NCI-H716 cells were exposed for 18hours to media only (Dulbecco’s Modified Eagles Media alone) or media containing the test compounds. Six test compounds were evaluated in this experiment: 3.47g/L essential amino acids, 6.9g/L essential amino acids, β-lactoglobulin digested with pepsin, β-lactoglobulin digested with pepsin and corolase, β-lactoglobulin and starch digested with pepsin and amylase and β-lactoglobulin and starch digested with pepsin, amylase and corolase. Total RNA extraction was performed as described by Roche Diagnostics Ltd. 1g of quality assessed total RNA was reverse transcribed in the presence of random hexamers. Real time PCR was performed using the Lightcycler and Sybr green technology with proglucagon gene specific primer pairs. Absolute quantification was performed using known concentrations of a 297bp cloned fragment from exon 4 of the proglucagon gene. GLP-1 ELISA was performed using cell supernatant collected via PMSF as per the manufacturers’ instructions (Linco Research).
RESULTS AND DISCUSSION
Proglucagon gene expression was similar for all four hydrolysates tested. In addition, proglucagon gene expression was not upregluated in response to 3.47g/L or 6.9g/L essential amino acids. However GLP-1 ELISA data demonstrated an increase in GLP-1 peptide secreted from NCI-H716 cells in response to 3.47g/L essential amino acids This is in agreement with previous studies4 .
Essential amino acids were shown to increase the secretion of GLP-1 peptide from NCI-H716 cells. However, parallel gene expression studies showed that the proglucagon gene was not upregulated in response to the essential amino acids nor any of the hydrolysates tested. The results would suggest that the effect of essential amino acids on GLP-1 secretion occurs at a post-transcriptional level.
This work is funded by the Department of Agriculture under the Food Institutional Research Measure (FIRM). C. Bruen is in receipt of a Teagasc Walsh Fellowship.
1 Drucker, D.J. (2006). Cell Metabolism 3: 153-165.
2 Ranganath, L.R. (2008). Journal of clinical pathology 61: 401-9.
3 Aaboe, K., Krarup, T., Madsbad, S. and Holst, J.J. (2008). Diabetes, obesity & metabolism 11: 994-1003
4 Reimer, R.A. (2006). Journal of Endocrinology 191: 159-70.
THE EFFECT OF HIGH INTENSITY LIGHT PULSES (HILP) ON MICROBIAL INACTIVATION AND QUALITY ATTTRIBUTES OF APPLE JUICE
I.M.Caminiti, I. Palgan, A.Muñoz, F. Noci, P. Whyte, D.J. Morgan, D.A. Cronin, and
Agriculture and Food Science Centre, School of Agriculture, Food Science and Veterinary Medicine, College of Life Science, UCD Dublin, Belfield, Dublin 4
High intensity light pulses (HILP) is an emerging, non thermal technology, which uses short (100 – 400 μs), high-intensity light pulses of wavelengths from 200 to 1100 nm for food decontamination. In this study, reconstituted apple juice was exposed to HILP in a batch system for 2, 4 and 8 s and a frequency of 3 Hz. Samples were evaluated for microbial inactivation and selected quality attributes. Product acceptability was also evaluated by sensory analysis.
Microbiological analysis was performed by inoculating apple juice with Listeria innocua or Escherichia coli DH5-α. A significant reduction (P<0.01) in the bacterial population was found in both species after exposure to pulsed light while no significant differences were observed in most of the quality parameters examined. Antioxidant capacity, however, showed a decrease after the juice was exposed to pulsed light for 8 s. The same treatment also caused significant differences in the perceived flavour (P<0.001) versus the untreated juice or any other treatment. Results show that short time exposure to HILP could be a potential hurdle as part of a non-thermal processing strategy for preservation of reconstituted apple juice.
In recent years consumers’ demand for safe, minimally processed foods has increased the amount of research in the area of “non-thermal” processing technologies1.
High intensity light pulses (HILP) is an emerging technique capable of decontaminating food surfaces by killing microorganisms using short time (100 – 400 μs) pulses of an intense (>30000 times the intensity of daylight) broad spectrum light ranging from ultraviolet to infrared wavelengths2. Inactivation of microorganisms is largely due to the UV-C part of the light spectrum (200-280 nm), which induces irreversible changes to the DNA structure3, inhibiting the process of cell replication and eventually causing the death of the microorganism. The aim of this study was to evaluate the impact of HILP on microbial inactivation and quality attributes of apple juice reconstituted from concentrate.
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