Functional and antioxidant properties of hydrolysates of sardine (S. pilchardus) and horse mackerel (T. mediterraneus) for the microencapsulation of fish oil by spray-drying.

The functionality of fish protein hydrolysates (FPH) for the microencapsulation of fish oil was investigated. Muscle protein from sardine (Sardina pilchardus) and horse mackerel (Trachurus mediterraneus) was hydrolysed using Alcalase or trypsin. Physically stable emulsions suitable for spray-drying were obtained when using FPH with a degree of hydrolysis of 5%. Microencapsulation efficiency amounted to 98±0.1% and oxidative stability of the encapsulated oil over a period of twelve weeks was in a similar range as it is reported for other matrix systems. Therefore, the suitability of FPH for use in spray-dried emulsions has been shown for the first time. Since no clear correlation between the antioxidative activity of the FPH and the course of lipid oxidation could be established future research is required to more specifically characterise the molecular structure of the peptides and its impact on protein alteration and role in lipid oxidation.

Turbidity in oil-in-water-emulsions - Key factors and visual perception.

The aim of the present study is to systematically describe the factors affecting turbidity in beverage emulsions and to get a better understanding of visual perception of turbidity. The sensory evaluation of the human visual perception of turbidity showed that humans are most sensitive to turbidity differences between two samples in the range between 1000 and 1500 NTU (ratio) (nephelometric turbidity units). At very high turbidity values >2000 TU in NTU (ratio) were needed to distinguish between samples that they were perceived significantly different. Particle size was the most important factor affecting turbidity. It was shown that a maximum turbidity occurs at a mean volume - surface diameter of 0.2µm for the oil droplet size. Additional parameters were the refractive index, the composition of the aqueous phase and the presence of excess emulsifier. In a concentration typical for a beverage emulsion a change in the refractive index of the oil phase may allow the alteration of turbidity by up to 30%. With the knowledge on visual perception of turbidity and the determining factors, turbidity can be tailored in product development according to the customer requirements and in quality control to define acceptable variations in optical appearance.

Off-flavour masking of secondary lipid oxidation products by pea dextrin.

The aim of the present study was to evaluate the off-flavour masking potential of pea dextrin (PD) in emulsions rich in ω-3 and ω-6-fatty acids in comparison with maltodextrin (MD) and 2-hydroxypropyl-ß-cyclodextrin (HPBCD). After optimisation of the homogenisation procedure, stable emulsions were prepared and stored for up to eight weeks. The development of six secondary lipid oxidation products: propanal, 1-penten-3-one, 1-penten-3-ol, hexanal, (E,E)-2,4-heptadienal and (E,Z)-2,6-nonadienal, was monitored via headspace gas chromatography after solid-phase microextraction. Sensory evaluation of the emulsions was performed by a trained panel. PD already showed masking properties for propanal, 1-penten-3-one, hexanal and (E,E)-2,4-heptadienal during validation of the gas chromatographic analysis, but not for 1-penten-3-ol or (E,Z)-2,6-nonadienal. During storage, the course of lipid oxidation was similar in all emulsions as concluded from the hydroperoxide value. Results from the sensory evaluation confirmed a masking of rancid off-flavour. In conclusion, pea dextrin is suitable for masking off-flavour resulting from early stages of lipid oxidation.

Structure formation in sugar containing pectin gels - influence of tartaric acid content (pH) and cooling rate on the gelation of high-methoxylated pectin.

The aim of the study was the application of a recently published method, using structuring parameters calculated from dG'/dt, for the characterisation of the pectin sugar acid gelation process. The influence of cooling rate and pH on structure formation of HM pectin gels containing 65 wt.% sucrose were investigated. The results show that the structure formation process as well as the properties of the final gels strongly depended on both parameters. With increasing cooling rates from 0.5 to 1.0 K/min the initial structuring temperature slightly decreased and the maximum structuring velocity increased. The lower the cooling rates, the firmer and more elastic were the final gels. With increasing acid content (decreasing pH from 2.5-2.0) the initial structuring temperatures were nearly constant. The final gel properties varied visibly but not systematically. Gels with the lowest and highest pH were less elastic and weaker compared to those with medium acid concentrations.

Characterization of the spray drying behaviour of emulsions containing oil droplets with a structured interface.

The aim of this study was to characterize the process of atomization and drying of layer-by-layer emulsions containing lecithin (single layer emulsion) and lecithin/chitosan (bilayer emulsion) and the oxidative stability of the microcapsules during storage. For this purpose, the analysis of the emulsion spray droplet size during two-fluid nozzle and rotary atomization was carried out to identify suitable process parameters. The drying behaviour of single and bilayer emulsions was investigated by calculation of the volume flow density during single-droplet drying during acoustic levitation. In spray-dried solid particles, the oxidative stability in the single layer microcapsules was higher than in the bilayer microcapsules. This was partly attributed to lower microencapsulation efficiency in the bilayer microcapsules compared to the single layer microcapsules. Furthermore, it could be shown, that excess chitosan in the bulk carrier matrix affects the free volume elements and thus oxygen diffusion.

Monitoring of autoxidation in LCPUFA-enriched lipid microparticles by electronic nose and SPME-GCMS.

Electronic nose and SPME-GCMS were used to monitor the autoxidation in long chain polyunsaturated fatty acid (LCPUFA)-enriched lipid microparticles produced by spray congealing with ultrasonic nebulization, during storage at 20 degrees C up to 6 weeks with sufficient air supply and limited air supply. Conjugated dienes and peroxide value as well as secondary lipid oxidation products were analysed to follow the course of autoxidation. Principal Component Analysis evidenced that only MOS sensors but not MOSFET sensors contributed to the discrimination of the samples and facilitated the ability of the electronic nose to distinguish the LCPUFA-enriched lipid microparticles into two groups according to the different oxidative status. The selected MOS sensor responses correlated well with quantitative dominating volatile compounds (propanal and hexanal) and with volatile compounds which have been associated with fishy and rancid off flavour (1-penten-3-one, 1-penten-3-ol, 2,4-heptadienal and 2,6-nonadienal). Bread mix supplemented with the LCPUFA-enriched microparticles was analysed as an example for a LCPUFA supplemented food. Data from the present study indicate that the electronic nose can be used as a sensitive tool to evaluate the lipid oxidative status of LCPUFA-enriched microparticles. In supplemented foods like bread mix, matrix-related changes, which occur in supplemented and non-supplemented samples, make a clear distinction more difficult.

Extractable oil in microcapsules prepared by spray-drying: Localisation, determination and impact on oxidative stability.

Aim of the present study was to investigate the localisation of the extractable oil in spray-dried microencapsulated fish oil prepared under different spray-drying conditions and to investigate the impact on lipid oxidation upon storage. Confocal laser scanning microscopy, scanning electron microscopy and different extraction procedures revealed that the extractable oil in microencapsulated fish oil is mainly located on the surface and in oil droplets close to the surface. Consequently, different methods for determination of the different fractions are proposed. Lipid oxidation as determined by hydroperoxide content or anisidine value was higher in microcapsules with 50% oil load spray-dried at 210/90°C, propanal content was increased in samples with 30% oil load spray-dried at 210/90°C. The differences in stability could only partly be explained by the varying amount of extractable oil. It is concluded that the surface oil protects other fractions of the extractable oil and that the extractable oil cannot be used to predict shelf-life of microencapsulated oils.

Degradation of heterocyclic aromatic amines in oil under storage and frying conditions and reduction of their mutagenic potential.

Heterocyclic aromatic amines (HAA) were systematically studied concerning their partition behavior in water/oil-systems and their thermostability in different animal derived fats and vegetable oils. Partitioning of IQx-compounds and PhIP in water/oil systems was found to depend on the polarity defined by the molecular structure and on the pH-value of the aqueous phase. In particular, beta-carbolines norharman and harman showed a significant strong lipophilic character at alkaline pH. After heating in frying fats at 130 degrees C, contents of IQx compounds and PhIP were reduced by more than 40% and after heating at 180 degrees C less than 10% of the HAA initial concentration was recovered. By contrast, norharman and harman were much more stable under equivalent conditions. The present study leads for the first time to the conclusion that degradation of HAA in frying fats strongly correlates to the type of frying fat and is promoted by lipid oxidation products. Firstly, addition of hydroperoxides to model oils lead to a decrease of HAA during storage at 40 degrees C. Secondly, stability of HAA correlated with the content of unsaturated fatty acids in the oil, which is indicative for the oxidative stability of the medium. Degradation of HAA by heat treatment was associated with a reduction of their mutagenic potential towards strain TA98 of Salmonella typhimurium.

Mycotoxins in fruits, fruit juices, and dried fruits.

This review gives an overview of the presence of mycotoxins in fruits. Although several mycotoxins occur in nature, very few (aflatoxins, ochratoxin A, patulin, Alternaria toxins) are regularly found in fruits. It has been shown that the presence of fungi on fruits is not necessarily associated with mycotoxin contamination. The formation of mycotoxins depends more on endogenous and environmental factors than fungal growth does. Mycotoxins may remain in fruits even when the fungal mycelium has been removed. Depending on the fruit and the mycotoxin, the diffusion of mycotoxins into the sound tissues of fruits may occur. The influence of the selection and storage of fruits and the influence of different processing steps involved in the production of fruit juices and dried fruits on possible mycotoxin contamination is described. It is shown that the careful selection, washing, and sorting of fruits is the most important factor in the reduction of mycotoxin contamination during the production of fruit juices. The processing of fruits does not result in the complete removal of mycotoxins.

[Not Available]. / Qualitätssichernde Maßnahmen hinsichtlich Mykotoxinen in der Getreidemühle.

In the present study the quality management system of 39 milling companies was investigated regarding the analysis and the prevention of mycotoxin contamination. 21 companies- mainly companies with a high processing volume - established a quality management system according to DIN EN ISO 9000ff. In view of previous studies the data indicated an improvement of quality management systems in the milling industry during the last years. Nevertheless some powerful instruments of preventive quality management like a supplier assessment have still not been efficiently used in many companies. The monitoring of mycotoxins or the participation in existing monitoring programmes is mainly limited to companies with a high production volume. It is recommended that monitoring programmes should become more attractive for small- and medium-sized companies. Further the development of quality management systems for small and medium-sized companies is required.

Selective fortification of lysinoalanine, fructoselysine and N epsilon-carboxymethyllysine in casein model systems.

In the present study, a promising strategy to study nutritional effects of selected chemical reaction products formed in heat treated protein containing foods is addressed. In due course, a selective fortification of different marker compounds for lysine damage in casein-sugar mixtures was performed to provide model systems being applicable to investigate biological effects of the cross-link lysinoalanine (LAL), the MRPs fructoselysine (FL) and N epsilon-carboxymethyllysine (CML) in a casein-linked preparation. The three different model proteins, casein-LAL, casein-FL and casein-CML were prepared by heating casein either in strong alkaline conditions at 105 degrees C for 1 h, in the presence of glucose at 65 degrees C for 68 h, or in the presence of glyoxylic acid at 37 degrees C for 19 h. Finally, the degree of lysine modification achieved was 39%, 75% and 55% for the casein-LAL, casein-FL and casein-CML, respectively. The calculation of lysine recovery and the respective analysis of each single modified casein (LAL-, FL- and CML-MP) for the selected fortified compound and each other compound vice versa proved that the individual procedure provides a specific fortification for LAL, FL and CML, respectively. The modified proteins are suitable as reference model proteins to be investigated for specific biological and toxicological effects of casein-linked LAL, FL and CML.

Effect of dietary fats rich in lauric, myristic, palmitic, oleic or linoleic acid on plasma, hepatic and biliary lipids in cholesterol-fed hamsters.

Effects of different dietary fats on plasma, hepatic and biliary lipids were determined in male golden Syrian hamsters (Mesocricetus auratus) fed on purified diets for 7 weeks. Diets were made by blending different fats containing characteristic fatty acids: butter (14:0 + 16:0), palm stearin (16:0), coconut oil (12:0 + 14:0), rapeseed oil (18:1), olive oil (18:1) and sunflowerseed oil (18:2). In all diets except the sunflowerseed oil diet dietary 18:2 was held constant at 2% energy. Total fat supplied 12% of energy and cholesterol was added at 4 g/kg diet. Plasma cholesterol and triacyglycerol concentrations were increased by dietary cholesterol. After 7 weeks, plasma cholesterol concentrations were highest with the palm stearin, coconut oil and olive oil diets (8.9, 8.9 and 9.2 mmol/l) and lowest with the rapeseed oil and sunflowerseed oil diets (6.7 and 5.5 mmol/l) while the butter diet was intermediate (8.5 mmol/l). Hepatic cholesterol concentration was highest in hamsters fed on the olive oil diet and lowest with the palm stearin diet (228 v. 144 mumol/g liver). Biliary lipids, lithogenic index and bile acid profile of the gall-bladder bile did not differ significantly among the six diets. Although the gallstone incidence was generally low in this study, three out of 10 hamsters fed on the palm stearin diet developed cholesterol gallstones. In contrast, no cholesterol gallstones were found with the other diets. Rapeseed and sunflowerseed oils caused the lowest plasma cholesterol and triacyglycerol concentrations whereas olive oil failed to demonstrate a cholesterol-lowering effect compared with diets rich in saturated fatty acids. Since 18:2 was kept constant at 2% of energy in all diets, the different responses to rapeseed and olive oils could possibly be attributed to their different contents of 16:0 (5.6% v. 12.8% respectively). Other possible explanations are discussed.