M. O’Sullivan

Correlation of sensory bitterness in dairy protein hydrolysates: Comparison of prediction models built using sensory, chromatographic and electronic tongue data

Sensory evaluation can be problematic for ingredients with a bitter taste during research and development phase of new food products. In this study, 19 dairy protein hydrolysates (DPH) were analysed by an electronic tongue and their physicochemical characteristics, the data obtained from these methods were correlated with their bitterness intensity as scored by a trained sensory panel and each model was also assessed by its predictive capabilities. The physiochemical characteristics of the DPHs investigated were degree of hydrolysis (DH%), and data relating to peptide size and relative hydrophobicity from size exclusion chromatography (SEC) and reverse phase (RP) HPLC. Partial least square regression (PLS) was used to construct the prediction models. All PLS regressions had good correlations (0.78 to 0.93) with the strongest being the combination of data obtained from SEC and RP HPLC. However, the PLS with the strongest predictive power was based on the e-tongue which had the PLS regression with the lowest root mean predicted residual error sum of squares (PRESS) in the study. The results show that the PLS models constructed with the e-tongue and the combination of SEC and RP-HPLC has potential to be used for prediction of bitterness and thus reducing the reliance on sensory analysis in DPHs for future food research.

Cold-set whey protein microgels as pH modulated immobilisation matrices for charged bioactives

The ability of cold-set whey protein microgels to function as pH-sensitive immobilisation matrices for bioactives was investigated. A pH dependent interaction was confirmed between the microgels and charged bioactives and this binding was impeded by the presence of competing ions in the solution, suggesting an electrostatic interaction. The use of a computer generated prediction model for the pH-dependent association of the microgels and further bioactives (including cationic and anionic peptides) was validated. The prediction model was efficient at determining the pH at which the maximum microgel-bioactive interaction occurred. This study highlights the capabilities of these food-grade whey based microgels as matrices that enable the immobilisation of a variety of bioactives by a charge interaction, and shows the potential for these matrices to function as smart delivery systems, in which uptake and release of bioactives is facilitated by environmental pH change.

Kinetics of immobilisation and release of tryptophan, riboflavin and peptides from whey protein microbeads.

This study investigated the kinetics of immobilisation and release of riboflavin, amino acids and peptides from whey microbeads. Blank whey microbeads were placed in solutions of the compounds. As the volume of microbeads added to the solution was increased, the uptake of the compounds increased, to a maximum of 95% for the pentapeptide and 56%, 57% and 45% for the dipeptide, riboflavin and tryptophan respectively, however, the rate of uptake remained constant. The rate of uptake increased with increasing molecule hydrophobicity. The opposite was observed in the release studies, the more hydrophobic compounds had lower release rate constants (kr). When whey microbeads are used as sorbents, they show excellent potential to immobilise small hydrophobic molecules and minimise subsequent diffusion, even in high moisture environments.

Harnessing the Structure Modifying Potential of Pulsed Electric Fields (PEF) – Food Processing Examples in Product Stabilization, Process Acceleration and Compound Extraction

Pulsed electric fields (PEF) can electroporate eukaryotic and prokaryotic cells which can be used in food processing for product preservation and extraction of intracellular components. In this paper a number of potential processing applications for PEF will be considered. These will include its incorporation in hurdle preservation strategies, its use in the termination of enzyme hydrolysis of proteins, its application in the waste stream valorization through enhancing compound extraction and also its potential for accelerating processes such as meat tenderization or curing. In terms of product pasteurization, the paired combinations of novel technologies examined certainly inactivated more microorganisms than each technology alone but the effect of the combinations was largely additive or overlapping with few examples of synergy. In addition some combinations introduced high specific energy into products (in some cases higher than conventional UHT). In terms of product sterilization, PEF applied at temperatures of 120°C gave a slight though not significant increase in spore inactivation compared to thermal treatments. The use of PEF for endoprotease inactivation in bioactive compound production also proved to be very promising and could have application in hydrolyses termination especially where the resultant bioactives are heat labile. PEF pre-treatments of potato peel and brewers spent grain increased the extraction of glycoalkaloids and β-glucans respectively which is promising as conventional methods for the extraction of these compounds are expensive and the market value of the target compounds is high. In terms of its application in meat processing, PEF can have a positive impact on meat tenderization, though ageing/conditioning is still necessary. It has also been shown to accelerate the curing of meat when it is applied as a pre-treatment prior to curing. Overall, these applications are all promising though it remains to be seen which of these niche areas are likely to achieve significant commercial uptake.