title: Ultimate pH and storage related changes to sheepmeat odour and flavour

authors: Braggins, Terence John

abstract: Gas chromatography/mass spectrometry (GC/MS), gas chromatography/olfactometry and a trained sensory panel were used to study the effects of meat ultimate pH on the odour and flavour of cooked sheepmeat. As part of methods development, supercritical carbon dioxide elution was evaluated as an alternative to thermal desorption of volatile compounds from Tenax-T A traps, but this technique did not offer any significant advantage. In a separate study, the sensory panel and an emerging technology, an electronic nose, were used to investigate the changes in cooked meat odour and flavour arising from long term storage of chilled lamb legs in a carbon dioxide atmosphere.

Pre-slaughter injection of adrenalin was used to produce sheepmeats of normal (5.66), moderate (6.26) and high (6.81) ultimate pH. Meat with a moderate or high ultimate pH had a significantly lower overall cooking odour and flavour intensity, as assessed by the sensory pane, than sheepmeat of a more acceptable pH (5.66). Panellists also found that desirable odour and flavour notes decreased and undesirable ones increased as ultimate pH increased. Purge-and-trap GC/MS of fat rendered during cooking identified 57 (out of a total of 325) volatile compounds that significantly decreased in concentration with increasing meat pH. The most common of these compounds were aldehydes. GC/olfactometry identified 54 odour-active compounds, 10 of which were also found to be responsive to changes in meat ultimate pH. Most of these compounds were again aldehydes.

High ultimate pH raw meat which was titrated with hydrochloric acid to pH levels close to that of low ultimate pH had odour and flavour intensities comparable to those of normal (low) ultimate pH meat. Most of the volatile compounds found by GC/MS analysis to decrease in concentration with increasing ultimate pH did not have a reduced concentration after this downward pH adjustment. These results and parallel analyses of soluble protein, free amino acids and free fatty acids led to the conclusion that pH-related changes in the odour and flavour of cooked sheepmeat are probably mediated by direct pH effects during the cooking process, rather than by a pH-related development of odour and flavour precursors in raw meat before cooking begins.

Meat pH values of lamb legs increased significantly between 4 and 14 weeks storage in the CO₂ aging. Sensory panellist found there were significant storage time effects in “overall”, “sheepmeat”, and “sweet” odours of cooked meat. Panellists also detected a significant decrease in “sweet” and “roasty” flavours in the CO₂-packed lamb legs stored at -1.5°C compared with vacuum packed controls stored frozen (-35°C). Of particular concern, after 14 weeks chilled storage in CO₂, the intensity of a “livery/offaly” flavour was significantly higher than for the frozen-stored control.

The electronic nose could detect differences in headspace volatiles of both raw and cooked minces from meat subjected to the different storage treatments. The results suggest that, under these experimental conditions, the electronic nose was more discerning and possibly gave more reproducible results than sensory panellists. What relationship the electronic nose’s measurements have to human perception of odour has yet to be determined.

The multidisciplinary approach used in this thesis has helped to explain some of the variations in meat flavour quality important to the New Zealand meat industry.

text: Ultimate pH and storage related changes to sheepmeat odour and flavour Gas chromatography/mass spectrometry (GC/MS), gas chromatography/olfactometry and a trained sensory panel were used to study the effects of meat ultimate pH on the odour and flavour of cooked sheepmeat. As part of methods development, supercritical carbon dioxide elution was evaluated as an alternative to thermal desorption of volatile compounds from Tenax-T A traps, but this technique did not offer any significant advantage. In a separate study, the sensory panel and an emerging technology, an electronic nose, were used to investigate the changes in cooked meat odour and flavour arising from long term storage of chilled lamb legs in a carbon dioxide atmosphere.

Pre-slaughter injection of adrenalin was used to produce sheepmeats of normal (5.66), moderate (6.26) and high (6.81) ultimate pH. Meat with a moderate or high ultimate pH had a significantly lower overall cooking odour and flavour intensity, as assessed by the sensory pane, than sheepmeat of a more acceptable pH (5.66). Panellists also found that desirable odour and flavour notes decreased and undesirable ones increased as ultimate pH increased. Purge-and-trap GC/MS of fat rendered during cooking identified 57 (out of a total of 325) volatile compounds that significantly decreased in concentration with increasing meat pH. The most common of these compounds were aldehydes. GC/olfactometry identified 54 odour-active compounds, 10 of which were also found to be responsive to changes in meat ultimate pH. Most of these compounds were again aldehydes.

High ultimate pH raw meat which was titrated with hydrochloric acid to pH levels close to that of low ultimate pH had odour and flavour intensities comparable to those of normal (low) ultimate pH meat. Most of the volatile compounds found by GC/MS analysis to decrease in concentration with increasing ultimate pH did not have a reduced concentration after this downward pH adjustment. These results and parallel analyses of soluble protein, free amino acids and free fatty acids led to the conclusion that pH-related changes in the odour and flavour of cooked sheepmeat are probably mediated by direct pH effects during the cooking process, rather than by a pH-related development of odour and flavour precursors in raw meat before cooking begins.

Meat pH values of lamb legs increased significantly between 4 and 14 weeks storage in the CO₂ aging. Sensory panellist found there were significant storage time effects in “overall”, “sheepmeat”, and “sweet” odours of cooked meat. Panellists also detected a significant decrease in “sweet” and “roasty” flavours in the CO₂-packed lamb legs stored at -1.5°C compared with vacuum packed controls stored frozen (-35°C). Of particular concern, after 14 weeks chilled storage in CO₂, the intensity of a “livery/offaly” flavour was significantly higher than for the frozen-stored control.

The electronic nose could detect differences in headspace volatiles of both raw and cooked minces from meat subjected to the different storage treatments. The results suggest that, under these experimental conditions, the electronic nose was more discerning and possibly gave more reproducible results than sensory panellists. What relationship the electronic nose’s measurements have to human perception of odour has yet to be determined.

The multidisciplinary approach used in this thesis has helped to explain some of the variations in meat flavour quality important to the New Zealand meat industry.

year: 1996

title: Fully supervised training of Gaussian radial basis function networks in WEKA

authors: Frank, Eibe

subjects: Machine learning

abstract: Radial basis function networks are a type of feedforward network with a long history in machine learning. In spite of this, there is relatively little literature on how to train them so that accurate predictions are obtained. A common strategy is to train the hidden layer of the network using k-means clustering and the output layer using supervised learning. However, Wettschereck and Dietterich found that supervised training of hidden layer parameters can improve predictive performance. They investigated learning center locations, local variances of the basis functions, and attribute weights, in a supervised manner.

This document discusses supervised training of Gaussian radial basis function networks in the WEKA machine learning software. More specifically, we discuss the RBFClassifier and RBFRegressor classes available as part of the RBFNetwork package for WEKA 3.7 and consider (a) learning of center locations and one global variance parameter, (b) learning of center locations and one local variance parameter per basis function, and (c) learning center locations with per-attribute local variance parameters. We also consider learning attribute weights jointly with other parameters.

text: Fully supervised training of Gaussian radial basis function networks in WEKA Radial basis function networks are a type of feedforward network with a long history in machine learning. In spite of this, there is relatively little literature on how to train them so that accurate predictions are obtained. A common strategy is to train the hidden layer of the network using k-means clustering and the output layer using supervised learning. However, Wettschereck and Dietterich found that supervised training of hidden layer parameters can improve predictive performance. They investigated learning center locations, local variances of the basis functions, and attribute weights, in a supervised manner.

This document discusses supervised training of Gaussian radial basis function networks in the WEKA machine learning software. More specifically, we discuss the RBFClassifier and RBFRegressor classes available as part of the RBFNetwork package for WEKA 3.7 and consider (a) learning of center locations and one global variance parameter, (b) learning of center locations and one local variance parameter per basis function, and (c) learning center locations with per-attribute local variance parameters. We also consider learning attribute weights jointly with other parameters.

year: 2014

title: The Development and Evaluation of a Cultural Competency Training Programme for Psychologists Working with Māori: A Training Needs Analysis

authors: Waitoki, Waikaremoana

subjects: Māori

abstract: The purpose of this study was to develop and evaluate a cultural competency training programme for clinical psychology students to work with Māori consumers.  A pilot programme (study 1) was developed from the international and national cultural competency and bicultural training literature.  Following the pilot, it was identified that the programme could be made more robust by conducting a second study the training needs analysis using the critical incident technique.  Study two was conducted with 30 experienced clinical psychologists who had worked with Māori clients.
  
The training needs analysis sought to identify the awareness, knowledge and skills (AKS) that the experienced psychologists used in their practice with Māori.  An unexpected finding from study two was that the psychologists used distinctly Māori-cultural practices incorporating Māori tikanga and Māori knowledge with their clients even though they had little or no bicultural course content in their clinical training.  The data from the pilot programme, and the training needs analysis were used to refine the final workshop.  
The workshop was delivered to two university sites over a two-day period using intern clinical psychologist.  The programme evaluation had three components: (1) analysis of pre and post programme questionnaires; (2) analysis of the retrospective questionnaires (3) and an analysis of a participant’s case report on a Māori consumer. 
The themes that evolved from this research are that the critical incident technique is a useful way of identifying bicultural training material that would otherwise go unnoticed.  In relation to training evaluation, there is a real need to develop meaningful measures of bicultural competency acquisition for clinical students.  The finding advances the proposition that a distinct Māori psychology exists that could potentially challenge the relevance of Western psychology for Māori.  
A contextual theme underpinning bicultural training programmes is that training and practice occurs against the backdrop of Pākehā dominance in all aspects of academia and society. Consequently, there is a need to find a balance between Māori and Western psychological knowledge.  Future uses of this research will be in developing and evaluating bicultural training programmes, developing appropriate measures of cultural competency acquisition and assessing the potential for a distinct Māori psychology.

text: The Development and Evaluation of a Cultural Competency Training Programme for Psychologists Working with Māori: A Training Needs Analysis The purpose of this study was to develop and evaluate a cultural competency training programme for clinical psychology students to work with Māori consumers.  A pilot programme (study 1) was developed from the international and national cultural competency and bicultural training literature.  Following the pilot, it was identified that the programme could be made more robust by conducting a second study the training needs analysis using the critical incident technique.  Study two was conducted with 30 experienced clinical psychologists who had worked with Māori clients.
  
The training needs analysis sought to identify the awareness, knowledge and skills (AKS) that the experienced psychologists used in their practice with Māori.  An unexpected finding from study two was that the psychologists used distinctly Māori-cultural practices incorporating Māori tikanga and Māori knowledge with their clients even though they had little or no bicultural course content in their clinical training.  The data from the pilot programme, and the training needs analysis were used to refine the final workshop.  
The workshop was delivered to two university sites over a two-day period using intern clinical psychologist.  The programme evaluation had three components: (1) analysis of pre and post programme questionnaires; (2) analysis of the retrospective questionnaires (3) and an analysis of a participant’s case report on a Māori consumer. 
The themes that evolved from this research are that the critical incident technique is a useful way of identifying bicultural training material that would otherwise go unnoticed.  In relation to training evaluation, there is a real need to develop meaningful measures of bicultural competency acquisition for clinical students.  The finding advances the proposition that a distinct Māori psychology exists that could potentially challenge the relevance of Western psychology for Māori.  
A contextual theme underpinning bicultural training programmes is that training and practice occurs against the backdrop of Pākehā dominance in all aspects of academia and society. Consequently, there is a need to find a balance between Māori and Western psychological knowledge.  Future uses of this research will be in developing and evaluating bicultural training programmes, developing appropriate measures of cultural competency acquisition and assessing the potential for a distinct Māori psychology.

year: 2012