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    Macronutrient self-selection in dogs and the impact on markers of health : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
    (Massey University, 2020) Roberts, Mark
    Dogs represent the only large carnivore to have been domesticated. By inheriting wolf ancestry, the domestic dog has retained several carnivorous traits, with for example teeth adapted for grasping and tearing a prey item. Both protein and fat are essential to the dog, but not carbohydrate. However, the most popular feeding option for a modern dog is a dry, extruded diet, with carbohydrate representing a major macronutrient. It is also apparent that domesticated dogs are currently eating diets that differ substantially from what their ancestors consumed. Based on this, the aim of this PhD was to determine what macronutrient intake dogs target, if given the option to select. Further investigations would then examine the impact of the diet selected on health. The first of the four studies involved dogs fed ad libitum for a ten-day duration. Three diets, involving a protein-fat-carbohydrate (PFC) metabolisable energy (ME) ratio of 18%:28%:54% (high carbohydrate HC), 13%:86%:1% (high fat HF) and 57%:42%:1% (high protein HP) were offered. The overall mean macronutrient intake of the dogs was PFC 34%:63%:3% (ME). However, over the duration of the study, fat intake (ME) decreased significantly (62% to 51% ME) and protein increased (34% to 45% ME). After completing this study, a follow on experiment was conducted to determine if ingredients or macronutrients were the key determinate in what a dog decides to eat. This question was answered by providing the animals with two HC diets (PFC 18%:28%:54% ME), but with different key carbohydrate sources (extruded maize or rice). The same method was again used, but this time with two HP diets (PFC 34%:66%:0% ME) and either lamb green tripe or venison meat being the main protein sources. The results shown that no significant difference in intake between both the two high carbohydrate and the two high protein diets was detected, thus macronutrient content was crucial to palatability. On completing this investigation, it was therefore decided to expand the initial study, to clarify the macronutrient selection had stabilised, this time over 28 days. This additionally provided the opportunity to assess the faecal microbiota and metabolites of the animals. The results showed of the third study showed that the dogs consumed a very similar macronutrient intake to the initial study (PFC: 34%:62%:4% ME). Moreover, differences in faecal microbiota and metabolomic data were apparent from when the dogs consumed a baseline extruded diet, to selecting a diet dominated by fat and protein. As the dogs had previously selected a high fat diet, typically associated with increasing the risk of pancreatitis, it was decided that the final study should involve investigating biomarkers of pancreatitis in dogs previously fed a baseline commercial extruded diet, before suddenly consuming a high fat meal. This was followed by switching either to a HF or HC diet for eight weeks and repeating the same measurements and consuming a final high fat meal. Although both the HC and HF diet fed dogs highlighted no meaningful differences in biomarkers of pancreatitis, differences were apparent with the baseline diet. A key factor was triglycerides, with both the HC and HF diet fed dogs that consumed the final HF meal having significantly lower (P<0.001) peak triglyceride values (1.51 mmol/L and (1.49 mmol/L) compared to dogs that had consumed the baseline diet (2.52 mmol/L). As both the baseline extruded and HC diets comprised of a similar macronutrient ratio (baseline diet PFC 23:26:52 ME and HC diet PFC 17%:32%:51%ME), other aspects likely had an influencing role. These include moisture, ingredients, level of diet processing, and possibly digestibility. In conclusion, this thesis has shown that a high fat meal fed to a healthy dog presents no detectable risk to health compared to being fed a high carbohydrate, low fat diet. In addition, a high fat diet has also been demonstrated to be more palatable than carbohydrate-based diets, typically seen in commercial extruded products. Finally, although the feeding of a HF meal to a dog did not increase the risk of pancreatitis per se, if a commercial extruded diet was fed prior, it does increase risk factors. As this response was not witnessed with a non-extruded HC diet, determining what factors in an extruded diet potentially increase the risk of pancreatitis if suddenly switched to a HF diet, should be the focus of future research.
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    Exploring the link between sweet taste and fat (creaminess) perception, dietary intake and metabolic health in women : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Sciences at Massey University, Auckland, New Zealand
    (Massey University, 2019) Jayasinghe, Shakeela Nathalia
    Taste perception plays an important role in dietary choice and intake. There is a significant link between the current obesogenic food environment of ubiquitously available, highly palatable, sugar- and fat-rich foods and adverse metabolic health outcomes. Therefore, it is important to understand the nature of the link between sweet and fat taste perception and dietary intake. Using a multi-disciplinary approach employing sensory science, dietary assessment methods and metabolic health and endocrine analyses, this thesis investigated the relationship between sweet taste and fat (creaminess) perception, dietary intake and metabolic health in women to understand factors contributing or leading to obesity. The experimental study in Chapter 3 investigated the relationship between four different psychophysical measurements of sweet taste perception and explored which measurements of sweet taste perception relate to sweet food intake. An interesting finding of this chapter was the dose-dependent change in the relationship between sweet taste intensity and hedonic liking, which illustrated that sweet hedonic liking was dependent on the magnitude of sweetness experienced. Importantly, this experimental study showed for the first time a clear dose-dependent link between a lower perceived sweet taste intensity and higher sweet hedonic liking and increased intakes of total energy and carbohydrate (starch, total sugar). Chapter 4 assessed whether sweet taste and fat (creaminess) perception differ across ethnic groups with known differences in metabolic disease and obesity risk (New Zealand European, Māori, Pacific) and across body composition groups based on body mass index and body fat. Furthermore, this chapter explored whether there is a link between taste perception and metabolic and endocrine biomarkers associated with adiposity and appetite. The overall findings showed no significant differences in sweet taste and fat (creaminess) perception between ethnic groups or body composition groups. Further, no robust links between sweet taste and fat (creaminess) perception and metabolic and endocrine biomarkers were found. The study described in Chapter 5 explored the links between dietary patterns, body composition, macronutrient intakes and metabolic and endocrine biomarkers of adiposity and appetite. Higher intakes of the ‘refined and processed’ dietary pattern was linked with higher total energy and percentage carbohydrate (starch, total sugar) intakes and higher body composition measurements (e.g., body mass index, body fat). Furthermore, higher intakes of the ‘refined and processed’ dietary pattern was linked with higher circulating levels of leptin and insulin and lower levels of ghrelin. Together these findings indicated a diet-induced metabolic dysregulation in women with higher intakes of the ‘refined and processed’ dietary pattern. The research study in Chapter 6 investigated whether body composition, dietary intake and metabolic and endocrine biomarkers differ between women with distinct patterns of sweet and fat (creaminess) hedonic liking. The overall results showed that higher hedonic liking for sweet and fat tastes are linked with increased intakes of sweet and fatty tasting food groups and dietary patterns such as the ‘refined and processed’ and ‘fats and meat’ patterns. Taken together, the experimental studies described in this thesis provide evidence in support of a clear link between sweet taste and fat (creaminess) perception and dietary intake, particularly the intake of foods and dietary patterns characteristic of an individual’s taste phenotype. We also found that sweet taste and fat (creaminess) perceptions were not directly linked with body composition, metabolic biomarkers or endocrine regulators in this group of healthy, pre-menopausal women. Furthermore, higher intakes of the ‘refined and processed’ dietary pattern highlighted a pathway to obesity which appears to be mediated by changes in body composition and key endocrine regulators.
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    The perception of sweet, bitter and fatty acid taste and sensitivity to fat by mouthfeel and olfaction : associations with dietary intake, eating behaviour and obesity in premenopausal women : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Albany, New Zealand
    (Massey University, 2019) Kindleysides, Sophie Jane
    Background: Individual variability in taste perception may influence diet, possibly modifying eating behaviour and long-term food choice. Research into taste perception and weight status, dietary intake, eating behaviour and endocrine regulators of metabolic health could provide new important insights. Taste perception may be modifiable, and as such may be a target for future intervention strategies which may have the potential to prevent or treat obesity. Objectives: The aims of this study were to determine associations between (1) fatty acid taste, olfaction, mouthfeel of fat, dietary intake, eating behaviour and body mass index (BMI), and (2) associations between taste perception of glucose (sweet taste), quinine (bitter taste) and milk (fat perception) with body composition and hormonal adiposity signals (fasting insulin and leptin), dietary intake and eating behaviour. Design: For the first cross-sectional study, 50 premenopausal women assessed oleic acid taste and olfaction thresholds. BMI was calculated from weight (kg) and height (m). Dietary intake and eating behaviour were evaluated using a food frequency and three-factor eating questionnaire (TFEQ), respectively. Binomial regression analysis was used to model fatty acid taste and olfaction data and fatty acid taster status was determined (hypersensitive, n= 22; hyposensitive, n= 28). For the second cross-sectional study (the PROMISE study), 351 premenopausal Pacific and New Zealand (NZ) European women were recruited and stratified by non-obese and obese groups. Suprathreshold intensity, hedonic liking, and discrimination of taste by a ranking task were measured using a range of concentrations of sweet, bitter, and fat solutions. Participants were classified as likers or dislikers for each tastant using a hierarchical cluster analysis. Body fat (BF) was quantified by dual x-ray absorptiometry. Total energy and macronutrient intake were assessed using a 5-day estimated food record and eating behaviour was assessed by TFEQ. Socioeconomic status was measured by deprivation index (NZDep2013). Logistic and linear regression analyses were used to analyse study outcomes and to adjust for potential confounders (socioeconomic position, age, etc). Both studies were undertaken in Auckland, NZ. Outcomes: The results of the first study showed taste and olfactory detection for oleic acid were positively correlated (r= 0.325; P< 0.02). The eating behaviour disinhibition and BMI were higher in women who were hyposensitive to oleic acid taste (P< 0.05). The PROMISE study showed women who incorrectly discriminated sweet taste by ranking task were nearly three times more likely to have >35 BF% (adjusted, OR 2.9, P< 0.01). Cluster analysis revealed distinct patterns of liking for each tastant. NZ European sweet likers were twice as likely to have >35 BF% compared to sweet dislikers (adjusted, OR 2.1, P< 0.05), however, this comparison was not significant in Pacific women. Conversely, bitter likers had a decreased likelihood of having >35 BF% in comparison to bitter dislikers (adjusted, OR 0.4, P< 0.01). Having higher fasting plasma leptin concentration significantly increased the likelihood of being a sweet liker in Pacific and in NZ European combined (adjusted; OR 1.7, P< 0.05), but in NZ European women, the likelihood of this was further increased (adjusted; OR 3.6, P< 0.001). Higher fasting plasma insulin concentration also increased the likelihood of being a sweet liker (adjusted, OR 1.7, P< 0.05). New Zealand European sweet likers had a significantly higher intake of carbohydrates, all sugars and starch (199.4 ± 51.1, 87.9 ± 27.4 and 111.1 ± 34.6 g/day) when compared to sweet taste dislikers (165.9 ± 48.7, 71.4 ± 25.2 and 94.1 ± 34.7 g/day, P< 0.001, P< 0.01, and P< 0.01, respectively), however, this comparison was not significant in Pacific women. NZ European women in the sweet likers group had an increased disinhibited eating behaviour score (P< 0.01). Conclusions: Fatty acid taste perception was found to be associated with olfaction, eating behaviour and body composition. The findings from the PROMISE study have shown differences in sweet taste perception in relation to adiposity which is further associated with circulating plasma leptin and insulin concentrations. Sweet taste perception was associated with dietary intake and eating behaviour in NZ European women. The taste-diet associations observed in NZ European women were not observed in Pacific women. Therefore, population groups with lower metabolic disease risk may have dissimilar taste-diet associations compared to those with a higher metabolic disease risk. Taste perception is a promising target for future weight-loss and intervention strategies due to demonstrating links with dietary intake, eating behaviour and body composition.
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    Selective removal of fat from acid whey during whey protein concentrate manufacture : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Technology in Food Technology
    (Massey University, 2000) Harford, Arron
    The purpose of this study was to develop a low cost technology for selective removal of lipids from acid whey during whey protein concentrate manufacture Attention was focused on gaining a better understanding of the structure and composition of the lipids in whey and ultrafiltration retentate The effects of varying dilutions, pH, salt concentration, temperature and holding time on the flocculation of lipids in the whey and retentate were investigated The composition and structure of lipids in acid whey and retentate were determined by ultracentrifugation, compositional analysis, integrated light scattering and confocal scanning laser microscopy (CLSM) techniques. Acid whey contained ~ 0.034% lipids The size of the milk fat globules (MFG) in whey varied from 0.1 and 10 μm. with the majority of the globules < 1 μm in diameter The retentate contained ~ 0.36% lipids The size of the MFG in the retentate ranged between 0.1 and 20 μm. generally larger than the MFG in the acid whey Investigation into the removal of lipids from acid whey revealed that flocculation of MFG in the acid whey occurred at temperatures between 40 and 50°C and at pH values from 5.8 to 7.0. It was observed that under these conditions, high-density lipid containing flocculent/precipitates was formed, which subsequently sedimented upon centrifugation (at 1126/g for 10 min) The MFG removed in the flocculent/precipitate appears to be either part of a calcium-MFG complex or MFG entrapped by precipitation of calcium precipitate Examination of the effects of physiochemical factors on the flocculation of MFG in between the retentate revealed that flocculation occurred upon dilution and at pH values between 4.5 and 4.7. It was found that at increasing dilutions, there was an increase in the removal of MFG and in the retention of protein in the supernatant. At retentate dilution of 1:6, the majority of the MFG was removed and a majority of protein was retained in the supernatant Flocculation of MFG in the diluted retentate was influenced by ionic strength (at Low pH values) of the system. This flocculation is thought to result from the hydrophobic association of proteins of MFGM, aggregates of serum proteins, lipoprotein complexes or individual denatured serum proteins Low fat whey protein concentrate powder (WPC) was produced on a pilot-scale plant using the process conditions determined at the laboratory scale to remove MFG from acid whey retentate. The resulting product contained ~ 1% fat. considerably less than the normal commercial WPC On a dry basis the protein content was ~ 96% as compared to ~ 85% in the commercial WPC Examination of the functionality of the low fat WPC revealed the heat-induced gels formed from 15% WPC were more elastic, had better water holding capacity, and were more "gelatinous" in nature Their gelation properties were markedly superior to the commercial WPCs currently manufactured Based on the results of this study, recommendations are made on possible areas of process improvement and development opportunities.
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    Exploring the relationship between dietary patterns, eating behaviour and fat taste detection thresholds : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand
    (Massey University, 2016) Henderson, Lisa
    Background: Dietary pattern analysis provides a unique opportunity to explore combinations of food intake in conjunction with factors known to affect dietary intake. Fat taste sensitivity is an emerging correlate of dietary intake and, when impaired, has a proposed role in the dysregulation of dietary intake and eating behaviours. Aim: To investigate dietary patterns, eating behaviours and fat taste detection thresholds in a group of New Zealand European women aged 19-45 years and identify associations between these factors. Methods: Fifty post-menarche, pre-menopausal New Zealand European (NZE) women, (18-40 years) completed a partially validated, semi-quantiative 220-item food frequency questionnaire and a validated Three-factor eating questionnaire. Height and weight were measured to calculate body mass index (BMI) (kg/m2) and a bioeletrical impedence analysis (BIA) was completed to measure body fat percentage (BF%). During sensory testing protocol participants were exposed to increasing concentrations of ultra-heat treatment (UHT) milk/oleic acid (OA) solutions using the three alternative forced choice method (3-AFC). A naïve OA detection threshold was determined at the point where the participant identified the OA solution correctly three times at the same concentration. Dietary patterns were determined using principal component factor analysis. Associations between dietary pattern scores, taste sensitivity, eating behaviour and baseline characteristics were investigated. Results: Three dietary patterns were identified: ‘unhealthy’, ‘healthy’ and ‘snacking’. Most women had low eating behaviour scores for cognitive restraint (90%) and disinhibition (74%). Hunger scores were comparatively higher, only 40% had low scores. Twenty-three participants (46%) were classified as hypersensitive and 54% were hyposensitive to OA taste. ‘Unhealthy’ pattern scores were inversely associated with cognitive restraint (r=.391, P=.005) and positively associated with age (r=.297, P=.036). ‘Healthy’ pattern scores were positively associated with cognitive restraint (r=.418, P=.003), OA taste detection thresholds (r=0.446, P=.001) and BMI (r=.325, P=.021). Women with low ‘snacking’ pattern scores were significantly older (31.7 years (24.7, 40.4)) than those with moderate scores (24.0 years (22.0, 28.1)) (P=.037). No relationship was found between OA taste detection thresholds and eating behaviour. Conclusion: Participants in this study showed a significant link between habitual dietary intake and measures for eating behaviour and fat taste sensitivity. Both ‘healthy’ and ‘unhealthy’ dietary patterns were associated with one, or both, of these factors. An unexpected positive association between the ‘healthy’ dietary pattern and fat taste sensitivity indicates a need for further investigation to better understand this relationship. Findings from the current study support the use of dietary patterns to better represent habitual intake in future research investigating fat taste sensitivity or eating behaviour. Key words: Habitual intake, dietary intake, fat taste sensitivity, cognitive restraint, disinhibition, hunger