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Item Identifying drivers of palatability in beef and lamb ingredients used in commercial pet food : 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 EMBARGOED until 13 March 2026(Massey University, 2023) Watson, PavineePalatability is an important criterion in pet food research and development and involves examining a pet’s liking for certain foods by assessing intake. In a sense, palatability is very much a human concept that has been applied to pet food research to assess the success or failure of a product. Whether a pet eats a food or not can alter an owner’s future repurchasing habits of pet foods. Within pet care, pet food makes up the largest proportion of the sector. In cats, domestication has placed great importance on pet food, as compared to their carnivorous ancestors, domestic cats obtain most (if not all) their daily nutrition from commercial pet food. However, as a species, cats have retained much of their ancestral traits particularly in terms of their nutritional requirements and are still known as obligate carnivores. Cats preferentially choose diets high in protein and palatability of food is known to be positively associated with the amount of protein, particularly if ingredients of animal origin are included. Nevertheless, there are few studies on the palatability of meat and its by-products as individual components. Additionally, reasons for differences in palatability between by-products have yet to be determined in detail. Research is particularly limited in new and emerging food formats such as air-dried and freeze-dried, which are of great interest to pet owners as providing nutrition to pets that has undergone minimal processing. With this being considered, this thesis examined the palatability of air-dried by-products (lung, heart, kidney, tripe, mechanically deboned meat (MDM), liver and spleen) from ovine and bovine sources and then examined potential nutrient drivers responsible for observed differences in palatability between the by-products. Finally, it aimed to understand whether inclusion of low- or highly- palatable ingredients would affect macronutrient selection in the cat. Firstly, Chapter 2 details the methodology used to manufacture air-dried by-products for testing in Chapters 3 and 4. Following the method development, three experimental trials using a designated panel of eight cats were conducted to make up Chapters 3, 4 and 5, respectively. Chapter 3 examined the within- and between-species differences in palatability between air-dried beef and lamb by-products. This was carried out to compare the same series of by-products that I investigated previously in their raw state to an air-dried state, to determine the influence of heat-treatment on palatability. The results reflected similar findings to previous research of raw by-products where greater amounts of organ meats were consumed over MDM and lamb was preferentially consumed over the equivalent beef by-products. In terms of the between species finding, lamb was also preferred over the same beef by-product. Furthermore, when compared on a dry matter basis, heat-treatment via air-drying had a negative impact on by-product palatbility compared to raw. Chapter 4 examined within species effects on palatability of by-products from young and old animals from ovine and bovine sources. Cats showed preferential consumption of organ meats from calves over beef and a general preference for lamb over mutton (except for mutton lung and tripe which were preferred from older animals), and no differences were observed between the liver of different ages. Metabolomic analysis of the by-products was also used as a tool to understand their metabolite composition and revealed that key compounds were associated with palatability in cats, particularly amino acids relating to umami taste, specifically glutamic acid, and kokumi dipeptides showed greater levels in the more palatable by-products. Whereas, dipeptides associated with lean meat, carnosine and anserine, were higher in the least palatable by-product MDM. These results highlight that although cats have a biological need for animal proteins, the type of by-product selected has a great influence on palatability. From here, I developed a series of high and low palatability diets varying in protein fat and carbohydrate content with limited ingredients, formulated with lamb kidney as the ingredient of high palatability and sheep heart as the ingredient of low palatability. These were used to examine the macronutrient selection by cats when presented in a geometric framework study. The highly palatable series did show greater intake, but both sets of diets were highly palatable with cats consuming greater than 100% of the maintenance energy requirements throughout the two phases. When the intake patterns were compared, the high palatability series saw cats consume similar metabolisable energy percentages from fat to the low palatability series but more protein and less carbohydrate. Whereas cats seemed to maximise their carbohydrate intake to reach the carbohydrate ceiling on the low palatability diet and consumed less protein. From this research, I have identified potential compounds of interest from Chapter 4 to undergo more controlled experimental protocols. Glutamic acid and the two γ-glutamyl dipeptides could be investigated further to determine the levels for inclusion in palatability enhancers and/or digests or in pet food formulations. Additionally, I have also discussed how further work could be done to reformulate the diets from the geometric framework study in Chapter 5 to achieve more variable protein, fat, and carbohydrate targets. The differences between the predicted and measured values for the series of diets with the consistent high fat contents of the diets across the study, need to be modified by using different or varying levels of meat ingredients to those selected. The study clearly demonstrated the variability of meat by-products and the challenges of using them in a controlled study. With the high utilisation of meat and by-products in pet food both locally in New Zealand and worldwide, the work carried out in this thesis highlights the importance of these ingredients at a fundamental level. This thesis also explores the known drivers of palatability in cats and their links to individual ingredients and begins to determine reasons for differences between by-products that have not be reported in the literature to date.Item Investigation into the palatability of lamb, beef and chicken offal used in the production of pet food : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatu, New Zealand(Massey University, 2019) Watson, PavineeThis series of studies investigated the palatability of individual offals used in the production of pet food for cats from lamb, beef and chicken species. Before initiating testing, a literature review was carried out to define palatability and identify possible drivers of palatability in both cats and dogs. Various palatability testing methods and the selection of suitable ingredients to analyse were also evaluated in the early stages of this study. A standardised testing protocol was established and followed for palatability trials. These trials included the use of two-bowl acceptance tests to develop an overall ranking of offal within each species. Two-bowl preference tests between equivalent beef and lamb offals were also conducted to observe whether the panel showed preferences for one species over the other whilst also evaluating the meal size, frequency and rate of consumption. The final three-bowl preference tests between the top and bottom ranked beef, lamb and chicken offals were used to observe whether there were differences in the species of offal first approached, first consumed and first/most completed by the panel. Acceptance testing revealed that within each species, liver was the most palatable offal presented, with kidney equivalent to it in the lamb acceptance testing. In all three sources of offal, liver possessed the highest amounts of protein compared to the other offals, which was identified in literature as a positive driver for palatability in cats due to their high requirements for protein. In addition, MDM was the least accepted offal, although heart was equivalent to it in the chicken acceptance testing. Furthermore, preferences for lamb over equivalent beef offals, with the exception of heart and liver, were also demonstrated. The final three-bowl preference tests between the top and bottom ranked beef, lamb and chicken offals revealed that cats showed high palatability for liver with no preference for one species of liver over the other. However, of the bottom ranked MDM ingredients, chicken was consumed preferentially over beef and lamb MDM. Compositional data for the MDM showed that chicken had the highest protein content of the three MDM varieties. As well as detecting difference in palatability between offals, this study suggested the amount of protein within individual offals may play a role in influencing offal acceptance and preference in cats.Item Investigations into feline (Felis catus) palatability : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science at Massey University(Massey University, 2004) Rutherford, Shay RebekahDue to the finicky nature of the domestic cats' feeding habits, palatability is a highly complex area of feline nutrition, but one which is vitally important, with pet owners today selecting a brand based on palatability rather than nutritional value (Trivedi and Benning 1999). To date there is little published literature about the specific compounds and ingredients responsible for the palatability of cat foods, however, some animal by-products, particularly fish offals have been reported as being highly palatable to the cat (MacDonald et al. 1984). There is much interest in the use of synthetic diets for palatability testing because these diets can be easily manipulated to control specific properties of the diet. The aims of this study, using the domestic cat as the test species were to: (1) test the efficacy of using synthetic diets in palatability trials, (2) determine the palatability of various fish by-products when included in synthetic and commercially canned diets, (3) develop a method suitable for fractionating fish by-products and fractionate selected by-products. (4) determine the palatability of the fish by-product fractions obtained and (5) determine the palatability of various pure compounds when dissolved in pet milk. All palatability trials carried out used the two bowl free choice testing method. The freeze dried forms of hoki, mussel, salmon and jack mackerel by-products were included in a synthetic diet and compared to an un-supplemented synthetic diet. Hoki, mussel, salmon and barracouta by-products and the three fish by-product fractions (salmon oil, salmon water and barracouta water) were included fresh in commercially made canned diets and compared to a common commercial diet (control). Finally various pure compounds (amino acids, malic acid, salts, urea, creatinine, creatine, etc.) were dissolved in pet milk and compared to un-supplemented pet milk (control). Feed intakes were recorded daily for all of the trials. The test animals used were domestic short haired cats obtained from the Centre for Feline Nutrition (Massey University, Palmerston North, New Zealand) and all were in excellent health before testing began. The panels of cats used were either all castrated males aged three to nine years old, or a mixture of castrated males, entire females and entire males aged two to eleven years old. The feed intake data collected during the trials were analysed using t tests, and repeat measures ANOVA. Feed intakes were low overall during the synthetic trial due to the un-supplemented control diet itself not being very palatable. These low feed intakes resulted in weight losses in the cats and the study had to be abandoned prematurely. Therefore, the results are only based on a sample size of two and are of limited value as such. The other three trials were highly successful, with all cats remaining healthy, apart from two which were taken from the milk trial due to health reasons unrelated to these trials. Salmon and jack mackerel by-products were both significantly (P<0.01 and P<0.001 respectively) more palatable than the control diet, hoki by-product was significantly (P<0.001) less palatable than the control and mussel by-product was not significantly different (P>0.05) from the control when they were included in synthetic diets. When the fish by-products were included in commercial diets, the salmon and mussel by-products were the most palatable of the test diets, however, the salmon, mussel and barracouta by-products were not significantly different (P>0.05) from the control in terms of palatability. The hoki by-product was significantly (P<0.001) less palatable than the control. The trials using the fish by-product fractions illustrated that salmon oil containing diet was significantly (P<0.05) more palatable than the control diet. The salmon water and barracouta water containing diets were not significantly (P>0.05) different from the control in terms of palatability. Lastly, the trials involving the testing of pure compounds highlighted that at the 0.3% dose proline, lysine (lysine hydrochloride), histidine, cysteine (cysteine hydrochloride), glycine and sodium dihydrogen phosphate were all significantly (P<0.001) more palatable than the un-supplemented pet milk. At the 0.3% dose, other compounds investigated were no more palatable than the un-supplemented control milk. Proline and lysine (lysine hydrochloride) were also significantly (P<0.001) more palatable than the control at the 0.6% dose, however, histidine was no more palatable (P>0.05) than the control at this inclusion level. In conclusion, salmon by-product was liked and hoki by-product was disliked by the cats when included in both synthetic and commercial diets. Mussel by-product was palatable when included in the commercial diets, but was no more palatable than the control when tested in the synthetic diet. Jack mackerel by-product was palatable in the synthetic diet and barracouta by-product was no more palatable than the control in the commercial diet. Salmon oil and the compounds proline, lysine hydrochloride, histidine, glycine, cysteine hydrochloride and sodium dihydrogen phosphate were highly palatable to the cat.If future work with synthetic diets occurs it needs to be aimed at pre-weaned kittens as it would be easier to wean young inexperienced kittens onto a synthetic diet than older cats which are used to receiving a commercially made diet. The fish by-products tested here, along with other New Zealand fish species need to be further investigated. It may also be of use to test the fish by-products and their fractions in a different type of base diet in order to determine how this affects their palatability. The dose dependency of the compounds found palatable in the milk trials also needs to be established, in order to find an optimum dose for them to be used as palatability enhancers.Item An investigation of the breakfast habits and dietary intakes of year 8 Auckland children : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutritional Science at Massey University(Massey University, 2006) Svendsen, Claire AnneBreakfast is often referred to as the most important meal of the day. Studies have consistently shown that regular breakfast consumption makes a significant contribution to nutrient intake. Additionally, individuals who have skipped breakfast often do not make up for the missed nutrients during the remainder of the day. Results from the National Children's Nutrition Survey show that breakfast consumption varies with ethnicity and age. In particular, Pacific Island children and older children were less likely than other ethnic and age groups to have breakfast. The overall aim of the current study was to collect detailed information on dietary intake, breakfast habits, choices, and preferences of intermediate school children. Two multi-cultural decile six intermediate schools in North Shore City, Auckland were selected to participate. A dietary assessment of over two hundred students (12-13 years of age) was completed using a dietary recall methodology. Data were also collected on breakfast habits and preferences, and anthropometric measurements made. A subset group of 52 students was randomly selected to provide detailed information on their nutrient intake. Each student within the subgroup completed two 24-hour recalls during the school week, and a food diary on a Saturday. Findings from this research showed that both male and female students had a high level of breakfast consumption, with over half of the students reporting that this represented their daily habit. Overall, only 4% reported that they rarely or never have breakfast. The most reported reason given for skipping breakfast was not being hungry in the morning, followed by preferring to sleep in, and then lack of time. There was some evidence from this study that the daily commitments of family members (e.g., working parents) may influence breakfast eating habits. Additionally, it is likely that the availability of preferred breakfast foods at home contributed to high breakfast consumption observed in this study population. Interestingly, breakfast consumption was not significantly associated with gender, but was however influenced by ethnicity, with Maori/Pacific Island children less likely to eat breakfast than children of other ethnic groups (P = 0.001). Breakfast skippers had a significantly higher body mass index (BMI) compared to breakfast eaters, although further research is required to assess the association between habitual breakfast consumption and BMI. The majority of breakfast consumers chose foods and beverages that contributed to a balanced breakfast. Of those subjects who had breakfast, over 60% consumed a cereal, with the most popular being Weet-Bix. Findings from the subgroup analysis showed that the consumpton of breakfast made a significant contribution to the daily intake of nutrients such as iron, calcium, folate, riboflavin, and thiamin, for both male and female breakfast eaters. The information gained from this study may facilitate the implementation of nutrition education and intervention programmes designed to improve eating patterns (in particular breakfast consumption) and the dietary intake of children and adolescents. Promoting and maintaining good breakfast habits in children of this age group may lead to improved breakfast consumption patterns and health as they progress through adolescence.Item Food preferences and food choices of eleven and twelve year old children as they relate to their television viewing habits : a thesis submitted in partial fulfilment of requirements for the degree of Master of Science (Nutritional Science) at Massey University(Massey University, 2004) Gordon, CushlaThe aim of this study was to examine the relationship between children's television viewing habits and their food preferences and food choices. The study was divided into two parts. Part one was an analysis of the frequency and content of food advertisements aired during children's television. Part two involved interviews with children and their parents to examine their eating, television and physical activity habits. From this the relationship between what they were viewing in advertisements and their food preferences and choices could be established. The children, forty in total, were aged eleven or twelve and were chosen from two Auckland Intermediate schools. Comparisons were made between boys and girls. The research showed that New Zealand children, through advertising, are constantly exposed to a variety of foods that fall within a very narrow range. These foods are predominantly individual servings of snacks or pre-prepared, pre-packaged foods that are high in saturated fat and/or sugar and/or salt. These foods are in direct contrast to the dietary recommendations provided by the Ministry of Health (1997) of eating a variety of foods from all the food groups and only eating treat foods now and then. Advertisers within New Zealand are not adhering to the Advertising Codes of Practice, particularly with regard to repetition and duration of advertisements. Thus, self-regulation within this industry does not appear to be effective. From part two of the research it was possible to conclude that television food advertisements do have a significant influence on children. This is through creating a desire in the child to try the foods they have seen advertised and as a result of viewing the advertisement, asking their parents to purchase the food. This effect was most likely to be for the life of the advertisement rather than long-term. Children in the study were watching on average just under two hours of television a day and the more television they were watching, thus the more advertisements they were viewing, the more they wanted to try foods they had seen advertised. More of the children's time was spent viewing television than engaged in formal or informal physical activity. Many were overweight or at risk of overweight, however this was not correlated with television viewing. Overall, television food advertisements influenced children through making the food look appealing and exciting and thus creating a desire to try the food. Children were also influenced by both the qualities of the food, such as taste and appearance, and the people and the environment around them. The research did support the finding in other studies that there is a correlation between children's food likes, dislikes and choices, however it is important to place the influence of advertising in the context of the numerous other influences on children's food choices.Item Habitual sweet food intake and eating behaviour are influenced by sweet taste perception : a thesis presented in partial fulfilment of the requirements for a degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2015) Rivers, StaceyBackground: Sugar consumption creates pleasure, and excessive sugar consumption leads to weight gain and is therefore a key driver of obesity. This study aims to assess sweet food and beverage intake, eating behaviours and how they may be explained by perceived sweet taste intensity and hedonic preference. Aim: To assess sweet food habits and eating behaviours in 20-40-year-old NZ European women, and understand how measures of sweet taste perception can help explain these sweet food choices and eating behaviours. Methods: Women (N=45), aged 20-40 years, were recruited for this cross-sectional study. A non-quantitative sweet food-food frequency questionnaire (SF-FFQ) was developed to assess sweet food intake. Liking of sweetened beverages was assessed on a 100 mm visual scale. The Three Factor Eating Questionnaire (TFEQ) was used to assess the eating behaviours. Perceived sweet taste intensity and hedonic preference of glucose concentrations (125 mM, 250 mM, 500 mM, 1000 mM) was rated (0-100) on a modified general Labelled Magnitude Scale (gLMS). Results: Frequency of daily intake was reported as daily frequency equivalents (DFE). Occasional sweet food DFE was high (4.23±2.29), with intake of baking and sweets especially high (1.20±0.83). Participants with a self-reported “sweet tooth” more frequently consumed baking (P=0.04), chocolate (P=0.03) and soft lollies (P=0.04) compared to participants with no “sweet tooth”. Chocolate DFE was higher in participants who experienced regular food cravings compared to those who did not (P<0.001). Higher consumption of sweet food was correlated with less sensitivity to 1000 mM glucose (P=0.02). A negative correlation was found between intensity rating (1000 mM), fruit juice liking (P=0.01) and fruit drink liking (P<0.001). Participants who preferred sweet snacks, were less sensitive to 1000 mM glucose than those who preferred savoury (P=0.04). Conclusion: Participants in this study habitually consumed foods high in sugar such as baking, sweets, chocolate and sweetened beverages. The participants’ sweet beverage choice was influenced by their liking of sweet beverages. Some participants were found to express certain eating behaviours that influenced their intake of sweet food such as hunger, food cravings and “sweet tooth”. Sensitivity to sweet taste was inversely associated with consumption of sweet tasting food. The data suggest that sweet taste intensity perception plays an important role in habitual sweet food and beverage intake.Item Food choice in context : the application of experimental choice analysis to investigate sensory and cognitive factors in consumer food choice : a thesis presented in partial fulfilment of the requirements for the degree of Ph. D. in Food Technology at Massey University(Massey University, 1999) Clark, Maxine RuthKnowledge about consumer food choices is fundamental to many areas of research and practice. Food choices can only be fully understood by identifying and measuring sensory and cognitive factors from the consumer's perspective and interpreted with reference to the context in which the food is to be used or consumed. Experimental choice analysis is a technique which integrates conjoint analysis with probabilistic discrete choice theories to investigate influences on consumer choices. This technique was applied and evaluated, in conjunction with qualitative research, to investigate consumer choices for yoghurt. Multiple sets of experimentally designed product alternatives were presented to consumers, and the impact of, and interaction between, different product features determined using a multinomial logit model. Choices for five different use contexts were made on the basis of product descriptions only, blind tasted products and the combined product (information plus tasting). Features to be manipulated for labels and products were sweetness and fat content, each at two levels. Label only attributes included statements related to acidophilus and no additives product features. The results demonstrated that consumers' choices, based on the attributes of the product, vary with different intended use contexts. Context-specific interactions were noted between fat content and sweetness. This suggested that consumers do not always assess product features independently or consistently, and interactions should be incorporated in research designs wherever possible. Participants' frequency of use and degree of health concern were incorporated into the model as interactions with attributes and these significantly improved the model over base models. Combined with the results of the qualitative studies, a comprehensive picture of how consumers' use of yoghurt affected their choices was obtained. This approach can provide valuable information for product development decisions and may be a step towards developing more integrated research methodologies for investigating consumer food choices.
