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    Cross-cultural differences and acculturation in affective response and sensory perception: a case study across Chinese immigrants and local consumers in New Zealand
    (Elsevier Ltd, 2025-01) Dupas de Matos A; Chen A; Maggs R; Godfrey AJR; Weerawarna N R P M; Hort J
    Understanding cross-cultural variation in perception is essential for identifying culture-specific factors impacting product acceptability. While immigrants may initially maintain their preferences, acculturation levels vary. To understand to what extent immigrants can be used as a proxy to model overseas markets, this study investigated short (CHS) and long-term (CHL) Chinese immigrant responses to plain yoghurts compared to New Zealand (NZ) Europeans (E). Three groups (CHS, CHL and NZE, n = 222) evaluated liking of, emotional response to, and sensory perception of 10 plain yoghurts. Groups liked yoghurts similarly. Notably, NZE rated emotions lower than both immigrant groups, with a few exceptions. Both Chinese groups rated most emotions similarly, but CHL rated some closer to NZE. Positive emotions correlated with higher liking scores. However, cross-cultural differences existed for ‘guilty’ which was associated with yoghurts liked by NZE; and for ‘wild’ and ‘mild’ associated with yoghurts disliked by both immigrant groups. Citation proportions for some sensory attributes differed among all groups, dependent on the sample. But level of acculturation between immigrant groups was limited. Sweetness, vanilla, stone fruit and cream flavours, smoothness, and creaminess drove liking across all groups, whereas only the Chinese valued umami, undoubtedly due to positive associations with it. Some effects of acculturation for long-term immigrants were evident, but responses were often closer to their short-term counterparts. Therefore, immigrants in general provide a useful proxy for measuring consumer responses in early stages of product development for this overseas market, but with consideration of their residence time in the host culture.
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    Headspace analysis of natural yoghurt using headspace solid phase microextraction : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Food Technology at Massey University (Turitea Campus), Palmerston North, New Zealand
    (Massey University, 2001) Sivalingam-Reid, Geedha
    The Solid Phase Microextraction (SPME) method was originally developed to extract volatile and semivolatile compounds from wastewater samples but has since been applied to flavour compounds in foods and beverages. Research using the HS-SPME in related areas such as cheese and skim milk powder has been carried out but, to date, no work has been done on yoghurt flavours. The main objective of this study was to devise a methodology for the Headspace Solid Phase Microextraction (HS-SPME) technique to investigate and quantify six flavour analytes in natural, set yoghurts made from recombined milk. The relevant literature was reviewed and from it, a research proposal for this work on yoghurts was drawn. The first step in analysing and quantifying the yoghurt volatiles was to set up a working methodology for the HS-SPME method. The 100 μm polydimethylsiloxane (PDMS) fibre was chosen along with 20 minutes being the optimum fibre adsorption time. General equipment, materials and methods used throughout this thesis are also detailed. The external standard (ES) method was used to calibrate the GC and quantify the analyte concentrations in this study. The internal standard (IS) method was not used as a quantitative tool in this study. Once the HS-SPME methodology had been set up for the analysis of yoghurts, the classical Static Headspace (SH) method was compared with the HS-SPME method for extraction efficiency. The results suggested that the two methods were complementary in that the SH method extracted the more volatile compounds (acetaldehyde, acetone and 2-butanone) whereas, the HS-SPME method extracted the semi- to non-volatile compounds (ethanol, diacetyl and acetoin) more readily. However, the HS-SPME was found to be the more sensitive and effective method of the two techniques tested. The next step in the thesis was to investigate the presence of the six analytes in milk and cultured yoghurt. The effects of the sample matrix, fat levels and incubation on the volatile concentrations were also examined. The results suggested that the six analytes were inherently present in milks but at low concentrations. No conclusive effects were found for the sample matrix, fat levels and incubation. However, it was evident that fermentation of the milks using bacterial starter cultures resulted in a large increase in some of the volatiles being investigated. Following this, the effects of fat levels, storage time and storage temperature on the six volatiles in yoghurts were examined. The results indicated that significant fat level effects were only seen for diacetyl and acetoin, while temperature effects were only observed for ethanol. In both trials, only general trends for the analytes concentrations were drawn because the data varied from day to day. The results suggested that most of the compounds decreased with time except for diacetyl, which seemed to increase. The final part of this study looked at applying the devised HS-SPME methodology to a series of commercial yoghurts as a preliminary trial, with a view to investigating a potential application for the HS-SPME method. Fourteen commercial yoghurts were analysed and the six analytes quantified. The data obtained was analysed using Principle Component Analysis (PCA), which divided the yoghurts into groups based on their analyte concentrations. From these groupings, eight yoghurts were selected and fresh samples were analysed using HS-SPME and PCA. This was carried out parallel with an untrained consumer panel, which had to distinguish differences between the yoghurts in a series of triangle tests by smelling the headspace on opening the yoghurt containers. The conclusions drawn were that, unlike the HS-SPME method with PCA, the average consumer could not differentiate the yoghurts based on smell alone. PCA also showed that the HS-SPME results obtained were fairly reproducible. In conclusion, the HS-SPME method was shown to be a useful analytical technique, which can be used to analyse and quantify flavour compounds in natural, set yoghurts. This area of investigation has a lot of scope, with the results from this study providing a basis or starting point for further investigations in this area. Future studies may lead to potential applications for the HS-SPME method, one of which may be quality control where correlation of sensory data with HS-SPME analytical data is required.
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    Application of flow cytometry for enumerating individual bacterial cultures from a mixed culture system : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2014) Horváth, Kylie
    Cultured dairy products are often made with more than one microbial culture. Yoghurt requires the cultivation of several bacterial species for its production and the level of each is important for different reasons. Differential plate count methods to enumerate the separate species in yoghurt are not ideal because many of the bacteria used have similar growth profiles and plate counts take several days to produce a result. A fast specific method for enumerating each culture would be beneficial because quick results would enable tighter control of processing or experimental conditions and the ability to track individual species amongst a background of similar bacteria. Flow cytometry combined with fluorescent in-situ hybridisation (FLOW-FISH) was investigated as a potential solution and successful enumeration was achieved within 1 day for a yoghurt microorganism, Streptococcus thermophilus (ST55), grown in M17 medium. This method may be improved to increase the signal-to-noise ratio and to reduce the assay time. The chemical propidium monoazide enabled a closer match to plate counts for flow cytometry results using a total viable count assay and may be useful combined with the FLOW-FISH assay for removing non-viable or viable, but non-culturable, cells from the results. An enzyme and/or detergent pre-treatment may achieve successful FLOW-FISH enumeration of cells grown in reconstituted skim milk – a similar matrix to yoghurt.
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    Innovative yoghurts: novel processing technologies for improving acid milk gel texture
    (Elsevier, 2013) Loveday, SM; Singh, Harjinder; Sarkar, Anwesha
    Consumers are demanding low-fat yoghurts without hydrocolloid stabilisers, but they are unwilling to compromise on texture for the sake of a ‘clean label’. Producing high quality low-fat yoghurt without stabilisers is challenging, and there is a need for new processing technologies to address consumer demand. Here we examine four technologies that can potentially improve the texture of yoghurt: high-pressure processing (HPP), high-pressure homogenisation (HPH), ultrasonic processing (USP) and protein crosslinking with the enzyme transglutaminase (TG). The benefits of HPH and USP depend on fat content, whilst HPP and TG work best in combination with other processes, and have strong potential for improving protein ingredients.
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    Development of a probiotics rich yogurt dry mix : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Albany, New Zealand
    (Massey University, 2011) Kosasih, Maureen Febriani
    The probiotic Lactobacillus acidophilus NCFM has been scientifically studied to confer health benefits in humans when consumed in sufficiently high numbers. The incorporation of the NCFM strain in yogurt has been widely applied due to the popularity of the fermented product. Probiotics and other yogurt microorganisms (Streptococcus thermophilus and Lactobacillus bulgaricus) can remain viable in high concentration when present in liquid or in high water activity products. However, such products are not convenient as they can not be stored at ambient temperature and have limited shelf life. The development of dehydrated yogurt base (DYB) has created opportunities for the delivery of probiotics. DYB is unique to the current market and provides the convenience of ambient storage and long term shelf life. Therefore, the objective of this study was to develop a stable DYB formulation with shelf life of up to 18 months at ambient storage and 2 weeks at 4°C in its ready-to-eat (RTE) form. Full experimental design was used to formulate the DYB. Characterization of DYB and RTE was analysed for physical, microbiological and chemical properties. The Arhenius model was used to predict the shelf-life of DYB. Liquid yogurt was prepared using selected DYB and the products were analysed by sensory consumers. Results showed that the level of oxygen, moisture, fat, sugar and the storage temperature affected the survival of NCFM in DYB. The cell counts of the NCFM however were above 106 cfu/g throughout storage. In liquid yogurt (RTE form), acidity and the initial level of microorganisms used were important in the stability of the NCFM cells during storage. The growth of the starter microorganisms and the NCFM was symbiotic. Based on this information and the sensory analysis, the developed DYB formulation in the current study showed good potential for commercialization.