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    Manufacture of cooked meat reaction flavour from mixed hydrolysates of lambskin and wool : 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, 2024) Mathew, Roshina
    The proposition was explored that woolly lambskin could be a useful substrate for cooked meat flavour production, in admixture with a suitable sugar source, both acting as Maillard precursors. This thesis explored making a thermal hydrolysate of collagen from the lambskin and an enzymatic hydrolysate from wool then combining the two extracts in a reaction mixture for flavour production and assessment. Proximate analysis of raw dewooled lambskin indicates its major components as moisture (75%) and crude protein (21%). Thermal extraction was initially conducted in steam at 5 psi (0.34 bar.g) pressure at various pH values. The maximum degree of solubilisation of solids was obtained at a pH of 3.55. A pH value of 4.5 was chosen for subsequent thermal hydrolysis, as further reduction in pH to 3.55 consumed large amounts of sulphuric acid. Thermal hydrolysis of lambskin was further explored at pH 4.5 to obtain collagen hydrolysates at three industrially convenient temperatures, 90°C, 108°C, and 121°C. The maximum degree of solubilisation of 89.3% was obtained for the lambskin treated at 121°C for 10 hours. Degree of solubilisation did not increase greatly with increases in temperature and time from 90°C to 121°C and from 2 hours to 10 hours. The optimal treatment condition from a process perspective was judged to be 108°C for 2 hours with a degree of solubilisation of 85%. The thermal hydrolysis itself was successful in producing collagen hydrolysates with low viscosity in the range of 2.2 to 5.6 mPa.s, which was measured using a Modular Compact rheometer at 40℃ and 11°Brix. The viscosity of the extract decreased as expected with an increase in treatment time. The degree of hydrolysis (DH), an indirect measure of the peptide chain length of the hydrolysate produced, was estimated based on the ninhydrin test. The DH increased from 26% to 37% with an increase in the processing times tested. The increase in the degree of hydrolysis indicates that smaller molecular peptides are formed, which in turn reduces the viscosity of the sample. Proximate analysis indicates that wool removed from lambskin is composed of 94.6% crude protein. Almost thrice the stoichiometric amount of sodium metabisulphite was used for sulphite pretreatment to soften the wool. Sulphite-treated wool was hydrolysed using the enzymes Neutrase® 0.8L, Alcalase® 2.4L FG, and Protamex®. The maximum degree of solubilisation of wool solids (50%) was obtained using Alcalase® 2.4L FG at an enzyme-to-substrate ratio of 3:100 at pH 7.5. Reaction mixtures were then prepared by mixing an organic sulphur source, ribose, and lambskin extract concentrated to 60°Brix. The ratio of organic nitrogen to organic sulphur was kept constant across all the reaction mixtures at about 10.6, whereas the ribose to collagen ratio was kept constant at 1:8. The organic sulphur sources trialled were cysteine, cysteic acid, sulphite assisted hydrolysate from wool, and alkali-assisted hydrolysate of wool (as a source of lanthionine). Sensory analysis of the samples by 25 untrained panellists confirms that cysteine is important in creating a meaty flavour profile. Sulphite-assisted hydrolysate from wool had the most pungent and animal-like flavour profile. Alkali-assisted hydrolysate of the wool, and hence lanthionine is not useful in creating flavours as the flavour note was very mild. Cysteic acid resulted in a burnt and caramel flavour note. This work did not liberate sufficient reactive cysteine from wool to indicate that woolly lambskin offers a useful meat flavour substrate.
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    Effects of freezing on physicochemical properties of Wagyu and crossbred beef : a thesis presented to Massey University for the partial fulfilment of the requirements of the degree of Master of Chemical and Bioprocess Engineering, Massey University, Manawatu, New Zealand
    (Massey University, 2024) Singh, Tarandeep
    This study investigates and compares the effects of different freezing rates (slow and fast freezing) on the meat quality parameters of Wagyu and crossbred beef. To study the effects on the meat quality of Wagyu and crossbred beef, different treatments were set up, and 60 beef rump samples were used in total. The samples were randomly assigned to three different regimens named FR (fresh, never frozen), FF (fast frozen), and SF (slow frozen), followed by thawing of the FF and SF samples at 4 °C for 24 hours. A compositional analysis was performed to compare the moisture and fat levels of both breed meat samples. The impact of moisture and fat levels on the freezing rate was then analyzed by mathematically modeling the freezing kinetics of Wagyu and crossbred beef. This analysis aimed to highlight the primary differences in thermal behavior between the two breeds. The effects of different regimens on meat quality were also evaluated using various meat quality measurements such as pH, color, tenderness, and water holding capacity. Both the uncooked and cooked meat samples of Wagyu and crossbred beef were used to compare various meat quality attributes. Other analyses used to indicate quality differences between raw meat samples were light and transmission electron microscopy (TEM). The experiment data shows that Wagyu beef generally outperforms crossbred beef in terms of tenderness (warner- bratzler shear force, WBSF), lower thaw, and cook losses. In addition, Wagyu beef consistently exhibited superior color characteristics, with higher values for lightness, redness, yellowness, chroma, and hue angle compared to crossbred beef. The freezing rate and breed significantly affected the moisture and fat content (p < 0.0001). Wagyu beef exhibited higher fat and low moisture content compared to crossbred beef. The freezing kinetics indicated that crossbred beef cools faster compared to Wagyu beef. During the pre-cooling phase of fast freezing, despite the rate constant (k = 1) being the same in both breeds, the cooling process for crossbred beef was faster, with a larger pre-exponential factor of 10.017 against 9.523. Additionally, during the subcooling phase of slow freezing, crossbred beef cools slightly faster than Wagyu beef, as evident by the larger value of the rate constant (0.69 versus 0.646) and the pre-exponential factor (17.245 versus 16.15). Regarding the meat quality analysis, Wagyu beef had a higher pH compared to crossbred beef for both uncooked and cooked samples. Freezing rate (slow or fast freezing) did not significantly affect pH (p > 0.05), but there was a statistically significant (p < 0.05) interaction between freezing rate and breed for both uncooked and cooked samples. Wagyu beef exhibited lower warner-bratzler shear force (WBSF) values for cooked samples, indicating greater tenderness compared to crossbred beef. Both freezing rate and breed type significantly affected warner-bratzler shear force (WBSF) (p < 0.05), with slow-frozen samples being the most tender. Crossbred beef (both fast and slow frozen samples) had a higher thaw loss (p < 0.05) than its Wagyu counterpart. Slow-frozen samples of both breeds exhibited greater thaw loss than fast-frozen samples (p < 0.05). Fast-frozen samples (both breeds) showed the least cook loss, while slow-frozen crossbred samples had the highest cook loss, indicating the freezing rate significantly affected cook loss (p < 0.05). Breed type did not significantly affect cook loss (p > 0.05), but there was a statistically significant interaction between freezing rate and breed (p < 0.05). Light microscopy (LM) and transmission electron microscopy (TEM) images of uncooked samples revealed that Wagyu samples, both slow and fast frozen, maintained their structure more effectively than crossbred samples under each regimen, as evidenced by their lower WBSF, thaw loss, and cook loss values. The difference between uncooked and cooked meat samples related to moisture retention, tenderness, and structural changes was also observed. Uncooked samples, particularly Wagyu, had higher fat and lower moisture, with thaw loss more pronounced in slow-frozen crossbred beef. Cooking reduced moisture further, with fast-frozen samples showing less cook loss. In terms of tenderness, uncooked Wagyu beef was naturally more tender than crossbred beef, but this difference became more pronounced after cooking, with slow-frozen samples of both breeds being more tender due to the structural breakdown of muscle fibers during freezing and cooking. Color differences, with Wagyu showing superior lightness and redness, persisted after cooking, maintaining better visual quality. Significant advantages were identified for the meat processing industry by the results of the Wagyu and crossbred beef quality experiments. Overall, these findings suggest that Wagyu beef, with its superior fat content and tenderness, offers distinct quality advantages over crossbred beef. The findings also suggest that fast freezing (FF) should be preferred method for both Wagyu and crossbred beef to minimize moisture loss during thawing and cooking. If tenderness is the primary concern, slow freezing (SF) method may be considered, particularly in case of Wagyu beef. However, the increase in thaw and cook loss must be taken into account.
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    The extraction, identification, and encapsulation of phenolic compounds from Prunus domestica subsp. institia towards their incorporation into a functional milk product : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatū, New Zealand
    (Massey University, 2022) Xia, Pu
    Damson plums are rich in bioactive compounds such as polyphenols, flavonoids, and anthocyanins, which are potent antioxidants with proven health-promoting properties. However, to date, there is no systematic publication/report about the type and concentration of various bioactive compounds in damson plums or using this type of plum as a food ingredient in the food industry. This study aimed to: 1) optimise the extraction of the bioactive compounds from Prunus domestica subsp. Institia (damson plums) grown in New Zealand using efficient extraction methods such as accelerated solvent extraction (ASE), ultrasound-assisted extraction (UAE), enzyme-assisted extraction (EAE), and their combined (E+UAE) extraction, in water or ethanol as the solvents; 2) analyse the total phenolic content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), and total antioxidant activities of the damson plums extract; 3) encapsulate the above-mentioned extract to protect the bioefficacy of its phenolic compounds; 4) compare the physical and chemical stabilities of the manufactured encapsulated ingredient in freeze-dried or liquid form during storage; and 5) assess the behaviour of the encapsulated plum extract after its incorporation into a functional milk product. Fresh New Zealand damson plums were freeze-dried and ground into a powder and extracted with different methods explained above. The freeze-dried damson plum powder (FDDPP) was then encapsulated in liposomes made of soy lecithin granules using high-shear homogenisation and/or microfluidisation. The encapsulation efficiency (EE) was assessed by the determination of various phenolic compounds using high-performance liquid chromatography (HPLC) before and after the application of Sephadex filtration to separate free phenolics and encapsulated phenolics. Finally, the encapsulants containing damson plum powder were incorporated into milk (whole/full-fat) as a functional beverage, and the effect on the physiochemical properties of the milk product was assessed. The results showed that the plum samples extracted using the ASE with water as the solvent for 40 min showed the highest phenolic, anthocyanin, and antioxidant properties. The EAE method appeared to improve the extraction of anthocyanins, possibly due to the retardation of anthocyanin hydrolysis as the consequence of inhibition of polyphenol oxidase (PPO). However, the UAE was likely to suppress the extraction of TAC because of the degradation of anthocyanin glucosides, resulting from the action of PPO induced by ultrasound. The E+UAE method demonstrated the maximum extraction efficacy for the TFC as the extraction time was increased to 60 min. Different extraction methods obtained various extraction efficacies for the seven phenolic compounds (neochlorogenic acid, gallic acid, rosmarinic acid, catechin, epicatechin, rutin, and naringenin) found in the FDDPP. For example, neochlorogenic acid, the predominant phenolic compound of New Zealand damson plums was significantly (p<0.05) higher in the samples extracted using the ASE method (with ethanol as the solvent) for 40 min (1393.2±29.7) than the other samples. On the other hand, rutin, one of the major flavonoids in damson plums, showed a significantly higher content (67.51±1.52) in the samples extracted using EAE for 40 min than the other extraction methods (p<0.05). Neochlorogenic acid achieved the highest EE (98.86%) with the additional microfluidisation step in liquid liposomal encapsulants. In comparison, EE was around 81.40% in the liquid liposomes produced by microfluidisation; whereas, high-shear homogenisation alone produced liposomes with a much lower recovery rate (about 75.52%) for this important phenolic component of damson plum extract. Thus, the additional microfluidisation step resulted in the manufacture of liposomes with higher physical stability and with a smaller average particle size (73.2±1.5 nm), and the highest zeta potential (-35.39±0.97 mV) for the empty liposomes in liquid form. This confirms the stability of the liposomal system manufactured for the current experiment. Milk was chosen as a suitable delivery vehicle (functional food) for the incorporation of the manufactured liposomes containing plum extract, due to its availability, convenience, and potential nutritional benefits. The physical and chemical stabilities of the phenolic compounds in the functional milk containing free and encapsulated plum extract were assessed using a pH meter, heometer, and HPLC analysis. No significant differences were seen in the viscosity of different milk samples containing free extract, encapsulated extract, and freeze-dried encapsulants. The encapsulants achieved by various homogenisation techniques showed different recovery rates for rutin, catechin, epicatechin, neochlorogenic acid, and rosmarinic acid from the milk containing the extract of New Zealand damson plum. However, further investigation is required to determine the effect of the extraction technique (i.e., ASE) and the liposomal encapsulation on the extraction and encapsulation efficiencies of New Zealand damson plums, respectively. Further study is also required to investigate the behaviour of encapsulated damson plum extract in different functional foods, the effect on their sensorial properties, and the bioaccessibility and bioavailability of its phenolic compounds after food consumption.
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    Characterisation of de-structured starch and its interactions in whey protein isolate gels : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Ang, Cai Ling
    Starch serves as an important additive to enhance the physico-chemical properties of many food products. With the increased pursuit of natural products, there is an increasing demand for “clean-label” starches. In this study, waxy potato starch was physically-modified at elevated temperatures of 120–150 °C for 30 min at 300 rpm, in a pressurised reactor. The treatment converted native starch granules into their macromolecular chains (denoted as de-structured waxy potato starch, DWPS). This doctoral thesis presents the: (i) method of modifying starch (i.e., the de-structuring process), (ii) the mechanism of starch de-structuring, (iii) the rheological changes in DWPS samples and the shear-thickening mechanism, and (iv) the interactions of these DWPS ingredients with whey protein isolate (WPI) in a protein-based gel system, at different pH and ionic strength. The molar mass (Mᵥᵥ), particle size, rheological properties, degree of branching (DB) and side-chain length distribution of DWPS samples were characterised to elucidate the starch de-structuring mechanism. DWPS treated at 120 °C DWPS showed similar Mᵥᵥ (~3.6 × 10⁸ Da) as its native form (~3.7 × 10⁸ Da) indicating that the treatment at 120 °C resulted in the disassembly of starch granules into their macromolecular chains. Reduction in viscosity, Mᵥᵥ and particle size was observed with an increase in temperature from 120 to 150 °C, suggesting a cleavage in amylopectin chains. The DB and side-chain distribution data suggest that the reduction in Mᵥᵥ is likely due to the cleavage at α-1,4 linkages near the middle of the main amylopectin backbone. Particle size analysis by laser diffraction measurements revealed the presence of large fragment particles (> 1 µm) in DWPS samples, indicating that the starch de-structuring process into its macromolecules was incomplete even at 150 °C for 30 min. The DWPS (5% w/w) samples were found to exhibit a wide range of rheological properties—Newtonian, shear-thinning, shear-thickening and anti-thixotropy behaviours—depending on their treatment temperature (120–150 °C). In particular, 120 °C DWPS exhibited interesting shear-thickening, anti-thixotropy and shear-induced gelation. These rheological properties are different from the shear-thinning and thixotropy behaviours observed in most conventionally gelatinised waxy potato starches treated at 95 °C. The complex shear-induced structures of 120 °C DWPS were attributed to a two-step process: (i) upon shear at the critical shear rate (~10–20 s⁻¹), the shear stress caused a size reduction in the starch fragments and (ii) the increased number of small fragments together with the amylopectin chains in very close proximity could lead to the formation of a complex network probably consisting of amylopectin chains and a large number of fragments (2–20 μm). Shear thickening properties were attributed largely to these soft fragment particles colliding and sliding past each other during shear. The data from this study has also shown that the hydrogen bonding, electrostatic, hydrophobic interactions, or the combination of these interactions did not cause the shear-thickening behaviour. The influence of 4% w/w DWPS on 13% w/w WPI gels was studied by characterising the phase stability of the liquid mixtures, and mechanical properties, microstructure, and water-immersion stability of fine-stranded polymeric and coarse-stranded particulate protein gels at pH 7 and pH 5, respectively. At neutral pH, synergistic gel hardness of WPI was obtained with the incorporation of 140 °C DWPS. The increased gel strength was attributed to the enhanced density of a very fine-stranded gel network. The ability of the gel to retain its shape when immersed in water for 40 h was most noticeable for the composite gels containing either gelatinised starch or DWPS samples (swollen gels but with intact shape). In contrast, pure WPI gel and composite gel containing maltodextrin turned into very weak fluid-like and disintegrated gels, respectively. At pH 5, WPI formed particulate gels. The addition of gelatinised starch or DWPS weakened the particulate protein gels, likely due to phase separation and interrupted protein network with starch polymers acting as inactive fillers. The effects of NaCl and CaCl₂ (i.e., type of salts and ionic strength) on the mechanical and microstructural properties of composite gels containing 13% w/w WPI and 4% w/w 140 °C DWPS were also evaluated. Thermodynamic incompatibility between WPI and 140 °C DWPS was observed upon the addition of NaCl (~75 mM) or CaCl₂ (10–75 mM). The combined effects of such thermodynamic incompatibility with the changes in protein connectivity induced by varied ionic strength led to the formation of distinctive gel structures (inhomogeneous self-supporting gels with a liquid centre and weak gels with paste-like consistency) that were different from thermodynamic compatible homogeneous self-supporting gels (pure WPI and WPI + maltodextrin gels). At ≥ 250 mM NaCl, instead of a paste-like texture, a recovered soft self-supporting gel structure was observed when using 140 °C DWPS. The ability to generate a range of textures in WPI gelation-based foods by using 140 °C DWPS under different ionic conditions, is a feasible strategy for structuring high-protein foods for dysphagia—aimed to be either thickened fluids or soft solids. Additionally, this acquired knowledge is also relevant when formulating food gels for 3-D printing. The desirable rheological properties of DWPS samples and their ability to alter WPI gel structure signify the potential of DWPS as a clean-label ingredient to structure foods of specific needs (e.g., whipping cream for enhanced structure upon shear and high-protein foods for dysphagia sufferers).
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    Extraction, optimization, and functional properties of a novel plant protein from kiwifruit (Actinidia chinensis) seeds using ultrasound : a clean and green extraction procedure : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatū, New Zealand
    (Massey University, 2022) Bisht, Ashutosh
    The current trend of protein production in New Zealand is primarily focused on proteins sourced from dairy and meat which are known to generate enormous amounts of greenhouse gases and carbon footprints. Thus, to establish a flexitarian world for future sustainability, novel plant proteins from several sources are being recognized and researched lately so that they could replace the meat proteins. One such source of protein are oleaginous plant seeds which are being imagined and explored as a renewable resource of plant proteins worldwide. The oleaginous seeds and seed meals from oil extraction industries, cosmetic industries, and beverage industries related to kiwifruit, represent a significant waste of protein present in these seeds. Moreover, in New Zealand Actinidia Chinensis production, exports and wastage have been increasing manyfold since last decade, as the fruit commodity is shifting from a high-end product to more generalised fruit. Thus, to explore the novel protein in seeds and seed meals of Actinidia Chinensis this study was carried out. Actinidia Chinensis seeds were purchased from Pure ingredients Ltd. New Zealand and were primarily investigated for their physicochemical characteristics to understand the properties of the starting material for the protein extraction process. The seeds were then pulverized, defatted, and analysed for its microstructure and proximate compositions to understand the effect of defatting and grinding on protein contents of defatted seed flour from the Actinidia Chinensis seeds. Further, seed protein was extracted using two different extraction technologies. A clean and green extraction technology; ultrasonication and the conventional stirring method of protein extraction. The results show that ultrasound extraction significantly increased the overall protein yield from the defatted seed flour by 12% if compared to the conventional method. The optimized extraction parameters for the ultrasonic extraction of defatted Actinidia Chinensis seed meal were pH 11.5, temperature 55⁰C, ratio of seed flour to solvent (4:100) and 100 mins of ultrasonic extraction. pH was identified as the most significant factor involved in successful extraction of proteins from kiwifruit seeds whereas temperature and ratio were respectively significant factors after pH. SEM was used to analyze the effects of ultrasonication on the seed meal, seed flour and seed protein extracted from the Actinidia Chinensis seeds. The results confirmed significant effects of fragmentation and cavitation caused by ultrasound waves on seed meal, flour, and protein respectively and increased the protein extraction yield by 12% in this study. The amino acid analysis of seed protein in this study defines a typical acidic profile for Actinidia Chinensis, where glutamic and aspartic acid were the dominating amino acids which defines an acidic profile. the most abundant essential amino acids were Leucine, Lysine and Valine respectively and the least available EAAs were the sulphur AAs such as Cysteine and Methionine. Moreover, in the final sections of this study a few functional properties of the seed protein concentrates are compared with the functional properties of conventionally extracted protein. The results reveal a significant increase in the WHC and OBC of the protein concentrate, whereas the least gelation capacity of the proteins was also positively affected by ultrasonic assisted extraction of kiwifruit seed proteins.
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    Optimisation of kombucha fermentation : a thesis submitted in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand
    (Massey University, 2022) Gangurde, Ashwini Navin
    Kombucha is a slightly acidic, self-carbonated and refreshing fermented beverage made from sugared tea by the symbiosis of yeast and acetic acid bacteria (AAB). The symbiotic culture exists in a biofilm commonly called ‘symbiotic culture of bacteria and yeast’ (SCOBY) and fermented broth. Kombucha is popular in many regions of the world and its production relies on natural fermentation by an undefined complex mixed starter culture. Therefore, the fermentation process results in products of variable quality among the producers and even by the same individual processor. The efficiency of non-alcoholic Kombucha fermentation is determined by the final ethanol content, residual sugar and acidity at the end of fermentation. Kombucha beverages sold in the market are biologically active, therefore the fermentation continues during storage as the yeast and bacteria thrive on the residual sugar present in the final product. During storage, secondary fermentation generates the desired carbonation and also reduces residual sugar in the final products, but the microbial activity may also result in the production of beverages with higher alcohol levels than permissible. In New Zealand, Kombucha is categorised as a non-alcoholic beverage with alcohol of no more than 1.15% ABV or 0.5 % ABV (Australia). Kombucha brewers generally find it difficult to produce consistently high-quality products with low alcohol as stipulated by the Food Standards Australia New Zealand regulations. The present study aimed to optimise the fermentation process using robust experimental plans to produce a stable low alcohol fermented Kombucha with low sugar. The present research work was conducted in three Phases and the experiments were repeated twice with duplicate analyses. Phase 1 involved selection of the best fermentation conditions to propagate the Kombucha starter culture comprising ‘fermented broth and cellulose pellicle (SCOBY)’ using fermented broth as the starting material. The factors used in this Phase were sugar (3% and 4.7%, w/v) and tea (0.3% and 0.5%, v/v), inocula (12.5% and 20%, v/v), fermentation temperature (22℃ and 24℃) and the formulations were fermented for 14 days. To select the best propagation conditions for the growth of starter culture comprising SCOBY and fermented broth, acidity, total soluble solids (TSS), weight of SCOBY and microbial concentrations (yeast, AAB, total counts) were determined during fermentation. Yeast were enumerated using yeast extract glucose chloramphenicol agar (YGC) agar, AAB were enumerated by yeast extract peptone mannitol (YPM), and total counts by plate count agar (PCA). The best fermentation conditions for the growth of the culture were then selected and adopted for use in the subsequent experiments. Phase 2 investigated the best conditions for the fermentation of Kombucha using a combination of SCOBY and fermented broth as starter culture, in two stages (Stage 1 and Stage 2). Two sugar concentrations (3% and 4.7%, w/v) and two fermentation temperatures (22℃ and 24℃) were used in Stage 1 to determine the optimum sugar concentration and fermentation temperature required to ferment Kombucha for 9 days (primary fermentation). Stage 2 investigated the effect of filtration on Kombucha during storage (4°C) for a week, post-primary fermentation (9 days). Physico-chemical (TSS, acidity, colour) and microbiological (yeast, AAB, total counts) characteristics of the beverages were determined in the two stages including the measurement of colour (CM-5 Konica Minolta spectrophotometer Japan). The beverages were also evaluated by 5-7 focus sensory panellists in Stage 1 and consumer sensory panellists (n=35) in Stage 2, using a 9-point hedonic scale. The storage stability (4 °C) of the selected formulations from Stage 2 (Phase 2) were evaluated in Phase 3 for three weeks (4℃). In addition to the analyses conducted in Phase 2, concentrations of sugars, ethanol organic acids and antioxidants were determined during fermentation and storage. The developed beverages were also evaluated by consumer sensory panellists (n= 108). Results showed that the formulation (Phase 1) that contained 3% sugar, 0.5% tea, 20% fermented broth and fermented at 24℃ produced the best growth of the starter culture. In Stage 1 (Phase 2), titratable acidity (T.A.) and microbial counts increased (p<0.05), while pH, TSS (p<0.05) and overall acceptability by a focus sensory panel decreased for samples fermented with low sugar concentration (3%, w/v) at 22℃ and 24℃. In Stage 2, T.A. and microbial counts increased (p<0.05), while pH, TSS and consumer sensory scores decreased (p<0.05) for the Kombucha samples (filtered and unfiltered) fermented at 24 ℃. Samples (filtered and unfiltered) containing 4.7% sugar and fermented at 22 °C received higher overall consumer sensory scores (7.30±0.32 ;6.98 ±0.19) compared to the sample that contained 4.7% sugar and fermented at 24℃. Therefore, this formulation (4.7% sugar; fermentation temperature 22℃) was selected for further evaluation of the filtered and unfiltered samples in Phase 3. In Phase 3, the filtered beverage containing 4.7% sugar, 0.5% tea, 20% fermented broth and fermented at 22℃ received the highest sensory scores for overall acceptability (7.26±0.88) after storage for three weeks (4°C). The lower acidity, ethanol, and sugar (sweetness) of filtered samples (p<0.05) compared to unfiltered samples may have contributed to the better overall liking by the panellists. The lower levels of organic compounds in the filtered sample may be due to reduced metabolic activities caused by the partial removal of trapped cultures in the matrices of the cellulose during filtration. The colour of the fermented beverages was stable during fermentation and no significant changes were observed during storage for 3 weeks (p<0.05). Overall, the filtered sample contained higher concentrations of antioxidants than the unfiltered which may be beneficial to human health. In conclusion, low alcohol Kombucha was successfully produced after filtration, post-primary fermentation at low temperature. The ethanol content of the filtered beverage was <0.5% ABV, which complied with the Australia NZ Food Standards Authority regulation. Furthermore, the residual sugar in the filtered beverage was markedly lower than reported in previous studies. The optimised beverage was stable during refrigerated storage and was well accepted by sensory panellists. The beverages had a pH<4.6, which is generally considered as safe. Therefore, the optimised Kombucha fermentation process resulting from this study has potential for commercialisation. However, further work is required to integrate the filtration step and scale-up.
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    Formation and characterisation of stirred yoghurts enriched with avocado pulp : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand
    (Massey University, 2021) Guo, Mingyang
    Avocado stirred yoghurt has huge market potential with the expanding market of fruit flavoured yoghurt and the increasing health concern of the public. However, the avocado is highly perishable due to its high content of monounsaturated fatty acids sensitive to lipid oxidation as well as its polyphenol compounds sensitive to enzymatic browning. Considering the conventional treatment like heating may not be suitable for use, there is a challenge of preserving the physicochemical properties and microbial stability of avocado added into yoghurt during storage. This study aimed at investigating the methods of appropriate treatments of avocado for extending the shelf life of avocado-fortified stirred yoghurt and characterising the yoghurt in terms of various properties. Firstly, to choose suitable treatments, different concentrations (1% and 2%) of citric acid and ascorbic acid, high-pressure processing (HPP) treatment (600 MPa, 5 min) and their combination were used to treat avocado before its incorporation into yoghurt containing 10% avocado pulp. Several parameters, such as pH and colour measurement (CIE L, a*, b* values), were analysed from avocado-fortified yoghurt samples during storage for 4 weeks at 4°C. The instrumental measurement of colour change was recorded for 26 days to determine which method of the treatments was more effective in preserving the colour of yoghurt samples. Results showed that the colour change of avocado yoghurt occurred predominantly in the first week which was caused by a decrease of L* value (lightness) and an increase of a* value. The total colour change (ΔE) of avocado yoghurt containing avocado treated with ascorbic acid was below 2 in 26 days. Lower efficiency was found from citric acid where the ΔE value (colour change) was below 4 compared to the untreated sample around 6. Besides, the pH change of avocado stirred yoghurt was more sensitive to citric acid which decreased the pH of avocado yoghurt from around 4.45 to 4.29 and 4.15 at 1% and 2%, respectively. Meanwhile, no significant influence was observed for the HPP treatment on colour stability as well as the pH value of the sample. The treatments of avocado with ascorbic acid (2%) and HPP (600 MPa/5 min) were further studied about their effects on yoghurt, including microbial quality (lactic acid bacteria and microbial contamination), rheological properties, syneresis, colour and pH. It was found that HPP treatment was the key factor to keep yoghurt syneresis (around 1%) low, minimizing the extra syneresis that could be caused by introduced avocado content. Also, the rheological test illustrated its function to increase and maintain the thickness of avocado stirred yoghurt during storage for 4 weeks. In terms of ascorbic acid, no significant effect on rheological properties was observed by the incorporation of ascorbic acid. Neither of these treatments (HPP or ascorbic acid) influenced the growth of lactic acid bacteria in yoghurt. No yeast and mould or coliform were detected in samples during the whole experiment trials. The effect of those treatments on sensory properties during the shelf-life of yoghurt (4 weeks) was also evaluated. The results showed that the sensory properties of untreated avocado-fortified yoghurt dropped dramatically in 2 weeks for an overall consumer acceptance score from 7.16 to 2.25. On the other hand, HPP treatment and incorporation of ascorbic acid significantly maintained the overall acceptance. HPP treatment specifically affected the texture profile of the sample by maintaining its thickness. Ascorbic acid significantly (p < 0.05) increased the flavour score from 2.72 to 6.89 and the appearance score from 4.79 to 5.55. It was found that the main effect of ascorbic acid to improve the sensory properties was to preserve the green colour and inhibit the development of rancid flavour in the product. Besides, neither of these treatments was observed to significantly influence the sourness of the sample, and the interactive effect was not observed between HPP treatment and ascorbic acid. In conclusion, combining 2% of ascorbic acid and HPP treatment on avocado was found to be most effective in various ways (colour, texture and sensory properties) in extending the shelf life of avocado stirred yoghurt with non-significant influence on pH after 1 week storage.
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    Preparation and characterisation of avocado cream cheese : effects of different treatments and ratios of avocado puree : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand
    (Massey University, 2021) Hu, Yinxuan
    Cream cheese fortified with the addition of avocado puree to improve its nutritional value has not been developed in the food industry, although some studies have researched the possibility of mixing cream cheese products with other fruits. This research study initially aimed to develop a novel cream cheese fortified with avocado puree by finding the appropriate concentration level and a proper processing condition to preserve avocado puree from colour degradation. Four levels of avocado puree (0, 10, 20 and 30%) were investigated in this research to figure out the effect of avocado puree concentrations on cream cheese quality and stability during 28-day storage to select one proper avocado concentration. Then, three different treatments of avocado puree were used for preserving avocado puree in this research, such as i) addition of ascorbic acid, ii) use of high-pressure processing (HPP), and iii) a combination of HPP and ascorbic acid, to investigate whether these treatments had any effects on the avocado puree fortified cream cheese quality and stability during the storage at 4°C for 4 weeks. This research characterised several essential properties of cream cheese, including textural properties, colour stability, microbiological safety, rheological properties, and microstructure. This research aimed to determine the impacts of avocado puree and treated avocado puree on cream cheese's formation, properties, and stability. The cream cheese samples prepared in this research were analysed weekly after preparation and during storage. After researching these basic cream cheese properties, a comprehensive sensory evaluation was conducted to determine consumers preferred avocado puree concentration and processing condition. The results revealed that adding 20% (w/w) of avocado puree in cream cheese and treating it with HPP with the addition of ascorbic acid was the most suitable approach to developing an avocado-fortified cream cheese with desired sensory properties and stability. All physicochemical properties of avocado-fortified cream cheese produced in this research appeared to be significantly affected by avocado levels, especially at 30% concentration, and the different methods of treatment applied to avocado puree had a slight impact on the cream cheese’s properties compared to the control sample (cream cheese with untreated avocado puree, i.e. without HPP and ascorbic acid). As mentioned above, the most appropriate avocado puree concentration in cream cheese was 20% in this study. To be specific, cream cheese added with 20% avocado puree showed relatively stable textural and rheological properties during storage for 4 weeks at 4°C. The sensory evaluation results showed that participants preferred cream cheese containing 20% avocado puree among the four levels of avocado puree (0, 10, 20 and 30%). As for the effects of avocado puree’s processing conditions, adding ascorbic acid as an additive in HPP-treated avocado puree was found to contribute better to lowering colour changes and syneresis in cream cheese samples. This treatment also showed a relatively small impact on changes in the cream cheese’s textural properties and the flow behaviour during storage at 4°C compared to other treatments. Also, it helped cream cheese containing avocado puree only had a slight change in colour with the total colour change (∆E) value of 1.31 and less syneresis (2.63%) after the storage period compared to the other samples. Besides, more than 50% of participants had positive opinions on this sample from sensory evaluation. However, this project did not research other possible concentrations of avocado puree and their treatments, such as adding other kinds of antioxidants, chelating agent and hydrocolloids. These other variables are recommended to investigate for further development. This project provides vital insight into developing a novel avocado-fortified cream cheese and suitable processing to protect avocado puree from degradation in cream cheese during storage.
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    Characterisation of plant oil bodies and their application as delivery systems of bioactive compounds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Manawatū, New Zealand
    (Massey University, 2021) Garcia, Francesca Louise P.
    Oil bodies are small, spherical organelles that store triacylglycerols (TAG) in plants. They are derived as natural oil-in-water emulsions and their unique interface composed of a monolayer of phospholipids embedded with proteins provides great stability against physical and chemical stresses. This study aimed to characterise oil bodies extracted from hemp and mustard seeds and determine their potential as delivery systems to encapsulate β-carotene, a model of hydrophobic bioactive compound. Hemp and mustard oil body fractions obtained after aqueous extraction were characterised in terms of particle size, surface charge, microstructure, and behaviour at different pH (2-10) conditions and ionic strengths (0-1,000 mM NaCl). β-carotene was then encapsulated into oil body systems at a concentration of 400 μg/g oil using intact and disrupted oil bodies. The colloidal and β-carotene stability of these oil body systems were analysed for 14 days at different storage temperatures (4°C, 22°C, and 50°C) and light conditions (with and without light at ambient temperature) by determining their particle size, surface charge, colour, and β-carotene content. Mustard oil bodies were entrapped in flocs of extraneous proteins even when extracted at alkaline pH (9), making it difficult to achieve their successful extraction. Hemp oil bodies, however, were isolated with minimal flocculation. They exhibited high electrostatic stability at neutral pH, aggregated at pH values close to the isoelectric point of the oleosins (pH 4 and 5), and had reduced ζ-potential with the addition of salt (NaCl ≥ 62.5 mM). Hemp oil bodies were used to encapsulate β-carotene in delivery systems. In intact oil bodies, the use of solvents (ethanol, hexane, and diethyl ether) did not enhance the partitioning of β-carotene to the TAG core of oil bodies (low encapsulation efficiency of <40%). In contrast, heating (50°C, 10 min) and mild sonication were able to directly incorporate crystalline β-carotene into the hemp oil body fraction. When oil bodies were homogenised, their membrane material fragments were able to stabilise the interface of newly formed oil droplets, but flocculation was observed. Heat-induced destabilisation of oil bodies (stirred for 1 h at 70°C) led to the extraction of oil body membrane materials (OBMM), which were used as emulsifiers of β-carotene-loaded hemp oil emulsions. During storage for 14 days, these β-carotene-loaded oil body systems remained stable at 4°C and 22°C, but storage at 50°C caused a significant reduction (p<0.05) in their colloidal and chemical stability. However, their stability was unaffected by the presence of light during storage at room temperature. Compared to the WPI-stabilised emulsion, the OBMM-stabilised emulsion exhibited a comparable colloidal stability while the homogenised and non-homogenised oil bodies had a similar retention of β-carotene. Overall, oil bodies can be utilised as encapsulation systems for bioactive compounds. These systems exhibit comparable stability to protein-stabilised emulsions during storage. However, a balance between their colloidal and chemical stability must be achieved to enhance their functionality for commercial application. Further characterisation of the composition of their membrane materials is recommended to fully elucidate the mechanisms by which they can stabilise emulsions and protect the bioactive compound against degradation.
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    Improving freeze thaw stability in dog rolls through selected meat binders : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Manawatu Campus, Palmerston North, New Zealand
    (Massey University, 2020) Sei, Jerry Wakon
    This Masters thesis was conducted to investigate the potential use of selected food gums, accepted and approved legislatively both within New Zealand and abroad, to improve the Freeze thaw stability of dog roll products. Dog rolls have evolved into popular pet food products marketed for the high-end user due to its high meat content and controlled use of additives. Given its popularity within New Zealand, it is currently only marketed locally due to having a short shelf life of up to three months at refrigerated storage. To increase market opportunities overseas, the shelf life of dog rolls must be increased, and freeze thaw stability must be maximised to allow export to market overseas under frozen storage. Improving the freeze thaw stability of dog rolls was carried out based on commercial considerations, customer acceptability and guided by a selection criterion to satisfy requirements of developing an acceptable commercial product within New Zealand and abroad. Product performance was based on analysing current commercial products under pilot scale performance using best performing functional ingredients and assessed using TPA hardness and measuring thaw drip loss after one freeze thaw cycle. Several hydrocolloids were considered potential candidates upon which only sodium alginate and iota carrageenan combined with the synergistic effect of xanthan gum and locust bean gum eventuated in an acceptable product when formulated with a chicken and pumpkin dog roll. The same combination of ingredients was tested using a beef and beetroot base product which did not achieve the same effect as in a chicken and pumpkin base product. The best performing combination of functional gums which improved the chicken-based dog rolls comprised kappa carrageenan (0.39 %), xanthan gum (0.07 %), LBG (0.22 %), CaCO₃ (0.04 %), and sodium alginate (0.23 %). Iota carrageenan performed similarly to sodium alginate when used in the same proportion in combination with the other gums and remained the favourable alternative ingredient over sodium alginate due to its lower cost while improving product performance for freeze thaw stability. Further optimisation for beef and beetroot dog roll products was recommended by assessing raw beef meat composition or using alternative vegetable filling.