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Item Characterisation and protein complexation of an anthocyanin-bound pectin extracted from New Zealand blackcurrant (Ribes nigrum) : 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) Salleh, NurhazwaniThe main objective of this thesis was to investigate the cause of physical instability in blackcurrant juice-milk system. Poor phase stability in fruit juice-milk beverages is a major challenge for the clean-label beverage industry as milk protein can interact with fruit components, like polysaccharides and polyphenols, generating unwanted characteristics such as coagulation of milk proteins and phase separation. Hence, the principal step to understand the causes of poor phase stability was to identify and study the key interactive components of the juice, which was extracted from the New Zealand blackcurrant (Ribes nigrum), and then investigate their interactions with milk proteins. The key components of the blackcurrant juice were first isolated using mild extraction procedures, via ethanol precipitation and dialysis, and were identified as a complex fraction particularly rich in pectin and anthocyanins (Chapter 4). Proximate analysis revealed that the fraction contained carbohydrate (78% w/w), uronic acid (21% w/w), protein (4.8% w/w), anthocyanin (3.9% w/w) and calcium (2.2% w/w). The pectin-rich fraction had a net negative surface charge of -23.1 mV (at pH 4.8), a pKₐ value of 1.7 and a relatively high degree of esterification (65.2%). Constituent sugar analysis showed that the fraction was mostly made of galacturonic acid, rhamnose, arabinose and galactose, and NMR spectroscopic analysis revealed that it was rich in rhamnogalacturonans with arabinogalactan side chains. This pectic fraction was unique as it was highly pigmented, with cyanidin 3-O-rutinoside as its major anthocyanin. Liquid chromatography revealed that the anthocyanins were tightly bound to the fraction as methanol used in the technique failed to separate them. Results from size-exclusion chromatography coupled with multi-angle laser light scattering showed that the blackcurrant juice contained two major pectic fractions—≈283 kDa present at 14.6% w/w and ≈97 kDa at 85.5% w/w—with the latter producing higher UV₂₈₀ ₙₘ signal, signifying that proteins and/or polyphenols were present mainly in the second fraction. Association of anthocyanins to biopolymers like pectin and protein can occur via multiple interactive forces (electrostatic, hydrophobic and hydrogen bonding forces), and pH is known to play a significant role as it can affect the associative mechanisms of anthocyanins by changing their molecular configuration and ability to electrostatically interact. An attempt to dissociate blackcurrant anthocyanins from the blackcurrant biopolymers was carried out by disrupting electrostatic interactions and changing the planarity of anthocyanins via pH adjustments and ultra-filtration (Chapter 5). Lowering the juice pH to 2 did not result in anthocyanins dissociation, likely because anthocyanins were bound to the biopolymers by other interactive forces apart from the electrostatic bonds. Increasing the juice pH to 4.5 might have dissociated some anthocyanins from the biopolymers, but this was not reflected in the analysis of anthocyanins, probably because the freed anthocyanins had degraded before the analysis was carried out. Overall, size segregation of the juice components via ultra-filtration was relatively effective. Regardless of the pH, majority of the anthocyanins were still tightly associated with the large molecular weight biopolymers, confirming the involvement of multiple interactive forces. In order to uncover the cause of phase instability in blackcurrant juice-milk system, a complexation study between the isolated pectin-rich fraction and whey proteins was conducted (Chapter 6). The impact of bound anthocyanins on pectin-protein interactions was studied by exploring the effects of pH (pH 3.5 and pH 4.5), heating (85 °C, 15 min) and heating sequence (mixed-heated or heated-mixed). The pH was found to influence the colour, turbidity, particle size and surface charge of the mixtures, but its impact was most drastic when heating was introduced. Heating increased the amount of blackcurrant pectin within the complexes—especially at pH 3.5, where 88% w/w of the initial pectin was found in the sedimented (insoluble) fraction. Based on physical stability measurements, the mixed-heated system at pH 4.5 displayed better stability than at pH 3.5. A noteworthy finding was that heating sequence was found to be effective in preventing the destabilisation of the systems. Mixing of components before heating produced a more stable system with small complexes (<300 nm) and relatively low polydispersity. However, heating whey proteins before mixing with blackcurrant pectin prompted protein aggregation, producing large complexes (>400 nm) that worsened the destabilisation. The influence of bound anthocyanins on pectin-protein complexation was further studied by comparing two types of pectin-protein mixtures: (i) a mixture that is rich in anthocyanin (blackcurrant pectin-whey protein, BCP-WP) and (ii) a mixture that is free of anthocyanin (citrus pectin-whey protein, CP-WP) (Chapter 7). The mixtures were prepared at pH 4.5 with and without heat treatment at 85 °C. The study revealed that there was no direct relationship between anthocyanin presence and the destabilisation of mixtures. The Fourier-Transform Infrared (FTIR) spectrum of the heated and non-heated BCP-WP sedimented fractions showed the emergence of a peak at 800-1200 cm⁻¹, signifying the presence of anthocyanin-protein interactions. This peak, however, was absent in the spectrum of any of the anthocyanin-free CP-WP sedimented fractions, indicating that the bound anthocyanins of blackcurrant pectin provided the whey proteins with additional binding sites. The findings from FTIR analyses also indicated that non-electrostatic forces were most likely the governing forces of the heated BCP-WP mixture, via hydrophobic interactions and later reinforced by hydrogen bonds upon cooling. This thesis revealed that poor phase stability of the blackcurrant juice-milk system should not be attributed exclusively to the blackcurrant juice components, particularly the polyphenols. Environmental factors like pH and heat were likely the leading cause of phase instability as they could intensify the interactions that occurred in the mixed system, which eventually destabilised the mixture. This suggests that appropriate processing conditions can be applied to positively affect the blackcurrant juice-milk system.Item Atomization of fruit juice with fibres as drying aid : nozzle : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemical and Process Engineering at Massey University, Palmerston North, New Zealand(Massey University, 2019) Mohd Rozali, Siti NadjihaSpray drying of fruit juices is desirable as it produces dry powders which extend the shelf-life, reduce storage and transport costs, and produce a free-flowing powder which makes it easier to blend as an ingredient. Commercially, maltodextrin is added to the juices as a drying aid to increase the efficiency of the spray drying process. In this project, pomace fibres were investigated as an alternative drying aid. The main attraction of pomace fibres as a drying aid is the pomace fibres are originally derived from the fruits itself. This study explores the rheological behaviour of juice-fibre suspensions inside the spraying device, specifically the nozzle, to ensure high efficiency powder production by enabling atomization of the mixtures. This study also sought to determine the type of nozzle and operating conditions for efficient atomization of the juice-fibre suspensions inside the spray dryer. Flow-fields inside a nozzle consists of shear and extensional flows. Previous studies on the shear rheology of fibre suspensions revealed the addition of fibres creates a non-Newtonian shear-thinning liquid. The studies on extensional rheology of fibre suspensions, however, were absent. It is widely known the atomization of liquids with both shear and extensional resistances, require additional energy for atomization when compared to Newtonian liquids or viscous non-Newtonian liquids of a similar intrinsic viscosity. In this work, four types of fibres with different aspect ratios were investigated. Some of the significant and notable methods achieved during the study include 1) the use of capillary viscometer to examine the shear rheology of fibre suspensions at shear rates up to 20 000 s⁻¹, which represents the calculated shear rate experienced during atomization, 2) the building of a portable capillary breakup extensional rheometer to accurately characterize the extensional rheology of the fibre suspensions at high extensional strain rates and 3) the use of flash photography technique to capture the atomization patterns. Important findings from this work include: • Fibre suspension is a non-Newtonian shear thinning liquid with shear viscosity dependents on the fibre aspect ratio. The shear thinning behaviour continued until the shear rate of 25 000 s⁻¹ and a plateau occurred at 25 000 s⁻¹ shear rate. The plateau is independent of the fibre aspect ratio. • The fibre suspension exhibited extensional resistance. The extensional rheological properties of the fibre suspensions were dependent on fibre aspect ratio. When comparing between the shear and extensional rheology of a specific fibre suspension, the transient extensional viscosity, 𝜂⁺𝐸 of the fibre suspension was relatively greater than its corresponding shear viscosity. • The entrance pressure drop into the nozzle was significantly increased with the addition of fibre. This made the use of a pressure nozzle inefficient. It was advised by personal discussion with industry experts that rotary atomizers usually fail in atomizing extensional liquids, so its application was not explored in this study. • Spray visualization showed the extensional resistance of the fibre suspensions significantly affected the atomization behaviour and pattern (droplet size distribution) by forming filament structures connecting successive droplets together. This pattern was absent in Newtonian atomization. • Successful atomization of fibre suspensions was achieved by using a two-fluid nozzle at high atomizing air velocities and at air-to-liquid ratio above 0.25. At an atomizing air velocity of 150 m/s, the atomization performance is dependent on the fibre aspect ratio, but this effect was reduced at higher atomizing air velocities. At the highest tested atomizing air velocity of 240 m/s, all fibre suspensions yielded a volume-based average droplet size, D(v,50), of 200 – 250 µm. • Using a two-fluid nozzle at high atomizing air velocities, the droplets sizes of the fibre suspensions insignificantly reduced when the temperature of the inlet fibre suspensions was increased. No change was observed to the atomization performance when an ultrasonic mechanism was added to the two-fluid nozzle as an attempt to improve the atomization performance. • A method of predicting the atomization performance of a given two-fluid nozzle from its dimensionless numbers, for actual spray dryer applications, was demonstrated and the results showed that the two-fluid nozzle can be used inside a spray dryer if the air-to-liquid ratio exceeds 0.25. Overall, the methodology used in this thesis provides a systemic means of investigating the suitability of an atomization method for the spraying of a non-Newtonian fluid with extensional rheological properties.Item Prediction of the glass transition temperature of fruit juice powders : a thesis presented in partial fulfilment of the requirements for the degree of Doctor in Philosophy in Process Engineering at Massey University, Manawatu, New Zealand(Massey University, 2019) Linnenkugel, SebastianTo overcome the limited shelf life of fresh fruit juice, manufacture aim to reduce the juice to a powdered form that can be available all year around. One technique of powder formulation is the use of spray dryer. However fruit juices are rich in fruit sugars and organic acids, which make them difficult to spray dry. Their low glass transition temperatures lead to stickiness problems in the spray dryer. This work investigates the prediction of the glass transition temperature (Tg) of fruit juice powders and mixtures including high molecular weight components often used as drying aids of their mixtures. The ability to predict glass transition temperatures enables optimization of powder formulations and spray dryer operation to avoid sticking problems. A semi-empirical model is presented to predict the glass transition temperature of fruit juice powders on the basis of the chemical composition and the Tg values of the individual pure components. The Flory-Huggins Free Volume theory is used to describe the relation between the water activity of the powders and the glass transition temperature based on the composition of the powders. These prediction models were tested for different freeze dried multicomponent systems and validated against the glass transition temperatures measured by Differential Scanning Calorimetry (DSC). The model was then applied to predict the Tg of values freeze dried juice and vegetable powders prepared from commercial juice concentrate. The six fruit and vegetable juice powders exhibited higher measured Tg values at zero water activity those that predicted from the model. The 6-14˚C difference between the measured and predicted Tg values cannot be explained purely by the main sugar and organic acid components, but are rather linked to the presence of residual breakdown products of pectins and other polysaccharides from the base fruit. For several powders, a second glass transition temperature was visible in the DSC thermogram, which can be attributed to these additional components. The prediction of the glass transition temperature of the pure juice powders at various water activities showed better agreement with the experimental data the closer the predicted and measured Tg value of the powders was at zero water activity. The Tg values of different low molecular weight components and the polysaccharide maltodextrin DE 9-13 often used as a drying aid was studied. The Tg for the binary and multicomponent systems was well estimated by the prediction model at zero water activity. The addition of higher amounts of maltodextrin DE 9-13 up to a weight fraction of 0.7 in the mixture resulted in a widening of the transition observed in the DSC thermogram, which can be attributed to dynamic heterogeneity of the samples due to the dynamic response times of different domains in the solid matrix. This could be demonstrated by annealing the samples below their glass transition temperatures for 16 hours. The analytical semi-empirical model proved to be a viable method for predicting the glass transition temperature of mixtures of low and high molecular mixtures. Multicomponent systems consisting of more than one high molecular weight component in the form of various soluble polysaccharides and the monosaccharide glucose were investigated for their Tg values at zero water activity. The different mixtures of the low molecular weight components and polysaccharides showed a shift in the glass transition temperature that depended strongly on the Tg value of the pure polysaccharide. However, the overall trend of Tg values for the mixtures of low and high molecular weight components was found to be similar for all mixtures. The Tg values of all systems with various polysaccharides were well predicted. It also highlighted that a weight fraction of above 0.5 for the polysaccharides with a degree of polymerization of sugar units above 5 is necessary in the solid matrix to have a significant impact on the glass transition temperature. Salts were tested as an alternative drying aid to high molecular weight components at various ratios to the monosaccharide glucose. The salts increased the glass transition temperature of the blends at lower concentrations. A weight fraction of 0.2 of salts in the system has the same effect on the Tg values as a 0.5 weight fraction of a higher molecular weight component. The difference in necessary amount to increase Tg can be attributed to the different mechanisms of salts and polysaccharide in the solid matrix. To demonstrate the utility of the model, it was applied to optimize the spray drying of blackcurrant juice concentrate, with the aid of maltodextrin DE 9-13. It has been reported that sticking can be avoided during drying if the operating temperature does not exceed T=Tg + 25˚C. By combining the prediction of the Tg of the solid mixture at various water activities and a mass and energy balance over the spray dryer, reasonable feed composition and operational conditions were found. This allowed the successful conversion of blackcurrant juice into a powder in a single trial without relying on trial-and-error approaches.Item Beverage consumption in Auckland primary school children : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2019) Smirk, EmmaBackground: The New Zealand (NZ) Ministry of Health advises that plain water and plain low-fat milk should be consumed daily and that if children are to drink sugar-sweetened beverages (SSB) they should be limited. The latest comprehensive NZ beverage intake data in 8 to 12 year old children was published in 2008, however, fizzy drink intake data is updated annually. This means that NZ is lacking a full picture of children’s beverage consumption. SSB intake has been associated with weight gain in some studies. However, most of these studies calculate adiposity using body mass index (BMI) and few measure body fat percentage (BF%). International and limited national evidence has identified home availability, parental encouragement, socioeconomic status, and knowledge in children as factors associated with SSB intake. Many NZ schools have become ‘water-only’ schools (WOS) to try to reduce SSB consumption. Aim: To investigate beverage consumption in 8 to 12 year old Auckland primary school children. Methods: This cross-sectional study evaluated beverage intake and associated factors using self-administered questionnaires. SSB consumption measurements consisted of 17 types of beverages, and different combinations of these. Body composition was measured using bioelectrical impedance analysis (BIA). Chi squared and Mann-Whitney tests were used to examine the associations between SSB consumption and the factors associated with it. Results: Children (n=695, 9.9±0.7 years, 44.8% male) were recruited from 6 schools (4 WOS). Plain water and plain milk were consumed less than once per day by 11.6% and 54.7% of the children, respectively. Soft drink and fruit juice were consumed more than once per week by 30.6% and 39% of the children, respectively. SSBs (p<0.001), including fruit juice (p=0.021), had a positive relationship with BF% in girls. There was an increased likelihood of consuming beverages at least once per week if they were usually available at home. Receiving a lot of encouragement for healthy beverage intake from parents or school had an inverse relationship with SBB intake (p<0.001). Low socioeconomic status was inversely associated with SSB intake (p<0.001). WOS had a higher consumption of SSBs compared to non-WOS (p<0.001). Conclusions: Too many children in this cohort were not meeting the NZ Ministry of Health recommendations for plain water and milk consumption. Thus, they may benefit from increasing their intake, whilst decreasing their SSB intake. If parents limited SSB home availability and encouraged intake of healthy beverages it may contribute to a decrease in their children’s SSB consumption. Our findings support a recommendation to include fruit juice in any public health actions to discourage SSB consumption. More research is needed to assess school water-only policies and their effect on SSB consumption.Item Phytochemical variation during blueberry juice processing : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology at Massey University, New Zealand(Massey University, 2015) Kasim, KhairulBlueberry is regarded as a ‘super fruit’ by many consumers and believed to offer health benefits for humans. It is well known for its high antioxidant levels and for the diversity of its anthocyanins. Blueberries can be eaten fresh but are very perishable, so are commonly kept frozen and available all year round. Frozen blueberries are suitable for a range of products including juice. During juicing, there are likely to be changes in phytochemical constituents arising from the various processing steps. These changes lead to variable composition of the finished juice and uncertain impacts on the ‘health value’ of the product. Therefore, this study focused on evaluating three major phytochemicals (anthocyanins, chlorogenic acid (CGA), and procyanidin B2) throughout juice processing in order to model compositional change. Blueberry juice processing involves a series of unit operations: thawing, blanching, mincing, enzyme treatment, separation of juice from pomace, pasteurisation, and bottling. Enzymatic degradation occurs during thawing of blueberries as they still contain ‘live’ oxidases. Prolonged thawing at warm temperatures would therefore be particularly bad for phytochemical degradation. If these oxidases are destroyed by blanching, thermal degradation also occurs but was found to be less aggressive than polyphenoloxidase (PPO) activity. Blanching at high temperature (= 70 °C) for 3 min eliminated PPO and significantly increased the phytochemical concentration in the juice but it induced pectin gel formation which reduced juice recovery. Depectinisation is essential after berry blanching to dissolve pectin gel and to avoid juice volume penalty. Significant losses of phytochemicals were also observed during pressing of the berries into juice, due to physical associations between the phytochemicals and the berry matrix, and entrapment. Blanching at 90 °C for 3 min followed by pectinase enzyme treatment at 50 °C for 2 h was the best way to deliver high phytochemical concentration in the juice with high juice volume recovery and acceptable viscosity. There is a risk that juices with high phytochemical concentration will seem bitter or astringent. This was found not to be the case in sensory trials, with consumers consistently preferring the high-phytochemical juices; it seems sugars in the juice masked any adverse perceptions. Because of the complexity of blueberry juice processing, the processing model developed in this study was simplified into three components: a defrost model, a recovery model and a thermal model. In short, the defrost model was used for the whole berry phase during thawing when PPO was still active; the recovery model accounted for losses into the pomace; and the thermal model covered the subsequent liquid phase. These processing models were able to predict anthocyanin and CGA changes throughout processing (particularly in blanched products) but procyanidin B2 behaviour was not predictable. This modelling approach provides the ability to predict variations in composition arising from changes in the juicing process and offers manufacturers the opportunity to produce consistent blueberry juice with a high phytochemical concentration.