Massey Documents by Type
Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294
Browse
19 results
Search Results
Item β-Casein A1 and A2: Effects of polymorphism on the cheese-making process(Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association, 2023-08) Vigolo V; Visentin E; Ballancin E; Lopez-Villalobos N; Penasa M; De Marchi MOf late, "A2 milk" has gained prominence in the dairy sector due to its potential implications in human health. Consequently, the frequency of A2 homozygous animals has considerably increased in many countries. To elucidate the potential implications that beta casein (β-CN) A1 and A2 may have on cheese-making traits, it is fundamental to investigate the relationships between the genetic polymorphisms and cheese-making traits at the dairy plant level. Thus, the aim of the present study was to evaluate the relevance of the β-CN A1/A2 polymorphism on detailed protein profile and cheese-making process in bulk milk. Based on the β-CN genotype of individual cows, 5 milk pools diverging for presence of the 2 β-CN variants were obtained: (1) 100% A1; (2) 75% A1 and 25% A2; (3) 50% A1 and 50% A2; (4) 25% A1 and 75% A2; and (5) 100% A2. For each cheese-making day (n = 6), 25 L of milk (divided into 5 pools, 5 L each) were processed, for a total of 30 cheese-making processes. Cheese yield, curd nutrient recovery, whey composition, and cheese composition were assessed. For every cheese-making process, detailed milk protein fractions were determined through reversed-phase HPLC. Data were analyzed by fitting a mixed model, which included the fixed effects of the 5 different pools, the protein and fat content as a covariate, and the random effect of the cheese-making sessions. Results showed that the percentage of κ-CN significantly decreased up to 2% when the proportion of β-CN A2 in the pool was ≥25%. An increase in the relative content of β-CN A2 (≥50% of total milk processed) was also associated with a significantly lower cheese yield both 1 and 48 h after cheese production, whereas no effects were observed after 7 d of ripening. Concordantly, recovery of nutrients reflected a more efficient process when the inclusion of β-CN A2 was ≤75%. Finally, no differences in the final cheese composition obtained by the different β-CN pools were observed.Item The Effect of the Liposomal Encapsulated Saffron Extract on the Physicochemical Properties of a Functional Ricotta Cheese(MDPI (Basel, Switzerland), 2022-01) Siyar Z; Motamedzadegan A; Mohammadzadeh Milani J; Rashidinejad A; Omri AIn this study, the encapsulation of saffron extract (SE) was examined at four various concentrations of soy lecithin (0.5%-4% w/v) and constant concentration of SE (0.25% w/v). Particle size and zeta potential of liposomes were in the range of 155.9-208.1 nm and -34.6-43.4 mV, respectively. Encapsulation efficiency was in the range of 50.73%-67.02%, with the stability of nanoliposomes in all treatments being >90%. Encapsulated SE (2% lecithin) was added to ricotta cheese at different concentrations (0%, 0.125%, 1%, and 2% w/v), and physicochemical and textural properties of the cheese were examined. Lecithin concentration significantly (p ≤ 0.05) affected the particle size, zeta potential, stability, and encapsulation efficiency of the manufactured liposomes. In terms of chemical composition and color of the functional cheese, the highest difference was observed between the control cheese and the cheese enriched with 2% liposomal encapsulated SE. Hardness and chewiness increased significantly (p ≤ 0.05) in the cheeses containing encapsulated SE compared to the control cheese. However, there was no significant difference in the case of adhesiveness, cohesiveness, and gumminess among different cheeses. Overall, based on the findings of this research, liposomal encapsulation was an efficient method for the delivery of SE in ricotta cheese as a novel functional food.Item An attempt to manufacture Cheddar cheese containing only one type of organism : thesis for the degree of M. Agr. Sc. (in Dairy Science) at the University of New Zealand, by Ascend(Massey University, 1931) Neil, William C.; AscendThere have been many investigations on the effect of various bacteria on the ripening of hard rennet varieties of cheese. Hucker (1922) in a review of the bacteriological aspects of cheese ripening summaries the position as follows: "As it stands to-day the investigations have closely demonstrated that the breaking down of the insoluble casein compounds is due to enzymes, either natural or bacterial; while characteristic flavors are produced by the action of certain groups of bacteria. (Bacterium casei or coccus group), which depend on the products of B. lactis acidi present in large numbers during the manufature and early ripening stages." The effect of lactic acid bacteria upon the flavour of Cheddar cheese has been studied by Hastings, Evans and Hart (1912), Evans, Hastings and Hart (1914), Evans (1918). Leitch (1923) and Hucker and Marquardt (1926). [From Introduction]Item The effects of pH-stat long-term lactic acid bacterial activity prior to curd formation on the development of cheese structure in a fat free model cheese : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy (PhD) in Food Technology at Massey University, Manawatu, New Zealand(Massey University, 2018) Khodamoradi Dashtaki, AbbasCheese ripening is an important step in most cheese production practices during which a tasteless fresh cheese is converted to a tasty and flavourful product with specific textural attributes. However, the complexity of its composition (pH, solubilisation of calcium from the colloidal casein proteins, salt concentration, acid production rate, indigenous and added enzymes, residual activity of the enzymes etc.) coupled with the length of time associated with manufacturing which in some cases can be in excess of two years has made it a complicated area of study. The influences of the composition and process contributors are confounded and it is impossible to connect the impact of one particular parameter on cheese making steps and quality attributes. pH has proven to be an important influential factor to influence the extent of effects of other parameters with significant influence on other ruling parameters in milk, curd and cheese. Proteolysis during ripening is the most important physicochemical pathway to define the quality of cheese. One of the major factors governing cheese ripening reactions is the starter bacteria. This study has aimed to characterise the effects of starter bacteria activity on curd formation and resultant cheese textural attributes of the long fermented cheesemilk. By developing a pH-stat system, long fermentations carried out to assess the proteolytic activity of selected starter lactic acid bacteria (LAB) on a milk based medium before rennet addition. It was attempted to assess the degree of hydrolysis of cheesemilk through extended bacterial fermentation, conducted under pH-stat conditions, prior to curd formation. The effects of the bacterial activity on casein proteins during pH-stat long term (PSLT) fermentations were evaluated by assessing proteolysis index from pH4.6 soluble nitrogen as a fraction of total nitrogen (pH4.6SN/TN). The proteolysis of proteins during PSLT was further assessed by doing reverse-phase high performance liquid chromatography (RP-HPLC) on 70%Ethanol soluble (70%EtOHS) and insoluble (70%EtOHI) fractions of pH4.6 soluble fraction of the samples. The effects of PLST fermentation on formation of small-size peptides were assessed by quadrupole time-of-flight mass spectrometry (Q-ToF MS) on the 70%EtOHS fraction. The effect of PLST fermentation on ‘depth of proteolysis’ during cheese ripening were assessed by analysing the quantity of free amino acid (FAA) formed in resultant cheese after 12 months storage at 4°C. The impact of PLST fermentation on gel formation attributes were assessed by doing dynamic law amplitude oscillatory rheometry (DLAOR). The consequent effects on resultant cheese texture were evaluated using texture profile analysis (TPA). The impact of PSLT on microstructure were assessed by confocal laser scanning microscopy (CLSM). The results provided evidence for the adequacy of developed fermentation to conduct PSLT with reproducible results. High correlation between the parameters of the PSLT fermentation system were obtained. The proteolysis index measured from the PSLT fermentations with different durations showed evidences on the significance of LAB proteolytic system on cheese milk prior to curd formation. The proteolysis index for the longest fermentation prior to curd formation was 5% which was comparable to day one cheese proteolysis index, in presence of rennet, in most cheeses varieties. Peptide profiling of the 70%EtOHS and 70%EtOHI sub-fractions of pH4.6S showed significant (p<0.05) effects arising from PSLT fermentations. Analysis of FAA of ripened cheese also showed a significant increase (p<0.05) in the samples with longer PSLT (20 times increase in total free amino acids compared to non-fermented treatment) fermentations. The differences in gelation behaviour of the sample and textural attributes of cheese and microstructure of final cheese were connected to the extent of proteolytic activity of LAB during PSLT fermentations. The hardness of cheese significantly (p<0.05) decreased (up to ~60%) by increasing fermentation duration over the studied timescale.Item The evaluation of milk extenders in unripened soft cheese :a thesis presented in partial fulfilment of the requirements for the degree of Master in Technology in food technology at Massey University(Massey University, 1989) Cruz, Lucila LMixtures of soybean milk, coconut cream and reconstituted skimmilk were utilized in the manufacture of unripened soft type cheese for the purpose of extending the milk supply. Different treatment combinations had been formulated replacing part of the reconstituted skimmilk used as milk base. The product formulation selected on the basis of product quality, stability and production costs analysis was that having low levels of soybean milk (10% w/w), coconut cream (20% w/w) and mixed starter culture h% w/v) for acid development. The sensory qualities of the resulting soft cheese were satisfactory although inferior to control cheese (fresh cow's milk) Compositional analysis showed that the experimental soft cheese is equally nutritious relative to soft cheese produced from cow's milk. It was observed that the presence of soybean milk particularly at high level (20% w/w) resulted in high fat and protein losses, increased water-holding capacity and decreased firmness. The experimental soft cheese had the tendency to soften further and to develop an unacceptable acid taste during prolonged storage in cheese with a starter culture. Experimental soft cheese without starter culture had organoleptically good acceptance and good storage life at 5°C. From the technological and nutritional standpoint, the use of milk extenders in combination for soft cheese manufacture is feasible and suitable for cottage industry. A major advantage is year-round availability regardless of fresh milk supply.Item Modelling primary proteolysis in cheddar cheese in commercial cool stores : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Bioprocess Engineering at Massey University(Massey University, 2000) Edmonds, RichardOne issue identified as a possible problem during the manufacture of cheddar cheese is the possibility of producing a non-uniform product. It was proposed that a pallet of cheese experiencing different time-temperature histories, depending on the position within the pallet, could cause the heterogeneity. This work involved the investigation of that issue. The level of primary proteolysis observed in cheese was measured over time in cheeses of different compositions, stored at different temperatures. The remaining intact αₛ₁casein was measured using reverse phase high performance liquid chromatography. Several trends were observed during maturation. High temperatures caused a faster rate of disappearance of αₛ₁casein. The temperature relationship followed Arrhenius law. High moisture content caused a faster rate of the disappearance of αₛ₁casein. The level of rennet added to the milk during production had a directly proportional effect on the rate of the disappearance of αₛ₁casein. Salt had no observable effect in the range investigated here. From the data a kinetic model was developed that described the rate of disappearance of αₛ₁casein in terms of the temperature, the moisture content, and the level of rennet in the cheese. The heat transfer occurring in the commercial pallet of cheese was mathematically modelled and solved numerically. The heat transfer model was then applied to produce data describing the time-temperature profile throughout a pallet of cheese for a variety of possible industrial storage conditions. The kinetic model developed was then used to predict the extent of proteolysis in each case. It was found that there would be significantly different levels of proteolysis within a pallet of cheese that had undergone chilling. A 10% difference in the level of proteolysis between the surface and the centre was observed after chilling for 40 days. During freezing the difference in the level of proteolysis after freezing was complete ranged from 10-25%. It was found that the heterogeneity was reduced during the thawing process and that the greatest reduction in non-uniformity was observed when thawed at lower temperatures.Item The renneting properties of skim milk solutions supplemented with milk protein concentrate : the effect of hydration and storage of the milk protein concentrate : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Physics at Massey University, Palmerston North, New Zealand(Massey University, 2004) Hunter, Robin JamesThe purpose of this study was to examine the effect of storage and hydration of milk protein concentrate with 85% protein (MPC85) on the renneting properties of skim milk solutions supplemented with MPC85. The following techniques were used in this investigation: solubility testing, rheology, polyacrylamide gel electrophoresis (PAGE), and mass spectrometry. The solubility of MPC85 samples which had been stored for different periods at temperatures ranging from 30°C to 50°C was found to decrease as storage time increased. In addition, as the storage temperature increased, so did the rate at which solubility decreased. This decrease in solubility dropped to approximately 22% of its original amount. Similar experiments were also performed on samples stored at 20°C (ie approximate room temperature), but showed no change over the time frame of the experiment. Rheology experiments were performed on 10% (w/w) skim milk supplemented with 2.5% MPC85 (w/w). The experimental conditions, such as temperature (30°C), reconstitution time frame, and rennet concentration (100 μL per 50 g sample), remained constant throughout testing. The rheological properties of the samples showed a large decrease in the formed gel strength ot the renneted samples, and an increase in gelation time, as storage time and or temperature were increased. Additionally, the viscoelastic moduli (G' and G") and fracture stress also decreased as storage time and/or temperature were increased. This again excludes samples prepared from MPC85 stored at 20°C which showed no change. The rheological properties of skim milk solutions supplemented with MPC85, with respect to hydration time was studied using three MPC85 powders of low, medium, and high solubility. Hydration time was varied between 1 and 24 hours, and results showed that samples made from high and medium solubility MPC85 increased gel strength with hydration, with high solubility MPC85 producing the stronger gels. Samples prepared with low solubility MPC85, produced very weak gels which only changed minimally with hydration time. Aggregation and gelation times for each set of samples were different, but did not change with hydration time. PAGE was used to analyse the composition of MPC85 to attempt to gain an understanding of what caused the change in properties with storage time and temperature. Experiments revealed that a large decrease in the solubility of caseins, and whey proteins decreased in solubility only minimally. Mass spectrometry was used to analyse samples stored at 50°C, and it was found that the casein proteins suffered glycation. Whey proteins were also analysed, but data proved too noisy for any conclusions. In general this thesis aims to provide useful information on the effects of storage and hydration of MPC85. especially with regard to the production of skim milk solutions supplemented with MPC85.Item Colloidal interactions in an alternate make cheese : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, (Manawatū), New Zealand(Massey University, 2017) Luo, JingThe role of emulsion structure and interactions on the material and technical functionality of an alternate make cheese (AMC) was investigated. Lab scale cheese samples (25 g comprising 23 wt.% fat and 20 wt.%) were prepared by recombining model emulsions with a separate protein phase under controlled temperature, shear speed and residence time in a rapid visco analyser (RVA). Sodium caseinate and Tween 20 were used respectively to stabilize fat globules for the model emulsions. Preliminary experiments were carried out for samples prepared using either calcium caseinate or sodium caseinate as protein phase. Structural characterisation of samples showed emulsion structure and distribution within these phases to be dependent on protein type. It was inferred that the calcium from calcium caseinate matrix modified the interfacial layer of the emulsions stabilised by sodium caseinate, as indicated by the increased fat globule size distribution after cheese making. In comparison, the size of fat globules covered with sodium caseinate appeared relatively stable in cheese produced form cheese curd. Based on these observations, caseinates were subsequently replaced by cheese curd as the protein phase for the remainder of the study. For cheese samples prepared with low fat cheese curd, fat droplets stabilised with sodium caseinate were hypothesised as binding with the surrounding protein matrix, and thereby these fat globules could be considered as ‘active fillers’. Confocal laser scanning microscopy supported this hypothesis showing homogeneously dispersed fat droplets within the protein network. This emulsion system did not show fat-protein phase separation in baking (170 °C 10 minutes) as droplets were prevented from coalescing as a consequence of entrapment within the protein phase. Fat globules covered with Tween 20 were hypothesised as behaving as ‘inactive fillers’, with the adsorbed layer not anticipated to form bonds with the surrounding protein network. Confocal and scanning electron microscopy instead showed localised domains of fat droplets within the protein structure that underwent partial coalescence on cooling of the cheese after manufacture. Cheeses comprising Tween stabilised droplets exhibited phase separation on baking and visible oil-off on the surface of cheese arising from extensive coalescence taking place within the localised regions of fat due to melting of the partially coalesced structures. Additional rheological analysis of cheeses was carried out to determine the effect of droplet-protein interactions on the material properties of the cheese samples. Notably, findings were presented in relation to a non-fat control cheese. Findings showed that, at temperatures below 30 °C when fat was crystallized, both inactive and active fillers had a higher relative modulus to the non-fat sample. However, at elevated temperature without fat crystals, inactive fillers resulted in a relative reduction in storage modulus when compared to the non-fat cheese, while active fillers increased relative storage modulus. Model cheeses prepared with either sodium caseinate or Tween 20 stabilised emulsions were then compared to cheese samples comprising non-homogenised cream as the emulsion phase. Structural analysis of samples determined that cheeses comprising fat globules stabilized with native milk fat globule membrane behaved in a manner analogous to samples prepared with the Tween stabilised emulsion, indicating the presence of inactive droplets. However, it was also observed that increasing the residence time of cheese production within the RVA caused a transition of the interaction behaviour of the emulsion from inactive to active, as evidenced by corresponding changes to structural, material and functional properties of the cheese. Further exploration of this transition determined that the mechanical work applied during cheese preparation was sufficient to homogenise fat droplets during extended shearing, resulting in a reduction to fat droplet size. Droplet homogenisation during shearing was also found to have disrupted the native milk fat globule membrane, allowing protein adsorption to take place. It was also determined that whey proteins were the predominant interfacial fraction adsorbed as a consequence of extended shearing, and were considered responsible for the transition of droplets from inactive to active. Combined findings have shown that the material and functional properties of an alternate make cheese composition could be strongly influenced by the interactions of the emulsion phase with the surrounding protein network. These interactions could, in turn, be manipulated through formulation and/or process design, providing greater control over product properties.Item Influence of commercial proteases on the proteolysis of enzyme modified cheese : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2000) Chen, Emily Yi ChuanThe influence of four commercial proteases, Protease A, Protease B, Protease C and a two enzyme blend Protease DE, on proteolysis in an enzyme modified cheese (EMC) base has been investigated. Also, a series of preliminary experiments to determine the basic characteristics of the four enzyme preparations in buffer systems has been undertaken. Generally, the exopeptidase activity of the four enzyme preparations was more stable than the endopeptidase activity of the preparations. The highest enzyme activity for all preparations was given at pH 6.5 and Protease B was found to be sensitive to chelating agents. In addition, Protease B was found to contain at least two exopeptidases. Residual protease activities in EMC using a 55% moisture cheese base were found to be 0.005%, 0.009%, 0.007% and 0.004% (w/v) for Protease A, Protease B, Protease C and Protease DE, respectively, following inactivation by heating at 95°C heating for 30 minutes. Under the same incubation conditions (0.15% enzyme at 40°C for 24 h), Protease DE gave greater proteolysis than the three other enzymes and Protease B was the weakest protease. EMC digestion with a combination of proteases was different from that obtained with individual proteases. The combinations of Protease A/Protease C, Protease DE/Protease C, Protease B/Protease C and Protease DE/Protease A showed that the higher the proportion of the former protease in the combinations, the higher the amounts of total amino acids produced in the EMC. The combinations of Protease A/Protease B and Protease B/Protease DE gave greater amounts of total amino acids with the ratio of each enzyme close to 50:50 than with the individual enzymes. With respect to the molecular mass distribution of peptides in the various EMC digestions, Protease DE produced the greatest amount of peptides of 3 or fewer residues and Protease C gave the greatest amount of more medium sized peptides with 11-20 residues. Compared with Protease C, Protease A was more efficient in giving small peptides, while Protease B gave the lowest levels of medium and small peptides, but a high level of free amino acids. In sensory testing, Protease DE produced EMC with a strong pungent and astringent flavour, Protease C gave bitterness, Protease A gave a sweet flavour at a low concentration but bitter flavours with a high concentration and Protease B produced more savoury flavour without bitterness.Item The survival and growth of Bacillus cereus and Listeria monocytogenes, during the manufacture of Ricotta Salata cheese : a thesis presented in partial fulfilment of the requirements for the degree of Masters in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2017) Su, BoyuanThis study was conducted with the following objectives: 1) to investigate the survival and growth of Bacillus cereus during the manufacture of Ricotta Salata cheese; and 2) to investigate the survival and growth of Listeria monocytogenes during the manufacture of Ricotta Salata cheese. The Ricotta Salata cheese was made by heating the whole milk to 95oC, and adding citric acid to coagulate the cheese curd. The cheese curd was inoculated with 7 log10 CFU/g B. cereus broth and 8 log10 CFU/g L. monocytogenes broth. After moulding for 12h, Ricotta Salata cheese was stored at 4oC for 1 week. During manufacture, the physico-chemical properties [pH, water activity (aw), and Sodium chloride (NaCl) concentration] and bacterial counts were recorded. The pH change fluctuated between 6.00 to 6.10 on the surface and 6.00 to 5.95 in the centre; the lowest aw was approximately 0.96 on the surface and 0.97 in the centre; and the highest NaCl concentration was 3.3% on the surface and 3% in the centre. The survival and growth of the two B. cereus strains (D1 and ATCC 13061) during the manufacture of Ricotta Salata cheese were similar. The B. cereus grew from approximately 5 log10 CFU/g to a maximum of 7.7 log10 CFU/g of cheese curd during moulding (20h at room temperature). The survival and growth of the two L. monocytogenes strains (W1 and ATCC 35152) during the manufacture of Ricotta Salata cheese were similar. The difference between the bacteria count on the surface and in the centre was very small. L. monocytogenes increased from 5 to 6 log10 CFU/g to a maximum of 8.6 log10 CFU/g during manufacture and maintained a level of around 8 log10 CFU/g in the final product. The Ricotta Salata supported the survival and growth of B. cereus and L. monocytogenes during manufacture. It is important to improve the management of process hygiene for reducing the environmental contamination. Ideally, some lethal treatments should be applied after the packaging of the cheese, to limit the contamination of Ricotta Salata with these two bacteria.