Massey Documents by Type
Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294
Browse
4 results
Search Results
Item Survival of Staphylococcus aureus during the manufacture and ripening of camembert cheese : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Palmerston North, New Zealand(Massey University, 2017) Kang, ZhetongStaphylococcal Food Poisoning (SFP) is the third most common cause of food poisoning internationally, caused by an enterotoxin produced by Staphylococcus aureus. S. aureus contamination in dairy products, including cheese, can lead to SFP. The survivability of S. aureus during the manufacture and ripening of Camembert cheese was the focus of this study. Camembert cheeses were manufactured using pasteurized milk inoculated with one of three S. aureus strains, comprising two reference strains ATCC 4163, ATCC 9144 and one dairy strain 172 RR. Each strain was tested in triplicate. The results showed that manufacturing and ripening of Camembert cheese reduced the risk of food safety associated with contamination with S. aureus with a 1.6 to 3.1 log reduction. The largest decrease occurred following drainage, which was particularly evident in 172 RR, and coincided with the lowest pH. The combined effect of culture blend (starter and secondary flora) activity and low pH are believed to contribute to the death of S. aureus.Item Comparative study on freeze-dried lactic cheese starters and ripening cultures for the production of camembert cheese : a thesis submitted in partial fulfillment of the requirements for the degree of Master of Food Technology, Massy [i.e. Massey] University, Albany, New Zealand.(Massey University, 2013) Qiao, WeiBackground and Methodology The key to success in producing cheeses is the performance of the starter cultures (Parente and Cogan, 2004). Storage of freeze-dried cheese cultures at refrigeration and ambient temperature or higher provides convenience to culture handling and transportation, as well as reduce cost. This study investigated the effects of 4 storage temperatures: -18°C, 4°C, 20°C and 37°C on the stability of mesophilic lactic cheese starters and ripening cultures intended for Camembert production. In phase one, a 22 randomized complete block design (RCBD) was used to determine the potential of 14 commercial freeze-dried direct-vat-set (DVS) mixed cultures to produce Camembert after 5 months storage at the 4 temperatures. The cultures used were: O-type: Lactococcus (L.) lactis subsp. lactis, L. lactis subsp. cremoris; LD-type: L. lactis subsp. lactis, L. lactis subsp. cremoris, L. lactis subsp. lactis biovar. diacetylactis and Leuconostoc species (Leuconostoc (Leuc.) lactis and Leuc. mesenteroides subsp. cremoris) and a mould, Penicillum (P.) camemberti. During storage, the cultures were analysed for cell viability, acid production, colour and species composition. The characterised cultures were screened to select the most stable cultures with good potential for Camembert production. In phase two, a 23 RCBD design was used to study the potential of the cultures to produce prototype Camembert cheese using I-Make® Limited domestic cheese kits. The prepared cheeses were characterised for acidity, viable cell counts content, texture, volatile aromatic compounds and proteolysis using standard procedures. Results and Discussion Viable cell counts and acidification potential of cultures decreased (P<0.05) during storage at selected temperatures for 5 months. Cultures stored at 37°C were the most affected. Proportion of citrate-fermenting lactic acid bacteria (LAB) in LD-type starters also decreased in a similar pattern. Cell inactivation at high temperature was probably attributed to high oxidation, browning reactions, lactose crystallization, changes in glass transition temperature (Tg) of culture-lactose matrix and loss of β-galactosidase enzyme activity, which were possibly also affected by water activity (aw) of the culture during storage (Higl et al., 2007; Kurtmann et al., 2009c). Viability and activities of cultures stored at 4 and 20°C after 5 months were comparable to those of -18°C cultures and levels normally used in industry. Thus, the cultures demonstrated good potential for Camembert cheese production. Similar patterns of microbial growth (LAB and P. camemberti) and acidification were observed in both cheeses (O- and LD-types) during cheese fermentation. However, cheeses fermented with O-type starters had better growth and acidification activity (P<0.05), which may be attributed to compositional differences of culture, leading to variable metabolic patterns (Mcsweeney and Fox, 2004). Cheeses produced with cultures stored at 4 and 20°C had lower levels of cell growth and acidity (P<0.05), suggesting that the microorganisms could have been affected by prolonged storage at relatively high temperatures. During cheese ripening, changes in microbial content, acidity, proteolysis, texture and aroma compounds, were similar, and significantly changed (P<0.05) with ripening time. Viable cell counts of LAB reduced, while pH and P. camemberti counts increased. Increase of pH may result from lactate metabolism by P. camemberti creating an alkaline environment due to the deamination activity of the mould (Spinnler and Gripon, 2004). Proteolysis of cheeses was correlated (P<0.05) with LAB and P. camemberti activity as well as the pH of Background and Methodology The key to success in producing cheeses is the performance of the starter cultures (Parente and Cogan, 2004). Storage of freeze-dried cheese cultures at refrigeration and ambient temperature or higher provides convenience to culture handling and transportation, as well as reduce cost. This study investigated the effects of 4 storage temperatures: -18°C, 4°C, 20°C and 37°C on the stability of mesophilic lactic cheese starters and ripening cultures intended for Camembert production. In phase one, a 22 randomized complete block design (RCBD) was used to determine the potential of 14 commercial freeze-dried direct-vat-set (DVS) mixed cultures to produce Camembert after 5 months storage at the 4 temperatures. The cultures used were: O-type: Lactococcus (L.) lactis subsp. lactis, L. lactis subsp. cremoris; LD-type: L. lactis subsp. lactis, L. lactis subsp. cremoris, L. lactis subsp. lactis biovar. diacetylactis and Leuconostoc species (Leuconostoc (Leuc.) lactis and Leuc. mesenteroides subsp. cremoris) and a mould, Penicillum (P.) camemberti. During storage, the cultures were analysed for cell viability, acid production, colour and species composition. The characterised cultures were screened to select the most stable cultures with good potential for Camembert production. In phase two, a 23 RCBD design was used to study the potential of the cultures to produce prototype Camembert cheese using I-Make® Limited domestic cheese kits. The prepared cheeses were characterised for acidity, viable cell counts content, texture, volatile aromatic compounds and proteolysis using standard procedures. Results and Discussion Viable cell counts and acidification potential of cultures decreased (P<0.05) during storage at selected temperatures for 5 months. Cultures stored at 37°C were the most affected. Proportion of citrate-fermenting lactic acid bacteria (LAB) in LD-type starters also decreased in a similar pattern. Cell inactivation at high temperature was probably attributed to high oxidation, browning reactions, lactose crystallization, changes in glass transition temperature (Tg) of culture-lactose matrix and loss of β-galactosidase enzyme activity, which were possibly also affected by water activity (aw) of the culture during storage (Higl et al., 2007; Kurtmann et al., 2009c). Viability and activities of cultures stored at 4 and 20°C after 5 months were comparable to those of -18°C cultures and levels normally used in industry. Thus, the cultures demonstrated good potential for Camembert cheese production. Similar patterns of microbial growth (LAB and P. camemberti) and acidification were observed in both cheeses (O- and LD-types) during cheese fermentation. However, cheeses fermented with O-type starters had better growth and acidification activity (P<0.05), which may be attributed to compositional differences of culture, leading to variable metabolic patterns (Mcsweeney and Fox, 2004). Cheeses produced with cultures stored at 4 and 20°C had lower levels of cell growth and acidity (P<0.05), suggesting that the microorganisms could have been affected by prolonged storage at relatively high temperatures. During cheese ripening, changes in microbial content, acidity, proteolysis, texture and aroma compounds, were similar, and significantly changed (P<0.05) with ripening time. Viable cell counts of LAB reduced, while pH and P. camemberti counts increased. Increase of pH may result from lactate metabolism by P. camemberti creating an alkaline environment due to the deamination activity of the mould (Spinnler and Gripon, 2004). Proteolysis of cheeses was correlated (P<0.05) with LAB and P. camemberti activity as well as the pH ofBackground and Methodology The key to success in producing cheeses is the performance of the starter cultures (Parente and Cogan, 2004). Storage of freeze-dried cheese cultures at refrigeration and ambient temperature or higher provides convenience to culture handling and transportation, as well as reduce cost. This study investigated the effects of 4 storage temperatures: -18°C, 4°C, 20°C and 37°C on the stability of mesophilic lactic cheese starters and ripening cultures intended for Camembert production. In phase one, a 22 randomized complete block design (RCBD) was used to determine the potential of 14 commercial freeze-dried direct-vat-set (DVS) mixed cultures to produce Camembert after 5 months storage at the 4 temperatures. The cultures used were: O-type: Lactococcus (L.) lactis subsp. lactis, L. lactis subsp. cremoris; LD-type: L. lactis subsp. lactis, L. lactis subsp. cremoris, L. lactis subsp. lactis biovar. diacetylactis and Leuconostoc species (Leuconostoc (Leuc.) lactis and Leuc. mesenteroides subsp. cremoris) and a mould, Penicillum (P.) camemberti. During storage, the cultures were analysed for cell viability, acid production, colour and species composition. The characterised cultures were screened to select the most stable cultures with good potential for Camembert production. In phase two, a 23 RCBD design was used to study the potential of the cultures to produce prototype Camembert cheese using I-Make® Limited domestic cheese kits. The prepared cheeses were characterised for acidity, viable cell counts content, texture, volatile aromatic compounds and proteolysis using standard procedures. Results and Discussion Viable cell counts and acidification potential of cultures decreased (P<0.05) during storage at selected temperatures for 5 months. Cultures stored at 37°C were the most affected. Proportion of citrate-fermenting lactic acid bacteria (LAB) in LD-type starters also decreased in a similar pattern. Cell inactivation at high temperature was probably attributed to high oxidation, browning reactions, lactose crystallization, changes in glass transition temperature (Tg) of culture-lactose matrix and loss of β-galactosidase enzyme activity, which were possibly also affected by water activity (aw) of the culture during storage (Higl et al., 2007; Kurtmann et al., 2009c). Viability and activities of cultures stored at 4 and 20°C after 5 months were comparable to those of -18°C cultures and levels normally used in industry. Thus, the cultures demonstrated good potential for Camembert cheese production. Similar patterns of microbial growth (LAB and P. camemberti) and acidification were observed in both cheeses (O- and LD-types) during cheese fermentation. However, cheeses fermented with O-type starters had better growth and acidification activity (P<0.05), which may be attributed to compositional differences of culture, leading to variable metabolic patterns (Mcsweeney and Fox, 2004). Cheeses produced with cultures stored at 4 and 20°C had lower levels of cell growth and acidity (P<0.05), suggesting that the microorganisms could have been affected by prolonged storage at relatively high temperatures. During cheese ripening, changes in microbial content, acidity, proteolysis, texture and aroma compounds, were similar, and significantly changed (P<0.05) with ripening time. Viable cell counts of LAB reduced, while pH and P. camemberti counts increased. Increase of pH may result from lactate metabolism by P. camemberti creating an alkaline environment due to the deamination activity of the mould (Spinnler and Gripon, 2004). Proteolysis of cheeses was correlated (P<0.05) with LAB and P. camemberti activity as well as the pH of samples. Softening of cheese was associated with increased proteolysis and pH due to the growth of P. camemberti (Spinnler and Gripon, 2004). A range of volatile organic compounds, dominated by fatty acids, alcohols and aldehydes were identified in cheese samples as reported in other studies (Sable and Cottenceau, 1999). Changes in 3-methylbutanal and 3-methylbutanol profiles of samples reflected the degradation of leucine,, synthesis of the aldehyde and its degradation to branched alcohols as a consequence of peptidolytic activity of LAB (Yvon and Rijene, 2001) and enzymatic activity of P. camemberti (Molimard and Spinnler, 1996). Increased concentrations of 2-heptanone, 2-nonanone and butyric acid in cheese samples suggested lipolytic activity in all samples (Molimard and Spinnler, 1996). The activity of P. camemberti involved in β-oxidation pathway for producing methyl ketones was also demonstrated confirmed by identified metabolites. Higher proteolysis and softness in LD-cheeses than O-type, suggested a higher degree of cheese ripening (Ardö, 1999), which may be attributed to proteolytic and peptidolytic activity of LD-starters (Tzanetaki et al., 1993). Higher proteolysis may be also associated with higher pH of cheese curd at draining, which facilitated higher syneresis. Increased whey content of curd may retain higher concentration of coagulant enzyme in the curd (Guinee and Wilkinson, 1992) and effectively stimulate the growth of P. camemberti, thus probably allowing proteolysis to occur more readily (Grappin et al., 1985). A relatively higher concentration of 3-methylbutanal was found in O-type cheeses than in LD-type. This suggests that LAB in O-type starters may exhibit higher activity in degrading leucine to 3-methylbutanal than LD-type starters (Yvon and Rijene, 2001). 2,3-butandione was suspected in LD-type cheeses but not in O-type samples, demonstrating the active role of citrate-fermenting bacteria of LD-starters (Mcsweeney and Fox, 2004). Results indicate that storage temperature of cultures had a significant (P<0.05) impact on viable cell counts and acidity of samples. In spite of reduced cell counts, proteolysis, texture and aroma of the prototype cheese samples were not affected (P<0.05). Although there were no differences between the Camembert cheeses, 4 and 20°C cultures used in cheese-making may enhance the ripening process (Ardö, 1999) than -18°C cultures, as indicated by relatively higher proteolysis and degree of softening. Lower levels of 3-methylbutanal in samples containing 4 and 20°C cultures was probably due to the reduced aminotransferases activity of LAB (Yvon and Rijene, 2001) after prolonged storage at the two temperatures. The slightly higher levels of 2-heptanone, 2-nonanone and butyric acids in samples with 4 and 20°C cultures were probably due to increased lipolytic activity of enhanced growth of P. camemberti (Molimard and Spinnler, 1996) during cheese ripening. Conclusion LAB starter cultures and P. camemberti can be stored for 5 months at 4 and 20°C without affecting their activities and the quality of prototype Camembert produced. Camembert cheese samples produced in this study had typical characteristics of this type of cheese. Cheese fermented with LD-type starters showed extra flavour enhancement potential and the products had higher degree of softening due pronounced proteolysis. Cultures stored at 37°C for 5 months were characterised by poor viable cells and capability to the produce acid, therefore, they were not suitable for Camembert cheese production.Item Methods to control the maturation of soft mould ripened cheese : a thesis submitted in partial fulfilment of the requirements of a Master of Technology (in Food Technology), at Massey University.(Massey University, 2011) Swan, ShannonSoft mould ripened cheeses such as Camembert, typically have a short shelf life in comparison to other cheese varieties, therefore restricting the opportunity to exploit new and developing markets. Preliminary trials were carried out to investigate the freezing point of Camembert cheese and the rate of freezing and thawing that could be achieved using the facilities at Massey University; Albany. Using the results from these trials, a freezing/ thawing protocol and an experimental plan was developed to increase the shelf life by altering the standard storage and maturation profiles of Camembert cheese. Firstly the effect of three storage temperatures and time (for up to four weeks) on the maturation at +4ºC (for eight weeks) of Camembert cheese was investigated. Maturation indicators included: extent of moisture loss of wrapped cheese samples; change in pH of the inside and outside portion of the cheese; change in the release of proteolytic products; change in the viable yeast and mould cells present on the surface of the cheese; and change in texture (uniaxial compression and puncture testing) following storage and throughout maturation. From these results it was found that storing the cheese samples below the freezing point (between -3 and - 3.5±0.1ºC) had a detrimental effect on the maturation of the cheese. The freezing process and time killed the cheese microflora, therefore inhibiting the release of enzymes which promoted the biochemical reactions within the cheese. As a result the cheese did not follow the same maturation trend as the control sample that was matured at only +4ºC for eight weeks. Cheese that was stored at below zero, but above the actual freezing point followed the same maturation trend as the control sample following storage for up to four weeks, therefore showing the most potential in controlling the maturation of the Camembert cheese. The effect of storage at -2ºC on Camembert cheese was then investigated, both throughout the storage of the cheese (for up to six weeks) followed by maturation at +4ºC for eight weeks. Maturation indicators included: change in pH of the inside and outside portion of the cheese; change in the moisture content of the cheese; change in the release of proteolytic products; change in texture (uniaxial compression and puncture testing); and Quantitative Descriptive Analysis using a panel of nine screened and trained panellists. Statistical analysis showed that at the 99% level of confidence, the storage temperature (and time) had no significant effect on the ripening of the cheese throughout maturation at +4ºC of the cheese for all maturation indicators. Therefore, storing Camembert cheese at -2ºC can be used to control the maturation of Camembert cheese, allowing for longer distribution chain delivery times.Item Ultra filtration (UF) process development for the production of camembert cheese : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University, Albany, New Zealand.(Massey University, 2010) Law, Ming Ho EdwinThe application of UF technology in cheese production has several potential advantages; product consistency, yield, lower costs and more automation. This study investigated the effects of four processing variables in the manufacture of Camembert cheese using UF and their impact on cheese quality. Using an incomplete block design, sixteen unique treatments were produced with combined processing variables (high-fat or low-fat; brine-salted or retentate-salted; acidified to pH 5.2 or pH 4.9; set in tubular moulds and small moulds). The cheeses were matured for seven weeks at 4±1 ºC and were analysed for total solids, fat, salt, non-protein nitrogen (NPN) and soluble nitrogen (SN) contents during the maturation period (seven weeks). Major defects were evaluated by experienced cheese graders in the fourth week. pH was measured and instrumental analysis was also conducted. Sensory evaluation on consumer acceptance was also conducted in the fourth week. All the cheese samples exhibited similar increases in rind and core pH, NPN/TN and SN/TN ratios, and were generally characterised by thick rind and softness. The lowfat cheese samples had significantly lower NPN/TN ratio and higher overall acceptance in sensory evaluation. The salt content was also significantly higher. The retentate-salted cheese samples had significantly lower NPN/TN ratios and more defects in rind discolouration and deformation, and saltiness. The cheese samples acidified to pH 5.2 had significantly lower NPN/TN ratios and fewer defects in rind discolouration, softness, sourness, and bitterness. The cheese samples made using tube moulds were significantly firmer with fewer defects in rind deformation, core unevenness, and softness. The level of fat and extent of acidification was found to have a profound effect on cheese quality, and cheeses produced with low-fat retentate and/or acidified to pH 5.2 generally had superior shelf-life with lower levels of proteolysis. The preference of the two salting methods may be debatable, but considering labour and time, retentatesalting is preferable. Tube mould generally produced better cheese with fewer defects.