Former Professor of Food Microbiology at Auckland University of TechnologyStudied Biochemical engineering at Sydney UniversityStudied Microbiology at Queen Elizabeth College, London
Modernization of Traditional Food Processes and Products, 2016
Kaanga wai (or kaanga kopiro) is a traditional fermented food prepared by the Maori of New Zealan... more Kaanga wai (or kaanga kopiro) is a traditional fermented food prepared by the Maori of New Zealand from maize since the early 1800s. The traditional process involved putting whole cobs of an old cultivar, known as Kaanga, into woven flax bags and completely immersing them either in a stream of running water or in slow-moving swamp water and keeping them submerged for 2–3 months. The fermented kernels have a distinctive flavour, probably as a result of the production of n-butyric acid, which was highly prized by some Maori. The product was consumed as a porridge, or dried and used as a flour in baking.
The efficacy of different cleaners and sanitisers for removing or killing Klebsiella oxytoca in b... more The efficacy of different cleaners and sanitisers for removing or killing Klebsiella oxytoca in biofilms on ultrafiltration (UF) membranes from the dairy industry was investigated. K. oxytoca B006 was grown individually and combined with another K. oxytoca strain, TR002, on polyethersulfone (PES) UF membranes in 5% whey medium in CBR 90 biofilm reactors. Both strains were previously isolated from New Zealand dairy plants. Three enzymatic cleaners were compared with sodium hypochlorite (pH 10.8-11) at 200 ppm free available chlorine (FAC) commonly used for cleaning-in-place (CIP) of UF membranes in the dairy industry. In addition, 4 sanitisers were used to treat the membranes after a CIP wash regime. The efficacy in reducing culturable bacteria in biofilms was measured using pour plate counting on standard plate count agar. QuatroZyme ® , which is composed of mixed enzymes, performed slightly better than the other cleaners. The treatments with all the sanitisers improved cleaning. MIOX ® EW anolyte (pH 6.8) (120 ppm) was the most effective sanitiser compared to the control CIP. However, PES UF membranes are known to be sensitive to oxidants at low pH and therefore the damage to these membranes by MIOX ® EW anolyte needs to be determined.
As the interval between methanol additions to methanol-limited cultures of Pseudomonas methylotro... more As the interval between methanol additions to methanol-limited cultures of Pseudomonas methylotropha was increased beyond 20 s the yield of bacterial dry wt/g of methanol fell significantly. Discontinuous methanol additions also caused cycling in the values of a number of parameters, including pH, dissolved oxygen tension, CO, production and amino acid pool concentration. It is suggested that after each addition of methanol a burst of growth occurred, followed by a period of starvation. These observations are discussed in the light of continuous culture practice and theory.
A study was performed to understand the physiology and biochemical mechanism of citric acid accum... more A study was performed to understand the physiology and biochemical mechanism of citric acid accumulation during solid state fermentation of sweet potato using Aspergillus niger Yang No. 2. A low citrate-producing mutant was isolated followed by a comparative study of the fermentation process and selected physiological and biochemical parameters. In contrast with the parent strain, the mutant strain displayed lower concentrations, yields and production rates of citric acid, accompanied by higher concentrations, yields and production rates of oxalic acid. In addition, the mutant utilized starch at a lower rate although higher concentrations of free glucose accumulated in the cultures. Biochemical analyses revealed lower rates of glucose uptake and hexokinase activity of the mutant strain in comparison with the parent strain. It is proposed that, in common with submerged fermentation, over-production of citric acid in solid state fermentation is related to an increased glucose ̄ux thro...
International Journal of Environmental Science and Development, 2010
Colorants produced by various Monascus sp. are well established in Asiatic foods. Industrial prod... more Colorants produced by various Monascus sp. are well established in Asiatic foods. Industrial production of Monascus pigments involves expensive submerged culture fermentation. A less expensive alternative is the use of solid state fermentation. This study reports on color production by Monascus ruber ICMP 15220 in packed bed solid state culture. The fungus was grown in packed beds (0.05 m in diameter and 0.17 m in depth of substrate) of moistened rice. The bed of rice was continuously aerated by sparging with humidified air (95-97% relative humidity). The effects of different aeration rates (0.05-2.0 L min-1) and initial moisture level (45, 57.5, 70% (w/w)) in the substrate, on color production are reported. The packed bed solid state fermentations were carried out at a nominal temperature of 30 o C. A forced aeration rate of higher than 0.5 L min-1 reduced the production of the pigments and biomass as a consequence of water loss from the bed. Highest levels of pigments were obtained at forced aeration rates of between 0.05 and 0.2 L min-1. Under these conditions, the pigment content reached ≥ 98 AU per g dry matter in the bed. An initial moisture level of 45% (i.e. g water per 100 g wet substrate) resulted in very low production of pigments and biomass with final moisture content of 29.6%. An initial moisture level of 70% gave the highest pigment production in the fermented dry solids and also the highest pigment productivity, which were 1,415 AU per g dry matter and 101 AU per g dry matter per day, respectively. The results suggest that forced aeration rate and initial moisture level in the substrate have a strong influence on pigment production in solid sate fermentation of M. ruber.
To determine the mechanism for both the removal and inactivation of 18-h biofilms of a thermophil... more To determine the mechanism for both the removal and inactivation of 18-h biofilms of a thermophilic Bacillus species that optimally grows at 55°C on stainless steel. Methods and Results: The cleaning strategies tested were based on biofilm biochemistry and physiology, and focused on the chemistry of the cleaners, the duration and temperature of the cleaning process and a combination of various cleaners. The success of the cleaning regimes was determined based on the removal of cells and organic debris and the elimination of viable cells. The results confirmed that a caustic (75°C for 30 min) and acid (75°C for 30 min) wash, relied upon heavily in most food processing industries for cleaning-in-place systems, was successful in removing these biofilms. However, any changes in the concentrations of these cleaners or the temperature of cleaning drastically affected the overall outcome. Alternative cleaning agents based on enzymatic or nonenzymatic breakdown of cellular proteins or polysaccharides, surfactant action, use of oxidative attack and free radicals varied in degrees of their success. Combining proteolytic action with surfactants increased wetability and therefore enhanced the cleaning efficiency. Conclusions: Several procedures, including caustic/acid and enzyme based cleaners, will be satisfactory, provided that the correct process parameters are observed i.e. concentration, time, temperature and kinetic energy (flow). Confirmation of these results should be carried out in a pilot plant through several use/clean cycles. Significance and Impact of the Study: Confidence in standard and alternative cleaning procedures for food manufacturing plant to prevent contamination with thermophilic bacilli that threaten product quality.
International Journal of Systematic and Evolutionary Microbiology, 1999
Thermophilic streptococci were isolated from biofilms on stainless steel samples exposed to paste... more Thermophilic streptococci were isolated from biofilms on stainless steel samples exposed to pasteurized skimmed milk and from dairy products from a dairy manufacturing plant. The phenotypic characters of these isolates were distinct from those of other thermophilic streptococci of dairy origin (Streptococcus thermophilus and Streptococcus bovis). Genotypic data [restriction endonuclease analysis, ribotyping, random amplified polymorphic DNA (RAPD) profiles, DNA-DNA hybridization and G+C contents] support the classification of these isolates as a new species. The sequence of the 165 rRNA was compared with that of 29 species of streptococci and shown to be significantly different. The sequence of the 165-235 rRNA intergenic spacer region also differed from published sequences of closely related species. A fluorescent in situ hybridization probe prepared to a specific part of the 165 rRNA gene sequence was able to distinguish the unknown isolates from reference isolates of S. thermophilus and S. bovis. It is proposed that these thermophilic streptococcal isolates from a dairy environment be classified in the genus streptococcus as a new species, Streptococcus waius (from waiu, the New Zealand Maori word for milk). The type strain is 3/IT (= NZRCC 20100T).
ABSTRACTPreconditioning ofAnoxybacillus flavithermusE16 andGeobacillussp. strain F75 with cations... more ABSTRACTPreconditioning ofAnoxybacillus flavithermusE16 andGeobacillussp. strain F75 with cations prior to attachment often significantly increased (P≤ 0.05) the number of viable cells that attached to stainless steel (by up to 1.5 log CFU/cm2) compared with unconditioned bacteria. It is proposed that the transition ofA. flavithermusandGeobacillusspp. from milk formulations to stainless steel product contact surfaces in milk powder manufacturing plants is mediated predominantly by bacterial physiological factors (e.g., surface-exposed adhesins) rather than the concentrations of cations in milk formulations surrounding bacteria.
ABSTRACTFree ions of Na+, K+, Ca2+, and Mg2+influenced the optical density of planktonic cultures... more ABSTRACTFree ions of Na+, K+, Ca2+, and Mg2+influenced the optical density of planktonic cultures of thermophilic bacilli.Anoxybacillus flavithermusE16 andGeobacillussp. strain F75 (milk powder manufacturing plant isolates) andA. flavithermusDSM 2641 andG. thermoleovoransDSM 5366 were studied. Ca2+and Mg2+were associated with increases in optical density more so than Na+and K+. Overall, it appeared that Ca2+and/or Mg2+was required for the production of protein in thermophilic bacilli, as shown by results obtained withA. flavithermusE16, which was selected for further study.
Dietary sodium is an important modifiable determinant of blood pressure, 1 and recent estimates s... more Dietary sodium is an important modifiable determinant of blood pressure, 1 and recent estimates suggest almost two thirds of the burden of stroke and half that of ischaemic heart disease are associated with non-optimal blood pressure levels. 2 Since blood pressure is ...
World Journal of Microbiology and Biotechnology, 2014
The carbon-to-nitrogen (C:N) ratio in the biomass of microfungi tends to be quite different (e.g.... more The carbon-to-nitrogen (C:N) ratio in the biomass of microfungi tends to be quite different (e.g. 10-15) compared with the C:N ratio in the red pigments (e.g. >20) of the fungus Monascus ruber. Therefore, determining an optimal C:N ratio in the culture medium for maximizing the production of the pigments is important. A culture medium composition is established for maximizing the production of the red pigment by the fungus M. ruber ICMP 15220 in submerged culture. The highest volumetric productivity of the red pigment was 0.023 AU L −1 h −1 in a batch culture (30 °C, initial pH of 6.5) with a defined medium of the following composition (g L −1): glucose (10), monosodium glutamate (MSG) (10), MgSO4•7H2O (0.5), KH2PO4 (5), K2HPO4 (5), ZnSO4•7H2O (0.01), FeSO4•7H2O (0.01), CaCl2 (0.1), MnSO4•H2O (0.03). This medium formulation had a C:N mole ratio of 9:1. Under these conditions, the specific growth rate of the fungus was 0.043 h −1 and the peak biomass concentration was 6.7 g L −1 in a 7-day culture. The biomass specific productivity of the red pigment was 1.06 AU g −1 h −1. The best nitrogen source proved to be MSG although four other inorganic nitrogen sources were evaluated.
The aim of the study was to compare the physicochemical and sensory characteristics of fermented,... more The aim of the study was to compare the physicochemical and sensory characteristics of fermented, cured sausages made from equivalent muscle groups of beef, pork, and sheepmeat. The last has no commercial examples and represents an unexploited opportunity. Using seven replicates of shoulder meat and subcutaneous fat, sausages were made with 64%, 29%, 4%, 2%, 0.2%, and 0.01% of lean meat, fat, NaCl, glucose, sodium pyrophosphate, and lactic culture, respectively. Following anaerobic fermentation (96 h, 30°C), there were no significant differences between the species in mean texture (hardness, springiness, adhesiveness, cohesiveness) and pH, and only minor differences were seen in color. However, although not consumer tested, it is argued that consumers would be able to pick a texture difference due to different fat melting point ranges, highest for sheepmeat. This work was followed by a sensory experiment to find out if characteristic sheepmeat flavors could be suppressed to appeal t...
A survey was undertaken at a whole milk powder manufacturing plant to determine the origin and th... more A survey was undertaken at a whole milk powder manufacturing plant to determine the origin and the rate of spore formation of thermophilic bacteria. Spores were generally not detected (< 10 cfu/mL) in either the pasteurization process or the pasteurized milk directed into the powder plant. The predominant sites of spore formation were the preheater plate heat exchanger and the evaporator. Spores began to be detected approximately 9 h into an 18-h manufacturing run. Spore isolates were identified as Anoxybacillus flavithermus and Geobacillus species. A. flavithermus predominated in the preheat section, whereas a mix of both organisms was present in the later manufacturing stages.
Modernization of Traditional Food Processes and Products, 2016
Kaanga wai (or kaanga kopiro) is a traditional fermented food prepared by the Maori of New Zealan... more Kaanga wai (or kaanga kopiro) is a traditional fermented food prepared by the Maori of New Zealand from maize since the early 1800s. The traditional process involved putting whole cobs of an old cultivar, known as Kaanga, into woven flax bags and completely immersing them either in a stream of running water or in slow-moving swamp water and keeping them submerged for 2–3 months. The fermented kernels have a distinctive flavour, probably as a result of the production of n-butyric acid, which was highly prized by some Maori. The product was consumed as a porridge, or dried and used as a flour in baking.
The efficacy of different cleaners and sanitisers for removing or killing Klebsiella oxytoca in b... more The efficacy of different cleaners and sanitisers for removing or killing Klebsiella oxytoca in biofilms on ultrafiltration (UF) membranes from the dairy industry was investigated. K. oxytoca B006 was grown individually and combined with another K. oxytoca strain, TR002, on polyethersulfone (PES) UF membranes in 5% whey medium in CBR 90 biofilm reactors. Both strains were previously isolated from New Zealand dairy plants. Three enzymatic cleaners were compared with sodium hypochlorite (pH 10.8-11) at 200 ppm free available chlorine (FAC) commonly used for cleaning-in-place (CIP) of UF membranes in the dairy industry. In addition, 4 sanitisers were used to treat the membranes after a CIP wash regime. The efficacy in reducing culturable bacteria in biofilms was measured using pour plate counting on standard plate count agar. QuatroZyme ® , which is composed of mixed enzymes, performed slightly better than the other cleaners. The treatments with all the sanitisers improved cleaning. MIOX ® EW anolyte (pH 6.8) (120 ppm) was the most effective sanitiser compared to the control CIP. However, PES UF membranes are known to be sensitive to oxidants at low pH and therefore the damage to these membranes by MIOX ® EW anolyte needs to be determined.
As the interval between methanol additions to methanol-limited cultures of Pseudomonas methylotro... more As the interval between methanol additions to methanol-limited cultures of Pseudomonas methylotropha was increased beyond 20 s the yield of bacterial dry wt/g of methanol fell significantly. Discontinuous methanol additions also caused cycling in the values of a number of parameters, including pH, dissolved oxygen tension, CO, production and amino acid pool concentration. It is suggested that after each addition of methanol a burst of growth occurred, followed by a period of starvation. These observations are discussed in the light of continuous culture practice and theory.
A study was performed to understand the physiology and biochemical mechanism of citric acid accum... more A study was performed to understand the physiology and biochemical mechanism of citric acid accumulation during solid state fermentation of sweet potato using Aspergillus niger Yang No. 2. A low citrate-producing mutant was isolated followed by a comparative study of the fermentation process and selected physiological and biochemical parameters. In contrast with the parent strain, the mutant strain displayed lower concentrations, yields and production rates of citric acid, accompanied by higher concentrations, yields and production rates of oxalic acid. In addition, the mutant utilized starch at a lower rate although higher concentrations of free glucose accumulated in the cultures. Biochemical analyses revealed lower rates of glucose uptake and hexokinase activity of the mutant strain in comparison with the parent strain. It is proposed that, in common with submerged fermentation, over-production of citric acid in solid state fermentation is related to an increased glucose ̄ux thro...
International Journal of Environmental Science and Development, 2010
Colorants produced by various Monascus sp. are well established in Asiatic foods. Industrial prod... more Colorants produced by various Monascus sp. are well established in Asiatic foods. Industrial production of Monascus pigments involves expensive submerged culture fermentation. A less expensive alternative is the use of solid state fermentation. This study reports on color production by Monascus ruber ICMP 15220 in packed bed solid state culture. The fungus was grown in packed beds (0.05 m in diameter and 0.17 m in depth of substrate) of moistened rice. The bed of rice was continuously aerated by sparging with humidified air (95-97% relative humidity). The effects of different aeration rates (0.05-2.0 L min-1) and initial moisture level (45, 57.5, 70% (w/w)) in the substrate, on color production are reported. The packed bed solid state fermentations were carried out at a nominal temperature of 30 o C. A forced aeration rate of higher than 0.5 L min-1 reduced the production of the pigments and biomass as a consequence of water loss from the bed. Highest levels of pigments were obtained at forced aeration rates of between 0.05 and 0.2 L min-1. Under these conditions, the pigment content reached ≥ 98 AU per g dry matter in the bed. An initial moisture level of 45% (i.e. g water per 100 g wet substrate) resulted in very low production of pigments and biomass with final moisture content of 29.6%. An initial moisture level of 70% gave the highest pigment production in the fermented dry solids and also the highest pigment productivity, which were 1,415 AU per g dry matter and 101 AU per g dry matter per day, respectively. The results suggest that forced aeration rate and initial moisture level in the substrate have a strong influence on pigment production in solid sate fermentation of M. ruber.
To determine the mechanism for both the removal and inactivation of 18-h biofilms of a thermophil... more To determine the mechanism for both the removal and inactivation of 18-h biofilms of a thermophilic Bacillus species that optimally grows at 55°C on stainless steel. Methods and Results: The cleaning strategies tested were based on biofilm biochemistry and physiology, and focused on the chemistry of the cleaners, the duration and temperature of the cleaning process and a combination of various cleaners. The success of the cleaning regimes was determined based on the removal of cells and organic debris and the elimination of viable cells. The results confirmed that a caustic (75°C for 30 min) and acid (75°C for 30 min) wash, relied upon heavily in most food processing industries for cleaning-in-place systems, was successful in removing these biofilms. However, any changes in the concentrations of these cleaners or the temperature of cleaning drastically affected the overall outcome. Alternative cleaning agents based on enzymatic or nonenzymatic breakdown of cellular proteins or polysaccharides, surfactant action, use of oxidative attack and free radicals varied in degrees of their success. Combining proteolytic action with surfactants increased wetability and therefore enhanced the cleaning efficiency. Conclusions: Several procedures, including caustic/acid and enzyme based cleaners, will be satisfactory, provided that the correct process parameters are observed i.e. concentration, time, temperature and kinetic energy (flow). Confirmation of these results should be carried out in a pilot plant through several use/clean cycles. Significance and Impact of the Study: Confidence in standard and alternative cleaning procedures for food manufacturing plant to prevent contamination with thermophilic bacilli that threaten product quality.
International Journal of Systematic and Evolutionary Microbiology, 1999
Thermophilic streptococci were isolated from biofilms on stainless steel samples exposed to paste... more Thermophilic streptococci were isolated from biofilms on stainless steel samples exposed to pasteurized skimmed milk and from dairy products from a dairy manufacturing plant. The phenotypic characters of these isolates were distinct from those of other thermophilic streptococci of dairy origin (Streptococcus thermophilus and Streptococcus bovis). Genotypic data [restriction endonuclease analysis, ribotyping, random amplified polymorphic DNA (RAPD) profiles, DNA-DNA hybridization and G+C contents] support the classification of these isolates as a new species. The sequence of the 165 rRNA was compared with that of 29 species of streptococci and shown to be significantly different. The sequence of the 165-235 rRNA intergenic spacer region also differed from published sequences of closely related species. A fluorescent in situ hybridization probe prepared to a specific part of the 165 rRNA gene sequence was able to distinguish the unknown isolates from reference isolates of S. thermophilus and S. bovis. It is proposed that these thermophilic streptococcal isolates from a dairy environment be classified in the genus streptococcus as a new species, Streptococcus waius (from waiu, the New Zealand Maori word for milk). The type strain is 3/IT (= NZRCC 20100T).
ABSTRACTPreconditioning ofAnoxybacillus flavithermusE16 andGeobacillussp. strain F75 with cations... more ABSTRACTPreconditioning ofAnoxybacillus flavithermusE16 andGeobacillussp. strain F75 with cations prior to attachment often significantly increased (P≤ 0.05) the number of viable cells that attached to stainless steel (by up to 1.5 log CFU/cm2) compared with unconditioned bacteria. It is proposed that the transition ofA. flavithermusandGeobacillusspp. from milk formulations to stainless steel product contact surfaces in milk powder manufacturing plants is mediated predominantly by bacterial physiological factors (e.g., surface-exposed adhesins) rather than the concentrations of cations in milk formulations surrounding bacteria.
ABSTRACTFree ions of Na+, K+, Ca2+, and Mg2+influenced the optical density of planktonic cultures... more ABSTRACTFree ions of Na+, K+, Ca2+, and Mg2+influenced the optical density of planktonic cultures of thermophilic bacilli.Anoxybacillus flavithermusE16 andGeobacillussp. strain F75 (milk powder manufacturing plant isolates) andA. flavithermusDSM 2641 andG. thermoleovoransDSM 5366 were studied. Ca2+and Mg2+were associated with increases in optical density more so than Na+and K+. Overall, it appeared that Ca2+and/or Mg2+was required for the production of protein in thermophilic bacilli, as shown by results obtained withA. flavithermusE16, which was selected for further study.
Dietary sodium is an important modifiable determinant of blood pressure, 1 and recent estimates s... more Dietary sodium is an important modifiable determinant of blood pressure, 1 and recent estimates suggest almost two thirds of the burden of stroke and half that of ischaemic heart disease are associated with non-optimal blood pressure levels. 2 Since blood pressure is ...
World Journal of Microbiology and Biotechnology, 2014
The carbon-to-nitrogen (C:N) ratio in the biomass of microfungi tends to be quite different (e.g.... more The carbon-to-nitrogen (C:N) ratio in the biomass of microfungi tends to be quite different (e.g. 10-15) compared with the C:N ratio in the red pigments (e.g. >20) of the fungus Monascus ruber. Therefore, determining an optimal C:N ratio in the culture medium for maximizing the production of the pigments is important. A culture medium composition is established for maximizing the production of the red pigment by the fungus M. ruber ICMP 15220 in submerged culture. The highest volumetric productivity of the red pigment was 0.023 AU L −1 h −1 in a batch culture (30 °C, initial pH of 6.5) with a defined medium of the following composition (g L −1): glucose (10), monosodium glutamate (MSG) (10), MgSO4•7H2O (0.5), KH2PO4 (5), K2HPO4 (5), ZnSO4•7H2O (0.01), FeSO4•7H2O (0.01), CaCl2 (0.1), MnSO4•H2O (0.03). This medium formulation had a C:N mole ratio of 9:1. Under these conditions, the specific growth rate of the fungus was 0.043 h −1 and the peak biomass concentration was 6.7 g L −1 in a 7-day culture. The biomass specific productivity of the red pigment was 1.06 AU g −1 h −1. The best nitrogen source proved to be MSG although four other inorganic nitrogen sources were evaluated.
The aim of the study was to compare the physicochemical and sensory characteristics of fermented,... more The aim of the study was to compare the physicochemical and sensory characteristics of fermented, cured sausages made from equivalent muscle groups of beef, pork, and sheepmeat. The last has no commercial examples and represents an unexploited opportunity. Using seven replicates of shoulder meat and subcutaneous fat, sausages were made with 64%, 29%, 4%, 2%, 0.2%, and 0.01% of lean meat, fat, NaCl, glucose, sodium pyrophosphate, and lactic culture, respectively. Following anaerobic fermentation (96 h, 30°C), there were no significant differences between the species in mean texture (hardness, springiness, adhesiveness, cohesiveness) and pH, and only minor differences were seen in color. However, although not consumer tested, it is argued that consumers would be able to pick a texture difference due to different fat melting point ranges, highest for sheepmeat. This work was followed by a sensory experiment to find out if characteristic sheepmeat flavors could be suppressed to appeal t...
A survey was undertaken at a whole milk powder manufacturing plant to determine the origin and th... more A survey was undertaken at a whole milk powder manufacturing plant to determine the origin and the rate of spore formation of thermophilic bacteria. Spores were generally not detected (< 10 cfu/mL) in either the pasteurization process or the pasteurized milk directed into the powder plant. The predominant sites of spore formation were the preheater plate heat exchanger and the evaporator. Spores began to be detected approximately 9 h into an 18-h manufacturing run. Spore isolates were identified as Anoxybacillus flavithermus and Geobacillus species. A. flavithermus predominated in the preheat section, whereas a mix of both organisms was present in the later manufacturing stages.
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Papers by John Brooks