title: Foaming Novatein Thermoplastic Protein

authors: Gavin, Chanelle Anne Rose

abstract: Most plastics are produced from non-renewable and/or non-biodegradable polymers. The negative environmental impact of these has been a strong driver for bioplastic development. Proteins are naturally occurring biopolymers which can be denatured and plasticised to produce thermoplastic materials. Novatein Thermoplastic Protein (NTP) is a patented blend of blood meal (a highly aggregated protein) and processing additives which: reduce hydrogen bonding, break cross links between cysteine residues, disrupt hydrophobic interactions, and facilitate protein unfolding. Water and triethylene glycol (TEG) are added as plasticisers to produce a powder which can be extruded, and subsequently injection moulded.
As Novatein is both bio-derived and biodegradable there is the opportunity for using it as an alternative loose fill packing material. This work aimed to develop an appropriate foaming method and the principles governing it. 
Foaming was initially investigated through extrusion which was unsuccessful due to the low speed and pressure drop. However, by using high speed and pressure, Novatein was successfully foamed in an injection moulder under free expansion. Foaming achieved densities between 0.2-0.5 g/cm3, at temperatures between 160-165°C. The mechanical properties varied with density but compressive strengths between 200 and 600 kPa and elastic moduli between 2.2 and 8 MPa were typical. Increasing temperature further did not improve expansion as the material degraded. The narrow processing window is characteristic of the material’s semi-crystalline nature which arises from residual protein secondary structure (α-helices and β-sheets). Although Novatein softens at high temperature, it does not form a typical melt.
Processing depends upon the interactions between protein, additives, and plasticisers. Highly plasticised Novatein phase separates into protein rich, protein-plasticiser, and plasticiser rich regions. This results in variable morphology characterised by: unfoamed regions, variable cell sizes and both open and closed cells. 

Varying water, urea and TEG impacted the foaming ability; adding urea lowered the extensional viscosity improving foaming while also acting as a blowing agent. Water and TEG reduced the shear viscosity and softening point respectively reducing expansion. Water was expected to improve expansion by acting as a blowing agent, however increasing water and TEG both increased cell size, but delayed stabilisation decreasing expansion.
Following nucleation a bubble grows by diffusion of gas molecules from the surrounding polymer. As these molecules leave, the viscosity increases, controlling bubble growth. Simultaneously, growth causes chain alignment within the surrounding polymer. Through FT-IR, bubbles were shown to appear in regions high in β-sheets. Two mechanisms were proposed; either a bubble nucleates near a β-sheet and grows until it encounters other β-sheet structures or that chain alignment enables hydrogen bonding between the chains, forming these structures. FT-IR also showed a high concentration of TEG at the bubble surface suggesting that nucleation occurred in regions high in water and TEG. The accumulation of TEG at a bubble surface occurs as water (steam) diffuses into the bubble causing expansion, pushing TEG into the surroundings.
Bubble stabilisation is achieved through either a loss plasticiser molecules or a decrease in temperature. In over plasticised blends, water keeps the viscosity in the surrounding polymer low, while increasing TEG reduced the softening point, both allowing more time for gases to diffuse out.
This work developed a suitable foaming method and an understanding of the role of protein secondary structure and rheology for Novatein, which can be foamed despite its high β-sheet content.

text: Foaming Novatein Thermoplastic Protein Most plastics are produced from non-renewable and/or non-biodegradable polymers. The negative environmental impact of these has been a strong driver for bioplastic development. Proteins are naturally occurring biopolymers which can be denatured and plasticised to produce thermoplastic materials. Novatein Thermoplastic Protein (NTP) is a patented blend of blood meal (a highly aggregated protein) and processing additives which: reduce hydrogen bonding, break cross links between cysteine residues, disrupt hydrophobic interactions, and facilitate protein unfolding. Water and triethylene glycol (TEG) are added as plasticisers to produce a powder which can be extruded, and subsequently injection moulded.
As Novatein is both bio-derived and biodegradable there is the opportunity for using it as an alternative loose fill packing material. This work aimed to develop an appropriate foaming method and the principles governing it. 
Foaming was initially investigated through extrusion which was unsuccessful due to the low speed and pressure drop. However, by using high speed and pressure, Novatein was successfully foamed in an injection moulder under free expansion. Foaming achieved densities between 0.2-0.5 g/cm3, at temperatures between 160-165°C. The mechanical properties varied with density but compressive strengths between 200 and 600 kPa and elastic moduli between 2.2 and 8 MPa were typical. Increasing temperature further did not improve expansion as the material degraded. The narrow processing window is characteristic of the material’s semi-crystalline nature which arises from residual protein secondary structure (α-helices and β-sheets). Although Novatein softens at high temperature, it does not form a typical melt.
Processing depends upon the interactions between protein, additives, and plasticisers. Highly plasticised Novatein phase separates into protein rich, protein-plasticiser, and plasticiser rich regions. This results in variable morphology characterised by: unfoamed regions, variable cell sizes and both open and closed cells. 

Varying water, urea and TEG impacted the foaming ability; adding urea lowered the extensional viscosity improving foaming while also acting as a blowing agent. Water and TEG reduced the shear viscosity and softening point respectively reducing expansion. Water was expected to improve expansion by acting as a blowing agent, however increasing water and TEG both increased cell size, but delayed stabilisation decreasing expansion.
Following nucleation a bubble grows by diffusion of gas molecules from the surrounding polymer. As these molecules leave, the viscosity increases, controlling bubble growth. Simultaneously, growth causes chain alignment within the surrounding polymer. Through FT-IR, bubbles were shown to appear in regions high in β-sheets. Two mechanisms were proposed; either a bubble nucleates near a β-sheet and grows until it encounters other β-sheet structures or that chain alignment enables hydrogen bonding between the chains, forming these structures. FT-IR also showed a high concentration of TEG at the bubble surface suggesting that nucleation occurred in regions high in water and TEG. The accumulation of TEG at a bubble surface occurs as water (steam) diffuses into the bubble causing expansion, pushing TEG into the surroundings.
Bubble stabilisation is achieved through either a loss plasticiser molecules or a decrease in temperature. In over plasticised blends, water keeps the viscosity in the surrounding polymer low, while increasing TEG reduced the softening point, both allowing more time for gases to diffuse out.
This work developed a suitable foaming method and an understanding of the role of protein secondary structure and rheology for Novatein, which can be foamed despite its high β-sheet content.

year: 2019

title: Art that moves and re imagines place: a case-study on Tron Rocks

authors: Adams-Hutcheson, Gail

subjects: Mobilities

abstract: This workshop and presentation pushes into public art spaces and mobilities by drawing attention to place, environmental exploration, movement and the politics of care and kindness. Ideas loop back to, and are inspired by Peter Young’s 2015 documentary The Art of Recovery and the Lost and Found Project’s (2012) crafts of kindness in Christchurch post-disaster cityscapes. Here I present an autobiographical account of engaging with Waikato spaces and art through Hamilton’s Tron Rock group. The Tron, the colloquial name for Hamilton, is one of the country’s major nexus for painting and hiding rocks in and around urban spaces, public gardens, parks, lakes and the university campus. By painting rocks and ‘releasing them into the wild,’ participants use the online platform Facebook to facilitate a game of treasure hunting. The core politics that facilitate the ‘game’ is environmental respect, gifting and sharing art. Art is mobilised, it literally and emotionally moves, with shared journeys documented on Tron Rock sites. The thrill of discovery and sharing has mobilised groups of children and adults, as artists who reconfigure places by hiding rocks. I argue that geography and mobilites are crucial to think about how Tron Rocks has dynamically changed people-place engagements, as well as the breakdown of the categorisation of art as site-specific. Art literally travels. Rocks continue, may return or may never be seen again, it is all part of the game. I invite participants to this workshop to create their own rock and either keep it, set it free during the Symposium or hide elsewhere.

text: Art that moves and re imagines place: a case-study on Tron Rocks This workshop and presentation pushes into public art spaces and mobilities by drawing attention to place, environmental exploration, movement and the politics of care and kindness. Ideas loop back to, and are inspired by Peter Young’s 2015 documentary The Art of Recovery and the Lost and Found Project’s (2012) crafts of kindness in Christchurch post-disaster cityscapes. Here I present an autobiographical account of engaging with Waikato spaces and art through Hamilton’s Tron Rock group. The Tron, the colloquial name for Hamilton, is one of the country’s major nexus for painting and hiding rocks in and around urban spaces, public gardens, parks, lakes and the university campus. By painting rocks and ‘releasing them into the wild,’ participants use the online platform Facebook to facilitate a game of treasure hunting. The core politics that facilitate the ‘game’ is environmental respect, gifting and sharing art. Art is mobilised, it literally and emotionally moves, with shared journeys documented on Tron Rock sites. The thrill of discovery and sharing has mobilised groups of children and adults, as artists who reconfigure places by hiding rocks. I argue that geography and mobilites are crucial to think about how Tron Rocks has dynamically changed people-place engagements, as well as the breakdown of the categorisation of art as site-specific. Art literally travels. Rocks continue, may return or may never be seen again, it is all part of the game. I invite participants to this workshop to create their own rock and either keep it, set it free during the Symposium or hide elsewhere.

year: 2018

title: Microbiological quality of Toroi:  A Māori food delicacy

authors: Dixon, Lorraine Louise

subjects: Maori

abstract: A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

text: Microbiological quality of Toroi:  A Māori food delicacy A study was undertaken to determine the food safety of the fermented Māori delicacy, Toroi.  Ten batches of Toroi were prepared by a commonly used traditional method that consisted of boiling the vegetable component, either watercress or puha, and combining it with chopped mussel flesh.  The mixture was cooled and then stored in a refrigerator for up to eight months to allow natural fermentation to take place.  All ingredients were sourced from retail outlets.  The Toroi was examined at intervals over eight months for a range of pathogens (seven in all) that have been related to incidents of food poisoning in ready-to-eat foods in New Zealand.  The survival of a faecal contamination indicator, the laboratory grown strain Escherichia coli NZRM 916, was mapped over eight months.  Two strategies to prevent the growth of Listeria monocytogenes in Toroi were also investigated.  

Only one of the seven pathogens sought was recovered from any sample.  This pathogen was Bacillus cereus, a spore-former known to be associated with vegetables.  All batches contained B. cereus on the day of preparation but after two weeks refrigerated storage there was no further recovery from any sample.  There was a very low incidence of natural E. coli in the Toroi, consistent with levels permitted in mussels sold in retail outlets.  The laboratory grown strain, E. coli declined substantially over two months and was not recovered from any samples at eight months.  
A laboratory grown strain of Listeria monocytogenes, (L70) was added to Toroi and grew well with an increase in concentration of about seven-fold, over 19 days storage in a refrigerator.  A bacteriocin producing lactic acid bacterium, Lactobacillus sake Lb706, was added in combined culture with L. monocytogenes to Toroi.  It was found that at least 5 x108 L. sake cells were required as an inoculum to ensure elimination of L. monocytogenes from the Toroi.  When a purified bacteriocin; nisin, was added, a concentration of 10 mg g-1 in the Toroi was required to eliminate L. monocytogenes.  The inhibition study results suggest that unacceptably high inocula or purified bacteriocin would be required to prevent the growth of L. monocytogenes in Toroi.

The results of this suggest that Toroi be prepared from mussels either purchased from a retail outlet or harvested from sites known to be free from contamination.  Toroi should be safe to eat if prepared carefully, chilled promptly and thoroughly and allowed to ferment for at least two weeks.  In addition, care should be taken to maintain Toroi at refrigerated temperatures until it is eaten.

year: 2007