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Item Third generation extruded snacks with ancient grains : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand(Massey University, 2015) Xiao, RuolingThird generation (3G) is a term that refers to the levels of processing used to produce a finished product. A 3G snack product starts with a starch based recipe that is extrusion cooked, formed into a dense shaped pellet and then dried. At this point, it is referred to as semi or half product because it needs to be further puffed to develop its texture and flavour. The objective of this project was to develop an unflavoured cereal-based 3G snack formulation with ancient grains. The snack must be unique in shape and suitable for hot air-puffing. Two 3G wholegrain base formulations were developed. One formulation was made from coarse rice flour, wholemeal wheat flour, potato starch, ancient grain blend (one third amaranth, one third quinoa and one third millet), wheat fibre 600 and salt. The second formulation was maize based by replacing coarse rice flour with maize polenta. These two base formulations contained ancient grains and nutrients that provide health benefits and were suitable for air-puffing. A lab-scale model Clextral BC21 twin screw co-rotating extruder was used for this study. Pasting properties of samples were evaluated using the Rapid Visco Analyser. It was found that ingredient selection and extrusion processing affected extruded pellets’ paste viscosities, the die swell and product expansion. Pasting properties of raw ingredient blend were affected by amylose and lipid content, and particle size of the cereal flour. The more even the raw material particle size was, the more even was the hydration of the material in the extruder. The results showed that inclusion of dietary fibre (wheat fibre 600, Beneo GR or Hi-MaizeTM 1043) in the 3G formulations decreased raw ingredients’ and extruded pellets’ paste viscosities, which resulted in reduced pellet expansion. It was found that wheat fibre 600 at 4 % was the best fibre choice to produce a 3G snack, because it accelerated extruded pellet drying, helped in ‘pellet checking’ control and producing more uniform cell sized expanded products. Hi-MaizeTM ingredients were found to lead to the deterioration of viscosity and snack pellet expansion, and therefore not recommended to be used for 3G snack base formulation. Increasing the water injection rate to the extruder (from 1.0 to 1.7 L/h) decreased the extruder apparent torque, thrust pressure, die pressure and SME. The degree of starch degradation was also reduced, but the product expansion was increased. Pellet expansion was found closely correlated to the pasting properties of the raw ingredient blend. Pellet expansion increased with the increase of peak viscosity (PV) and final viscosity (FV) of the raw ingredient blend. A suitable laboratory drying method was developed for 3G snacks. It was found that drying and holding at 1 h ± 5 min intervals including a pre-drying step had minimal pellets defects. Humidity control (60 %) was required throughout this drying process. After puffing, the product sectional expansion index (SEI) increased with the increase in salt concentration from 0.5 % to 1.0 % and increase in moisture content from 9.5 % to 12.1 %. The extruded pellets moisture was found to have the most significant effect on the finished product expansion, and maximum expansion due to puffing was found at 10.6 % pellet moisture. A shear-compression analysis of the 3G product prototypes and competitor products showed that most of low moisture commercial snack products available in the market have low bulk density and were brittle. The products produced from the proposed 3G formulations were much harder than the commercial products. Qualitative consumer focus group studies were conducted to gain insights into consumers’ attitudes towards extruded snacks, desirable texture and product claims to be included in the product. The results showed that five themes typically associated with snack consumption (nostalgia, special social occasions, distraction, convenient treat and hunger). Taste and price were the most important to the participants, and the health benefits were only an extra bonus. Participants were not tempted by an ancient grain claim. Product prototypes did not receive very positive feedback due to the taste and the product size. Product texture was found acceptable by most participants. This study produced initial formulations for a 3G snack, provided a good starting point for understanding of the 3G extruded snack process and provided valuable information for further development work. Further work is required to scale up the recipe, to increase the snack size, to further improve of the 3G snack flavour without significantly increasing the salt content and to carry out a consumer acceptance study on the scaled up 3G snack products.Item Consumer market research for optimization of an extruded snack product and process for the Indonesian market : a thesis presented in partial fulfilment of the requirements for the degree of Master of Technology in Food Technology at Massey University(Massey University, 1996) Indrawati, YulyA coextruded snack based on corn, defatted soya flour and Indonesian ingredients (rice and/or tapioca) was developed for Indonesian consumers, particularly to fit into the young adult niche market. Market and consumer research was carried out through collecting primary and secondary data and the results were utilized in the formulation of the extruded snack. Information about the snack market situation in Indonesia and consumer attitude towards extruded snack products indicated that there is an opportunity for success for a new-western style snack (extruded snack) in Indonesia and the key for success are product awareness and product attributes, notably crispiness and flavour. The snack base was manufactured using a co-rotating and intermeshing twin screw extruder (Clextral BC-21) with a constant feed rate and optimized by changing ingredients and extrusion conditions set by a constrained mixture design scheme (Echip computer software). The effect of the extrusion conditions and ingredients on the functional, physical properties of the snack product was also studied in this project. The product cost was also optimized with a constraint of no more than Rp. 4000 per kg (NZ$ 2.70) finish snack product. The study on the extrudate properties showed that an increase in rice flour increased moisture content (MC), Water Absorption Index (WAI), Nitrogen Solubility Index (NSI) and Breaking Strength (BS), while an increase in soya reduced the protein solubility and the extrudate became brownish. Consumer acceptability was mainly affected by the rice content, soya content and temperature in the last section (T4). Specific Mechanical Energy (SME), an extrusion parameter, was calculated directly through torque measurements. Higher SME indicated higher energy used in the extrusion process, thus more starch degradation and protein denaturation occurred, producing extrudates with lower BS. Sensory evaluation showed that snacks with lower BS (a crispier product), higher L* and b* colour (light brownish yellow colour) had a higher acceptance. The most preferred snack base was made from 28% defatted soya flour, 12% rice flour, 59.6% corn grits and 0.4% baking soda. These ingredients were processed in a twin screw extruder with a feed rate of 4.47 kg/hr. The four barrel temperature zones were set at 40°C, 80°C, 115°C and 140°C, respectively and 150 ml/hr of water was pumped to the barrel. The screw speed was set at 300 rpm. The snack acceptance was improved by coating the samples with flavours and the most preferred flavour determined by a sensory panel was a spicy flavour (Ethican – QZ 02346; Quest International). The optimum product formulation was then tested in a larger scale consumer test in Indonesia. The results from the final product testing showed that the developed snack was accepted by the target consumers. However some improvements of the product in terms of oil content and product stickiness in the mouth are still necessary. The developed product had a better acceptance over the snacks already in the market in terms of nutritional image, crispiness, product appearance and main ingredients. In addition a feasibility study on snack production in a single screw extruder was carried out and functional and physical properties of the resulting extrudates were compared with those produced using the twin screw extruder. The comparison of WAI, Glass transition temperature (Tg), NSI and BS of snacks manufactured using a single (Lalesse, Universal single screw extruder) and a twin screw extruder (Clextral BC21) showed that the extent of molecules degradation was lower in the single screw extruder than in the twin screw extruder. Sensory properties also indicated that the twin screw extrudate was crispier and suited to the consumers' preference than the single screw extrudate. The developed product could be produced commercially either using a twin screw extruder or a single screw extruder, depending on the available equipment, although it was recognized that the snack manufactured using the twin screw extruder had a higher preference compared to those produced using the single screw extruder.Item Consumer input and product concept testing in developing dried fruit snack prototype for Malaysian market : thesis presented in partial fulfilment of the requirement for the degree of Master of Technology in Product Development at Massey University(Massey University, 1996) Ibrahim, Aida HamimiThe input of the consumer when developing a dried snack fruit for the Malaysian market using the product development process was studied. A consumer panel made up of Malaysian students was used in each step of the product development process in this study. Preliminary consumer research was carried out using the focus group and the survey method. The results indicated that the two ethnic groups, Malay and Chinese, within the Malaysian student community could be treated as a homogenous group as they had similar attitude and behaviour characteristics towards the dried snack fruit product. Both student groups had been studying in New Zealand for less than two years. In the idea generation stage, the consumer panel generated 41 product ideas for the dried snack fruit using the nominal group technique. The 41 product ideas were reduced to three using a series of scoring techniques for screening. At this stage, consumer input was used to determine the market acceptability of the three possible products. These three product ideas with a benchmark were tested in concept product testing using the target consumer panel to evaluate consumer acceptability. Two different forms, concept description and concept prototypes, of concept testing using two different techniques, the focus group technique and the survey method, were tested in order to determine any significant effects they had on consumer acceptability. It was found that the concept prototypes had a significant effect on the consumers' preferences for product concept appearance, attractiveness and, buying intention. The two different techniques however, did not have a significant effect on the consumer acceptability of the product concepts. Of the two techniques, the focus group required less time for data collection compared to the survey technique, but the focus group was more expensive to run. By using the ECHIP programme and the line scale with floating ideals, which was the input of the consumers in the sensory evaluation stage, an optimum product formulation for the dried fruit snack was obtained. The prototype consisted of six types of fruit namely, apple (0.25), kiwifruit (0.25), banana (0.175), pineapple (0.13) strawberry (0.125) and jackfruit (0.07) with their natural flavours. The prototype was tested on the target consumer using in- house tests in order to determine the acceptability potential of the prototype. The results showed that the idea of developing the dried fruit snack with their natural flavours was acceptable among the Malaysian students. Freeze drying was found to be the most preferred drying process for the dried snack fruit product. The acceptable package size of the product by consumer panel was 40gm. Consumer input played a major role in the product development process in this project and it gave direction in the development of the dried snack fruit product for the Malaysian market. Consumer input was found to be vital during the preliminary consumer research, idea generation, concept testing, product formulation stages, and the final product testing phase in this study.Item Development of expanded snack foods containing pumpkin flour and corn grits using extrusion technology : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University, Palmerston North, New Zealand(Massey University, 2013) Md Nor, NorfezahThe production of expanded snack foods using vegetable powder as an ingredient in ready-to-eat food is rare. In view of its natural desirable colour, flavour, sweetness and health benefits, pumpkin was chosen as an additive to the traditional corn grits or rice used as the basis of an extrusion expanded snack or breakfast food concept. Pumpkins also have a large range of uses as a potentially valuable food for humans and animals. However, they are an underutilised product. This study was undertaken to demonstrate the potential of pumpkin products as additives in expanded snack food products. Processing the fresh pumpkin into flour dramatically extends the shelf life and makes the ingredient available throughout the year. The flour is more convenient for extrusion as it is stored and handled as a dry powder. Research was conducted to produce and characterise pumpkin flour made by convection oven and freeze drying of a pumpkin fractions such as peel, pulp (rind), flesh and seed. The flour was combined with corn grits in various proportions up to a maximum of 20% w/w. After determining suitable processing conditions and the maximum acceptable concentration of pumpkin flour for an edible product, the effect of process parameters on product quality were determined. Finally the product was optimised using response surface methodology (RSM). The proximate compositions of pumpkin flour from convection oven and freeze drying were as expected identical to commercial pumpkin flour. The carbohydrate content ranged between 69.8 and 89%, protein ranged between 1.3 and 21%, and fat between 0.03 - 0.53%. Pumpkin flour produced by freeze drying revealed L, a and b values higher than in commercial pumpkin flour, indicating that the flour was lighter in colour and appeared more orange than that oven dried. The effect of varying pumpkin flour proportion at two mass flow rates of 7.5kg/hr and 8.5kg/hr revealed that mass flow rate did not have any significant correlation to the extrusion parameters and the final quality of the expanded snack product. However, a high quality final product can be achieved at all mass flow rates with less than 20% pumpkin flour incorporated into the blend. Varying the proportion of pumpkin flour between 5% and 20% in combination with corn grits using screw speeds of 250rpm and 350rpm showed that, increasing the proportion of pumpkin flour to 20% significantly (P<0.05) decreased specific mechanical energy (SME) and torque. The extruded pellets using a 20% blend of pumpkin with corn grits were harder, more denser and less expanded than those made with higher proportions of corn grits. The crispiness and hardness of the final product was not closely related to the number or area of bubbles present in the structure. Screw speed did not significantly (P>0.05) affect the specific mechanical energy (SME) or the physical characteristics of the final product. Hardness seemed to be due to bubble wall stiffness i.e. effectively the thickness and rigidity of the set starchy matrix. Response surface methodology (RSM) was predicted four solutions for optimum conditions which can be achieved at barrel temperature ranging from 165°C to 167°C at a constant feed rate of 10.50kg/hr and pumpkin flour percentage ranged from 16% to 17%. With these conditions, the optimum SME of 0.15 was achieved and this product had a maximum radial expansion of 11.00%, hardness less than 142.0N with a total carotenoid content of 2.07ppm to 2.13ppm. Sensory analysis revealed most consumers preferred expanded snack products containing 5% pumpkin flour and produced by extruding at a barrel temperature of 170°C and mass flow rate of 12.0kg/hr. The panellists indicated that they would buy this product due to its acceptable taste, texture, odour and overall product characteristics. However, the expanded snack with 15% pumpkin flour was found to have highest total carotenoid content (5.78ppm) and protein content (28.8%) after processing and may have been, in nutritional terms, the best product. The slowly digestible starch (SDS) value and carbohydrate content of this product was found at 97.03mg/g and 59.29% respectively. From this work useful information regarding pumpkin flour and its application in extruded expanded snack production was obtained. This work has the potential to diversify the application of pumpkin flour and offer new uses for pumpkin in the food industry.Item Development of a bakery snack for export from New Zealand to Malaysia : a thesis presented in partial fulfilment of the requirement for the degree of Doctor of Philosophy in Product Development(Massey University, 1987) Lai, Pai WanThe use of consumers in the product development system for developing a food product was investigated. The investigation studied the techniques suitable for use with consumers and how well the development system worked in a cross-cultural situation. A bakery snack was developed for export from New Zealand to Malaysia, targetted at two major ethnic groups, the Malays and Chinese. Initial market research (including a consumer survey and a focus group) provided general information on the eating of snacks by the Malays and the Chinese. Multidimensional scaling also provided general information on their perceptions of bakery snacks and uncovered an area for further development work. The initial market research findings indicated that the Malays and Chinese were similar in their perceptions and preferences of bakery snacks. Their purchasing patterns of bakery products from bread and cake shops were somewhat different. Bread and cake were more popular among the Malays, while the Chinese bought more filled buns and currys puffs. Consumers generated 100 new product ideas for bakery snacks using brainstorming and nominal group technique. Both techniques were found to be useful under different conditions. The product ideas were reduced to seven using a series of quantitative techniques. The final selection of a macaroni and minced meat pie for further development was made by Malay and Chinese consumer groups. Formulation of the pie was studied, using sensory profiling with fixed "ideals", by a small panel in New Zealand. The panel consisted of Malaysian students who had been in New Zealand for one or two years. Data obtained from the sensory profiling were used to derive empirical equations relating sensory attributes and acceptability to ingredient levels, so that the formulation could be guided quickly and systematically. The final product was consumer tested in Malaysia using a central location test, focus groups and sensory profiling. Consumer input was useful in every stage of the development of the product. Their input was particularly important during the initial market research, the formulation stage and product testing. It was concluded that consumers were best utilised in as many stages of the development of a consumer product as possible, using groups of 10-30 people. Most techniques were found suitable for cross-cultural research. Exceptions occurred where questionnaires were involved (i.e. the initial consumer survey and the central location test) where it was found that Malays were reluctant to answer questions. Results from the different techniques at the various stages of the project correlated well with few exceptions. The pie developed was acceptable to Malaysians, both Malays and Chinese, but improvements are still necessary, particularly in the sensory properties before test marketing. The beef flavour was too strong and could possibly be reduced by decreasing the beef content and replacing it with textured vegetable proteins.Item An investigation into the nutritional and physicochemical properties of extruded products containing tomatoes : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2012) Dehghan-Shoar, ZeinabExtruded expanded products are becoming an important part of the diet in today’s fast-paced life, however due to the presence of high amounts of fully gelatinised starch and low amounts of other nutrients, regular consumption of these products can result in health issues such as obesity and cardiovascular disease. Limited information is available on the addition of tomato derivatives that contain fibre and lycopene, the red pigment of tomatoes, to extruded products. Furthermore, the effect of extrusion processing on lycopene, especially how this process may affect lycopene bioavailability is not known. The aim of the present study was to evaluate the possibility of adding tomato derivatives, mainly tomato waste skin, to improve the nutritional value of extruded snacks without detracting from their organoleptic properties. Varying the formulation of the extruded products showed that ingredients that have higher starch contents such as corn and rice as compared with wheat, and also lycopene sources that are resistant to shear such as tomato skin as compared with tomato paste, result in higher lycopene retention values in the final products. Although, the utilization of tomato skin alone resulted in hard and dense products, the addition of limited amounts of tomato paste to the tomato skin resulted in consumer acceptable products. In-vitro digestion of the extruded products containing tomato derivatives showed that a large portion of the lycopene in the extruded products was released into micelles, thus it was potentially bioavailable. The uptake rate by Caco-2 cells (a human carcinoma cell line) from the extruded product was similar to the unextruded control. The utilization of tomato paste powder in the extruded snacks significantly reduced the starch digestibility, while tomato skin was less effective. Finally, the majority of lycopene present in the extruded products containing tomatoes was shown to be inaccessible to solvent extraction and only after digestion was it able to be extracted. Enzymatic hydrolysis of the extruded product confirmed that lycopene was associated with the starch component of the food matrix and an amylolytic digestion procedure was required to break the bonds with starch and release the lycopene. The findings from the present study confirm that it is possible to produce consumer acceptable extruded tomato products that contain bioavailable lycopene and fibre. The results obtained improve our understanding on the fate of heat-labile molecules such as lycopene during extrusion cooking and can have potential applications for the industry.Item Development of nutritionally-balanced snack product for urban school-age Thais : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Product Development at Massey University(Massey University, 1986) Sinthavalai, SirilakA product development system for developing a nutritionally-balanced snack product for urban school-age Thais was designed. Systematic quantitative methods and techniques were planned and used in the major steps of the product development process. Five prototype models for the major product development activity steps evolved during the research. These included a model for formulation development, a model for process development, a model for sensory analysis development, a model for product evaluation, and the overall model for systematic nutritional product development (NPD model). A fruit and nut snack bar was designed and then a commercial process developed to produce a product that was acceptable to the child consumers in Bangkok schools. Thai snack foods were classified scientifically and then three types - Thai cookie, Thai pastry, and "rice-crisp" - were identified as the most suitable for nutritional snacks for school children. The selection of appropriate ingredients, method of cooking and snack-type was based on a consumer survey with school children from 7-18 years old in Bangkok. Product ideas were generated by brainstorming and a literature review, and then were systematically screened and evaluated using the collected statistical data and also predicted information on the aspects of finance, technology, market and consumer. The "ideal product profile" was determined from the children's attitudes and behaviour towards snack foods. The effective and reliable method developed for the formulation system comprised the major steps of "best-estimate" experimentation, experimental trials, linear programming experiments, acceptability tests and final adjustment of the formula. Selection of suitable formulae was based on acceptability tests with a laboratory taste panel using a profiling technique. For process development, a Plackett and Burman experimental design was used for screening the process variables and factorial experimentation for optimising the process. Stepwise Regression and Yates' analysis methods were compared in the analysis of the results. The latter was considered more suitable for this project because it was easy to use, needed less time and money, and was effective. A ratio profile test developed at Massey University was used in the development of product profiles through the whole system to develop the product. This technique was found effective in distinguishing the difference of the samples from the "ideal" product. A profile test using linear scaling was found suitable for a panel with some level of training, while that using category scaling for a panel with lower capabilities for sensory judgment. Four types of taste panels used during the sensory analysis development process were laboratory panel, special panel, consumer panel and consumer survey. The sample numbers of the panels were 6, 5, 30 and 1094 respectively. In general, the laboratory panel could predict the reactions of the consumer panel and the consumer survey in evaluating the product subjectively, and the special panel could differentiate the characteristics of the intermediate products desired by the next process. An evaluation system used in this study comprised nutritional quality test, microbiological test, and storage test. Accelerated Shelf-Life Test using a factorial design was found an effective method for a storage test, while the Arrhenius Relationship Model was used for product shelf-life prediction. The most suitable factorial matrix was found to be "70, 90% RH; 25, 35, 45 C". These conditions of storage could be used for optimisation of storage condition, by Yates' analysis of the product quality at each storage time, and for estimation of shelf-life, by linear plotting technique of the product quality during the whole time of storage. This project is worth continuing for commercialization by the private sector, and the designed prototype models are recommended for use in the systematic PD process to develop nutritional snack products.Item Characterisation of the rehydration behaviour of milk protein concentrates in the presence of sugar : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy in Food Science and Technology at Massey University, Manawatu campus, New Zealand.(Massey University, 2013) Paracha, Ghulam Mohi UddinThe main focus of this study was to characterize the hydration of milk protein in high protein powders to provide insights and strategies that might improve the use of these powders in foods. While the majority of hydration studies reported in the literature have been conducted on systems where there is an excess of water there has been little research characterising hydration in models that more closely approximate powder hydration in real food systems. This study investigates the impact on protein powder hydration of one of the most common ingredients in food systems: sugar. Results from this study show that rehydration of MPC85 powders is much more sensitive to aging compared to rehydration in water. An aged MPC85 powder was found to have the same solubility profile with respect to temperature in pure water compared to the fresh powder. However the degree of solubility was markedly reduced when the same powder was rehydrated in water containing sugar (20%). This should also be kept in mind while calculating the solubility of milk powders during the processing as other ingredients will interfere with them to affect solubility of milk powders which in turn will affect the shelf life of the food products. It was also shown that the specific volume of the insoluble material sedimented during solubility studies increased as the solubility of the overall increased to about 50%. At higher degrees of solubility the specific volume of the sediment material decreased. Microscopy showed that in the lower solubility range predominantly small particles dissolved and the large particles retained their structural integrity through centrifugation and thus the volume of sediment was relatively unchanged despite material dissolving and becoming part of the supernatant. At higher levels of solubility the large particles dissolve primarily through the outer particle surface which therefore resulted in a progressive decrease in volume with solubility. The rate of change in the specific volume of the sediment and mass of the sediment with the increase in the solubility and temperature was also dependent on the solvent. The rate of change in water was higher than in the 20% sugar solution. A new mechanism for MPC powder rehydration was also proposed wherein water ingress into the particles occurs over a very short time scale. Water ingress equilibrium was assumed to occur when the concentration of sodium ions reached equilibrium on the assumption that all sodium salts are highly soluble and that the sodium salts are evenly dispersed throughout the primary powder particle. This occurred over a time-period of a couple of minutes compared with about thirty minutes for the bulk total soluble solids as measured through centrifugation. Increases in solubility with increasing rehydration temperature is proposed to result from shrinkage of the micelles in the particles due to increased hydrophobic bonding that in turn separates the micelles from each other allowing further ingress of water and solubilisation.Item Milling and extrusion characteristics of New Zealand corn : development of a hardness test and an on-line extruder viscometer : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University(Massey University, 1998) Li, Patrick Xiao-Ping; Li, Patrick Xiao-PingReady to Eat (RTE) snack foods are commonly manufactured using single and twin screw extruders and com grits as raw materials. Variations in product quality caused by grits from different hybrids and grain hardness have not been investigated. Furthermore, the relationship between rheological properties of the extrudate melt and the operating conditions in the extruder is not fully understood. Appropriate methods to determine com grain hardness to characterise com hybrids and the on-line viscosity of the extrudate melts have not yet been developed. These methods could provide sound and appropriate techniques to investigate the areas of milling and extrusion of com based food products. In this study, milling characteristics of 38 com hybrids from the 92-93 season and 12 com hybrids from the 94-95 season produced in New Zealand were studied. A modified Stenvert Hardness Test (SHT) using new parameters including milling energy and milling resistance time was developed. It was found that the modified SHT was simple and easy to use with low variability. The SHT milling energy can be used as an effective hardness index. It increased with grain bulk density and the ratio of hard to soft endosperm. All measured properties were highly dependent on the moisture content. For the same hybrid, SHT hardness increased and the grain bulk density decreased when the moisture content of the com grains increased. A roller-milling test was also developed to study the dry milling characteristics of these com hybrids. During milling, the breaking force measured in the roller-milling test increased with grain hardness. Analysis of particle size distributions in the ground samples after the modified Stenvert Hardness tests and the roller-milling tests showed that grit recovery rate increased with the grain hardness. Grits produced from hybrids harvested in the 92-93 and the 94-95 seasons, along with other grits and starches commercially manufactured in New Zealand, were used for the extrusion experiments. A new Slit-Die-Viscometer (SDV) was developed to measure the viscosity of extrudate melts on-line. Unlike many other viscometers used on-line, the operation of the new SDV did not interfere with the operating conditions of the extruder. The rheological properties and the degree of starch gelatinisation were affected by the operating conditions of the extruder and the characteristics of the raw materials: It was found that the melt viscosity decreased as moisture content increased. The apparent viscosity had a maximum value at barrel temperature of about 130DC, changed very little when screw speed increased at constant feed, and decreased slightly when the feed increased at constant screw speed. The grits were less gelatinised at high moisture content. The degree of starch gelatinisation increased slightly with screw speed and linearly with barrel temperature between 90DC and 130DC. At barrel temperatures higher than 130DC, the extrudate was almost fully gelatinised. Melts produced with starch of high amylopectin content had an overall lower viscosity with less shear thinning and a higher degree of starch gelatinisation than that produced with starch of high amylose content. Grit size affected the rheological properties and the degree of starch gelatinisation. Melts produced from medium and coarse grits had a lower viscosity and a lower degree of starch gelatinisation than that produced with fine grits. The effect of different hybrids of the same season on the rheological properties of the melt was negligible. However, the rheological properties were affected by the methods used to produce the grits. Grits from degermed grains had less oil and produced melts with lower viscosity and less shear thinning than grits from whole grains (higher oil content).