The effect of fish protein powder on the physiochemical, nutritional and sensory properties of cereal based products : A thesis submitted in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Lincoln University

Abstract

Starch based snack foods from wheat, corn, and rice are rich in carbohydrate and low in protein, essential amino acids and ω- fatty acids. These snacks are considered nutritionally imbalanced as a food. Consumption of highly digestible starch products may be linked to nutritional and health issues with high glycaemic index. Demand for healthier food products is increasing all over world and cereal food industry has attempted to enhance the nutritional content of products by addition of protein and lipid rich ingredients. Fish proteins are rich in all the essential amino acids (particularly methionine, lysine, histidine, threonine and valine) and long chain polyunsaturated fatty acids (LC-PUFA) (ω-3) including docosahexaenoic (DHA) and eicosapentaenoic (EPA) acid. This is in contrast to most protein from plant sources such as wheat, rice, maize, barely, soybean and pea, which lack adequate amounts of one or more essential amino acids and LC-PUFA. Cereal products can be fortified with protein and lipid rich ingredients such as fish protein concentrate (Brennan, 1992). From a nutritional point of view, fish and fishery products represent a good potential source of protein, essential amino acids and fatty acids for balanced nutrition and good health. Fish proteins have strong interactions with other proteins and high gelation ability and now a days are used in the food industry as a binder, dispersing agent and emulsifier. Cereal products can be fortified with fish proteins to reduce the glycaemic impact of such foods and provide a balanced nutritional profile for human beings as well as maintain the quality characteristics suitable for consumer acceptability. The nutritional value of such fortified foods is dependent not only on the quantity of protein incorporated but also the quality of such proteins used, for instance their essential amino acid content and score, potential protein digestibility and digestible indispensable amino acid score (DIAAS). Fish proteins are effectively more readily digested than those of plant protein. In this study, two different types of fish powder, cod (Pseudophycis bachus) and salmon (Oncorhynchus tschawytscha), were added into fresh pasta (cold extrusion and cooking) and bread (fermented cooking).The physical, chemical, textural, nutritional and sensory properties of these products were determined. These developed products may alter the Western consumer diet habits to fulfil the protein, essential amino acid and ω6:ω3 ratio though cod and salmon fish powder. Replacement of durum wheat semolina with different levels of cod (P. bachus) fish powder (CFP) was undertaken to increase the physicochemical, nutritional and sensory value of pasta. The result showed that fortification with CFP increased cooking loss as well as decreased optimal cooking time, swelling index and water absorption, whilst increasing firmness and resistance to uniaxial extension of pasta. The addition of CFP increased yellowness (b*) of the pasta compared to control sample. Furthermore, CFP enriched protein, ash and energy content of pasta samples compared to control sample. Incorporation of CFP showed a significant decrease (P < 0.05) in reducing sugar released during an in vitro digestion and standardised AUC values compared to control pasta. The potentially bio-accessible fraction of pasta enriched with 20% fish powder (FP) was characterised by a 177-191% increase in phenolic content and a 145-556% higher antiradical activity. Supplementation of fish powder also influenced protein digestibility (a reduction from 84.60% for control pasta to 80.80% for pasta with 20% fish powder). The sensory evaluation of CFP enriched pasta products was conducted using sensory panel. The result exhibited that all samples (5-15% CFP) were acceptable. A partial substitution of durum wheat semolina with different levels of salmon (O. tschawytscha) fish powder (SFP) was undertaken to increase the nutritional and sensory value of pasta. The results demonstrated that pasta with SFP had increased protein (12.88%-23.40%), lipid (0.46%-7.20%), ash (0.39%-0.57%) and energy (122.26-161.08 kcal) contents) as well as increased cooking time and cooking loss. The addition of SFP resulted in significantly decreased swelling, water absorption index and firmness whilst increasing resistance to uniaxial extension of pasta. Colour parameters indicated comparable brightness between the samples and higher redness values for enriched pasta. Furthermore, the starch digestibility of pasta decreased significantly as SFP levels increased with glycaemic measurements ranging between 505-382 mg/g (108 to 143% lower than control) and the values for the glycaemic area under curve (AUC) 385-261 for 5-20% of supplemented pasta, respectively. Incorporation of SFP affected the in vitro bioaccessbility of nutrients. The phenolic bio-accessible fraction of pasta enriched with 20% SFP was 179% (gastric) – 133% (pancreatic) increased compared to the control pasta, and the antioxidant activity was 263% (gastric)-190% (pancreatic) higher. Supplementation of SFP reduced protein digestibility (86.41% for control pasta; 81.95% for 20% SFP pasta).The sensory evaluation of SFP enriched pasta products was conducted using sensory panel. The result exhibited that all samples (5 -15% SFP) were acceptable. The research was undertaken to enhance the protein quality of pasta with partial substitution of durum wheat semolina with SFP. The results demonstrate that fortification of pasta with SFP increased indispensable amino acid (IAA) content compared to the control. As well as decreased the n6:n3 ratio from 19:1 (the control pasta) to 5:1 to 3:1 respectively. Digestible indispensable amino acid scores (DIAAS) were calculated using published data on amino acids digestibility to evaluate the protein quality of the pasta. IAA values (mg IAA/g protein), were found to be highest in the enriched pasta with SFP (372 to 453) and lowest in the control pasta (328), all exceeded the FAO recommended daily allowance (277 mg IAA/g protein) and contributed on average 41% to total amino acid contents. The DIAAS value in the control pasta was 36 % (lysine) and the pasta enriched with SFP containing had a DIAAS between 75 to 99 %. The study was undertaken to evaluate physical (moisture, volume), technological (texture and colour) nutritional (amino acid content, starch and protein digestibility) and nutraceutical (total phenolic content (TPC) and antioxidant capacity) properties of bread fortified with different levels of CFP and compared with a control bread. The result showed that there was a significant increase in the bread specific volume, crumb colour, and textural properties. The nutritional quality of the bread was analysed using an in vitro glycaemic response and protein digestibility digestion method. The results illustrate that the incorporation of CFP into wheat flour decreased the potential glycaemic response of bread. However, this study also shows that addition of CFP increased protein content and phenolic content, antioxidant capacity. Furthermore, incorporation of CFP into bread increased the protein quality in terms of essential amino acid content and score, protein digestibility and protein digestibility corrected amino acid score (PDCAAS). The study was conducted to investigate protein, amino acid, fatty acid composition, in vitro starch and protein digestibility, phenolic and antioxidant composition of bread fortified with SFP. The proximate composition in control and SFP breads were ranged between (34-31.42%) moisture, (13.91-20.04%) protein, (3.86-9.13%) fat, (2.13-2.42%) ash, (80.10-68.42) carbohydrate and (410.8-435.96 kcal) energy. The essential amino acid of control and SFP breads ranged between 261.75-306.96 mg/g protein which satisfies the score recommended by FAO/WHO/UNU (2007). The in vitro assay for protein digestibility, protein digestibility amino acid score, essential amino acid index, biological value and nutritional index ranged between 79.96-80.80%, 0.15-0.42%, 62.51-76.68%, 56.44-71.68%, 8.69-15.36% respectively. Control and SFP breads contained 60.31-43.60 g/100g total fatty acids (saturated fatty acids) and 13.51-17.00 g/100g total fatty acids (polyunsaturated fatty acids) and SFP breads fulfil the ω6/ω-3 score recommended by food authority. There was a significant effect of SFP on bread specific volume, crumb colour, and textural properties. The in vitro starch digestibility results illustrate that the incorporation of SFP into wheat bread decreased the potential glycaemic response of bread and increased the antioxidant capacity of bread. The study was undertaken to examine the effect of inclusion salmon oil (SO), cod oil (CO), coconut oil (CONT) and wheat gluten (WG) to wheat starch (WS) on pasting, textural and in-vitro starch digestibility properties. The TCMs and BCBs sample showed better complex index (CI) as compared to WS and WS-WG and decreased with increasing carbon chain length. The inclusion of lipids to WS significantly reduced pasting and textural characteristics than that of WS alone. In TCMs and BCBs samples V type amylose-lipid complexes peak at 20o 2θ and greater short range molecular order were formed with fatty acids producing more crystalline structure. Similar observation was noted by FTIR, Raman, and 13C NMR spectroscopy. Differential scanning calorimetry (DSC) results suggested that decreased in the gelatinisation temperature and enthalpy after addition of different oil sources to WS. The amount of reducing sugar released during starch digestion appears to be dependent on starch hydrolysis. In this study, due to amylose-lipid complex formation, in vitro glycaemic response decreased in TCMs (three component mixtures) and BCBs (binary component blends) samples followed by WS-WG with the ability to act as a barrier to supress the activity of digestive enzymes to hydrolyse the starch molecules. These altered characteristics of WS might help to formulate the foods to overcome the digestibility concern in human nutrition.