Pacific whiting and its by-products were good raw materials for high quality fish sauce production. Heat stable and salt activated enzymes were responsible for autolytic activity in Pacific whiting and by-products. According to temperature profiles of raw materials at various salt concentrations, two fermentation temperatures, 35°C and 50°C, were selected and compared at 25% salt under static atmospheric condition. Higher yields and faster production rate were obtained from samples incubated at 50°C. Therefore, the apparent optimum condition for fish sauce fermentation using Pacific whiting and its by-products was at 50°C with 25% salt under static atmospheric condition. All physicochemical characteristics, except color and browning color, reached the level of commercial fish sauce within 20 days. Nitrogen contents in all samples reached the level of commercial fish sauce (16.3 g-N/mL) within 112 days. Predominant microorganisms found during fermentation were Staphylococcus, Bacillus and Micrococcus. Alpha-amino acid content appeared to be identified as a good parameter to estimate total nitrogen content during fermentation (adjusted R²=0.84). Soluble solid was a good index for protein degradation in fermentation (adjusted R²=0.71). Proteolytic activity in Pacific whiting and its by-products were investigated using hemoglobin as substrate. Specific substrates and specific inhibitors were also used to classify the types of enzymes responsible for protein degradation in fish sauce fermentation. Serine proteases, cathepsin L-like enzymes and metalloproteases were active at 50°C in whole fish. However, trypsin-like enzymes, and cathepsin L-like enzymes were responsible for protein degradation in by-products at 50°C. At 35°, whole fish was degraded by serine proteases, cathepsin B-like enzymes, trypsin-like enzymes, and metalloproteases. Cysteine proteases were mainly responsible for the degradation of proteins in by-products, and serine proteases and trypsin-like enzymes had a minor role in hydrolyzing of by-products during fermentation. / Graduation date: 2000

Biochemical properties, functional properties, and market potential of Pacific whiting (PW) fish sauce were investigated. Biochemical properties of fish sauce made from whole fish (W) and a mixture (1:1) of whole fish and surimi byproducts (WB) were compared. Market potential was evaluated through phone interviews and consumer panelists. Proteolysis was primarily affected by cathepsin B-like and L-like enzymes. Acidic pH (4-5) with low salt concentration (15-20%) provided a greater degree of hydrolysis (DH), total nitrogen, and amino nitrogen content in PW fish sauce compared to the traditional process. The greatest Angiotensin Converting Enzyme (ACE) inhibition (96.8%) was found in samples fermented with 15% salt at pH 5.0 for 30 days. Anti-oxidative activity (AT) increased when fermentation continued and depended on fermentation pH. Peptides with MW <590 Da possibly played an important role in ACE inhibition. Consumer tests disclosed no significant difference in flavor liking and overall liking among fish sauce samples (W, WB, and commercial anchovy fish sauce). / Graduation date: 2004

Thesis (MSc Food Sc )--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The focus of this study was the development of food products produced from the neck flesh of Cape hake (Merluccius capensis) as a means of adding value to hake heads. The product prototypes that have been developed include curried fish chowder (packaged in stand-up pouches), fish spread (packaged in plastic casings) and Chakalaka hake (packaged in both cans and retortabie pouches). A formula for fish stock, which was used as a base ingredient in the three product prototypes, has also been standardised. Shelf life testing was regarded an essential part of the development processes for the refrigerated product prototypes i.e. the curried fish chowder and the fish spread. Shelf life determinations involved microbiological testing based on set microbiological standards as well as sensory monitoring and pH testing. Proximate chemical- and mineral analyses were performed on freeze-dried samples of the developed product prototypes. The efficiency of the antimicrobial peptides enterocin 1071 A and 1071 B, as biological preservatives, versus that of conventional artificial preservatives was evaluated in the fish spread prototype. Three batches of fish spread were prepared: one containing the enterocin crude extract; the second a combination of sodium benzoate and potassium sorbate, while the third batch containing no preservatives served as the control. Microbiological- and histamine tests coupled with organoleptic monitoring and pH testing were carried out over a 21-day period. It was concluded that although enterocins 1071A and 1071B had some preserving effect in the fish spread, the artificial preservative combination was the superior preserving agent. However, neither the biological preservatives nor the artificial preservative combination succeeded in providing a satisfactory shelf life. The preserving agents used in this study were however not necessarily included at optimum levels and higher levels could possibly lead to an improved shelf life. The influence of two processing temperatures [121°C (249.8°F) and 116°C (240.8°F)] and two food container types (retortable pouch and can) on the sensory quality characteristics of the Chakalaka hake-prototype was investigated. The results indicated that the shorter processing time obtained with a higher processing temperature resulted in a product of better sensory quality. The sensory quality characteristics of Chakalaka hake processed in cans at 121°C were closest to that considered desirable for the product. / AFRIKAANSE OPSOMMING: Die fokus van hierdie studie was die ontwikkeling van voedselprodukte geproduseer uit die nekvleis van stokvis (Merluccius capensis) met die doeI om waarde by stokviskoppe te voeg. Die volgende produk-prototipes is ontwikkel: 'n dik vissop met 'n kerriegeur (verpak in regopstaande sakkies), 'n vissmeer (verpak in plastiekomhulsels) en Chakalaka hake (verpak beide in blikkies en retortbestande sakkies). 'n Formule vir visaftreksel, wat as 'n basis-bestanddeel in die drie produk-prototipes gebruik is, is ook gestandaardiseer. Rakleeftydstudies het 'n belangrike deel van die ontwikkelingsprosesse van die verkoelde produk-prototipes, d.i. die dik vissop en die vissmeer, uitgemaak, Rakleeftydbepalings het mikrobiologiese toetsing, gebaseer op vasgestelde mikrobiologiese standaarde, sowel as die monitor van sensoriese eienskappe en pH metings behels. Proksimale chemiese- en mineraal analises is uitgevoer op gevriesdroogde monsters van die ontwikkelde produk-prototipes. Die effektiwiteit van die antimikrobiese peptiede enterosien 1071 A en 1071 B, as biologiese preserveermiddels, is ondersoek in vergelyking met dit van konvensionele kunsmatige preserveermiddels in die vissmeer-prototipe. Drie mengsels vissmeer is berei waarvan die eerste enterosien kru-ekstrak bevat het; die tweede 'n kombinasie van natrium bensoaat en kalium sorbaat, terwyl 'n derde mengsel geen preserveermiddels bevat het nie en gedien het as kontrole. Mikrobiologiese- en histamien toetse is gelyklopend met organoleptiese monitering en pH metings oor 'n tydperk van 21 dae op monsters van die drie vissmeermengsels uitgevoer. Die ondersoek het getoon dat enterosien 1071 A en 1071 B wel 'n mate van bederfwering in die vissmeer meegebring het, maar dat die kunsmatige preserveermiddelkombinasie 'n beter preserveringseffek gehad het in die produk. Nie die biologiese preserveermiddels óf die kunsmatige preserveermiddelkombinasie kon 'n bevredigende rakleeftyd teweegbring nie. Die preserveermiddels in hierdie studie is egter nie noodwendig in optimale hoeveelhede gebruik nie en hoër vlakke kan moontlik tot 'n verbeterde rakleeftyd lei. Die effek van twee prosesseringstemperature [121 °C (249.8°F) en 116°C (240.8°F)], sowel as twee verpakkingstipes (retortbestande sakkie en blik), op die sensoriese kwaliteitseienskappe van die 'Chakalaka hake' -prototipe is ondersoek. Die resultate het aangedui dat die korter prosesseringstyd verkry met 'n hoër prosesseringstemperatuur, gelei het tot 'n produk van beter sensoriese gehalte. Die sensoriese kwaliteitseienskappe van 'Chakalaka hake' geprosesseer in blikke by 121°C was die naaste aan dit wat beskou word as gewens vir die produk.