Call number: LD2668 .T4 1952 N44 / Master of Science

Thesis (MSc Food Sc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Cassava flour is recommended for substitution with wheat flour in composite flour for baking. The potential use of cassava flour in the food and pharmaceutical industries is attributed to its gluten-free nature and excellent functional properties. However, optimum packaging solution and storage conditions for cassava flour is critical in maintaining the quality attributes and shelf-life stability during storage. Therefore, this study focused on investigating the effects of package types (plastic buckets, low density polyethylene (LDPE) bags and brown paper bags) and storage conditions (cool condition (15 °C, 90% RH); ambient condition (23 °C, 60% RH); and higher condition (38 °C, 60% RH)) on the functional properties, quality attributes and shelf-life stability of cassava flour (cvs. ‘TME 419’ and ‘UMUCASS 36’) developed at the National Root Crops Research Institute, Umudike, Nigeria. Proximate composition, physicochemical attributes, functional properties, and microbial safety of flour were analysed every 4 weeks for 12 weeks storage duration. Flour stored under cool condition with paper bags became moist and sticky with appearance of mould growth before 4 weeks of storage. However, at the end of 12 weeks storage, a decline in moisture content of 11.00 ± 0.02 and 7.05 ± 0.01% flour of ‘TME 419’ was observed at ambient and higher conditions, respectively. Rate of moisture decline was similar in flour of ‘UMUCASS 36’. A slight decrease in protein content of flour was observed during the 12 weeks storage from 1.9 ± 0.07 to 1.30 ± 0.001% for cv. ‘TME 419’ and 3.0 ± 0.05 to 2.27 ± 0.001% for cv. ‘UMUCASS 36’; however, no significant difference was observed under ambient and higher conditions. Cassava flour packed in paper bags and stored under higher condition (38 °C, 60%) had the highest loss (50%) of carotenoid content from 1.84 ± 0.10% to 0.91 ± 0.08%, while a minimal loss (24%) of carotenoid was observed in flour packed in plastic buckets under ambient condition. The concentration of hydrogen cyanide (HCN) decreased across all treatments and was below the safe cyanide level of 50 µg/ mL for food products. After the 12 weeks of storage, flour packed in plastic buckets had the highest aerobic mesophilic bacterial counts (3.43 ± 0.04 log cfu/ g) followed by flour in LDPE bags (3.37 ± 0.03 log cfu/ g) and paper bags (3.35 ± 0.01 log cfu/ g). No significant difference was observed in the package types; however the counts observed were within the acceptable microbial limit Swelling power (SP), solubility and peak viscosity were used to characterise the changes in functional and pasting properties of cassava flour relevant in food industries. Flour packed in plastic buckets under ambient condition had the lowest swelling power (8.48 ± 0.55%) and peak viscosity (260 ± 0.51 RVU) compared to flour packed in LDPE and paper bags with (9.10 ± 0.13 and 9.32 ± 0.41%) SP and (263.67 ± 4.04 RVU and 302 ± 9.52 RVU) peak viscosity, respectively. The essential minerals (sodium, potassium, copper, and iron) were significantly higher in flour of ‘TME 419’ compared to ‘UMUCASS 36’. In summary, for the production of high grade foods such as bread where higher swelling power and viscosities are required, flour from ‘TME 419’ packed with paper bags under higher condition could be desirable. In addition, for infant formulation, flour from ‘UMUCASS 36’ packed in plastic buckets and stored under ambient condition which best maintained nutritional contents (protein and fat) and had the lowest peak viscosity would be more suitable. Flour from both cassava cultivars could be stored up to 12 weeks duration under ambient and hot tropical conditions using all package types evaluated. However, storage with paper bag under higher condition offers the chances of better shelf -life stability of cassava flour. / AFRIKAANSE OPSOMMING: Daar word aanbeveel dat kassavameel in plaas van koringmeel in saamgestelde meel by gebak gebruik word. Die potensiële gebruik van kassavameel in die kos- en farmaseutiese industrieë word toegeskryf aan die glutenvrye aard en funksionele kenmerke daarvan. Optimale verpakking en stoortoestande is egter belangrik vir die instandhouding van die gehalte kenmerke en raklewe stabiliteit tydens stoor. Daarom is die fokus van hierdie studie op die effek van verskillende tipes verpakking (plastiekemmers, lae densiteits politelien (LDPE) sakke en bruin papiersakke) en stoortoestande (koel toestande (15 °C, 90% RH); omringende temperature (23 °C, 60% RH); en hoër temperature (38 °C, 60% RH) op die funksionele kenmerke, gehalte kenmerke en raklewe stabiliteit van kassavameel (kultivare. ‘TME 419’ en ‘UMUCASS 36’) wat by die Nasionale Wortelgewasse Navorsingsinstituut, Umudike, Nigerië ontwikkel is. Die komposisie, fisiochemiese kenmerke, funksionele kenmerke en mikrobiale veiligheid van meel is elke vier weke tydens die 12-weke stoortydperk ontleed. Meel wat onder koeltoestande in papiersakke gestoor word, word klam en taai en swamme maak by vier weke van stoor ’n verskyning. Teen die einde van 12 weke stoortydperk is daar ’n afname in klammigheid van 11.00 ± 0.02 en 7.05 ± 0.01% in ‘TME 419’ meel by onderskeidelik omgewings- en hoër temperature. Die afname in klammigheid is soortgelyk by ‘UMUCASS 36’ meel. ’n Effense afname in die proteïen inhoud van die meel is tydens die 12- weke stoortydperk vanaf 1.9 ± 0.07 tot 1.30 ± 0.001% by die kultivaar . ‘TME 419’ en 3.0 ± 0.05 tot 2.27 ± 0.001% vir kultivaar ‘UMUCASS 36’ opgemerk. Geen noemenswaardige verskil is egter onder omgewings- en hoër temperature opgemerk nie. Kassavameel wat in papiersakke en onder hoër temperature (38 °C, 60%) gestoor is het die hoogste verlies (50%) aan karotien inhoud vanaf 1.84 ± 0.10% tot 0.91 ± 0.08% getoon , terwyl ’n minimale verlies (24%) by meel wat in plastiekemmers onder omgewingstemperature verpak is, opgemerk is. Die konsentrasie van waterstof hidrosianied (HCN) het tydens alle behandelinge afgeneem en was onder die veilige vlak van 50 µg/ mL vir kosprodukte. Na ’n 12-weke stoortydperk het die meel wat in plastiekemmers verpak is, die hoogste mesofiliese bakterië telling getoon \ (3.43 ± 0.04 log cfu/ g) gevolg deur die meel in die LDPE sakke (3.37 ± 0.03 log cfu/ g) en papiersakke (3.35 ± 0.01 log cfu/ g). Daar was geen merkbare verskil ten opsigte van verpakkingstipes nie; die tellings wat geneem is, was almal binne die aanvaarbare mikrobiale perk. Swelkrag (SP), oplosbaarheid en piek viskositeit is gebruik om die veranderinge in funksionele kenmerke van kassavameel wat betrekking het op die kosindustrie, te ondersoek. Meel wat onder omgewingstemperature in plastiekemmers verpak is, het die laagste swelkrag (8.48 ± 0.55%) en piekviskositeit getoon (260 ± 0.51 RVU) getoon vergeleke met meel wat in LDPE- en papiersakke (9.10 ± 0.13 en 9.32 ± 0.41%) swelkrag en (263.67 ± 4.04 RVU en 302 ± 9.52 RVU) piekviskositeit, onderskeidelik toon. Die belangrike minerale (natrium, kalium, koper en yster) was noemenswaardig hoër in die ‘TME 419’ meel vergeleke met ‘UMUCASS 36’. Ten slotte, vir die produksie van hoëgraad kossoorte soos brood waar hoë swelkrag en viskositeit belangrik is, is In ‘TME 419’ meel onder hoër toestande verpak in papiersakke, die beste keuse. In die geval egter van babakosse is ‘UMUCASS 36’meel wat in plastiekemmers verpak en onder omgewingstemperature gestoor is, en wat dus koswaardes (proteïen en vette) behou en wat die laagste piek viskositeit het, meer geskik. Meel van albei kultivaars kan vir tot twaalf weke onder omgewings- en hoë, tropiese temperature in al die verpakkingstipes wat evalueer is, gestoor word. Stoor in papiersakke onder hoër temperature verbeter egter die kanse op beter raklewe stabiliteit.

Master of Agribusiness / Department of Agricultural Economics / Bryan Schurle / The milling of wheat into white flour is a high volume, low margin business. Flour is a commodity. Competition is fierce. Over the past several years, there have been several mergers and acquisitions leading to fewer, but larger flour mills. The number of companies in the flour milling business has diminished as well. Flour sold in small packages on the grocery store shelf is but a small part of the business these days. Most flour is sold to commercial bakers in large bags or bulk trucks. The process of milling wheat into white flour consists of numerous variables within an extensive collection of equipment. It is the job of the miller to minimize the negative impact of these variables or at least hold constant as many of these variables as possible while achieving the best efficiency possible. To lessen the effect of these numerous variables on a large extensive system makes for a well running operation. When efficiency is achieved, a flour milling operation can be a profitable venture. A number of the variables that influence efficiency are affected by the amount of flour storage that a flour mill has. This thesis examines the benefits of flour storage as related to flour process efficiencies in milling. With flour mills operating at large output capacities, it is necessary for a flour mill to have adequate bulk flour storage bins as well as the right amount of warehouse space. Changes from one type flour to another in a flour mill require some time and an abundance of intervention by a skilled operator or miller. Having the proper amount of storage space makes it possible to minimize changes as well as the opportunity to optimize production of each specific flour type that is processed on the mill. To justify capital project money to invest in the proper amount of storage can be a challenge. Warehouse space and bulk flour storage can be expensive, and it is difficult to quantify how theoretical improvements will increase production and quality in the end product of flour. Using regression methods, production data obtained from an average sized commercial flour mill was used to estimate the increase in extraction due to a longer length of run allowed by the addition of storage space. By increasing the time a mill stays on a specific wheat mix to a minimum of twenty hours, there is a theoretical increase in extraction of 1.02 percentage points, resulting in wheat savings of over $500,000 per year. This resulting savings on the raw input material showed that capital expenditures on storage can be justified. A positive net present value and good internal rate of return show that the increased efficiency due to longer lengths of run justified the additional expense of the additional storage capacity. As volatility and the price per bushel of grain continue to increase, having the proper plant infrastructure with regard to storage space is of the utmost importance. Other benefits of storage will be realized as well in the area of flour quality and customer service.

Master of Science / Department of Grain Science and Industry / Jon Faubion / Whole wheat flour has become a popular ingredient in baked goods. Consumers are seeking the added benefits of consuming healthy phytochemicals and bioactive compounds. As the demand for wholemeal flour increases it is important to understand the factors contributing to changes in whole wheat flour breadmaking quality as a function of both wheat and flour age. In wholemeal flour, the lipid composition appears to be a factor causing variable baking quality. Changes that occur in both freshly harvested wheat and milled flour can cause variations in baking quality. Bakers’ attempts to adjust formulations and processes are often unsuccessful. The objective of this study was to determine the effects of aging both new crop wheat and freshly milled flour at 2 different temperatures on baking quality and glycolipid composition. This study aged freshly harvested Overley hard red winter wheat at RT (23˚C) and FZ (-26˚C) for 8, 50, and 91 days before milling. Whole wheat flour baking and lipid extraction studies were performed incrementally over 31 days of flour storage after each milling. Glycolipid structure and amounts were measured using automated electrospray ionization-tandem mass spectrometry. The glycolipids analyzed in this study were DGDG (digalactosyldiglycerol), MGDG (monogalactosylmonoglycerol), MGMG (monogalactosylmonoglycerol), and DGMG (digalactosylmonoglycerol). Both the wheat and flour stored at -26˚C produced larger mean loaf volumes than did the 23˚C treatment for all 3 wheat ages. The FZ and RT DGDG:MGDG ratios were similar over both wheat and flour age so changes to the glycolipid fraction did not appear to be the cause of the significant difference between volumes of bread baked from samples stored at RT and FZ. There was limited change in mean volume over flour age except for an increase at the FZ 91 day point. The DGDG:MGDG ratios were generally unchanged over flour age. Loaf volumes were the same over wheat age except for an unexpected drop during the 50 day wheat study. The corresponding DGDG:MGDG ratios did not show any significant differences over wheat age. The FZ storage temperature might be inhibiting some biochemical change not affecting the glycolipids, leading to higher volumes than the RT storage treatment.