Henrietta Letitia De Kock

Undesirable sulphur and carbonyl flavor compounds in UHT milk: a review.

Ultra High Temperature (UHT) processing leads to the formation of “cooked” and “flat” flavors in milk. These undesirable notes occur due to the volatile formation of a variety of sulphur containing compounds, methyl ketones and aliphatic aldehydes, derived from the constituents of the milks matrix during thermal processing and storage. The “cooked” flavor of UHT milk is associated with the presence of a variety of sulphur containing compounds while the “stale” flavor is characterized by the dissipation of these sulphur volatiles and an increase of the formation and presence of both methyl ketones and aliphatic aldehydes over time. The extent to which the individual volatiles contribute to the overall flavor of UHT milk is not clear. The proposed formation of these volatiles, that is, the methods to control the intensity of “cooked” and “stale” flavors associated with UHT milk and extraction techniques for the isolation of these volatiles from milk, have been reviewed.

The morama bean (Tylosema esculentum): a potential crop for southern Africa.

The morama bean is an underutilized leguminous oilseed native to the Kalahari Desert and neighboring sandy regions of Botswana, Namibia, and South Africa (Limpopo, North-West, Gauteng, and Northern Cape provinces), and forms part of the diet of the indigenous population in these countries. It is also known as gemsbok bean, moramaboontjie, elandboontjie, braaiboonjie, marama, marumana, tsi, tsin, gami, and ombanui. It is reported as an excellent source of good quality protein (29-39%); its oil (24-48%) is rich in mono- and di-unsaturated fatty acids and contains no cholesterol. Morama is a good source of micronutrients such as calcium, iron, zinc, phosphate, magnesium, and B vitamins including folate. It is also reported to be a potential source of phytonutrients including phenolic compounds (e.g., tannins), trypsin inhibitors, phytates, and oligosaccharides, components which have been shown in other foods to contribute to health in particular, prevention of noncommunicable diseases such as cardiovascular diseases, diabetes, and some cancers. From a nutritional and health perspective, the morama bean has potential commercial value as a cash crop and value-added products, particularly in the communities where it is found.

Effect of soy flour addition and heat-processing method on nutritional quality and consumer acceptability of cassava complementary porridges

BACKGROUND The nutritional quality of cassava complementary porridge was improved through extrusion cooking and compositing with either defatted or full fat soy flour (65:35 w/w), and product acceptability by mothers with children of the target population was evaluated. RESULTS The protein digestibility-corrected amino acid score (PDCAAS) of extrusion- and conventionally cooked composite porridges was within the recommendations for complementary foods. The kinetics of starch digestibility showed that all porridges had a rapid rate of starch digestibility, but the rate was lower when defatted soy flour was added and lowest when full fat soy flour was added. The formation of amylase-lipid complexes as shown by X-ray diffraction and differential scanning calorimetry can be attributed to the lower digestibility of extrusion-cooked porridge with full fat soy flour. If fed thrice per day, extrusion-cooked porridge with defatted or full fat soy flour would meet the energy, protein and available lysine requirements of a child aged 6-8 months receiving low or average nutrients from breast milk. All porridges were well received by Mozambican mothers who use cassava as a staple food. The mean scores for sensory liking of all porridges were 3 and above on a five-point hedonic scale. CONCLUSION Extrusion-cooked cassava/soy flour porridges have good potential for use as high-energy/high-protein complementary foods and have acceptable sensory properties.

Quality characterization of wheat, maize and sorghum steamed breads from Lesotho.

BACKGROUND In Lesotho, traditional bread covers different types of dumplings prepared with cereal flour, water, salt and sourdough. This study characterized eight steamed breads prepared from wheat, maize and sorghum. Breads were prepared from both commercial and self-milled flours according to the procedures followed in rural and urban areas of Lesotho. Descriptive sensory evaluation was conducted to profile sensory properties of the breads. Flour particle sizes, sourdough properties and bread colour, volume and texture were also characterized. RESULTS The type of cereal and milling properties of the flour used had substantial effects on the physical and sensory properties of the bread. Steamed wheat breads had greater volume, softer crumb and more bland flavour compared with sorghum and maize breads. Both sorghum and maize steamed breads prepared according to traditional Basotho procedures were characterized by low loaf volume, denser crumb, more complex and strong flavours and aroma, notably sour, musty, malty, dairy sour and fermented aroma. The texture of the non-wheat bread types was heavy, chewy, dry, fibrous and more brittle and needed a higher compression force to deform. CONCLUSION This study provided insight on the sensory properties of steamed bread as prepared in Lesotho. Further research is needed to optimize sensory properties of the non-wheat steamed breads by controlling the flour particle size, compositing non-wheat flours with different levels of wheat flour, addition of protein sources and gums, altering the amount of water, improving the pre-gelatinization process and optimizing the steaming method of cooking bread.

Sensory and physicochemical analyses of roasted marama beans [Tylosema esculentum (Burchell) A. Schreiber] with specific focus on compounds that may contribute to bitterness.

The role of phenolics and saponins in contributing to bitterness in marama beans, an underutilized legume, especially when roasted, was investigated. Marama beans were roasted at 150°C for 20, 25 or 30 min, then dehulled to separate cotyledons, and pastes were prepared from these. Water extracts were prepared from full fat and defatted flours from roasted and unroasted marama cotyledons. A sensory panel evaluated the sensory attributes of marama pastes and water extracts. Marama water extracts were analysed for total phenolic content, phenolic composition and saponin content. Roasting of marama beans for more than 20 min resulted in negative properties, such as bitterness. The major extractable phenolic acids present in marama water extracts were gallic and protocatechuic acids which increased as a function of roasting time. Saponin content of the water extracts was in the range of 55-63 mg/l. The identified phenolic acids, saponins and other as yet unidentified compounds may contribute to the perceived bitterness.

Rapid sensory profiling and hedonic rating of whole grain sorghum-cowpea composite biscuits by low income consumers

BACKGROUND The challenges of malnutrition and urbanization in Africa demand the development of acceptable, affordable, nutritious complementary-type foods. Biscuits (i.e. cookies; a popular snack) from whole grain staples are an option. The present study aimed to relate check-all-that-applies (CATA) sensory profiles of sorghum-cowpea composite biscuits compared to economic commercial refined wheat biscuits with hedonic ratings by low income consumers. In addition, the nutritional composition and protein quality, L* a* b* colour and texture of the biscuits were determined. RESULTS The CATA method is suitable for rapidly determining which attributes consumers perceive in food products and relating these to acceptability. Consumers preferred the lighter, more yellow wheat biscuits with ginger, vanilla, sweet and cinnamon flavours compared to the stronger flavours (sorghum, beany and nutty) and harder but brittle, grittier, dry and rough textured sorghum or sorghum-cowpea biscuits. However, a substantial proportion of consumers also liked the latter biscuits. The composite biscuits had higher dietary fibre content and a similar protein quality to the standards. CONCLUSIONS Whole grain sorghum-cowpea biscuits could serve as acceptable value-added nutritious complementary snacks for consumers in sub-Saharan Africa. The biscuits are simple to produce for the creation of viable small enterprises.

The effects of antioxidants and shelf life conditions on oxidation markers in a sunflower oil salad dressing emulsion (SOSDE).

The effects of levels of antioxidant [gallic acid or ethylene diamine tetraacetate (EDTA)] in a sunflower oil salad dressing emulsion (SOSDE) and shelf life affecting conditions on aroma, anisidine values (AV) and peroxide values (PV) were determined. Aroma differences between products with different concentrations of antioxidants were more apparent for ambient than accelerated stored SOSDEs. Aroma differences were more noted between SOSDEs with different antioxidants than antioxidant concentrations per se. PV differences between accelerated stored SOSDEs with high and low EDTA concentrations were found. AV differences existed between SOSDEs with different gallic acid concentrations for both storage conditions, and for accelerated stored SOSDEs with different EDTA concentrations. The accelerated storage model is more suitable for SOSDEs with metal chelator antioxidants e.g. EDTA, than free radical scavenging antioxidants e.g. gallic acid. PV, AV and aroma of accelerated stored SOSDEs do not clearly predict ambient shelf life.

Relating physico-chemical properties of frozen green peas (Pisum sativum L.) to sensory quality

BACKGROUND The acceptability of frozen green peas depends on their sensory quality. There is a need to relate physico-chemical parameters to sensory quality. In this research, six brands of frozen green peas representing product sold for retail and caterers markets were purchased and subjected to descriptive sensory evaluation and physico-chemical analyses (including dry matter content, alcohol insoluble solids content, starch content, °Brix, residual peroxidase activity, size sorting, hardness using texture analysis and colour measurements) to assess and explain product quality. RESULTS The sensory quality of frozen green peas, particularly texture properties, were well explained using physico-chemical methods of analysis notably alcohol insoluble solids, starch content, hardness and °Brix. Generally, retail class peas were of superior sensory quality to caterers class peas although one caterers brand was comparable to the retail brands. Retail class peas were sweeter, smaller, greener, more moist and more tender than the caterers peas. Retail class peas also had higher °Brix, a(*) , hue and chroma values; lower starch, alcohol insoluble solids, dry matter content and hardness measured. CONCLUSIONS The sensory quality of frozen green peas can be partially predicted by measuring physico-chemical parameters particularly °Brix and to a lesser extent hardness by texture analyser, alcohol insoluble solids, dry matter and starch content.

Diversity and functionality of bacillus species associated with alkaline fermentation of bambara groundnut ( Vigna subterranean L. Verdc ) into dawadawa-type African condiment

The aim of this study was to investigate the diversity of Bacillus species in dawadawa; aiding potential starter cultures selection for alkaline fermentation of bambara groundnut into dawadawa-type condiments based on their genotypic and volatile compound profiles. Bacillus species (n = 71) isolated from spontaneously fermented dawadawa were identified using matrix assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS) as B. cereus (35%), B. licheniformis (30%), B. pumilus (21%), B. subtilis (10%) and B. amyloliquefaciens (4%). Further molecular typing was performed using GTG5 rep-PCR typing, 16S rRNA and gyrA gene sequencing. The gyrA gene sequence analysis exhibited the highest species discriminatory power with B. subtilis subsp. subtilis, B. amyloliquefaciens subsp. plantarum, B. pumilus and B. licheniformis as the distinct clusters. Representative strains from each cluster were then used as starter cultures for the production of dawadawa from bambara groundnut. Volatile compounds analysis using headspace solid phase microextraction (SPME) and comprehensive gas chromatography coupled to time of flight mass spectrometry (GC × GC–TOF MS) identified distinct chemical profiles produced by each of the four strains. Volatile compounds produced by B. subtilis subsp. subtilis (strain SFBA3) were categorized by dimethyl disulfide, methanethiol and nonanal while B. amyloliquefaciens subsp. plantarum (strain SFBA2) produced acetic acid and hexadecanoic acid. B. cereus (strain PALB7) produced 2,5-dimethyl pyrazine and 2-butanone which were not detected in the other condiments. Hexanal was the main compound produced by B. licheniformis (strain OALB7).

Designing Consumer Research Studies for Low-Income Populations

Abstract Incorrect business or policy decisions may be made because conventional consumer sensory methods are not able to reliably measure opinions of consumers in low socioeconomic environments. An important reason is that these methods take literacy and language capabilities for granted. There are opportunities for more research to optimize current methods and develop new approaches to measure food acceptability and preferences of consumers of low socioeconomic status. The objective of this chapter is to give insights into what is needed for the design and execution of research studies aimed at collecting quantitative information reflecting the opinions of low-income consumers.