Nina Muller

A review of triticale uses and the effect of growth environment on grain quality

Triticale (× Triticosecale sp. Wittmack ex A. Camus 1927) is an anthropogenic cereal designed to incorporate the functionality and high yield of wheat (Triticum spp. Linnaeus 1753) and durability of rye (Secale cereale Linnaeus 1753). The potential of triticale has remained largely unrealised, and in the 135 years since A. Stephen Wilson first crossed wheat and rye, triticale has mostly been used as animal feed. Growing demand for food resources has led to an increased interest in triticale development. Efforts to breed cultivars appropriate for baking have met with difficulty, although relatively new approaches to triticale end-use propose greater applicability for human consumption. Further, environmental awareness has generated interest in the use of triticale within biofuel production. We review environmental and genetic effects on triticale yield with a view towards increased demand on a hardy and useful cereal crop. We find triticale could satisfy many of the hopes originally placed upon it, and may be useful in foodstuffs and fuel, but only when growth environment is carefully considered.

Instrumental measurement of bitter taste in red wine using an electronic tongue

An electronic tongue (ET) based on potentiometric chemical sensors was assessed as a rapid tool for the quantification of bitterness in red wines. A set of 39 single cultivar Pinotage wines comprising 13 samples with medium to high bitterness was obtained from the producers in West Cape, South Africa. Samples were analysed with respect to a set of routine wine parameters and major phenolic compounds using Fourier transform infrared-multiple internal reflection spectroscopy (WineScan) and high-performance liquid chromatography, respectively. A trained sensory panel assessed the bitterness intensity of 15 wines, 13 of which had a bitter taste of medium to high intensity. Thirty-one wine samples including seven bitter-tasting ones were measured by the ET. Influence of the chemical composition of wine on the occurrence of the bitter taste was evaluated using one-way analysis of variance. It was found that bitter-tasting wines had higher concentrations of phenolic compounds (catechin, epicatechin, gallic and caffeic acids and quercetin) than non-bitter wines. Sensitivity of the sensors of the array to the phenolic compounds related to the bitterness was studied at different pH levels. Sensors displayed sensitivity to all studied compounds at pH 7, but only to quercetin at pH 3.5. Based on these findings, the pH of wine was adjusted to 7 prior to measurements. Calibration models for classification of wine samples according to the presence of the bitter taste and quantification of the bitterness intensity were calculated by partial least squares-discriminant analysis (PLS-DA) regression. Statistical significance of the classification results was confirmed by the permutation test. Both ET and chemical analysis data could discriminate between bitter and control wines with the correct classification rates of 94% and 91%, respectively. Prediction of the bitterness intensity with good accuracy (root mean square error of 2 and mean relative error of 6% in validation) was possible only using ET data.

The use of sensory attributes, sugar content, instrumental data and consumer acceptability in selection of sweet potato varieties

BACKGROUND As eating quality is important for adoption of new varieties, nine orange-fleshed and three cream-fleshed sweet potato varieties were assessed for sensory characteristics, dry mass and free sugar content, instrumental texture and colour and consumer acceptability (n =  216) in a peri-urban South African setting. RESULTS Cream-fleshed varieties were higher in yellow-green colour and sweet potato-like flavour and lower in graininess. Orange-fleshed varieties were higher in pumpkin-like flavour, orange colour, discolouration and sucrose content. Partial least squares regression analysis showed that the most accepted varieties (Impilo, Excel, Resisto, 2001_5_2, Serolane, W-119 and Monate) were associated with sweet flavour, dry mass and maltose content, while the least accepted varieties (Beauregard, Khano and 1999_1_7) were associated with wateriness. Pearson correlation analysis highlighted correlations of sensory attributes yellow and orange with instrumental colour measurements (colour a* and colour b*), instrumental firmness with sensory firmness, dry mass with sensory wateriness, and maltose content with sensory sweet and sweet potato-like flavour. The varieties were clustered into three groups. Consumer acceptability for eating quality correlated with maltose content, dry mass and sweet flavour. CONCLUSION Chemical and instrumental measurements were identified to evaluate key attributes and will be useful in the intermediate phases of sweet potato varietal development.

Occurrence and sensory perception of Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid in rooibos (Aspalathus linearis).

Z-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid (PPAG), a compound postulated to contribute to the taste and mouthfeel of fermented rooibos tea (Aspalathus linearis), was isolated from unfermented rooibos plant material. Its structure was unequivocally confirmed by LC-MS, -MS(2), FT-IR and NMR of the underivatised natural product, and optical rotation measurements of the hydrolysed sugar moiety. A similar compound, postulated to be E-2-(β-d-glucopyranosyloxy)-3-phenylpropenoic acid, was also detected. Analysis of the leaves of a large number of rooibos plants (n=54), sampled at commercial plantations, showed that PPAG is not ubiquitously present in detectable quantities in the leaves of different plants. This leads to large variation in the fermented plant material, infusions and food-grade extracts. PPAG was shown to have a slightly bitter to astringent taste and a detection threshold of 0.4 mg/l in water.

Gamebirds: A sustainable food source in Southern Africa?

In order to alleviate the current food security situation the world is faced with, it is essential to investigate meat sources which have the potential to be used in a sustainable manner. This review provides substantial arguments to prove the viability of sport hunted wildfowl as a food source in Southern Africa. However, before the use of wildfowl meat can be realised, there are certain challenges to overcome in order to ensure meat of the best possible quality reaches the consumer. Important aspects to consider regarding the eating quality of wildfowl meat are identified and include the physical activity of the different portions and muscle fibre types, diet, breeding, age and gender as well as the post mortem handling/ageing of the meat. The safety issues involved in producing gamebird meat i.e. shot contamination (microbial or lead), are also discussed. Other areas that warrant scientific research include investigating the intrinsic and extrinsic factors that may have an influence on the ultimate meat quality and exploring possible techniques of improving the eating quality of wildfowl meat. The insights these investigations will provide have the potential to increase the commercial viability, directly or indirectly, of African wildfowl meat and thus contribute to food security.

Aspects of the nutritional value of cooked Egyptian goose (Alopochen aegyptiacus) meat compared with other well-known fowl species

There is no scientific research regarding Egyptian goose (Alopochen aegyptiacus) meat; therefore, a chemical analysis to establish the nutritional characteristics of the breast portion is described. Meat from guinea fowl, Pekin duck, ostrich, and broiler chicken were used as a reference. The high intramuscular fat content of Egyptian goose meat (5.6 g/100 g) may be linked to the fact that this species relies on fat for heat insulation and buoyancy. Egyptian goose meat is very high in polyunsaturated fatty acids (39.7%). The polyunsaturated fatty acid/saturated fatty acid ratio is within the recommendations (>0.4), although the n-6/n-3 ratio is higher than the suggested value of 5. The high Fe content of 7.5 mg/100 g is the differentiating factor within the mineral compositions and is related to the physical activity endured by the breast muscle of Egyptian geese. This study provides new insight into the nutritional characteristics of a meat species providing crucial information that is, as of yet, not available in the literature.

The relationships between consumer liking, sensory and chemical attributes of Vitis vinifera L. cv. Pinotage wines elaborated with different Oenococcus oeni starter cultures

BACKGROUND Malolactic fermentation (MLF) mediated by lactic acid bacteria (LAB) has been shown to modulate chemical and sensory attributes of wine. This study investigated the relation between consumer liking, chemical and sensory attributes of Vitis vinifera L. cv. Pinotage wines that were made over two vintages by four different lactic acid Oenococcus oeni starter cultures as well as a control treatment where MLF was prevented. RESULTS Descriptive analysis showed that the sensory attributes buttery, caramel, vegetative flavour, fruity and nutty aroma differed significantly between the wines. These effects on the wines were not the same for the two vintages tested. Preference mapping results showed that the sensory attributes influenced the average consumer liking. The main chemical and sensory correlations found for MLF-treated wines were related to 2,3-butanedione (diacetyl) with the buttery character and various esters with fruity aromas. CONCLUSION Although the direct effect of the bacterial starter cultures on wine sensory attributes is difficult to establish, and subject to variation over vintage, the present work suggests that the contribution of LAB starter cultures to wine sensory attributes can influence consumer liking. Selection of an MLF starter culture can thus potentially be used to develop specific wine styles.

Enhancing the polyphenol content of a red-fleshed Japanese plum Prunus salicina Lindl. nectar by incorporating a polyphenol-rich extract from the skins

BACKGROUND Plum skins are a waste product generated during production of plum juice or pulp. Polyphenols, shown to have various health-promoting properties, can be recovered from this waste product. Red-fleshed plum nectar formulations containing plum skin extract in varying amounts were characterised in terms of intensity of sensory attributes, consumer acceptability, colour, polyphenol content and antioxidant activity. Commercial beverages containing red fruits were used as benchmarks. RESULTS The polyphenolic profile of the plum skin extract was similar to that of the pulp, including anthocyanins, flavonols, flavan-3-ols and a phenolic acid. Addition of the extract to plum nectar, which enhanced the colour, polyphenol content and antioxidant capacity, was limited by its negative sensory impact. The formulations were deemed acceptable by consumers, although a decrease in positive sensory attributes (plum flavour, plum aroma and sweetness) and an increase in negative sensory attributes (plant-like flavour, plant-like aroma, acidity and astringency) were observed with increasing skin extract content. The formulations compared favourably with commercial beverages in terms of colour total polyphenol content and antioxidant activity. CONCLUSION Plum skins were successfully used to enhance the functional status of plum nectar. Use of a functional ingredient from plum skins is, therefore, a feasible value-addition strategy.

The effect of season, sex, and portion on the carcass characteristics, pH, color, and proximate composition of Egyptian Goose (Alopochen aegyptiacus) meat

The carcass yield, physical characteristics, and proximate composition of Egyptian geese (Alopochen aegyptiacus), a southern African gamebird species, have been studied. A total of 69 geese were harvested during 2 seasons: summer (n = 36) and winter (n = 33). This total group of geese consisted of 27 female birds and 42 male birds. Sex alone affected (P ≤ 0.05) the live and carcass weights, and the average muscle weight (g) of each portion was higher for the male fowl. The data does not indicate differences between the meats physical characteristics on account of sex; however, the meat from the female birds did have a higher intramuscular fat content. Season (winter vs. summer) did not influence the average muscle weights (g) of the breast, thigh, and drumstick portions, but the intramuscular fat content content of the birds hunted in winter was higher. Muscle color and pH differed as a result of season with the summer meat having a higher pH and more vivid red color compared with winter. The physical characteristics and the proximate composition of the breast, thigh, and drumstick portions varied considerably. This is essentially connected to a difference in physical activity of the muscles in the portions. Overall, this study revealed that to ensure a consistent eating quality the harvesting periods of Egyptian geese should be considered.

Post mortem rigor development in the Egyptian goose (Alopochen aegyptiacus) breast muscle (pectoralis): factors which may affect the tenderness

BACKGROUND Baseline research on the toughness of Egyptian goose meat is required. This study therefore investigates the post mortem pH and temperature decline (15 min-4 h 15 min post mortem) in the pectoralis muscle (breast portion) of this gamebird species. It also explores the enzyme activity of the Ca(2+)-dependent protease (calpain system) and the lysosomal cathepsins during the rigor mortis period. RESULTS No differences were found for any of the variables between genders. The pH decline in the pectoralis muscle occurs quite rapidly (c = -0.806; ultimate pH ∼ 5.86) compared with other species and it is speculated that the high rigor temperature (>20 °C) may contribute to the increased toughness. No calpain I was found in Egyptian goose meat and the µ/m-calpain activity remained constant during the rigor period, while a decrease in calpastatin activity was observed. The cathepsin B, B & L and H activity increased over the rigor period. CONCLUSION Further research into the connective tissue content and myofibrillar breakdown during aging is required in order to know if the proteolytic enzymes do in actual fact contribute to tenderisation.