Compositional analysis of locally cultivated carob (Ceratonia siliqua) cultivars and development of nutritional food products for a range of market sectors
Thesis (Msc Food Sc (Food Science))--Stellenbosch University, 2008.
Carob (Ceratonia silliqua) is an evergreen, drought resistant tree of Mediterranean origin. Popularly known as St John’s bread, the carob pod has a long history of use in food (over 4 000 years). Carob has a good nutritional value, a long shelf-life (2-3 years) and it is relatively cheap. Due to its high sugar content, carob is naturally sweet. It also has a nutty chocolate-like flavour, but unlike chocolate or cocoa, carob does not contain any caffeine, thiobromine or oxalic acid. In addition, carob is normally regarded as a healthy food because of its low fat content (0.2 – 2.3%). Carob trees are also found in South Africa, especially in the Western Cape Province. Locally, carob trees have been used mainly ornamentally or as a source of animal fodder, with minimal use of the pods as a nutritious food source. Knowledge of the nutritional composition and the overall nutritional potential of locally (South African) grown carob cultivars is also limited. Carob could potentially be used as an alternative food source in South Africa as currently, most of this nutritious product goes to waste each year. In this study, the feasibility of using carob pods as an alternative source of food in South Africa was investigated. This was done by firstly, analysing the cultivars for proximate composition (moisture, carbohydrates, sugars, dietary fibre, protein, polyphenols, fat and ash) as well as for amino acids, fatty acids and minerals, in order to determine and compare their nutritional contents. Five cultivars (Tylliria, SFax, Aaronsohn, Santa Fe and an “Unknown” cultivar) were examined. The average proximate composition of raw carob pods was 8.17 – 9.56% moisture, 89.57 – 91.12% carbohydrates, 40.69 – 54.74% total sugars (33.70 – 45.09% sucrose, 1.79 – 4.95% glucose and 1.80 – 5.19% fructose), 29.88 – 36.07% dietary fibre, 3.07 – 4.42% protein, 2.58 – 3.08% polyphenols, 0.45 – 0.86% fat and 2.13 – 2.69% ash. Seven essential amino acids were present in all the cultivars, except for methionine which was not detected in the Single unknown cultivar. This study has shown that all the cultivars had good long-chain fatty acid (LCFA) proportions in terms of the saturated to polyunsaturated fatty acid (SFA: PUFA) and n-6 to n-3 ratios. The short-chain fatty acid content of the cultivars was low. All nine minerals (calcium, phosphorus, potassium, magnesium, sodium, manganese, iron, copper and zinc) analysed for in this study were detected in all five carob cultivars and all cultivars were very low in sodium. The impact of various roasting times (45, 60 and 75 min) at 150ºC, on the temperature sensitive components such as sugars, protein and fat, was also examined. Roasting had no significant (P>0.05) effect on the fat content. Although roasting significantly (P<0.05) reduced the sugar and protein content from 54.74 to 32.53% and 3.59 to 3.18%, respectively, levels in both raw and roasted carob still represented a potentially nutritious food source and alternative to cocoa. A variety of food products targeted at the various food market sectors were developed with carob as an ingredient. The formulations for five new food products (bread, porridge, breakfast cereal, mousse and milk-based drink) were developed where carob had successfully been incorporated as an ingredient. Microbiological and consumer sensory analyses carried out showed that all products developed were safe and acceptable. The findings of this study provide useful scientific evidence towards the fact that carob could potentially be used as an alternative food source in South Africa.