Incorporation of fat-soluble bioactive compounds during development processing of a fermented-maize yogurt- like food containing phytosterols and papaya extracts

The aim of this work was to design a functional yogurt-like food obtained from fermented maize, and to study the behaviour of stability and quality parameters during three unit operations: pasteurisation, fermentation and cooking. The products were made with maize grains, wet-milled and sieved (350- mesh). The starch containing liquid was added with skim milk and sugar (C: control and K: kefir treatments), dispersible phytosterols and papaya fresh puree concentrated (DPC) or lyophilized (DPL). Pasteurisation was performed at 65 °C for 20 min. Starters from commercial preparation (Kefir or Lactobacillus bulgaris and Streptococcus thermophillus, Lactina R, Bulgary) were added in a proportion of 1.2/5 sample (K, ),) at a proportion of 5.6 x 106 CFU/g to C, DPL and DPC treatments. Fermentation was performed in batch system at 37 °C for 16 hrs. Cooking: preparations were cooked at 90 °C under continuous stirring for10 min. The final product was stored at 4 °C in the darkness. pH progressed differently between treatments after fermentation, being lower in C than K and DPC/L treatments (3.81 vs 3.99, P_<_0.05) and augmented slightly after cooking (around 4). Oxidation increased after cooking (TBARS), being 2 -fold higher in the DPC/L treatments than in the controls. Total tocopherols were about 3.7- fold higher in the DPC/L products than in the controls, and they were not affected by processing. The addition of papaya augmented the levels of the _-tocopherol isomer, whereas the _-isomer was the most important in C and K samples. Minor carotenoids, lutein and zeaxanthin, were higher in DPC/L products than in the controls (P_<_0.05) and were also not affected by processing. Instead, fermentation favored the release of biologically active lycopene, 0- carotene and 0-cryptoxanthin in DPC/L samples, probably due to the effect of bacterial metabolism. These compounds were further affected (P_<_0.05) by cooking (decrease of about 10 to 30 percent). Phytosterols were not affected during processing. Enriched yogurt had lower syneresis comparing to the control yogurt during storage (P_<_0.05). Lower syneresis in enriched yogurt was probably due to higher total solids (TS) and the gel network, being DPC<DPL<K<C. We obtained a functional “cereal yogurt-like product”, which contains around 2.3g of free phytosterols, 0.5 mg of 0-cryptoxanthin, 0.4 mg of 0-carotene (both pro-vitamin A carotenoids) and 1.64 mg of trans-lycopene. Fermentation favoured the release of the three carotenoids from papaya preparations in both concentrate and lyophilised forms. The addition of dispersible phytosterols and papaya favoured the stability of the product in terms of syneresis. Moreover, maize fermentation succeeded with both commercial starters (bacteria or kefir), which may add probiotic properties. This type of product may be a complement to conventional dairy products and an alternative to enhance the potential functionality of “vegetal milk” derivate.