In vitro evaluation of the effect of yogurt acid whey fractions on iron bioavailability.

A side effect of the raised consumption of Greek yogurt is the generation of massive amounts of yogurt acid whey (YAW). The dairy industry has tried several methods for handling these quantities, which constitute an environmental problem. Although the protein content of YAW is relatively low, given the huge amounts of produced YAW, the final protein amount in the produced YAW should not be underestimated. Taking into consideration the increased interest for bioactive peptides and the increased demand for dietary proteins, combined with protein and peptides content of YAW, efforts should be made toward reintroducing the latter in the food supply chain. In this context and in view of the prevalent dietary iron deficiency problem, the objective of the present study was the investigation of YAW fractions' effect on Fe bioavailability. With this purpose, an in vitro digest approach, following the INFOGEST protocol, was coupled with the Caco2 cell model. To evaluate whether YAW digest fractions exert positive, negative or neutral effect on Fe bioavailability, they were compared with the ones derived from milk, a well-studied food in this context. Milk and YAW showed the same effectiveness on both Fe bioavailability and the expression of relative genes (DCYTB, DMT1, FPN1, and HEPH). Focusing further on YAW fractions, by comparison with their blank digest control counterparts, it resulted that YAW 3- to 10-kDa digests fraction had a superior effect over the 0- to 3-kDa fraction on Fe-uptake, which was accompanied by a similar effect on the expression of Fe metabolism-related genes (DCYTB, FPN1, and HEPH). Finally, although the 3- to 10-kDa fraction of bovine YAW digests resulted in a nonsignificant increased Fe uptake, compared with the ovine and caprine YAW, the expression of DCYTB and FPN1 genes underlined this difference by showing a similar pattern with statistically significant higher expression of bovine compared with ovine and bovine compared with both ovine and caprine, respectively. The present study deals with the novel concept that YAW may contain factors affecting Fe bioavailability. The results show that it does not exert any negative effect and support the extensive investigation for specific peptides with positive effect as well as that YAW proteins should be further assessed on the prospect that they can be used in human nutrition.

Effect of pulsed electric fields and high pressure on improved recovery of high-added-value compounds from olive pomace.

Olive pomace is considered a solid by-product and a rich source of valuable compounds such as polyphenols, flavonoids with antioxidant properties, and proteins. Nonthermal technologies, which cause alterations to cell permeability, are being explored to assist conventional recovery techniques. The aim of this study was to assess the effect of pulsed electric fields (PEF) and high pressure (HP) on improved recovery yield of the high-added-value compounds or to shorten the extraction time of these compounds. Olive pomace (Tsounati cv) was pretreated with PEF (1.0 to 6.5 kV/cm, 0.9 to 51.1 kJ/kg, and 15 µs pulse width) or HP (200 to 600 MPa and 0 to 40 min). Evaluation of the intracellular compounds extracted via solid-liquid extraction (50% ethanol-water solution) was performed. More intense PEF and HP conditions resulted in a significant increase of the phenolic concentration up to 91.6% and 71.8%, respectively. The increased antioxidant capacity of each extract was correlated to phenolic compound concentration. The protein concentration that was achieved with PEF pretreatment was doubled; however, HP-pretreated extracts reached 88.1% higher yield than untreated for pressures up to 200 MPa. HP and PEF pretreatment decreased extraction completion time t98 (needed time to recover the equal amount of phenolics and proteins of untreated after 60 min of conventional extraction) to 12 min and lower than 1 min, respectively. To conclude, both pretreatments are effective in improving the conventional extraction process for increased yield recovery of high-added-value compounds from olive pomace.