Addition of Olive Leaf Extract (OLE) for Producing Fortified Fresh Pasteurized Milk with An Extended Shelf Life.

Palmeri Palmeri,Siracusa Siracusa,Fallico Fallico,Parafati Parafati,Restuccia Restuccia,Trippa Trippa,Arena Arena

doi:10.3390/antiox8080255

Palmeri Palmeri, Siracusa Siracusa + Show 5 more

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https://doi.org/10.3390/antiox8080255

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Abstract

An olive leaf extract (OLE) has been tested in vitro for its antibacterial activity and ability to inhibit α-glucosidase enzyme. OLE was also evaluated for its potential, when added to pasteurized milk, to preserve nutritional parameters and to limit microbial growth, thus prolonging shelf life. In vitro assays demonstrated a strong antibacterial efficacy of OLE mainly against Bacillus cereus and the capacity to inhibit α-glucosidase enzyme (IC50) when used at 0.2 mg oleuropein/mL. The milk fortification with OLE at 3.6 mg of oleuropein/mL of milk reduced total mesophilic bacteria at undetectable level after 6 d (expiration date) and by 1 log CFU/mL after 10 d. Moreover, OLE addition at 1.44 and 3.6 mg of oleuropein/mL of milk significantly reduced fat and lactose losses up to 10 d. The results motivate the use of the OLE to make a new functional milk with an extended shelf life.

Highlights

Milk is an important source of nutrients and energy, containing valuable macro and micronutrients as carbohydrates, proteins, fat, minerals, and vitamins.Treatments that use high temperatures, such as ultra-high temperature (UHT), allow to extend milk shelf life up to 6–12 months when stored at ambient temperatures [1,2,3] but can damage the biological properties of its components
Quality of pasteurized milk during storage can be affected by the presence of spoilage bacteria, mainly spore-forming species, such as Bacillus cereus [4], which is able to produce proteinase, lipase, and phospholipase enzymes originating off-flavors (“sweet curdling” and “bitty cream” defects)
The HPLC/diode array detector (DAD) chromatogram corresponding to olive leaf extract (OLE) is depicted in Figure 1 (λ = 280 nm)

Summary

Introduction

Milk is an important source of nutrients and energy, containing valuable macro and micronutrients as carbohydrates, proteins, fat, minerals, and vitamins.Treatments that use high temperatures, such as ultra-high temperature (UHT), allow to extend milk shelf life up to 6–12 months when stored at ambient temperatures [1,2,3] but can damage the biological properties of its components. On the contrary, pasteurized milk, subjected to a thermal treatment with high temperature for short time (HTST), is a product of excellent nutritional quality but with a shelf life of only 6 days at cold storage and relatively expensive if compared to the UHT milk. Quality of pasteurized milk during storage can be affected by the presence of spoilage bacteria, mainly spore-forming species, such as Bacillus cereus [4], which is able to produce proteinase, lipase, and phospholipase enzymes originating off-flavors (“sweet curdling” and “bitty cream” defects). Previous studies investigated the in vitro antimicrobial activity of the olive leaf extract (OLE) or its phenolic compounds against a wide range of bacteria, including B. cereus [5,6], and its efficacy in extending the shelf life of food [7,8,9]. The phenolic substances present in olive leaves, mainly oleuropein [10], possess many human health benefits [11,12,13], including the capacity to prevent the fast breakdown of sugar and to control blood sugar level, representing a tool for management of postprandial hyperglycemia, in particular by the inhibition of α-glucosidase activity [14]

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