TABLE 4.

Different uses of olive leaf extract in food processing and preservation.

Food	Used olive part	Impact of usage	References
Different refined oils	Methanol OLE extract	Olive leaves extract (OLE) addition substantially improved antioxidant capacity and oxidative stability for all the oils studied after supplementation	(218)
Refined olive oil	Hydroxytyrosol and other antioxidants	The addition of antioxidants (OLE) prevents the formation of toxic products like cholesterol oxides and increases their nutritional value	(219)
Sunflower oil	Microwave OLE and methanol extract	The OLE blocked the oxidation process while heating the oil at 70°C. Methanol extract gave better results.	(220)
Soybean oil	Nano-encapsulated OLE	Soybean oils had more oxidative stability when nano-encapsulated OLE was added.	(148)
Extra virgin olive oil	OLE methanol extract	Adding OLE to olive oil improves its nutritional value and antioxidant stability. That proved that adding OLE to a standard olive oil makes it similar to high-quality olive oil.	(148)
Table olives	Water OLE extract	Sensory evaluation of treated table olives showed an increase in bitterness	(221)
Apple	OLE (Ethanolic extract)	They sprayed a chitosan coating solution with OLE on apples. They found that “the addition of OLE to chitosan coating films meaningfully reduced the gradual decline in total phenolic, flavonoids and antioxidants.”	(222)
Milk	OLE Water extract	Addition of OLE to pasteurized milk. The results have been excellent, as OLE was effective against Bacillus cereus and inhibited the enzyme α-glucosidase, which is related to the degradation of milk.	(223)
Tomato paste	Encapsulated OLE. Methanol/Water extract	Encapsulated OLE in tomato paste compared to non-encapsulated ones have better results.	(224)
Backed snacks	Water extract	OLE reduced lipid oxidation increasing its shelf life consequently. The addition of OLE is highly recommended when low-quality olive oil is used.	(225)
Beef cubes	OLE	A study immersing beef cubes in an OLE solution found that “using 2 and 3% OLE had the beneficial effect in controlling the microbial load of beef cubes during 9 days of storage at 4°C.”	(226)
Salmon burgers	Hydrolyzed OLE and OLE	OLE decreased lipids oxidation in salmon. Salmon mince treated with hydrolyzed OLE showed lower microbial counts than OLE during the study, which extended the shelf life of the fish product to 4°C and vacuum-packed.	(227)
Shrimp	OLE (Ethanol extract)	OLE reduced the count of the aerobic and coliforms bacteria by at least 1 log cycle colonies forming unit (CFU) g–1 in comparison to the non-treated control group by immersing shrimp in a solution containing OLE at a concentration of 1% (w/v).	(19)
Smoked salmon	Olive leaf powder (OLP) and water ethanol extract (OLE)	OLE was tested against L. monocytogenes in a food matrix well known as being a food that can be infected by L. monocytogenes, which is the cold-smoked salmon. Edible fish gelatin films with OLE showed antibacterial activity against L. monocytogenes in agar diffusion tests and the fish over storage. They found that de optimal film formulation is 5.63% OLE to be effective against L. monocytogenes	(228)
Minced beef	Irradiated OLE	Test of OLE in minced beef focused more on the antibacterial activity with important activity from the microbiological against B. cereus, S. aureus, E. coli, K. pneumoniae, P. aeruginosa, and S. typhimurium “The results indicated that when 2, and 3 ml OLE were added to 100 mg of minced beef could improve quality attributes and extend shelf life of minced beef from 1 week to 3 and 4 weeks under cold storage.”	(229)
Lamb meat patties	Olive waste extract	Similar results to other studies concluding that “This application reduced lipid and protein oxidation while maintaining an acceptable color for a longer period, representing a 3-day in the shelf-life extension compared to patties without the added extract.”	(230)
Frozen hamburger	Pure oleuropein	This study added a specific concentration of oleuropein to frozen burgers and compared it to the food additive sodium erythorbate to compare their antioxidant activity. In this test, both antioxidants had similar results suggesting that oleuropein is a potential substitute for synthetic antioxidants in food like sodium erythorbate.	(231)
Frankfurt sausages	OLE (Ethanol extract)	OLE in frankfurter-type sausages showed that OLE has antioxidant activity and significantly reduces the total count of bacteria in a 45 days study at 4°C.	(232)
Anchovies	Lyophilized methanol extract	OLE does not change organoleptic properties and is effective against spoilage bacteria for 22 days.	(233)
Strawberry	OLE (Ethanol extract)	The experiment was done by spraying different coating formulas. They found that chitosan coating with OLE “led to keep the bioactive substances of cold-stored strawberry fruits.”	(234)
Minced meat	Olive leaf powder	Olive leaf powder added to minced beef significantly reduced bacteria (mesophilic aerobic bacteria) in meat products. In this study, they found that olive leaf powder has an instantaneous antimicrobial effect and controls the microbial count for 6 days at 4°C.	(235)
Fresh hamburger	OLE and oleuropein	0.5% of oleuropein and 1.5% of OLE were considered adequate to preserve fresh hamburger.	(236)
Lard	Olive-oil mill wastewater	Olive mill wastewater is highly effective for oxidative stabilization of lard also at low temperatures	(237)
Yogurt	Olive pomace	Olive pomace made the yogurt fulfill the nutritional claim of being a “source of fiber,” improved the nutritional value of the yogurt, and made it more stable from the nutritional point of view.	(238)
Gluten-free bread	Water extract	The addition of OLE and lactic acid bacteria (LAB) in gluten-free bread improved sensorial properties and reduced the fungi count, increasing consequently its shelf life	(239)