Classifications

• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/006—Refining fats or fatty oils by extraction
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/001—Refining fats or fatty oils by a combination of two or more of the means hereafter
• • C—CHEMISTRY; METALLURGY
  • C11—ANIMAL OR VEGETABLE OILS, FATS, FATTY SUBSTANCES OR WAXES; FATTY ACIDS THEREFROM; DETERGENTS; CANDLES
  • C11B—PRODUCING, e.g. BY PRESSING RAW MATERIALS OR BY EXTRACTION FROM WASTE MATERIALS, REFINING OR PRESERVING FATS, FATTY SUBSTANCES, e.g. LANOLIN, FATTY OILS OR WAXES; ESSENTIAL OILS; PERFUMES
  • C11B3/00—Refining fats or fatty oils
  • C11B3/02—Refining fats or fatty oils by chemical reaction

Definitions

• the present invention is concerned with non-bitter olive oil with a high content of antioxidants and with processes for preparing such olive oil.
• Olive oil is appreciated as a salad oil and as a frying oil for its delicious taste, not only in the traditional olive oil consuming countries, the Mediterranean area, but to an increasing extent also in Western Europe and the USA.
• olive oil is prepared by harvesting the olive fruits and subjecting these to malaxation: crushing and kneading the olives with water so that a mash is obtained containing the whole content of the olive fruit including an aqueous phase.
• the mash contains also enzymes, including oil hydrolysing lipases, which originate from the olive fruits.
• the aqueous phase with all olive enzymes is separated from the oil phase e.g. by decanting, as soon as possible, anyway within one hour.
• the bitter taste of olive oil is caused by so-called polyphenols, compounds which are native to olive oil.
• Those olive oil derived polyphenols comprise relatively apolar, oil soluble phenolic compounds as well as relatively polar, water soluble phenolic compounds. In the context of the present invention both groups are denoted as polyphenols.
• the bitter taste is caused mainly by the more apolar polyphenols.
• Apolar polyphenols comprise the compounds oleuropein, ligstroside and their aglycons. These are the main bitter polyphenols (Grasas y Aceites, 46, 1995, 299-303).
• the less bitter ones are polar polyphenols and comprise tyrosol, hydroxytyrosol, caffeic acid and vanillic acid.
• Polyphenols are potent antioxidants. Recently it was found that they play a role in enhancing the oxidation stability of olive oil (Nutr. Metab. Cardiovasc. Dis. (1995) 5:, 306-314). Moreover it has been discovered that a diet comprising food containing a substantial amount of olive oil polyphenols helps to prevent the harmful oxidation of low-density lipoproteins (LDL) in the blood. In a population with a high polyphenol intake the incidence of coronary heart disease is relatively low. Therefore the presence of polyphenols in an edible oil, including olive oil, and preferably at high levels, is much desirable. However, when the polyphenols content in olive oil raises over 300 ppm, the oil becomes unacceptably bitter, which correlates with a (K225) bitter index value over 0.3.
• LDL low-density lipoproteins
• the present invention enables the reduction of bitterness not by usual removing bitter compounds from the olive oil, but predominantly by transforming them into compounds with reduced bitterness.
• the process according to the present invention starts with olive oil which possesses a relatively high content of bitter polyphenols.
• the process comprises the following steps: preparing an emulsion of olive oil with an aqueous phase, exposing the olive oil to the dispersed aqueous phase for at least 30 seconds and removing the aqueous phase from the olive oil, characterized in that the emulsified aqueous phase is maintained at a pH of at least 5.5, preferably of at least 6, more preferably of at least 7, still more preferably of at least 8 for at least 30 seconds of the exposure time.
• Hydrolysis at a pH > 5.5 has been found to be essential for the conversion of bitter fat soluble polyphenols into less bitter water soluble polyphenols within a proper period of time. At said pH such conversion has been found to occur after at least 30 seconds exposure of the olive oil to an aqueous phase.
• the pH may not remain constant during the process. During exposure it may sink temporarily below the required minimum value of 5.5.
• a minimum exposure time of 30 seconds, preferably 2 minutes, more preferably 5 minutes to a pH of at least 5.5 is required for debittering.
• the full effect is attained after still longer exposure times, preferably at least 30 minutes. Generally, after 120 minutes no further debittering effect is observed.
• the aqueous phase consists of water, which contains reactive ions which are able to sustain the maintenance of the proper pH.
• reactive ions which are able to sustain the maintenance of the proper pH.
• the resulting pH is too low for suitable polyphenols hydrolysis. It has been found that use of common hard drinking water provides the proper conditions for obtaining the found debittering effect.
• the presence of acid-binding reactive ions is believed first to constitute a pH > 5.5, and then to maintain it for a time which is long enough to hydrolyse the bitter polyphenols into less bitter polyphenols.
• Such acid-binding ions are found in hard drinking water which is produced from natural resources, particularly from surface water and from water pumped from deep ground layers.
• Such ions are e.g. one or more of the ions in the group constituted by carbonate, sulphate, magnesium and calcium. Maintenance of the required pH can be supported further by the presence of a proper buffer substance such as a (pH 8) citric acid/phosphate buffer.
• Polyphenols originating from olive oil will migrate to the emulsion's aqueous phase.
• This aqueous phase may be separated by settling and decantation or by centrifugation, but preferably the aqueous phase is removed from the olive oil by evaporating the water under reduced pressure (vacuum drying).
• the polyphenols and possibly other ingredients in the aqueous phase phase are forced to get dispersed in the olive oil and then cause some turbidity.
• the oil/aqueous phase emulsion is filtered by a membrane using established membrane filtration technology such as known for the production of drinking water.
• the pores of the membrane allow passage of the water molecules, but not of the larger polyphenol molecules which stay in the olive oil.
• Use of membrane filtration also retains desirable olive oil volatiles, which otherwise would be evaporated when using the previously mentioned vacuum drying technique.
• the ratio of aqueous phase and olive oil in the emulsion preferably is 1 : 10 to 4 : 1, more preferably 1 : 4 to 2 : 1. Large amounts of water are not functional, and even not desired, because removal of water at the end needs energy and time. The best results are obtained when the emulsion has a continuous oil phase.
• a stirrer with a relatively large diameter and a relatively low stirring rate is suitable, e.g. a paddle type stirrer or a ribbon stirrer, preferably a stirrer with baffles.
• an olive oil can be prepared with polyphenol contents as high as 300 - 1000 ppm, while nevertheless the bitter index K225 is not higher than 0.3 and as high as 200 - 300 ppm, while the bitter index is not higher than 0.2.
• An olive oil which has been debittered according to the present invention can be recognized by its polyphenols composition as detected by high performance liquid chromatography (HPLC).
• HPLC high performance liquid chromatography
• the bitter polyphenols show up at a retention time of 40 - 52 minutes. Before treatment substantial peaks are found in that part of the HPLC spectrum. After the treeatment those peaks are still visible but are much reduced. At the same time the peaks for water soluble polyphenols, which show up at 7 - 20 minutes retention time, have increased. The decrease and increase respectively of said peaks is characteristic for olive oil as an effect of the treatment according to the invention.
• the invention therefore provides an olive oil which is characterized in that it contains at least 200 ppm of polyphenols, while the weight ratio of apolar polyphenols and polar polyphenols is less than 3, preferably less than 2, more preferably less than 1.
• a surprising additional benefit of the found process is that the treated olive oil may exhibit unexpected flavour improvements.
• Native Andalusian olive oil for example, may show flavour defects. These defects have disappeared fully or to a large extent after the treatment of the invention using common hard drinking water.
• the drop in ppm values is relatively large, and is ascribed to the hydrolysed polyphenols being lighter molecules.

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• 1999
  • 1999-01-21 EP EP19990200161 patent/EP0933419B1/fr not_active Expired - Lifetime

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