Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS, OR NON-ALCOHOLIC BEVERAGES, NOT COVERED BY SUBCLASSES A21D OR A23B-A23J; THEIR PREPARATION OR TREATMENT, e.g. COOKING, MODIFICATION OF NUTRITIVE QUALITIES, PHYSICAL TREATMENT; PRESERVATION OF FOODS OR FOODSTUFFS, IN GENERAL
  • A23L21/00—Marmalades, jams, jellies or the like; Products from apiculture; Preparation or treatment thereof
  • A23L21/10—Marmalades; Jams; Jellies; Other similar fruit or vegetable compositions; Simulated fruit products
  • A23L21/11—Marmalades; Jams; Jellies; Other similar fruit or vegetable compositions; Simulated fruit products obtained by enzymatic digestion of fruit or vegetable compositions

Definitions

• the present invention concerns a process according to the preamble of claim 1 for making jam from berries having a low solid matter content.
• berries are selected and the selected berries are heated in the presence of sucrose and pectin to provide a jam.
• Cooking jams, jellies and marmalades from fruits, sugar, pectin and edible acids is one of the oldest food preserving processes and presents a way of making food stable by increasing the content of soluble solids. It is required (by EU regulations) that all jam products have a minimum soluble solids content of 60 % and that a minimum quantity of fruits be used. The fruit quantity requirement differs for the various products depending on the type of fruit and on quality denomination (whether the product is an "extra jam" or a conventional jam). For example, a strawberry "jam extra" should have a minimum of 450 g of strawberries in 1000 g of the finished product.
• the present invention is based on the concept of pretreating the fruit (which term in this context encompasses berries) in order to modify its structure while maintaining the original shape of the fruit. This is achieved by contacting the fruit in a liquid, in particular an aqueous, medium with calcium ions together with an enzyme, pectin methyl esterase.
• the firmness of the strawberries treated with a suitable calcium salt, e.g., CaCl 2 , and PME in a vacuum is greater than that of strawberries treated in other ways.
• Jams made from strawberries treated with CaCl 2 and PME in a vacuum have about twice as high firmness values than reference samples.
• CaCl 2 and PME in a vacuum affects the microstructure of strawberry tissues.
• the pretreatment appears to stabilize the vascular tissue and to affect pectin, protein, lignin and structural carbohydrate as well as other carbohydrates.
• the use of a vacuum seems to affect the pretreatment solutions affording more effective absorption to the cortex and pith and providing stabilization there, especially for pectin, protein and structural carbohydrates.
• the present invention is particularly interesting for the jam making industry because the harvesting conditions, the sizes and the chemical structure of berries selected for jam making varies
• For industrial jam making it is of primary interest to ensure consistent conditions of jam making and of the integrity of the berries.
• the present invention gives the option of using on an industrial scale several different strawberry varieties, whereas the domestic jam industry nowadays is solely employing Senga Sengana. Thus the dependency on just one variety is eliminated.
• the jam industry uses only frozen berries, which means that the freezing step is an integral part of jam making.
• the freezing step is an integral part of jam making.
• the freezing damages are greater than when the fresh berries are pretreated according to the invention before freezing.
• the dry matter content of strawberries is only about 10 %. This means that the pretreatment at reduced pressure should not be too long and that the magnitude of the pressure should be reasonably high.
• "Firmer” fruits or berries such as cherries, plums, blueberries and lingonberries, can be treated for extented periods of time, even up to several hours.
• the enzyme is capable of acting already during a short treatment of only 1 to 10 minutes so effectively that free carboxylic groups are formed because PME catalyzes the de-esterif ⁇ cation of the methoxyl groups of the natural pectin of the strawberries.
• the jam made according to the present invention contains significant amounts of calcium ions.
• This calcium ion content is advantageous for many people in need of calcium, e.g. people allergic to milk and milk products.
• the jam making can be carried out at normal pressure or at reduced pressure.
• the particular advantage of jam making under reduced pressure is that the nutrient content and the colour of the berries are better preserved.
• the berries are more susceptible to degradation during vacuum boiling and frothing impairs cooking.
• a pretreatment according to the present invention eliminates frothing typical of strawberry jam making at least for cooking at normal pressure. It is possible that calcium bound also to the proteins may denaturate a part of the proteins, but this is only a theory. Further, it appears that the vacuum reduces the concentration of air in the strawberries, so that there is less air which may cause frothing.
• Crystalline sugar, sucrose, in the form of a powder sprayed on the surface of strawberries has a beneficial influence on the firmness of strawberries.
• sucrose during pretreatment is that it is difficult to obtain an even distribution thereof, in particular when operating on an industrial range.
• the PME enzyme is soluble in the liquid pretreatment medium and can therefore be evenly distributed throughout.
• the berries used typically have a solid matter or dry matter (these expressions are herein used interchangeably) content of 15 % or less, such as about 8 to 12 %.
• These kinds of berries are, for example, the following: strawberries, raspberries, blueberries, cranberries, cloudberries, lingonberries, whorleberries and crowberries.
• the jam making process will be described with particular reference to strawberry jam, but it should be noted that the same procedures can be followed for producing jams from other berries.
• the advantages of the invention apply in particular to making jam from whole berries, but it is of course also possible to use sliced berries, such as strawberry slices having a thickness of about 1 to 10 mm.
• the jam making process according to the present invention comprises two main steps: pretreatment and jam cooking.
• the berries selected for jam making are, after dehulling and other optional preliminary mechanical treatments including slicing, contacted with calcium ions and an enzyme having pectinase activity, preferably pectin methyl esterase.
• the contacting is carried out in a solution for a predetermined period of time.
• reduced pressure is applied.
• the present vacuum impregnation treatment is carried out by immersing the pore structure of the fruit in a liquid phase. Simultaneously, reduced pressure is imposed on the solid-liquid system, and after the predetermined time, there is restoration of atmospheric pressure.
• the aqueous solution used for the vacuum step comprises a dissociating calcium compound which will provide calcium ions in a liquid medium.
• inorganic or organic calcium salts and compounds e.g. calcium chloride, calcium hydroxide, calcium ascorbate and calcium gluconate, can be used.
• the concentration of the calcium ions in the solution or dispersion is about 0.001 - 0.5 mol/1, preferably 0,01 - 0,2, in particular 0,07 - 0,15 mol/1 whereas the concentration of the inorganic salt, such as calcium chloride, is about 0.5 to 2 wt-%, preferably about 0.8 to 1.2 wt-%, calculated from the weight of the medium.
• the amounts of the organic salts can be, calculated by weight, somewhat greater. Too large amounts may impair gelling of the pectin during jam cooking causing the medium to become fluid. High amounts of calcium ions may also affect the taste of the jam.
• the berries are simulataneously treated with both the dissociating calcium compound and an enzyme. Therefore the above solution or dispersion also contains an enzyme capable of achieving hydrolysis of the methyl ester bonds present in the pectin of the berry.
• Pectin is a high molecular weight heteropolysaccharide, which consists of a chain structure of ⁇ -(l,4)-linked D-galacturonic acid units containing blocks of rhamnose- rich regions. Other constituent sugars are attached in side chains, the most common being D-galactose, L-arabinose and D-xylose.
• the carboxyl groups of the galacturonic acid are partly esterified by methyl groups.
• the pectinase used primarily catalyzes the cleavage of the ester bonds between the methyl groups and the carboxyl groups thus forming free acid groups.
• the pectinase used is preferably a pectin methyl esterase (EC 3.1.1.11).
• EC 3.1.1.11 a pectin methyl esterase
• the enzyme dosage is generally in the range of 100 to 10,000 nkat/kg, preferably about 200 - 6000 nkat/kg calculated from the fresh weight of the substrate, i.e. the berries subjected to the pretreatment.
• the pretreatment medium may contain other components such as buffering agents and other agents for adjusting the pH.
• the medium has generally a pH of about 5 to 7.
• the temperature of the vacuum step is about 20 to 60 °C, preferably 30 to 50 °C. The upper limit is determined by the temperature acceptable for the berries, because the enzyme usually stands temperatures of up to about 60 °C.
• the pretreatment is carried out in order to stabilize the vascular tissue, the cortex and the pith of the berries.
• the berries will contain calcium ions in an amount of about at least 200 mg/kg d.m., preferably 230 to 1000 mg/kg. It has been found that the combination of pectin methyl esterase with calcium ions will strongly increase the amount of calcium bound to the berries.
• the berries are preferably drained for removing surplus liquid and then frozen.
• the freezing process is carried out as known in the art by lowering the temperature of the berries to at least - 18 °C.
• the frozen berries are used for jam making.
• the temperature of the berries is lowered to -18 °C or less within 24 hour, preferably to -20 °C or less within 15 hours.
• the freezing can be accelerated by carrying it out in a tunnel freezer, whereby the temperature of the berries is lowered to -50 °C within 20 minutes, preferably to -80 °C within 10 minutes.
• the pretreatment step of the present process comprises immersing selected berries into an aqueous solution containing a calcium salt and pectin methyl esterase, maintaining said solution at reduced pressure for a predetermined time, and - optionally draining the treated berries to separate at least a part of the aqueous solution then freezing the berries.
• the berries are heated together with sugar (sucrose) in predetermined proportions.
• sugar sucrose
• the mixture formed by the berries and the sugar may also contain some water.
• the sucrose used is preferably a crystallized powder. It may contain some pectin.
• high mechanical forces are used for mixing the berries and the sugar.
• the temperature is raised to the boiling point of the mixture.
• the sugar melts and the level of dissolved solids is raised from less than 10 % to almost 70 % in a matter of minutes.
• the heating time at the boiling point is, depending on the amount of berries, generally 1 to 120 min, typically about 5 to 30 min.
• the aim is to diffuse sugar syrup into the fruit, whilst osmotic effects are tending to remove water and cause collapse. Intercellular air is also being replaced by syrup.
• the temperature of the surrounding matrix is being raised to the boiling point of the syrup at which temperature the cell contents are being super-heated, resulting in elevated internal pressure.
• the berries as such contain pectin, which is gelled during heating, it is preferred to add more pectin during jam cooking.
• a separately dissolved, mixed and heated pectin solution is typically added to the mixture formed by the berries and the sugar.
• the pectin is preferably added when the berry mixture is boiling or close to boiling (about 90 to 100 °C.
• the berry mixture is cooled to about 50 to 60 °C or less (even ambient temperature, i.e. about 20 - 30 °C) to allow for gelling of the pectin.
• the pH of the mixture is usually about 2 to 4.
• preservatives and buffering agents may also be fed into the berry mixture, if necessary.
• the amount of dissolved solid matter (the "Brix” value) is usually checked. In the present process, the Brix value is usually about 50 to 60.
• the jam cooking temperatures and times are largely dependent on the pectin used.
• a calcium salt can be separately added together with the pectin.
• pectins There are two main kinds of pectins, namely high methoxylated (HM) or low methoxylated (LM) type pectins.
• HM high methoxylated
• LM low methoxylated
• the LM and LA (amidated LM pectin) pectins need calcium ions.
• Low sugar content jams are usually made using LM pectin.
• jam can be made by mixing the selected berries with sucrose, - heating the mixture to its boiling point, maintaining the temperature at the boiling point for at least 1 minute, adding pectin and optionally, an acidity regulator and preservation agent, allowing the jam to cool to at least 50 to 60 °C to provide for gelling of the pectin, and filling the jam into jars.
• Fresh Spanish strawberries (Fragaria ananassa, cv. Camarosa) grown in the spring of 1999 were used. The fresh, whole fruits were randomly distributed among the experiments.
• Fresh non-pretreated strawberries were used as a reference (Test 1).
• the strawberries were dipped in PME solution at 37 °C for 15 min.
• the enzyme dosage used was 4200 nkat/kg fresh strawberries (Test 2).
• Pectin methylesterase (EC 3.1.1.11) from orange peel was purchased from Sigma (P 5400).
• the PME activity was assayed by titration of the liberated carboxyl groups of 1 %-citrus pectin with 50 mM NaOH solution using an automatic titrator at room temperature.
• One unit of PME activity (nkat) was defined as the amount of enzyme, which liberated 1 nmol of carboxyl groups per second under the assay conditions.
• Another reference example comprised a sucrose treatment; Strawberries were sprinkled with crystallized sucrose (Test 4). The amount of sucrose added wasl50 g/kg strawberries.
• the dipping bowl was kept in a temperature-controlled bath at 37 °C.
• the dipping bowl was kept in a temperature-controlled vacuum chamber (Heraeus GmbH, Germany) at 37°C either at normal air pressure or in a vacuum, respectively.
• desired vacuum level 125 mmHg, was achieved in 2.5 min.
• the dipping bowl was kept at the desired vacuum level for 10 min after which the vacuum was shut off and the bowl was taken out of the chamber.
• the total dipping time of Test 3b was 15 min.
• 1.25 kg strawberries were dipped in a 1.5 L dipping solution. A light weight was put on the strawberries to ensure that all the berries were under the dipping solution.
• the total amount of strawberries per test was 2.5 kg. After dipping, the berries were drained for 5 min in a plastic strainer and packaged in 0.5-kg portions in 1-L PET cases. About 1 h after each dipping the strawberries were frozen in a freezer at -20°C. The temperature of the strawberries stayed at -2°C for 5 h. After 10 h the temperature of the strawberries reached -20°C. The strawberries were stored at -20°C for 2 days before jam making and for two weeks before thawing and analysis, respectively.
• Frozen untreated reference and pretreated strawberries were used for calcium analyses.
• Ca was analysed after dry ashing by atomic absorption spectrometer (AAS) using the flame technique (method VTT-4289-91, accredited).
• the total Ca content of jam was calculated by summing the Ca contents of the strawberries and the medium.
• thawed strawberries were dried with tissue paper and subjected to firmness measurements with a Texture Analyser (model TA-HDi, Stable Micro Systems, England) with a 250 kg load cell using an Ottawa Cell (A OTC) with Holed Extrusion Plate (A/HOL).
• the untreated reference and pretreated strawberries were thawed and freeze-dried for 20 hours (Dr Morand freeze-drier, Germany).
• the freeze-dried strawberries were cut into smaller pieces, mixed gently in an infiltration solution for 5 h, polymerized in a Historesin Embedding Kit (Jung, Germany) and cut into thin section (4 m) with a Microm HM355 (Microm Laborgerate GmbH, Germany) microtome for microstructural studies.
• the firmness of strawberries treated with CaCl 2 and PME in a vacuum was greater than that of other strawberries.
• the firmness of strawberries treated with PME (Test 2) or crystallized sucrose (Test 4) was even less than that of the untreated reference berries.
• the situation was totally different in jams in which all the pretreated strawberries were firmer than the untreated strawberries.
• Jams made from strawberries treated with CaCl 2 and PME in a vacuum had the highest firmness values (approximately twice as great as the reference).
• the firmness of jam berries correlated negatively with the firmness of jam mediums, i.e. the jams with firmer strawberries had softer mediums.
• the amount of Ca in the strawberries that had been dipped in Ca-solution in vacuum was about three times greater than the amount of Ca in the strawberries that were not dipped in Ca-solution (Tests 1, 2 and 4). The same effect can be seen in the amounts of Ca in jam strawberries and mediums.
• pectin in the middle lamella of the cortical cells was poorly stained compared to the Ca- and PME-treated strawberries in a vacuum. Moreover, the cell walls seemed to be broken and pectin appeared outside the middle lamella. In the PME-treated strawberries, pectin was more strongly stained than in the reference sample but partly appeared outside the middle lamella as in the reference sample. In the Ca- and PME-treated strawberries in a vacuum, pectin was well stained and quite homogeneously spread in the middle lamella. In some parts the middle lamella had swollen and was filled with pectin. Swelling was not observed in the reference. In the vascular tissue of the Ca- and PME-treated strawberries in a vacuum, protein was well stained and homogeneously spread. Furthermore, the lignin spirals seemed to be quite intact and coherent.
• Calcium chloride and pectin methylesterase in a vacuum improves the structure of strawberry tissues. Pectin, protein, lignin and structural carbohydrate components of the pretreated strawberries were more stable than those of the untreated reference samples.
• the calcium chloride and pectin methyl esterase pretreatments in a vacuum seems to stabilize first the structure of the vascular tissue and then the cortex and pith. Treatments with CaCl 2 - and PME-solutions in a vacuum retained the shape of the strawberries better than without these treatments.
• Fresh Finnish strawberries (Fragaria ananassa, cv. Jonsok) grown in Central Finland in the summer of 1999 were used for the studies.
• the mature strawberries were harvested and hulled manually and stored in 1-L PET (polyethylene) cases at 5°C before being treated.
• Strawberries (5.0 kg) were randomly chosen for each treatment.
• the average weight of a strawberry was 10.9 g.
• Liquid enzyme preparation of a microbial pectin methylesterase from Aspergillus oryzae microorganism (E.C. 3.1.1.11, Novo Shape, Novo Nordisk Ferment Ltd., Dittingen, Switzerland) was used in tests.
• the PME activity was 100,000 nkat/ml.
• Fresh non- pretreated strawberries were used as a reference (Test la).
• Strawberries were dipped in 1-% CaCl 2 solution (solution made from CaCl 2 x 2 H 2 O, Riedel-de Haen AG, Seelze, Germany and tap water, 90 mmol/L) with PME at 37°C either at normal air pressure (760 mmHg) for 15 min (Test 3a) or in a vacuum (125 mmHg) for 10 min (Test 3b).
• the enzyme dosage used was 2 ml/kg (i.e. 200 000 nkat/kg) fresh strawberries.
• Pectin solution Pectin 21.1 0.57
• Citric acid solution (50 % w/v) 25.2 0.68
• the analysis results of frozen strawberries are presented in Table 6.
• the amounts of calcium in the strawberries that had been dipped in CaCl 2 - and PME- solution in a vacuum was about three times greater than the amount of calcium in the reference strawberries.
• the pretreatment in vacuum increased the calcium content of strawberries when compared to the pretreatment in normal air pressure.
• the firmness of strawberries treated with CaCL, and PME in a vacuum was over two times greater than the firmness of the untreated reference strawberries.
• the firmness of the strawberries treated in normal air pressure was only sligthly higher than the firmness of the untreated strawberries.
• Table 6 Frozen untreated strawberries and strawberries treated with calcium chloride and PME either in normal air pressure (CaCl 2 + PME) or in a vacuum (CaCl 2 + PME in a vacuum) before freezing.
• the firmness of jam berries of treated in CaCl 2 + PME -solution in a vacuum was over three times as great as the reference berries and twice as great as berries pretreated at normal air pressure.
• the firmness of jam berries correlated negatively with the firmness of jam mediums, i.e. the jams with firmer strawberries had softer mediums.
• the prefreezing treatments were shown to have a significant influence on all the sensory attributes evaluated.
• the jams prepared from pretreated strawberries were evaluated to consist of more whole berries than the untreated reference jam.
• the medium was more clear and transparent in the jam made from strawberries treated with CaCl 2 +PME in a vacuum than in the reference sample.
• the berries in the jams were least soft in the jam made from berries treated with with CaCl 2 +PME in a vacuum. Dipping of strawberries into a CaCl 2 solution with PME in a vacuum showed to result significantly different profile than the other jams did, and the attribute intensities of this jam reflected the highest sensory quality among the strawberry jams.
• Table 7 Jams made from untreated strawberries or from strawberries treated with calcium chloride and PME either in normal air pressure (CaCl 2 + PME) or in a vacuum (CaCl 2 + PME in a vacuum) before freezing.

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• Health & Medical Sciences (AREA)
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• Life Sciences & Earth Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Food Science & Technology (AREA)
• Polymers & Plastics (AREA)
• Jellies, Jams, And Syrups (AREA)
• Preparation Of Fruits And Vegetables (AREA)
• Storage Of Fruits Or Vegetables (AREA)

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Citations (4)

• 1999
  • 1999-10-27 FI FI992315A patent/FI19992315A/sv unknown
• 2000
  • 2000-10-27 WO PCT/FI2000/000937 patent/WO2001030178A1/en active Search and Examination
  • 2000-10-27 AU AU11494/01A patent/AU1149401A/en not_active Abandoned

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