WO1991011911A1

WO1991011911A1 - Method for scalding raw materials in the making of bakery products

Info

Publication number: WO1991011911A1
Application number: PCT/SE1991/000032
Authority: WO
Inventors: Kurt Andersson
Original assignee: Pågen Ab
Priority date: 1990-02-19
Filing date: 1991-01-17
Publication date: 1991-08-22
Also published as: SE9000576D0; SE464496B; SE9000576A; AU7315991A

Abstract

A method is described which comprises scalding raw materials in the making of bakery products, which raw materials include an aqueous mixture of rye, wheat, oats, barley, maize, millet and rice in differently comminuted states, alone or in combination, and optionally also malt, sweetener and salts, the method being characterized in that it is continuous and comprises the steps of: a) feeding the raw materials in the form of an aqueous slurry to at least one heat exchanger (7) for heating to a temperature of 70-110 °C at a pressure of 4.0-10.0 kPa in a time of at most 1 min; b) maintaining the mixture of raw materials at the temperature attained at the heating for a time of at most 5 min, and c) feeding the mixture of raw materials to at least one cooler (15) for cooling to a temperature of 20-50 °C in a time of 0.5-3.0 min.

Description

METHOD FOR SCALDING RAW MATERIALS IN THE MAKING OF

BAKERY PRODUCTS

This invention relates to a method for scalding raw materials in the making of bakery products, said raw mate¬ rials including an aqueous mixture of rye, wheat, oats, barley, maize, millet and rice in differently comminuted states, alone or in combination, and optionally also malt, sweetener and salts. In today's baking industry, raw materials intended to be used for making bakery products are scalded batchwise in a mixing vessel. The raw materials, such as rye flour and water, are first supplied to the mixing vessel in requisite amounts and proportions. The raw materials in the mixing vessel, which are mixed and homogenised into a slurry by means of suitable mixing devices, are thereafter heated to a temperature of at most about 70°C during a requisite period of time. The heated mixture of raw mate¬ rials is thereafter allowed to cool to a temperature of about 30°C. The mixture of raw materials, which is first heated and then cooled, is thereafter added, together with other required ingredients, such as yeast and flavourings, as a preparatory product to a dough which should be allow¬ ed to rise by fermentation so as to yield the final bakery product.

In the conventional batchwise scalding method, the exact scalding temperature of the mixture of raw materials is difficult to measure. To this end, use is currently made of an ammeter connected to the mixing vessel. How- ever, since different temperatures prevail at different points in the mixture of raw materials during scalding, the process is difficult to control. This also means that it is difficult to obtain a perfectly homogeneous scalding of the ingredients in the mixture of raw materials. When the scalded and cooled mixture of raw materials is to be added as a preparatory product to the dough mixture before the final fermentation step, the mixing vessel must be displaced and emptied manually, which is a demanding and physically troublesome work. After emptying, the mixing vessel must be returned to the dosing step to be charged again. Other drawbacks of the currently used scalding technique is that it requires much space and is both time- consuming and labour-intensive, thus making it unecono¬ mical. The major drawback however is that the preparatory product obtained after the scalding step is of such a nature that 'the final bakery product will have unsatisfac- tory properties. Thus, the bakery product often becomes hard after a very short time and crumbly, and its keeping quality and flavour soon deteriorate. These unsatisfactory properties are primarily due to insufficient water-absorb¬ ing capacity and limited gelatinisation of the starch in the mixture of raw materials.

There is thus a need of an improved scalding method for making bakery products having satisfactory properties, which at the same time overcomes the production-engineer¬ ing drawbacks encountered in the scalding steps. The object of the present invention is to overcome the above problems and drawbacks by providing an improved continuous method for scalding raw materials in the making of the bakery products.

This object is achieved by a method of the type stated in the introduction to this specification, which has the features recited in the characterising clauses of the accompanying claims.

The term "scalding" as used in this specification and in the claims relates, strictly speaking, to the step of heating the raw materials used, but is here, as in the everyday language of those skilled in the art, considered also to include the entire process from dosage of the raw materials up to and including cooling of the heated mix¬ ture of raw materials. The term "raw materials" as used herein relates to raw materials which are normally used in the making of bakery products, such as the different seed cereals, such as rye, wheat, barley, oats, maize, rice and millet in differently finely divided states, e.g. either in the fo of flour or in the form of crushed or whole grains. Thes products may be used alone or in combination. Examples o other raw materials are water, malt, sweetener and salts. The term "bakery products" as used herein relates t all products made from the above-mentioned raw materials, e.g. different breads, cakes, pastries etc.

The method according to the present invention com- prises the steps from heating the mixture of raw materia up to and including cooling the heated mixture of raw materials, whereupon a preparatory product for the final bakery product is obtained. This preparatory product is added together with other ingredients, such as yeast, flavourings, colourants and preservatives, to a dough before the final leavening or fermentation step.

The grains of all the cereals contain, inter alia, starch, proteins, enzymes etc. in different amounts and different types, depending on the particular cereal. Starch is made up of amylose and amylopectin. Examples o enzymes present are r-amylase and β-amylase, which e.g. split the polysaccharide starch into different lower sugars according to prevailing conditions. Starch is insoluble in cold water, but in hot water the grains become gelatinous. The amylases primarily split gelati¬ nised starch, but to some extent also starch grains, α- -a ylase hydrolyses gelatinous starch into maltoses, maltotrioses and dextrins, while /?-amylase liberates maltoses from non-reducing bonds. The degree of splittin of the starch is highly dependent on the temperature and, thus, the amylase activity, - and β-amylases exhibit different activities at different temperatures. At high scalding temperatures, such as about 85°C (harder scald¬ ing), the - and |5-amylases are inactivated, and the starch is gelatinised, so as to be given a high water- absorbing capacity. At a scalding temperature of about 70°C (normal scalding), the β-amylase is inactivated, whereas the ot-amylase is still active. In this case, the starch has a lower water-absorbing capacity. At "mild" scalding at a temperature of 60°C, both the - and the ^-amylases are active and split starch to a great extent. This however results in a further deterioration of the water-absorbing capacity of the starch. At scalding tem¬ peratures below 50-60°C, the starch is but little gelati¬ nised, and the amylases can split the starch into, inter alia, maltoses and dextrins. In this case, the starch has a very low water-absorbing capacity.

The keeping quality of a bread or its inability to remain fresh depends on the degree of splitting of amylo¬ pectin. The more the degree of splitting is reduced, the longer will the bread keep. The presence of the decomposition products dextrin and maltose, and maltodextrins, contributes to a great extent to the good qualities of bakery products, such as bread. The presence of small dextrins and maltoses favours the subsequent fermentation of the preparatory product. Also, the dextrins prolong the fresh character of the bread. The presence of maltoses and maltodextrins promotes the build-up of aroma and flavouring substances in the bread.

The main reason why final products of inferior quali- ty are obtained in the scalding technique currently used is that this is performed at a maximum temperature of only 70°C. This temperature is not sufficient for achieving the desired water-absorbing capacity of starch that yields a final product of high quality. In the present invention, however, the parameters water-absorbing capacity and starch splitting are balanced optimally. This balance is achieved by heating the starch- containing mixture of raw materials to a temperature in the range of 70-110°C, preferably 80-150°C, and most pre- ferably 90-100°C. A condition for obtaining a satisfactory end product is that the starch during the initial dosage and mixing step at lower temperatures has been split to the required extent to lower sugars, such as maltoses, dextrins etc. These lower sugars are not affected by the high heating temperatures, but remain intact in the mix¬ ture of raw materials after the heating step and also in the final bakery product which, as mentioned above, will thus exhibit a number of good qualities. At the tempera¬ ture increase during the heating step, the splitting of starch into lower sugars proceeds until the temperatures at which the amylases are inactivated are attained. The optimum temperature is dependent on which end product is to be made, and thus also on the ingredients employed in the mixture of raw materials. The ingredients, their amounts and proportions can be determined by a person skilled in the art, as desired. The method according to the present invention yields bakery products of enhanced, richer taste. Also, a more uniform pore structure is obtained, and the product becomes elastic and "soft-crumbly". Further, the product does not crumble easily, its keeping quality is improved to some extent, and a higher yield is obtained in terms of increased water-absorbing capacity. Moreover, the method becomes more cost-effective since, as opposed to known techniques, it can be carried out in a continuous fashion and with higher production capacity. The troublesome manual operations are eliminated, and fewer operators are needed for carrying out and supervising the scalding pro¬ cess. The parameters of the scalding process can also be controlled in a much more accurate manner, as opposed to prior art techniques. Further, the plant used for carrying out the method of the present invention requires less space than conventional plants.

The invention will now be described in more detail with reference to the accompanying drawing illustrating a plant for carrying out a preferred example of the method according to the present invention. As illustrated in the drawing, the required ingre¬ dients are batched in requisite proportions into a con¬ tainer 1 and are fed and mixed in one and the same opera¬ tion by means of eccentric screw pump 2 into a feed hopper 3. An eccentric feed screw 4 connected to a pump 5 feeds the thoroughly homogenised mixture of raw materials through a conduit 6 to a heat exchanger 7, preferably a scraper-type heat exchanger. When entering the scraper- type heat exchanger, the mixture has a temperature of 20- 70°C. The heat exchanger 7 is heated by means of a steam flow 8 leaving the heat exchanger 7 through a condensate outlet 9. In the heat exchanger, the mixture is heated to a temperature of 70-110°C, preferably 80-105°C, and most preferably to a temperature of 90-100°C, in a time of at most 1 min and at a pressure of 4.0-10.0 kPa, preferably 4.5-6.5 kPa. In practice, a heating temperature as high as 140°C is possible without the occurrence of detrimental chemical reactions, such as Maillard reactions. A prere¬ quisite then is that the transit time in the scraper-type heat exchanger is extremely short, e.g. a few seconds. The higher the heating temperature, the shorter must the tran¬ sit time be. In the heat exchanger 7, the ingredients of the mixture of raw materials will come into close contact with the heat-exchanger surfaces, and the temperature to which the starch present in the mixture of raw materials is heated can be adjusted and determined in a much more accurate manner than has been previously possible.

In a preferred embodiment, use is made of a scraper- type heat exchanger, e.g. of the APV Crepaco 1 HRT-672 type, but any suitable scraper-type heat exchanger or exchangers can be used. The temperature of the heated mix¬ ture of raw materials is then maintained for at most 5 min, preferably 2-3 min. This is achieved by feeding the mixture of raw materials by means of a pump 11 through a conduit 10 to a holding cell 12 designed as a loop. In the holding cell, the mixture of raw materials is maintained at the same temperature as that to which it was heated in the scraper-type heat exchanger 7. The length and the di meter of the holding cell 12 are not critical, but in a preferred embodiment it has a length of 30-90 m and a di meter of 6-10 cm. The holding cell 12 is used for bringi about geletinisation of substantially all starch in the mixture of raw materials. From the holding cell 12, the gelatinised mixture of raw materials is fed by a pump 14 through a conduit 13 to a heat exchanger 15, preferably scraper- ype heat exchanger which is provided for coolin the mixture and hereinafter referred to as scraping cool 15. Any suitable type of scraping cooler can be used in connection with the invention. Both the scraper-type hea exchanger 7 and the scraping cooler 15 can be supplement ed, if desired, with further series-connected scraper-ty heat exchangers and scraping coolers, respectively. The cooler 15 is cooled by a recirculating flow 16 of glycol and water. The mixture of raw materials is cooled in the scraping cooler 15 to a temperature of about 20-50°C, pr ferably 30-40°C, and most preferably 35-37°C. In a pre- ferred embodiment of the present invention, the mixture raw materials is cooled in the scraping cooler in a time of about 0.5-3.0 min, preferably 45 s-2 min. After the mixture has been cooled, it is fed by a pump 18 through conduit 17 to a buffer tank 19 for storage. From the buf fer tank 19, the scalded mixture of raw materials (in Sw dish sometimes called "rasker") can either be directly withdrawn for adding as a preparatory product to the dou before the subsequent fermentation step and completion o the end product, or be fed on to storage tanks for long- term storage. When the preparatory product, the "rasker", ^• is fed to the subsequent fermentation step, it preferabl has a temperature of about 35°C.

Depending on what bakery product is to be made, the size of the batch and the capacity of the equipment, use is made of a raw material flow rate through the plant in the continuous method according to the invention which i in the range of about 250-4000 kg/h. The different parameters in the method according to the invention, i.e. heating temperature, cooling tempera¬ ture, raw material flow rate, holding times etc. can be set in advance on the basis of the properties of the raw materials used, such as flour yield, ash content etc., by means of different control systems provided to that end, and then be easily monitored during the process so as to achieve a high-quality bakery product.

All the devices, such as scraper-type heat exchang- er, holding cell and scraping cooler, used in the method of the present invention are known per se, but it is not previously known to use them in combination, nor in a continuous method with the process parameters of the invention, and particularly not in connection with the scalding of raw materials for making bakery products.

Two conventional types of scalding are "rye scalding" and "rasker scalding". In "rye scalding", the raw mate¬ rials are rye flour, salt, malt, breadcrumbs and water. "Rye scalding" according to the present invention does not use the cooling step, but the scalded mixture of raw mate¬ rials is fed directly from the holding cell 12 to the buf¬ fer tank 19. In "rasker scalding", where cut rye and water are used as ingredients, the cooling step is however part of the method. Tests carried out in accordance with the present invention using "rye scalding" and "rasker scalding" at heating temperatures of 70, 80, 85, 95 and 100°C, respec¬ tively, pressures of 4.5-6.5 kPa, flow rates of at least 250 kg/h and heating in a time of at most 1 min, yielded bakery products of the highest quality at higher heating temperatures, especially at a temperature of 95°C. All the bakery products which had been heated to temperatures above 70°C had better qualities in the above-indicated respects than corresponding bakery products made according to conventional methods.

Claims

1. A method for scalding raw materials in the mak- ing of bakery products, said raw materials including an aqueous mixture of rye, wheat, oats, barley, maize, mille and rice in differently comminuted states, alone or in combination, and optionally also malt, sweetener and salts, c h a r a c t e r i s e d in that the method is continuous and comprises the steps of a) feeding the raw materials in the form of an aqueous slurry to at least one heat exchanger (7) for heating to a temperature of 70-110°C at a pressure of 4.0-10.0 kPa in a time of at most 1 min, b) optionally maintaining the mixture of raw mate¬ rials at the temperature attained at said heating for a time of at most 5 min, and c) feeding the mixture of raw materials to at least one cooler (15) for cooling to a temperature of 20-50°C in a time of 0.5-3.0 min.

2. Method as claimed in claim 1, c h a r a c t e r i s e d in that the mixture of raw materials is heated t 80-105°C at a pressure of 4.5-6.5 kPa in step a).

3. Method as claimed in claim 1, c h a r a c t e r i s e d in that the holding time in step b) is 2-3 min.

4. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the heat exchanger (7) is a scraper-type heat exchanger.

5. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the cooler

(15) is a scraper-type cooler.

6. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the tempera¬ ture of the mixture of raw materials in step b) is main- tained in a holding cell which consists of a tube coil having a length of 30-90 m and a diameter of 6-10 cm.

7. Method as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the mixture of raw materials is cooled to a temperature of 30-40°C in a time of 45 s-2 min in step c).