WO2017028041A1

WO2017028041A1 - Method to reduce spore count in grain kernels

Info

Publication number: WO2017028041A1
Application number: PCT/CN2015/087060
Authority: WO
Inventors: Bin Zhao; Bob E DIAZ; Frank Feng SUN; Lynn C Haynes; Jennifer K THOMAS; Andy Chen; Kenchu A Tham; Manhu Gu
Original assignee: Intercontinental Great Brands Llc
Priority date: 2015-08-14
Filing date: 2015-08-14
Publication date: 2017-02-23
Also published as: CN108024547A

Abstract

There is provided a method of tempering grain kernels, comprising keeping the grain kernels in contact with tempering water for about 1 hour to about 40 hours; and drying the tempered grain kernels until the relative humidity of the resulting flour product with a range of 60％to 70％humidity is obtained; in which the tempering water is in an amount of up to about 8％by weight based on the weight of the grain kernels and comprises no less than 500 ppm chlorine by weight based on the weight of the tempering water. Spore count in the products thus obtained is reduced.

Description

METHOD TO REDUCE SPORE COUNT IN GRAIN KERNELS

Technical Field

The invention generally relates to grain kernels processing and particularly relates to methods to reduce the spore count in grain kernels.

Background Art

Before being milled, grain normally undergoes tempering (a water conditioning) process, during which tempering water is added to the grain to soften the husks. During this stage, the grain kernels absorb water, which elevates the moisture levels and results in an increase in grain size. Such grain is then conveyed to tempering bins where it resides for up to about 48 hours. It is well-known that there is always a level of superficial contamination on grain surfaces, including dormant toxigenic fungal spores. GB7100-2003 stipulates that the spore count should be 750 cfu/g or less in cookies and 2000 cfu/g or less in sandwich biscuits, and therefore, it is preferred that the spore count remaining on grain kernels shall at least meet these standards such that the flour milled from the grain kernels is capable of being used to make cookies.

The introduction of tempering water during the grain tempering process is a key step in grain milling since it provides the only substantial opportunity for impacting upon the microbial quality level of the final milled product, especially for whole grain flour where substantially all of the external seed coat is retained in the milled product. Traditionally, grain is tempered by adding 1-2％water for 4-24 hour before milling process according to the incoming grain moisture. It hasn’t demonstrated any spore count reduction.

In an effort to address the problem of spores on the grain surface, chemicals and especially chlorine and stabilized chlorine-based solutions are often added to the tempering water to assist with surface decontamination. However, chlorine and stabilized chlorine-based solutions are deleterious and pose a risk that introduction of such solutions into the tempering water may lead to the creation of hazardous chlorine or derivative residues on the final grain product, which may be detrimental for human or animal consumption. Where low concentrations of chemicals, especially molecular chlorine and stabilized chlorine-based solutions, are used for treating tempering water to obviate any unwanted residues on the grain surfaces, these levels are inevitably too low to afford adequate biocidal capacity, and may promote the development of tolerance by the same microbes to the chemical agents in use.

US 8147889 discloses a decontamination and/or conditioning procedure where, grain, nut or seed product is contacted with an aqueous anolyte product, which predominantly includes the species ClO； ClO^-； HOCl； OH^-； HO₂； H₂O₂； O₃； S₂O₈ ^2-and Cl₂O₆ ^2-, and has a mixed oxidant concentration of less than 250 ppm.

US 4956190 discloses that the yield of durum flour obtained from the milling of durum wheat can be increased by the addition of a reducing agent such as sulfhydryl substances to the tempering step prior to milling.

US 2009/0297672 A1 discloses a process for extending the shelf life of food product comprising heating the food in a sealed container to inactivate undesirable microorganisms likely to be present in the food and rapidly cooling the heated food to substantially prevent germination of undesirable microbial spores likely to be present in the food.

WO 2012/142399 A2 discloses that stabilized flour, such as stabilized whole grain wheat flour, may be produced with or without heating to inhibit lipase by subjecting whole grain or a bran and germ fraction or component to treatment with a lipase inhibitor, such as an acid or green tea extract.

There is still a need for a simple and efficient method for reducing the heat resistant spore count in grain kernels.

Summary of Invention

In one aspect of the invention, there is provided a method of tempering grain kernels, comprising:

keeping the grain kernels in contact with tempering water for about 1 hour to about 36 hours； and

optional drying the tempered grain kernels until the relative humidity of the resulting flour product, with a range of 60％to 70％humidity, is obtained；

in which the tempering water is in an amount of up to about 8％by weight based on the weight of the grain kernels and comprises no less than 500 ppm chlorine by weight based on the weight of the tempering water.

In some embodiments of the invention, the tempering water is added to increase the moisture content of the grain kernels up to an amount of 14％-21.5％, preferably 17％-21.5％, by weight based on the weight of the grain kernels.

In some embodiments of the invention, keeping the grain kernels in contact with tempering water is conducted at room temperature.

In some embodiments of the invention, keeping the grain kernels in contact with the tempering water is conducted for about 4 hours to about 36 hours, preferably for about 4 hours to about 24 hours.

In some embodiments of the invention, the drying is conducted at a temperature in a range of about 30℃ to about 60℃, preferably about 45℃ to about 55℃.

In some embodiments of the invention, the drying of tempered grain kernels is conducted for about 0 min to about 3 hours, at a temperature in a range of about 30℃ to about 60℃, preferably, for about 20 min to about 3 hours at a temperature in a range of about 30℃ to about 60℃, more preferably, for about 30 min to about 2 hours at a temperature in a range of about 45℃ to about 55℃.

In some embodiments of the invention, the tempering water comprises about 500 ppm to about 3600 ppm chlorine by weight based on the weight of the tempering water.

In some embodiments of the invention, the grain kernels are selected from a group consisting of barley, wheat, maize, rye, oats, corn, rice and the combination thereof. In some embodiments of the invention, the grain kernels are selected from a group consisting of barley, wheat, maize, rye, oats, corn, and the combination thereof.

In some embodiments of the invention, keeping the grain kernels in contact with the tempering water is conducted in a manner selected from a group consisting of soaking the grain kernels in the tempering water, spraying the tempering water to the grain kernels, maintaining the grain kernels under a moisture of the tempering water saturated atmosphere, and the combination thereof.

In some embodiments of the invention, the drying is conducted by microwaving, freeze-drying, or air drying.

In another aspect of the invention, there is provided a method of tempering grain kernels, comprising:

keeping the grain kernels contact with tempering water for about 1 hours to about 36 hours； and

drying the tempered grain kernels until the relative humidity of the resulting flour product with a range of 60％to 70％humidity is obtained；

in which the tempering water comprises no less than 500 ppm chlorine and the keeping of grain kernels in contact with tempering water results in the moisture content of the grain kernels being increased by up to about 8％.

In some embodiments of the invention, the moisture content of the grain kernels is increased by 14％-21.5％, preferably increased by 17％-21.5％.

Brief Description of Drawings

The present invention will be better understood by referring to illustration of embodiments thereof, in which:

FIG 1 is a plot showing the effect of water amount and chlorine concentration on spore count in wheat.

Description of Embodiments

Reference now will be made to certain detailed aspects of various embodiments of the invention. It is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in numerous and alternative forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for any aspect of the invention and/or as a representative basis for teaching one skilled in the art to variously employ the invention.

Except in the examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material and/or use to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred.

It is also to be understood that this invention is not limited to the specific embodiments and methods described below, as specific components and/or conditions may, of course, vary. Furthermore, the terminology used herein is used only for the purpose of describing particular embodiments of the present invention and is not intended to be limiting in any way.

It must also be noted that, as used in the specification and the appended claims, the singular form “a” , “an” , and “the” comprise plural referents unless the context clearly indicates otherwise. For example, reference to a component in the singular is intended to comprise a plurality of components.

The term “milling” as used herein includes the steps of rolling, breaking sifting and sorting the grain to separate it into its constituent parts, which may also result in some reduction of particle size of the constituent parts.

The term “tempering” as used herein is the process of adding water to grain before milling to toughen the bran and mellow the endosperm of the kernel and thus improve flour separation efficiency.

The term “grain” as used herein includes barley, wheat, maize, rye, oats, rice, corn, and the combination thereof.

The phrase “contacting with the tempering water” as used herein includes soaking the grain kernels in the tempering water, spraying the tempering water to the grain kernels, maintaining the grain kernels under a moisture of the tempering water saturated atmosphere, and the combination thereof.

The term “drying” as used herein includes microwaving drying, freeze-drying, or air drying.

The invention discloses both the level of tempering water and an optional subsequent drying before the milling process. The idea is increasing the chlorine level in the tempering water, and then, drying the tempered grain to target moisture for milling. The grain kernels are kept to contact with tempering water in an amount of up to about 8％by weight, preferably 2％-8％, more preferably 5％-8％, based on the weight of the grain kernels, for about 1 hours to about 36 hours, preferably for about 4 hours to about 36 hours, more preferably for about 4 hours to about 24 hours at room temperature. Keeping the grain kernels contact with tempering water results in the moisture content of the grain kernels is increased by up to about 21.5％, preferably 14％-21.5％, more preferably 17％-21.5％. The amount of tempering water is based on the grain kernel weight. For example, if the incoming grain kernel moisture is 12.5％, the grain moisture will be around 14.5％, 17.5％, or 20.5％after tempering. By increasing the amount of the tempering water to 5-8％, there are two things happen, one is that the chlorinated water can uniformly distribute on the entire grain kernel surface (make all the grain wet) , the other is that the spore is more sensitive to the chlorine at high moisture.

The invention also discloses both the level of tempering water (1％-2％) and chlorine content without a subsequent drying before the milling process. The idea is increasing the chlorine content in the tempering water. The grain kernels are kept to contact with chlorine tempering water in an amount of up to about 6000 ppm by weight, preferably 500 ppm–5000 ppm, more preferably 3000 ppm–4000 ppm, based on the weight of the tempering water, for about 1 to 36 hours, preferably for about 4 to about 36 hours, more preferably for about 4 hours to about 24 hours at room temperature.

In the tempering water, no less than 500 ppm chlorine, preferably about 500 ppm to about 3600 ppm chlorine, is added to reducing the spore count in grain kernels. When the chlorine solution is applied to the grain kernels, after the tempering and milling the process, the chlorine was evaporated in the air. The chlorine content in the final flour is very low, less than 10 ppm, even less than 6.46 ppm.

In the tempering water, no less than 500 ppm chlorine, preferably about 500 ppm to about 3600 ppm chlorine, and combine with no less than 17000 ppm nisin, preferably about 18000 ppm to about 50000 ppm nisin, is added to reducing the spore count in grain kernels. When the chlorine solution is applied to the grain kernels, after the tempering and milling the process, the chlorine was evaporated in the air. The chlorine content in the final flour is very low, less than 10 ppm, even less than 6.46 ppm.

Then, the tempered grain kernels are dried at a temperature in a range of about 30℃ to about 60℃, preferably about 45℃ to about 55℃, until the relative humidity of the resulting flour product with a range of 60％to 70％humidity is obtained. In some embodiments, the tempered grain kernels is dried for about 0 min to about 3 hours at a temperature in a range of about 30℃ to about 60℃, preferably, about 20 min to about 3 hours at a temperature in a range of about 30℃ to about 60℃, more preferably, for about 30 min to about 2 hours at a temperature in a range of about 45℃ to about 55℃. The resulting flour product relative humidity is an optimum range of 60％to 70％, so that maximum shelf-stability is possible. The drying step disclosed in the invention is optional, and used when tempering water is applied, resulting flour product>70％relative humidity and limited shelf-stability during storage, prior to use.

This invention only needs minimal capital investment and has minimal effect on the flour functionality. The low spore count of grain flour can reduce the baking operation complexity without the concern of high spore count in the finish baking goods.

The present invention is illustrated by the following non-limiting example wherein all parts, percentages, and ratios are by weight, all temperatures are in ℃, and all temperatures are atmospheric, unless indicated to the contrary.

Examples

Evaluation of the factors effecting the reduction of the spore count in grain kernels during the tempering

Three batches of wheat kernels are provided. Ten samples are from each batch of wheat kernels. The wheat kernels to be tempered are kept contacting with tempering water at ambient temperature for 16 hours, and optionally dried at 51℃ for 2 hours. The tempered wheat samples are milled by using a Chopin Laboratory Mill CD1 (Chopin, France) with two units. The first unit is a regular mill consisting of two break rolls and the second unit is a smooth mill roll used for reduction. Three main fractions are obtained from the mill: coarse semolina in the right-hand collecting-pan； break flour in the left-hand collecting-pan and coarse bran. The semolina is processed through the reduction roll from which reduction overtails are obtained； and in the collecting-pan, the reduction flour is collected. The amount of tempering water and the chlorine concentration in tempering water are list in Table 1. Wheat spore count, break flour plus semolina flour spore count and chlorine concentration in tempered wheat are tested according to the relevant standards and list in Table 1 as well.

Table 1: Spore count change during tempering

From the data it can be seen that the amount of tempering water and the chlorine concentration in tempering water show significant effects on spore count in wheat. The spore count decreases as the amount of tempering water and the chlorine concentration increase. However, there is no significant effect shown due to the drying treatment. FIG 1 schematically shows the effect of water amount and chlorine concentration on spore count in wheat.

Although several exemplary embodiments have been described in detail above, the embodiments described are exemplary only and are not limiting, and those skilled in the art will readily appreciate that many other modifications, changes, and/or substitutions are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of the present disclosure. Accordingly, all such modifications, changes, and/or substitutions are defined in the attached claims.

Industrial Applicability

The method of the present invention can be applied to the field of grain kernels treatment.

Claims

A method of tempering grain kernels, comprising:

keeping the grain kernels in contact with tempering water for about 1 hour to about 36 hours； and

optional drying the tempered grain kernels until the relative humidity of the resulting flour product with a range of 60％ to 70％ humidity is obtained；

in which the tempering water is in an amount of up to about 8％ by weight based on the weight of the grain kernels and comprises no less than 500 ppm chlorine by weight based on the weight of the tempering water.
The method according to claim 1, wherein the tempering water is added to increase the moisture content of the grain kernels up to an amount of 14％-21.5％ by weight based on the weight of the grain kernels.
The method according to claim 2, wherein the tempering water is added to increase the moisture content of the grain kernels up to an amount of 17％-21.5％ by weight based on the weight of the grain kernels.
The method according to claim 1, wherein the keeping the grain kernels contact with tempering water is conducted at room temperature.
The method according to claim 1, wherein the keeping the grain kernels contact with the tempering water is conducted for about 4 hours to about 36 hours.
The method according to claim 5, wherein the keeping the grain kernels contact with the tempering water is conducted for about 4 hours to about 24 hours.
The method according to claim 1, wherein the drying is conducted at a temperature in a range of about 30℃ to about 60℃.
The method according to claim 7, wherein the drying is conducted at a temperature of about 45℃ to about 55℃.
The method according to claim 1, wherein the drying the tempered grain kernels is conducted for about 0 min to about 3 hours at a temperature in a range of about 30℃ to about 60℃.
The method according to claim 9, wherein the drying the tempered grain kernels is conducted for about 30 min to about 2 hours at a temperature in a range of about 45℃ to about 55℃.
The method according to claim 1, wherein the tempering water comprises about 500 ppm to about 3600 ppm chlorine by weight based on the weight of the tempering water.
The method according to claim 1, wherein the grain kernels are selected from a group consisting of barley, wheat, maize, rye, oats, corn, rice, and the combination thereof.
The method according to claim 1, wherein the keeping the grain kernels contact with the tempering water is conducted in a manner selected from a group consisting of soaking the grain kernels in the tempering water, spraying the tempering water to the grain kernels, maintaining the grain kernels under a moisture of the tempering water saturated atmosphere, and the combination thereof.
The method according to claim 1, wherein the drying is conducted by microwaving, freeze-drying, or air drying.
A method of tempering grain kernels, comprising:

keeping the grain kernels in contact with tempering water for about 1 hour to about 36 hours； and

drying the tempered grain kernels until the relative humidity of the resulting flour product with a range of 60％ to 70％ humidity is obtained；

in which the tempering water comprises no less than 500 ppm chlorine and the keeping the grain kernels contact with tempering water results in the moisture content of the grain kernels is increased by up to about 8％.
The method according to claim 15, wherein the moisture content of the grain kernels is increased by 14％-21.5％.
The method according to claim 16, wherein the moisture content of the grain kernels is increased by 17％-21.5％.
The method according to claim 15, wherein the keeping the grain kernels contact with tempering water is conducted at room temperature.
The method according to claim 15, wherein the keeping the grain kernels contact with the tempering water is conducted for about 4 hours to about 36 hours.
The method according to claim 19, wherein the keeping the grain kernels contact with the tempering water is conducted for about 4 hours to about 24 hours.
The method according to claim 15, wherein the drying is conducted at a temperature in a range of about 30℃ to about 60℃.
The method according to claim 21, wherein the drying is conducted at a temperature of about 45℃ to about 55℃.
The method according to claim 15, wherein the drying the tempered grain kernels is conducted for about 0 min to about 3 hours at a temperature in a range of about 30℃ to about 60℃.
The method according to claim 23, wherein the drying the tempered grain kernels is conducted for about 30 min to about 2 hours at a temperature in a range of about 45℃ to about 55℃.
The method according to claim 15, wherein the tempering water comprises about 500 ppm to about 3600 ppm chlorine.
The method according to claim 15, wherein the grain kernels are selected from a group consisting of barley, wheat, maize, rye, oats, corn, and the combination thereof.
The method according to claim 15, wherein the keeping the grain kernels contact with the tempering water is conducted in a manner selected from a group consisting of soaking the grain kernels in the tempering water, spraying the tempering water to the grain kernels, maintaining the grain kernels under a moisture of the tempering water saturated atmosphere, and the combination thereof.
The method according to claim 15, wherein the drying is conducted by microwaving, freeze-drying, or air drying.