METHOD FOR PRODUCING FERMENTED MILK USING RAW MATERIAL MIX CONTAINING MATERIAL STERILIZED AT ULTRA-HIGH TEMPERATURE

Abstract

The present invention addresses the problem of solving problems of the conventional techniques and producing, by an economically advantageous means, fermented milk having hardness to such an extent that the texture of the fermented milk can be kept during distribution. The present invention relates to a method for producing fermented milk, comprising homogenizing a raw material mix under a high pressure to reduce the average particle diameter of a fat and then fermenting the homogenized product. More specifically, the present invention relates to: a method for producing fermented milk using a material that is sterilized at an ultra-high temperature, said method comprising homogenizing a fat in a raw material mix, which contains a material sterilized at an ultra-high temperature, under a high pressure and then fermenting the resultant product; and fermented milk produced by the method.

Claims

1. A method for producing fermented milk using a material sterilized by ultra-high temperature treatment, comprising homogenizing the fat of a raw material mix containing the material sterilized by ultra-high temperature treatment, and conducting fermentation.

2. The method according to claim 1, wherein the material sterilized by ultra-high temperature treatment is one or more selected from the group consisting of milk, concentrated milk, whole milk powder, skimmed milk, concentrated skimmed milk, skimmed milk powder, partially-skimmed milk, concentrated partially-skimmed milk, partially-skimmed milk powder, cream and butter.

3. The method according to claim 1, wherein the temperature of the ultra-high temperature treatment is 120° C. to 150° C.

4. The method according to claim 1, wherein the fat in the raw material mix is homogenized such that its average particle diameter becomes 0.8 μm or less.

5. The method according to claim 1, further comprising heat sterilizing the raw material mix.

6. The method according to claim 1, further comprising reducing the dissolved oxygen concentration of the raw material mix.

7. The method according to claim 6, comprising reducing the dissolved oxygen concentration of the raw material mix before heat sterilizing the raw material mix.

8. The method according to claim 6, comprising reducing the dissolved oxygen concentration of the raw material mix before fermenting the raw material mix.

9. The method according to claim 1, wherein the fermentation of the raw material mix is carried out in a container of the product.

10. Fermented milk produced by the method according to claim 1.

11. The fermented milk according to claim 10, wherein the fermented milk is a set type yogurt.

12. The fermented milk according to claim 11, wherein the hardness is 26 g or more.

Description

EXAMPLES

[0051] Embodiments of the present invention will be described in more detail while showing examples below; however, the present invention is not limited to the following examples.

[Measurement Method of Average Particle Diameter]

[0052] The average particle diameter and standard deviation of a raw material mix were measured using a laser diffraction type particle size distribution analyzer SALD-2200 (Shimadzu Corporation). Specifically, the raw material mix was diluted with ion exchanged water to adjust the maximum value of the distribution of light intensity of diffraction/scattering to be 35 to 75% (absolute value: 700 to 1500). Using software WingSALD II for the particle size distribution analyzer, distribution of the light intensity was analyzed and average fat particle diameter and standard deviation were determined.

[Measurement Method of Hardness of Fermented Milk]

[0053] Hardness (strength or curd tension) of fermented milk was measured using a curdmeter MAX ME-500 (I. Techno Engineering). Specifically, a yogurt knife with 100-g weight attached was placed on the top surface of the fermented milk, the fermented milk was continuously elevated while applying a load at about 2 g/sec, and with the elapsed time of this load application, measured values of this load are represented by a curve. Here, elapsed time (second) of this load application is represented on the vertical axis, measured value of this load is represented on the horizontal axis, and 10 g on the vertical axis and 4 seconds on the horizontal axis are expressed as the same di stance. Then, when the fermented milk breaks, the yogurt knife invades from the top surface of the fermented milk, generating an inflection point (breaking point) in this time-load curve, and the value of the load to reach this breaking is defined as an indicator of the hardness (g).

Production Example 1

[0054] A cream sterilized at 125° C., skimmed milk powder prepared from skimmed milk sterilized by UHT treatment at 125° C. for 15 seconds, and water were mixed to prepare a raw material mix (yogurt mix) so as to achieve the fat content of 3.0 wt % and the milk solids-not-fat of 9.5 wt %. The prepared raw material mix was heated to about 80° C. and then homogenized in two stages of 500 kg/cm.sup.2 and 50 kg/cm.sup.2. Subsequently, the homogenized raw material mix was heat sterilized at 95° C. (batchwise sterilization by heating at a reaching temperature of 95° C.) and then cooled to about 10° C. The obtained raw material mix had an average fat particle diameter of 0.58 μm.

[0055] After warming the obtained raw material mix to 43° C., nitrogen (N.sub.2) was injected to reduce the dissolved oxygen concentration (DO) of the raw material mix to 5 ppm, and then a lactic acid bacteria starter (Lactobacillus bulgaricus and Streptococcus thermophilus isolated from Meiji Bulgaria Yogurt LB81) was added (inoculated) at 3 wt %. Thereafter, the mixture was filled in a plastic cup container (100 g capacity) and a paper cup container (450 g capacity), allowed to stand for about 3 hours in a fermentation chamber (43° C.) until the lactic acid acidity reached 0.70%, and then cooled in a refrigerating room (10° C. or lower) to produce set type yogurt (Example 1).

Production Example 2

[0056] A cream sterilized at 125° C., skimmed milk powder prepared from skimmed milk sterilized by UHT treatment at 125° C. for 15 seconds, and water were mixed to prepare a raw material mix (yogurt mix) so as to achieve the fat content of 3.0 wt % and the milk solids-not-fat of 9.5 wt %. The prepared raw material mix was heated to about 80° C. and then homogenized in two stages of 100 kg/cm.sup.2 and 50 kg/cm.sup.2. Subsequently, the homogenized raw material mix was heated (sterilized) at 130° C. for 2 seconds, and then cooled to about 10° C. The obtained raw material mix had an average fat particle diameter of 0.94 μm.

[0057] After warming the obtained raw material mix to 43° C., nitrogen (N.sub.2) was injected to reduce the dissolved oxygen concentration (DO) of the raw material mix to 5 ppm, and then a lactic acid bacteria starter (Lactobacillus bulgaricus and Streptococcus thermophilus isolated from Meiji Bulgaria Yogurt LB81) was added (inoculated) at 3 wt %. Thereafter, the mixture was filled in a plastic cup container (100 g capacity), allowed to stand for about 3 hours in a fermentation chamber (43° C.) until the lactic acid acidity reached 0.70%, and then cooled in a refrigerating room (10° C. or lower) to produce set type yogurt (Comparative example 1).

[0058] Curd strength of the obtained set type yogurt of Example 1 and Comparative example 1 was measured. Curd strength was measured using Neo-curdmeter M302 (I. Techno Engineering).

[0059] The curd strength of Example 1 reached 39 g, which was larger than the curd strength (24 g) of Comparative example 1. From this result, it was confirmed that the yogurt of Example 1 satisfied the target hardness sufficiently and had hardness capable of resisting the impact at the time of distribution of the product.

[0060] Namely, the yogurt of the present invention is considered to be able to achieve the desired hardness and smoothness of mouth feel, by reducing the average particle diameter of the fat in the raw material mix.

Production Example 3

[0061] Raw milk was heat sterilized (pasteurized) at 65° C. for 30 minutes and then homogenized in two stages of 350 kg/cm.sup.2 and 50 kg/cm.sup.2. It was then cooled to about 10° C. The average fat particle diameter of the obtained raw material mix was 0.74 μm.

[0062] After warming the obtained raw material mix to 43° C., nitrogen (N.sub.2) was injected to reduce the dissolved oxygen concentration (DO) of the raw material mix to 5 ppm, and then a lactic acid bacteria starter (Lactobacillus bulgaricus and Streptococcus thermophilus isolated from Meiji Bulgaria Yogurt LB81) was added (inoculated) at 3 wt %. Thereafter, the mixture was filled in a plastic cup container (100 g capacity) and a paper cup container (450 g capacity), allowed to stand for about 3 hours in a fermentation chamber (43° C.) until the lactic acid acidity reached 0.70%, and then cooled in a refrigerating room (10° C. or lower) to produce set type yogurt (Reference example 1).

Production Example 4

[0063] Fresh milk, skimmed milk powder prepared from skimmed milk sterilized by UHT treatment at 125° C. for 15 seconds, and water were mixed to prepare a raw material mix (yogurt mix) so as to achieve the fat content of 3.0 wt % and the milk solids-not-fat of 9.5 wt %. The prepared raw material mix was heated to about 80° C. and then homogenized in two stages of 100 kg/cm.sup.2 and 50 kg/cm.sup.2. Subsequently, the homogenized raw material mix was heat sterilized at 95° C. (batchwise sterilization by heating at a reaching temperature of 95° C.), and then cooled to about 10° C. The obtained raw material mix had an average fat particle diameter of 1.21 μm.

[0064] After warming the obtained raw material mix to 43° C., nitrogen (N.sub.2) was injected to reduce the dissolved oxygen concentration (DO) of the raw material mix to 5 ppm, and then a lactic acid bacteria starter (Lactobacillus bulgaricus and Streptococcus thermophilus isolated from Meiji Bulgaria Yogurt LB81) was added (inoculated) at 3 wt %. Thereafter, the mixture was filled in a plastic cup container (100 g capacity), allowed to stand for about 3 hours in a fermentation chamber (43° C.) until the lactic acid acidity reached 0.70%, and then cooled in a refrigerating room (10° C. or lower) to produce set type yogurt (Reference comparative example 1).

Test Example 1

[0065] Curd strength of the obtained set type yogurt of Reference example 1 and Reference comparative example 1 was measured. Curd strength was measured using Neo-curdmeter M302 (I. Techno Engineering).

[0066] The curd strength of Reference example 1 reached 55 g and it was larger than the curd strength (24 g) of Reference comparative example 1. From this result, it was confirmed that the yogurt of Reference example 1 satisfied the target hardness sufficiently and had hardness capable of resisting the impact at the time of distribution of the product.

Test Example 2

[0067] A raw material mix was prepared in the same manner as Reference example 1, fermented after reducing the dissolved oxygen concentration (DO) to 5 ppm, and the fermentation time until lactic acid acidity reached 0.70% was measured (Reference example 2).

[0068] In addition, a raw material mix was prepared in the same manner as Reference example 1, fermented without reducing the dissolved oxygen concentration (DO), and the fermentation time until lactic acid acidity reached 0.70% was measured (Reference example 3).

[0069] The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Effect of deoxygenated fermentation on reduction of fermentation time Time to reach lactic acid acidity of 0.7% Reference example 2 Reference example 3 3 hours 4 hours

[0070] It was confirmed that the fermentation time can be shortened by conducting deoxygenation treatment before fermentation. The shorter fermentation time means that the time required for production is shorter and the production efficiency is higher.

INDUSTRIAL APPLICABILITY

[0071] The present invention can be used for the production of fermented milk such as yogurt, and in particular it can be suitably used for the production of set type yogurt. In addition, the present invention broadens the application of materials sterilized by ultra-high temperature treatment which are generally difficult to utilize from the viewpoint of coagulability of yogurt, as materials for fermented milk such as yogurt, etc.