Background technique
Yoghourt has unique organoleptic attribute, since its unique nutrient health effect and good flavor are deep by consumer
Favor.The main quality feature of Yoghourt includes quality, taste and flavor.Flavor is an important indicator of Yoghourt quality, simultaneously
It is also an important factor for consumer considers acceptance level and preference.Though restoring lactate milk has rheological characteristic, in cold chain transportation mistake
Phenomena such as being damaged in journey in the presence of brings such as inevitably carrying, collisions, soured milk whey precipitation, curdy texture caused to destroy,
The original structure of Yoghourt and mouthfeel are destroyed, the quality of Yoghourt is seriously affected.
Many scholars are to sides such as the extraneous factors such as quality of production, holding conditions, flavor substance regulation for influencing Quality of Yoghourt
Face is studied, but the influence research of the traffic condition of sour milk products and distance to Quality of Yoghourt is also seldom, not can solve factory
Contradiction between interests and consumer taste's requirement.The influence to yoghourt-flavored is transported thus, has become many creams of puzzlement at present
The problem of product enterprise.Biacetyl is one of most important composition in yoghourt-flavored compound, is become by research diacetyl content
Change, controls the influence to yoghourt-flavored, solve this problem.
Summary of the invention
In view of the problems of the existing technology, it is an object of the invention to design to provide to control in a kind of transportational process to restore
The technical solution of the method for lactate milk diacetyl content.
The method of lactate milk diacetyl content is restored in control in a kind of transportational process, it is characterised in that takes reconstituted milk
Yoghourt cold chain transportation, and the vibration frequency for guaranteeing to restore lactate milk during transportation is 20-140r/min.
The method of lactate milk diacetyl content is restored in control in a kind of transportational process, it is characterised in that guarantees cold chain
Transport temperature is 4 DEG C ± 1 DEG C.
The method of lactate milk diacetyl content is restored in control in a kind of transportational process, it is characterised in that haulage time
Control is 6h.
The method of lactate milk diacetyl content is restored in control in a kind of transportational process, it is characterised in that transportational process
It is middle to guarantee that the vibration frequency for restoring lactate milk is 20-60r/min.
The method of lactate milk diacetyl content is restored in control in a kind of transportational process, it is characterised in that described answers
Former lactate milk is made by following steps: 1) milk powder restores simultaneously homogeneous;2) post-fermentation is sterilized;3) demulsification and tinning;The step
It is rapid 2) in sterilization conditions be 90-95 DEG C of holding 5min;The fermentation condition is access lactobacillus bulgaricus and thermophilus
The mixed bacteria of bacterium, access amount reach 0.08%, and ferment 8h at 40 DEG C;4 DEG C of refrigeration 3h after tinning in the step 3).
Influence present invention utilizes diacetyl content to yoghourt-flavored, control vibration frequency is to yoghourt-flavored and β-half
The enzyme activity of lactoside enzyme and content etc. influence, and improve Yoghourt nutrition and flavor to realize.Make by means of the present invention
Restore lactate milk has more preferable mouthfeel and smell after transit is complete.
Embodiment 1
(1) milk powder restores: meet Yogurt reconstituted milk incoming inspection standard, antibiotic-free is required to raw material milk powder, it is antibacterial
Factor lysozyme cannot detect;
(2) 6% white granulated sugar is added;
(3) milk temperature preheating and homogeneous: is increased to 50oC or so;Homogenization pressure: 18MPa;
(4) pasteurize: sterilization temperature is 90-95 DEG C of holding 5min, cooling;
(5) it is inoculated with: access lactobacillus bulgaricus and streptococcus thermophilus (business strain), inoculum concentration 0.08%, interval after inoculation
Property positive and negative stirring 10min, revolving speed controls in 35r/min;
(6) it ferments: being kept for 40 DEG C, ferment 8 hours, be quickly cooled to 20 DEG C, material temperature fall time is no more than 45min;
(7) demulsification and tinning, 4 DEG C of refrigeration 3h obtain finished product;
(8) at 4 DEG C under the conditions of, finished product Yoghourt is placed on analog vibration experimental bench, by vibration frequency 20,60,100,
140r/min successively vibrates, and time of vibration is that 6h(Yoghourt is usually no more than 6h in actual shipment, and vibration frequency is from low frequency
High-frequency is transformed to, the influence to Quality of Yoghourt is more comprehensive, therefore taking time of vibration is 6h).
Control group is the sample without vibration processing, and experimental group is the sample after vibration processing 6h, passes through o-phenylenediamine
Colorimetric method measures diacetyl content in Yoghourt.
The preparation of beta galactosidase:
20g Yoghourt accurately is weighed, is dissolved in 4 DEG C of 5mL 1% EDTA (pH=12) solution, is mixed.Then 8000 turns of centrifugations
10min removes supernatant, and is washed twice with phosphate buffer, and 10mL buffer is added, and is sufficiently mixed that (precipitating is suspended in liquid
Body), 0.4% lysozyme 2mL is added, water-bath 1h at 37 DEG C adds 4 mol/L NaCl solution 2mL, after being sufficiently mixed, filtering
Enzyme solution is obtained, measures enzyme activity immediately.
The measurement of beta galactosidase:
1mL enzyme solution is taken, the phosphate buffer of 1mL ONPG containing 20mmol/L, water-bath at 37 DEG C is added in 37 DEG C of water-bath 5min
0.5mol/L sodium carbonate liquor 3mL is added in 10min immediately after, terminates reaction.3mL is first added after enzyme solution is added in blank group
Sodium carbonate liquor adds 1mL buffer, measures light absorption value with ultraviolet specrophotometer 420nm.
The diacetyl content that different frequency is handled it can be seen from Fig. 1 is all higher than the diacetyl content of control group, but all
Max-thresholds are less than, yoghourt-flavored is preferable.Occur in the physicochemical structure of high-frequency (100-140r/min) treated Yoghourt
The problems such as great changes, such as viscosity are inadequate, and acidity is too high, and whey is precipitated.Under low frequency (20-60r/min) processing
The variation of Yoghourt physicochemical structure less, and helps to increase the yield of flavor, keeps Yoghourt more fine and smooth smooth, forms flavor and mouth
Feel better Yoghourt.
Show that the increase of vibration frequency will lead to β-in Yoghourt by the analysis of the Rate activity of experimental group in Fig. 2 and control group
The decline of galactoside specific activity of enzyme, obtains changing in the correlation analysis with Rate activity to Yoghourt diacetyl content, has pole
It is significant to be positively correlated (P < 0.05), illustrate that beta galactosidase can influence the yield of Yoghourt biacetyl.
It can be seen that the recovery lactate milk smooth in taste handled at vibration frequency 20-60r/min is fine and smooth, have relatively strong
Stability and smoothness, for the diacetyl content in Yoghourt in critical field, sensory evaluation is good, there is fermenting aroma, is protecting
No whey is precipitated in the matter phase.
Test example:
The advanced row diacetyl content analysis of recovery lactate milk of the ring food limited liability company of Zhejiang one production is taken, wherein biacetyl
Content is 11.96 μ g/mL, then carries out length cold chain transportation to the recovery lactate milk, and guarantees to restore lactic acid during transportation
The vibration frequency of milk is that the 20-60r/min(vibration frequency can be adjusted according to the vibration absorber of vibration shake table or routine
It is whole), by 60r/min, diacetyl content analysis is carried out to the Yoghourt after transport in 6 hours, wherein diacetyl content is
25.48μg /mL.And the recovery lactate milk not vibrated diacetyl content after 6 hours is 15.82 μ g/mL.
It is analyzed and concludes that the diacetyl content for restoring lactate milk after vibration has increase, but be all less than most
Big threshold value, yoghourt-flavored are good.Illustrate that Yoghourt is conducive to the generation of yoghourt-flavored under low frequency (20-60r/min) vibration, and
Influence to yogurt gel structure is little, and then improves the mouthfeel of Yoghourt.But to the gel structure of Yoghourt under high-frequency vibration
Considerable damage is generated, the raising of Yoghourt mouthfeel is unfavorable for, therefore suggests to guarantee Quality of Yoghourt in low-frequency vibration.