Mechanisms of food microbial growth and quality changes under low temperature storage conditions

Figure 1.

Figure 2.

Figure 3.

Figure 4.

Figure 5.

Figure 6.

Shows the relationship between growth parameters and shelf life

Microorganism	Growth parameter	Correlation coefficient (r)
		Microbial shelf life	Sensory shelf life
Total flora	N0	-0.2374	-0.1963
	Nmax	0.7302	0.6785
	μ	-0.7343	-0.7016
	λ	0.8924**	0.9128**
Coliform bacteria	N0	-0.8273*	-0.7976*
	Nmax	0.6852	0.6725
	μ	-0.9582**	-0.9694**
	λ	0.7592*	0.7195
Mold	N0	-0.7024	-0.6546
	Nmax	0.6899	0.6236
	μ	-0.8374*	-0.8056*
	λ	0.9813**	0.9829**
Lactic acid bacteria	N0	-0.7679*	-0.7651*
	Nmax	-0.0763	-0.1425
	μ	-0.7290	-0.7016
	λ	0.9894**	0.9848**

Kinetic parameters of total colony growth at different concentrations

O2 concentration/%	CO2 concentration/%	N0 /In(CFU/mL)	μmax/h-1	λ/h	Nmax /In(CFU/mL)	R2	RMSE
2	1.7	11.7	0.032	187.43	17.03	0.9578	0.5115
	22.0	11.51	0.02538	236.3	17.21	0.9905	0.215
	31.0	11.4	0.02272	263.96	17.41	0.9965	0.1134
	43.0	11.51	0.02021	296.73	16.52	0.9898	0.1576
6.5	1.7	11.61	0.0362	165.69	17.27	0.9895	0.2814
	22.0	11.51	0.02927	204.91	17.02	0.9969	0.1471
	31.0	11.61	0.02642	227	17.03	0.985	0.2732
	43.0	11.52	0.02263	265.01	16.55	0.9908	0.1691
8.7	1.7	11.73	0.03704	161.93	17.16	0.9726	0.448
	22.0	11.61	0.02943	203.79	17.12	0.9946	0.1808
	31.0	11.66	0.02673	224.37	17.18	0.9853	0.2761
	43.0	11.54	0.02315	259.06	16.69	0.9904	0.181
10.5	1.7	11.5	0.03714	161.5	17.54	0.9814	0.4026
	22.0	11.51	0.03072	195.24	17.85	0.9974	0.1451
	31.0	11.55	0.0269	222.96	17.56	0.9639	0.4348
	43.0	11.53	0.02334	256.95	18.09	0.9861	0.1907
30.5	1.7	11.53	0.03915	153.21	17.45	0.9946	0.2162
	22.0	11.47	0.03093	193.91	18.02	0.995	0.1942
	31.0	11.69	0.02718	220.66	17.98	0.9274	0.6463
	43.0	11.43	0.02344	255.85	18.4	0.9959	0.1463
47.5	1.7	11.57	0.03913	153.29	17.39	0.9926	0.2488
	22.0	11.47	0.03069	195.43	17.15	0.9912	0.2534
	31.0	11.73	0.02799	214.28	17.79	0.9016	0.7696
	43.0	11.39	0.02364	253.69	18.03	0.9959	0.148

-36℃ after 35 days of lactic acid bacteria determination results

Storage days t/d	Ordinary bouillon			Skin on milk
	Coliform number / CFU·g-1	Mold count / CFU·g-1	Lactic acid bacteria number / CFU·g-1	Coliform number / CFU·g-1	Mold count / CFU·g-1
35	<10	20	1.0*105	<10	52
65	<10	25	3.6*105	<10	55
95	<10	35	7.5*105	<10	60

Verification data of the prediction model (0℃)

O2 concentration/%	CO2 concentration/%	√ μmax Predicted value/h-1/2	√ μmax Measured value/h-1/2	Af	Bf	Residual
4.5	1.7	0.1858	0.1841	1.002	0.998	-0.0016
	22.0	0.1671	0.1617			-0.0053
6.5	1.7	0.1893	0.1902			0.0008
	22.0	0.1703	0.171			0.0006
	31.0	0.1615	0.1625			0.0009
	43.0	0.1497	0.1504			0.0006
8.7	1.7	0.1914	0.1924			0.0009
	43.0	0.1513	0.1521			0.0007
31.5	1.7	0.1928	0.1978			0.0049
	31.0	0.1644	0.1648			0.0003
47.5	22.0	0.1734	0.1751			0.0016
	43.0	0.1524	0.1537			0.0012

Microbiological and sensory shelf life of different storage groups

Storage group	Microbial shelf life /d	Sensory shelf life /d
A	19	18
B	12	11
C	6	6
D	19	17
E	7	6
F	5	5