Lethality and quality evaluation of in-packaged ready-to-eat cooked Jasmine rice subjected to industrial continuous microwave pasteurization

Figures & data

Table 1. Pasteurization process time, PU, and log reduction of each treatment.

	CV	MW 1	MW 2	MW 3
Heating time (s)	180	48	62	79
Holding time (s)	120	48	62	79
Cooling time (sec)	120	120	120	120
Total time (s)	420	216	244	278
PU	8.56	9.64	47.66	124.82
Log reduction*	5.12	5.77	28.54	74.74

*Log reduction meant for only L. monocytogenes.

Figure 1. Time–temperature profiles of RTE rice during MW and CV pasteurization process.

Table 2. Micro-organisms counts during storage.

Day	Treatments	L. monocytogenes (in 25 g)	C. perfringens (cfu/g)	S. aureus (cfu/g)	Yeasts and molds(cfu/g)	TPC (cfu/g)
0 d	CV	ND	ND	ND	ND	ND
	MW	ND	ND	ND	ND	ND
7 d	CV	ND	ND	ND	ND	4.50E + 03
	MW	ND	ND	ND	ND	ND
10 d	CV	2.6E + 02	10	ND	1.60E + 02	1.9E + 06
	MW	ND	ND	ND	ND	1.8E + 02
14 d	CV	—	—	—	—	—
	MW	ND	ND	ND	ND	20
21 d	CV	—	—	—	—	—
	MW	ND	ND	ND	ND	3.1E + 02
30 d	CV	—	—	—	—	—
	MW	ND	ND	ND	ND	2.40E + 03

ND: not detected.

Table 3. Whiteness index and hardness of pasteurized cooked rice during storage.

Properties	Treatments	0 d	7 d	14 d	21 d	30 d
WI	CV	21.68^a	21.49^a	(21.68^a)*	(21.68^a)*	(21.68^a)*
	MW 1	23.64^b,A	23.39^b,A	22.96^b,A	23.27^b,A	22.64^b,A
	MW 2	23.41^b,A	23.21^b,A	23.14^b,A	23.19^b,A	22.57^b,A
	MW 3	23.38^b,A	23.30^b,A	23.12^b,A	22.89^ab,A	22.45^b,A
Hardness (Newton)	CV	14.67^a	16.28^b	(14.67^a)*	(14.67^a)*	(14.67^a)*
	MW 1	13.48^a,A	15.58^ab,B	17.34^b,C	17.64^b,C	20.60^b,D
	MW 2	13.66^a,A	14.98^a,B	17.85^b,C	16.70^b,C	23.31^d,D
	MW 3	14.63^b,A	16.16^b,B	18.26^b,C	19.20^c,C	22.00^c,D

Different lowercase letters show differences between heating treatments. Different uppercase letters show differences between storage times.

()* are data of product under CV process at day 0 used for comparing with products under MW process because product under CV process was destroyed after 10-day storage.

Table 4. Sensory scores of pasteurized cooked rice during storage.

Attributes	Treatments	0 d	7 d	14 d	21 d	30 d
Appearance	CV	7.60^a	7.35^a	(7.60^b)*	(7.60^b)*	(7.60^c)*
	MW 1	7.65^a,D	7.55^a,CD	7.25^b,BC	7.05^a,AB	6.70^b,A
	MW 2	7.65^a,C	7.60^a,C	6.70^a,AB	6.80^a,B	6.25^a,A
	MW 3	7.65^a,C	7.55^a,C	6.65^a,B	6.70^a,B	6.00^a,A
Color	CV	7.50^a	7.25^a	(7.50^b)*	(7.50^b)*	(7.50^c)*
	MW 1	7.60^a,B	7.50^a,B	7.10^ab,A	7.05^a,A	6.75^b,A
	MW 2	7.55^a,B	7.50^a,B	6.80^a,A	6.95^a,A	6.65^b,A
	MW 3	7.60^a,C	7.45^a,C	6.85^a,B	6.95^a,B	6.10^a,A
Flavor	CV	7.25^a	7.20^a	(7.25^b)*	(7.25^b)*	(7.25^b)*
	MW 1	7.40^a,C	7.40^a,C	7.00^ab,BC	6.80^ab,AB	6.40^a,A
	MW 2	7.45^a,B	7.35^a,B	6.55^a,A	6.50^a,A	6.15^a,A
	MW 3	7.35^a,B	7.40^a,B	6.65^a,A	6.40^a,A	6.20^a,A
Texture	CV	7.40^a	7.45^a	(7.40^b)*	(7.40^b)*	(7.40^b)*
	MW 1	7.45^a,D	7.30^a,CD	6.85^a,BC	6.55^a,AB	6.30^a,A
	MW 2	7.50^a,B	7.35^a,B	6.60^a,A	6.75^a,A	6.25^a,A
	MW 3	7.50^a,C	7.55^a,C	6.75^a,B	6.85^a,B	6.00^a,A
Overall liking	CV	7.45^a	7.40^a	(7.45^b)*	(7.45^b)*	(7.45^b)*
	MW 1	7.55^a,D	7.45^a,CD	7.00^ab,BC	6.75^a,AB	6.30^a,A
	MW 2	7.50^a,C	7.45^a,C	6.75^a,B	6.85^a,B	6.10^a,A
	MW 3	7.55^b,C	7.50^a,C	6.85^a,B	6.90^a,B	6.20^a,A

Different lowercase letters show differences between heating treatments. Different uppercase letters show differences between storage times.

()* are data of product under CV process at day 0 used for comparing with products under MW process because product under CV process was destroyed after 10-day storage.

Table 5. Whiteness index and hardness of pasteurized cooked rice with anti-retrogradation agents during storage.

Properties	Treatments	0 d	7 d	14 d	21 d	30 d
WI	Control	26.78^d,C	24.03^e,B	23.93^c,B	24.17^e,B	22.17^d,A
	SB 5%	25.42^c,C	23.20^d,A	24.36^cd,B	22.88^d,A	22.89^e,A
	SB 15%	27.46^e,C	24.42^e,B	24.72^d,B	21.26^c,A	21.32^c,A
	TL 5%	25.38^c,C	21.41^b,A	22.22^b,B	20.94^c,A	21.32^c,A
	TL 15%	23.74^b,C	20.77^a,B	24.21^cd,C	18.79^a,A	19.20^b,A
	SO 1%	23.33^b,E	22.24^c,D	20.51^a,C	19.78^b,B	17.83^a,A
	SO 3%	22.15^a,A	21.60^b,A	21.90^b,A	22.86^d,B	22.07^d,A
Hardness (Newton)	Control	18.037^c,A	19.728^d,AB	19.655^c,AB	19.840^c,AB	21.158^d,B
	SB 5%	15.105^a,B	17.768^bc,CD	18.775^c,D	17.118^b,C	13.721^b,A
	SB 15%	16.262^ab,A	17.520^bc,AB	18.269^c,B	18.192^b,B	16.773^c,A
	TH 5%	16.769^bc,C	17.812^bc,A	19.030^c,B	17.161^b,C	13.865^b,C
	TH 15%	16.377^ab,B	18.463^cd,C	18.620^c,C	17.344^b,B	13.121^b,A
	SO 1%	16.198^ab,C	16.314^ab,C	15.810^b,C	13.609^a,B	11.571^a,A
	SO 3%	16.076^ab,C	15.310^a,C	14.055^a,B	13.592^a,B	11.906^a,A

Different lowercase letters show differences between anti-retrogradation agents. Different uppercase letters show differences between storage times.

Control: no added anti-retrogradation agent; SB: sorbitol; TH: trehalose; SO: soybean oil.

Table 6. Sensory scores of pasteurized cooked rice with anti-retrogradation agents during storage.

Attributes	Treatments	0 d	7 d	14 d	21 d	30 d
Appearance	Control	7.07^a,B	6.53^ab,A	6.33^ab,A	6.07^ab,A	6.33^b,A
	SB 5%	7.40^a,B	7.07^b,B	7.13^c,B	6.13^ab,A	6.27^b,A
	SB 15%	7.40^a,C	7.07^b,BC	6.47^bc,AB	6.20^ab,A	6.07^b,A
	TL 5%	7.00^a,B	6.87^b,B	6.80^bc,AB	6.67^b,AB	6.13^b,A
	TL 15%	7.20^a,B	6.73^ab,AB	6.60^bc,A	6.73^b,AB	6.33^b,A
	SO 1%	7.20^a,B	6.47^ab,A	6.40^ab,A	6.53^b,A	6.47^b,A
	SO 3%	7.20^a,C	6.20^a,B	5.73^a,AB	5.80^a,AB	5.60^a,A
Color	Control	7.27^a,B	6.47^a.A	6.27^ab,A	6.13^ab,A	6.27^b,A
	SB 5%	7.47^a,B	7.13^b,B	7.13^c,B	6.27^ab,A	6.20^b,A
	SB 15%	7.33^a,B	7.13^b,B	6.40^ab,A	6.40^ab,A	6.07^b,A
	TL 5%	7.00^a,B	6.80^ab,B	6.73^bc,B	6.67^b,B	6.00^b,A
	TL 15%	7.07^a,B	6.73^ab,AB	6.60^bc,AB	6.67^b,AB	6.40^b,A
	SO 1%	7.13^a,B	6.47^a,A	6.33^ab,A	6.60^b,A	6.40^b,A
	SO 3%	7.13^a,C	6.27^a,B	5.80^a,AB	5.87^a,AB	5.53^a,A
Flavor	Control	6.67^a,C	6.20^a,BC	5.93^a,AB	5.73^ab,AB	5.33^a,A
	SB 5%	7.13^a,B	6.8^ab,B	6.73^b,B	5.93^ab,A	5.87^ab,A
	SB 15%	7.00^a,B	6.93^b,B	6.40^ab,AB	6.13^ab,A	5.67^ab,A
	TL 5%	6.80^a,B	6.33^ab,AB	6.40^ab,AB	6.27^b,AB	5.87^ab,A
	TL 15%	7.00^a,B	6.47^ab,AB	6.07^ab,A	6.47^b,AB	6.07^b,A
	SO 1%	6.73^a,B	6.13^a,AB	6.13^ab,AB	6.00^ab,A	6.20^b,AB
	SO 3%	6.87^a,C	6.13^a,B	5.80^a,AB	5.47^a,A	5.27^a,A
Texture	Control	6.67^a,C	6.33^a,BC	6.00^ab,AB	5.87^a,AB	5.67^ab,A
	SB 5%	7.27^ab,B	7.00^b,B	7.00^c,B	6.07^a,A	6.13^bc,A
	SB 15%	7.13^ab,B	7.13^b,B	6.27^ab,A	6.00^a,A	6.07^bc,A
	TL 5%	6.73^ab,A	6.67^ab,A	6.60^bc,A	6.47^a,A	6.20^bc,A
	TL 15%	6.87^ab,A	6.67^ab,A	6.40^bc,A	6.53^a,A	6.27^c,A
	SO 1%	7.33^b,B	6.33^a,A	6.13^ab,A	6.47^a,A	6.33^c,A
	SO 3%	7.00^ab,B	6.13^a,A	5.73^a,A	5.80^a,A	5.47^a,A
Overall liking	Control	6.80^a,C	6.40^ab,BC	6.07^ab,AB	5.80^ab,A	5.73^ab,A
	SB 5%	7.20^a,B	6.87^bc,B	7.00^d,B	6.13^abc,A	6.27^bc,A
	SB 15%	7.00^a,B	7.13^c,B	6.33^abc,A	6.13^abc,A	6.20^bc,A
	TL 5%	6.87^a,B	6.60^abc,AB	6.73^cd,AB	6.47^bc,AB	6.07^bc,A
	TL 15%	7.00^a,B	6.60^abc,AB	6.33^abc,A	6.60^c,AB	6.33^c,A
	SO 1%	7.00^a,B	6.40^ab,A	6.40^bcd,A	6.53^c,A	6.40^c,A
	SO 3%	6.93^a,B	6.13^a,A	5.73^a,A	5.73^a,A	5.53^a,A

Different lowercase letters show differences between anti-retrogradation agents. Different uppercase letters show differences between storage times.