Effect of a Lactobacillus sakei and Staphylococcus xylosus protective culture on Listeria monocytogenes growth and quality traits of Italian fresh sausage (salsiccia) stored at abusive temperature

Figures & data

Table 1. Description of attributes and associated scales’ anchor points used for sensory evaluation of sausage samples.

Attributes	Description	Anchor points
Raw sausages
Appearance
External appearance	External appearance with the casing	1, normal; 3, modified; 5, extremely modified or anomalous
Colour of lean portion	Colour of the lean portion in the internal part of the sausages	1, intense pinkish/red; 3, modified or darkened; 5, extremely modified or darkened
Colour of fat portion	Colour of the fat portion in the internal part of the sausages	1, whitish; 3, modified; 5, extremely modified or not white
Odour
Odour intensity	Intensity of the typical odour of fresh sausage	1, absent; 3, present; 5, extremely present
Rancid	Odour associated with rancid/oxidised fats	1, absent; 3, present; 5, extremely present
Acid	Odour associated with diluted aqueous solutions of acids	1, absent; 3, present; 5, extremely present
Off-odours	Uncharacteristic or undesirable odours, usually associated with transformation or degradation of the sample	1, absent; 3, present; 5, extremely present
Texture
Texture	Structural, mechanical and surface characteristics of fresh sausage	1, normal; 3, modified; 5, extremely modified or anomalous
Cooked sausages
Odour
Odour intensity	Intensity of the typical odour of cooked fresh sausage	1, absent; 3, present; 5, extremely present
Rancid	Odour associated with rancid/oxidised fats	1, absent; 3, present; 5, extremely present
Acid	Odour associated with diluted aqueous solutions of acids	1, absent; 3, present; 5, extremely present
Off-odours	Uncharacteristic or undesirable odours, usually associated with transformation or degradation of the sample	1, absent; 3, present; 5, extremely present
Flavour
Flavour intensity	Intensity of the typical flavour of cooked fresh sausage	1, absent; 3, present; 5, extremely present
Rancid	Flavour associated with rancid/oxidised fats	1, absent; 3, present; 5, extremely present
Acid	Flavour associated with elementary taste caused by diluted aqueous solutions of acids	1, absent; 3, present; 5, extremely present
Off-flavours	Uncharacteristic or undesirable flavours, usually associated with transformation or degradation of the sample	1, absent; 3, present; 5, extremely present
Texture
Texture	Structural, mechanical and surface characteristics of fresh sausage	1, normal; 3, modified; 5, extremely modified or anomalous

Table 2. Growth potential (δ, log CFU/g) and significative interaction (p < .001) of protective culture presence (PC + and PC–) and temperature (abusive temperatures and control refrigerated conditions) at different sampling times on Listeria monocytogenes mean counts (log CFU/g) of experimental sausages.

	Storage temperature and use of PC
	2 °C		7 °C		12 °C
Sampling time (days)	PC–	PC+	PC–	PC+	PC–	PC+
t0	1.97^g	2.24^g	1.97^g	2.24^g	1.97^g	2.24^g
t3	2.27^g	2.31^g	2.73^f	2.56^f	3.95 ^cd	3.09^de
t7	2.22^g	2.27^g	4.15^c	2.55^f	4.90^b	2.75^f
t9	2.88^e	2.60^f	4.86^b	2.64^f	5.55^a	3.58^d
Growth potential (δ)
t7	0.54	0.15	2.85	0.42	3.78	1.00
t9	1.43	0.60	3.58	0.58	4.07	1.72

a-g: Means with no common superscripts are significantly different (p < .05). RMSE = 0.344..

Figure 1. Evolution of bacterial counts (log CFU/g, mean ± SD) at different sampling times (t0, t3, t7 and t9, days) of experimental sausages, with (PC+) and without (PC–) protective culture, stored at 7 °C. In case of significant interaction (PC × Time), different letters show statistically significant differences among samples.

Figure 2. Evolution of pH values and TBARS content (mg/kg of malondialdehyde, MDA, mean ± SD) at different sampling times of experimental sausages, with (PC+) and without (PC–) protective culture, stored at 7 °C. In case of significant interaction (PC × Time), different letters show statistically significant differences among samples.

Table 3. External and internal mean colour parameters at different sampling times (t0, t3, t7 and t9, days) of experimental sausages, with (PC+) and without (PC–) protective culture, stored at 7 °C.

	PC–				PC+				RMSE	p
										PC	Time	PC × Time
	t0	t3	t7	t9	t0	t3	t7	t9
External without casing
L*	50.45	47.81	48.35	49.43	51.60	49.20	50.88	50.77	3.693	0.004	0.027	0.798
a*	17.13^a	15.83^ab	15.13^bc	13.70^c	16.08^ab	15.11^abc	11.71^d	10.62^d	2.050	<0.001	<0.001	0.003
b*	10.89	11.27	11.28	10.60	10.24	11.08	10.33	9.88	1.456	0.003	0.037	0.729
Internal
L*	49.92	48.16	49.47	48.62	49.74	47.71	50.66	51.32	5.346	0.250	0.288	0.498
a*	17.06^ab	16.78^ab	17.60^a	16.91^ab	16.77^ab	18.85^a	17.31^ab	15.16^b	2.603	0.513	0.012	0.018
b*	10.21	9.83	10.82	9.89	10.24	10.13	9.90	8.54	1.736	0.034	0.007	0.099

a-d: Means with no common superscripts in the same row are statistically different (p < .05) for significant PC x Time interaction.

Figure 3. Evolution of sensory parameters of raw experimental sausages, with (PC+) and without (PC–) protective culture, stored at 7 °C at different sampling times, grouped by presence of protective culture and sampling time. *Statistically significant differences (p < .05).

Figure 4. Evolution of sensory parameters of cooked experimental sausages, with (PC+) and without (PC–) protective culture, stored at 7 °C at different sampling times, grouped by presence of protective culture and sampling time. *Statistically significant differences (p < .05).