Hydrothermal treatment for inactivating some hygienic microbial indicators from food waste–amended animal feed

Figures & data

Table 1. Physicochemistry properties of food waste samples (wt. %)

	Physicochemistry Properties ^†
	pH	Moisture	Organic Matters*	Crude Protein*	Ether Extract*	Crude Fiber*	Salt Content*	Floatable Oil *
Mean	6.67	77.18	91.07	28.64	31.45	3.05	2.68	10.2 × 10^−6
SD	0.33	4.22	4.87	3.37	2.13	1.89	0.59	2.23 × 10^−6
Notes: ^†Six samples were analyzed in triplicate. *Data measured on dry-weight basis of food waste.

Figure 1. Schematic diagram of the inactivation apparatus used for the hydrothermal treatment process.

Table 2. Concentrations of indicator microorganisms in the raw food waste (based on wet weight)

	Microorganisms
	TPC (log10 cfu/g)	TC (log10 MPN/g)	MY (log10 cfu/g)	SA	Salmonella
Mean ± SD	7.09 ± 0.91	5.63 ± 0.91	4.88 ± 0.81	81.25% PR ^d	ND ^e
N ^a	16	14	16	13	0
MDL ^b	0	2	0	3	16
Total ^c	16	16	16	16	16
Notes: ^aNumber of samples included in the statistical analysis (mean and SD determination). ^bNumber of samples below minimum detection limits (10 cfu/g wet weight or 3 MPN/g). ^cTotal number of samples analyzed. ^dPositive rate of staphylococcus aureus. ^eNot detected above background.

Figure 2. Survivor curves for indigenous microbial indicators in food waste were determined by various thermal (60, 80, and 110 °C) conditions. The dotted vertical line indicates the ramping time. The dash horizontal line means at least 3 decimal reductions of TPC, whereas the dash dot horizontal line shows the 3 decimal reductions of MY. (▪) TPC; (○) molds and yeast.

Table 3. Typical experimental conditions and logarithmic reduction of indigenous microorganisms during ramping time of the hydrothermal processing

			Microorganisms
Process Temperature (°C)	Process Relative Pressure (MPa)	Ramping Time (min)	TPC (log10 cfu/g)	MY (log10 cfu/g)	SA
60 ± 2 *	0.06	12	0.02 ± 0.03 ^a	0.01 ± 0.01 ^a	100% PR* *
80 ± 2*	0.12	20	0.04 ± 0.03 ^a	0.03 ± 0.02 ^a	100% PR* *
110 ± 2^+	0.20	60	0.92 ± 0.14 ^b	0.31 ± 0.24 ^b	100% PR* *
Notes: ^a,bMean (± standard deviation), with different superscripts within a column indicating a significant difference (P < 0.05). *No significant difference between TPC and MY within a row (P > 0.05). ^+Significant difference between TPC and MY within a row (P < 0.05). **Positive rate of staphylococcus aureus.

Table 4. Microbiological specifications for hygienic safety of animal feed

	Microorganisms
	TPC ^#	MY ^#	Salmonella ^#	SA ^§	TC ^†
Microbiological specifications	2 × 10^6 cfu/g	2 × 10^4 cfu/g	No detection	10 cfu/g	No detection
Notes: References: ^# AQSIQ (2001a); ^§ MAPA (1988); ^† AQSIQ (2001b).

Figure 3. Plot of logarithmic survival for indigenous bacteria in food waste subjected to various thermal conditions. (○) 60 °C, (▪) 80 °C, and (Δ) 110 °C.

Figure 4. Plot of log D versus temperature.

Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China (AQSIQ) . 2001a . “ GB/T 13078-2001 ” . In Hygienical Standard for Feeds , Beijing : AQSIQ .

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