ISO 20976-1:2019 食物連鎖の微生物学—食品および飼料製品のチャレンジテストを実施するための要件とガイドライン—パート1：成長の可能性、遅延時間、および最大成長率を研究するためのチャレンジテスト | ページ 6

3.1

bacterial spore

resistant form of bacteria that is dormant until the germination (3.9) step

3.2

batch

group or set of identifiable food obtained through a given process under practically identical circumstances and produced in a given place within one defined production period

Note 1 to entry: The batch is determined by parameters established beforehand by the organization and may be described by other terms, e.g. lot.

[SOURCE:Commission Regulation (EC) No 2073/2005]

3.3

cardinal value

estimated minimal, optimal and maximal values of physico-chemical factors (e.g. temperature, pH, a_w) that characterize the growth of a given microbial strain

3.4

control unit

unit of food identical to the test unit (3.24) but not artificially contaminated (used as a blank)

3.5

challenge test

study of the growth or inactivation of microorganism(s) artificially inoculated in food

3.6

experimental datapoint

result of analysis of a test unit (3.24) per unit weight (log₁₀ cfu/g), per unit volume (log₁₀ cfu/ml), or per unit area (log₁₀ cfu/cm²)

Note 1 to entry: For specific cases, the enumeration results may be expressed in log₁₀ MPN.

3.7

exponential growth phase

phase in which the microbial population is exponentially multiplying as rapidly as possible; growth is dependent on the growth medium and environment (temperature, humidity, etc.)

Note 1 to entry: Figure 1 describes the three phases of microbial growth kinetics.

3.8

generation time

tg

time it takes for the microorganisms to increase by a factor 2, also known as doubling time

3.9

germination

mechanism in which a bacterial spore (3.1) starts becoming a vegetative cell (3.25)

3.10

growth potential

Δ

difference between the decimal logarithm of the highest concentration of the target microbial population (log_max) and the decimal logarithm of the initial concentration of this microbial population (log_i)

Note 1 to entry: The log_max and log_i refer to concentrations and are expressed in log₁₀ cfu/g or log₁₀ cfu/ml or log₁₀ cfu/cm²

3.11

maximum growth rate

kinetics parameter to characterize the exponential growth phase (3.7) , represented by the slope of the curve showing the evolution of the natural logarithm (μ_max) or decimal logarithm (V_max) of the population as a function of time, under constant growth conditions

3.12

inoculum

microbial suspension at the desired concentration used to contaminate test units (3.24)

3.13

lag phase

phase, directly after inoculation, during which the microbial population is adapting to the environment, before it enters the exponential growth phase (3.7)

Note 1 to entry: Figure 1 describes the three phases of microbial growth kinetics.

3.14

lag time

λ

kinetics parameter in time unit to characterize the lag phase (3.13)

3.15

pH value

measure of the concentration of acidity or alkalinity of a material in an aqueous solution

[SOURCE:ISO 5127:2017, 3.12.2.29, modified — Notes 1 and 2 to entry have been removed.]

3.16

primary model

mathematical model describing the changes of microbial counts as a function of time

3.17

organizing laboratory

laboratory with responsibility for managing the challenge tests (3.5)

3.18

sampling

selection of one or more units or portions of food such that the units or portions selected are representative of that food

3.19

sampling point

time at which the test units (3.24) are analysed and which are represented as experimental datapoints (3.6) on the kinetics graph

3.20

secondary model

mathematical model describing the effects of the environmental factors (e.g. temperature, pH, a_w) on the parameters of the primary model (3.16) (e.g. growth rate)

3.21

sporulation

mechanism by which vegetative cell (3.25) forms spore

3.22

stationary phase

phase in which the microbial population is at its maximum level

Note 1 to entry: Figure 1 describes the three phases of microbial growth kinetics.

3.23

test portion

measured (volume or mass) representative sample taken from the test unit (3.24) for use in the analysis

[SOURCE:ISO 6887-1:2017, 3.5, modified — The end of the definition has been changed from “taken from the laboratory sample for use in the preparation of the initial suspension” and the Note 1 to entry has been removed.]

3.24

test unit

measured (volume or mass) amount of the food used for inoculation

3.25

vegetative cell

state of microbial form that is capable of growing under favourable environmental conditions

3.26

water activity

a_w

ratio of the water-vapour pressure in the foodstuff to the vapour pressure of pure water at the same temperature

[SOURCE:ISO 18787:2017, 3.1, modified — The definition has been condensed and the formula and Notes 1 and 2 to entry have been removed.]