Commercially, cold-filled acidic pickles, sauces (e.g. salad cream, mayonnaise) and food dressings are preserved, and their microbiological safety assured, by the use of acetic acid, salt (NaCl) and sugar. This article provides an overview of a preservation model and access to the model to enable the effect of sauce components and pH to be investigated.

The Comite´ des Industries des Mayonnaises et Sauces Condimentaires de la Communaute´ Économique Européenne (CIMSCEE) has provided guidance on a safety value, Σs, for a microbiologically safe product preserved using acetic acid (Anonymous, 1993). A safe product has been defined as one which is so formulated that when an inoculum of viable cells of  Escherichia coli is  added to the product this is reduced by 3 log cycles in less than 72 h. Products exhibiting this level of antibacterial activity have a CIMSCEE safety value (Σs) of greater than 63. Σs is calculated using equation 1: Σs =15.75 (1 - ɑ) (total acetic acid %) + 3.08 (salt %) + (hexose %) + 0.5 (disaccharide %) + 40 (4-pH).

So you want to start an ice cream and Gelato shop business?

The purpose of this article is to help anyone interested in starting their own ice cream business to get started. I am an artisan ice cream maker with extensive experience of industrial scale ice cream making. While I will discuss both artisanal or traditional and industrial or large scale ice cream manufacture, the main emphasis will be on artisanal production.

Characteristics - Tomino di Talucco is a fresh cheese produced from goats’ milk or a mixture of goats’ and cows’ milk. The concentration of cows’ milk used must be less than 90%. Tomino di Talucco cheese is cylindrical with flat surfaces. The cylindrical shape has a diameter of 4-5 cm, an edge of 3-4 cm and a weight of 50-80 g. In fresh cheeses, there is no rind and the dough is white or ivory-white without holes. The texture is soft and slightly consistent. The odour is fine, delicate, and is rarely pungent. The taste is mainly acid and fine. In ripened cheeses, the rind is hard and the dough is yellow. The texture is also hard. The odour is strong, persistent and pungent. The taste is savoury and salty.

Ian McCluggageIan McCluggage is married with five children. The son of a Co. Antrim dairy farmer, and growing up and working on the farm, he gained a practical knowledge and understanding of milking cows and the many challenges facing dairy farming.

In 1984 Ian commenced work with the Department of Agriculture Northern Ireland (DANI) initially as a general adviser, then dairy specialist and progressing to senior business consultant. He gained additional experience and viewed life from the commercial world's perspective, spending several years in the private sector before returning to DARD in 1998.

In 1999 he became head of advisory / development work in the beef and sheep sector before taking up his current role in 2000 as Head of Dairying & Pigs Development Branch at the Greenmount Campus of the College of Agriculture, Food and Rural Enterprise (CAFRE)Greenmount Campus, CAFRE.

Because phage lysin has a much broader lytic range than phage, infection of paired and multi-strain cultures with a lysin-producing phage has the potential to cause fermentation failure, dead-vats, and consequent economic loss.

Commercial cheese correctly manufactured with pasteurised milk and lactic starter cultures has a well deserved reputation as a nutritious and safe product. However, under certain circumstances cheese may support the growth of food poisoning bacteria or serve as a ‘vehicle’ for their transmission.

Four pathogens are of particular significance, Listeria monocytogenes, Salmonella species, enteropathogenic Escherichia coli and Staphylococcus aureusListeria monocytogenes, the causal agent of listeriosis, is arguably the most significant of this group.

L. monocytogenes is particularly significant since it can grow / survive for long periods in cheese and cause serious illness leading to death; the death rate arising from listeriosis can exceed 30%. It can also induce abortion in humans and its ability to cross the placenta, and access the brain makes it a particularly dangerous pathogen.

 This article provides an introduction to the binary and ordinal logistic regression models developed by Bolton and Frank (1999) for predicting the probability of L. monocytogenes growing in cheese after 42 days storage at 10°C.

Characteristics of Listeria monocytogenes

L. monocytogenes is a Gram-positive, non-sporing bacterium that can grow in high salt environments (up to 10 % sodium chloride), and over a wide pH (5.0-9.6) and temperature range (< 3° – 45°C); it can grow aerobically and microaerophilically ( Bajard et al., 1996; Pearson and Marth, 1990).

In Northern Europe and North America there is relatively little use made of whole milk powder (WMP) in commercial  ice cream manufacture. However small scale ice cream or gelato manufacturers sometimes use these ingredients.  In Vietnam and other Asian countries ice cream is frequently made from whole milk powder and cream.

 

The tables of data from the gassy cheese article.

 

Table 1. Major microbial groups that can produce gas in cheese

Microbial group

Substrate

Gaseous products

Clostridia
  Clostridium tyrobutyricum

Lactate

CO2, H2

Lactobacilli
  E.g. Lactobacillus brevis
  E.g. Lactobacillus casei

Lactose

Citrate

CO2

Streptococci
  Streptococcus thermophilus1

Urea

CO2

Coliforms

Lactose

CO2, H2

Yeasts

Lactose

CO2

Lactococci
 Lactococcus lactis ssp. lactis biovar. diacetylactis

Citrate

CO2

Bacillus species
  Bacillus subtilis

Lactose

CO2, H2

Leuconostocs
  E.g. Leuconostoc mesenteroides
  E.g. Leuconostoc dextranicum

Lactose/citrate

CO2

Propionibacteria
  Propionibacterium shermani

Lactate

CO2

Notes:1 Streptococcus thermophilus can also produce gas from other substrates.

 

Table   2. Microbiological analysis of blown and normal cheese from factory X

 

CFU/g

 

Blown cheese-A

Blown cheese-B

Normal cheese

'Total count' on milk agar

1.3 x 10 8

6 x 107

2 x 107

Yeasts and moulds

<10

<10

<10

Coliforms

<10

<10

<10

Catalase-negative citrate   utilisers(1)

8 x 107

4 x 107

<1 x 106

Clostridia

<1 x 10 2

<1 x 102

<1 x 102

Group D streptococci

<1 x 102

1.3 x 103

2 x 102

Lactobacilli(2)

4.1 x 104

4.1 x 105

1 x 103

Aerobic sporeformers

1 x 102

1 x 102

1 x 102

Notes:

All cheeses were obtained from the same commercial plant and from the same production run.
Cheeses had been held at 7°C for 8 weeks after manufacture before sampling. Moisture, pH and salt
levels were within acceptable limits and similar in all samples.
(1)Determined using differential agar media13,14.
(2) Determined using Rogosa agar15

TABLE 3.   Relationship between citrate level in cheese, ex-press, and gas production in   Cheddar cheese

Days after manufacture

Starter code

Milk citrate level (% w/w)

Cheese citrate level(2) (% w/w)

Condition of barrier bag(3)

1

1607

ND

0.05

Blown

3

1607

ND

< 0.001

Slack

15

1607

0.17

0.09

Blown

29 (vat 1)

1607

0.17

0.01

Blown

29 (vat 3)

SLA(1)

0.17

0.21

Blown

53

MS(1)

0.17

0.19

Tight, no gas

60

1607

0.18

0.14

Blown

Notes:

(1) Defined multi-strain cultures that did not contain citrate utilising strains.
(2) Cheese analysed immediately after pressing for citrate (12 hours).
(3) Cheese was stored at 7C for 6 weeks before examination.
ND - not determined

 

TABLE 4.   Characteristics of Rogosa-agar isolates from a commercial mixed-strain   culture

Isolate

HM8/4

HM8/11

HM8/10

HM8/14

Morphology

Cocco/ bacillus

Cocco/ bacillus

Cocco/ bacillus

Cocco/ bacillus

Gram reaction

+

+

+

+

Catalase

-

-

-

-

NH3 from arginine

-

-

-

-

Nitrate reduction

-

-

-

-

Lactic acid (isomer present)

(D)

(D)

(D)

(D)

Acid produced in RSM(1)

0.25%

0.20%

0.48%

0.39%

Gas from glucose

+

+

+

+

Gas from gluconate

+

+

+

+

Acid from arabinose

-

-

-

-

Acid from xylose

(+)

-

(-)

+

Acid from maltose

+

+

+

+

Growth at 40ºC

-

-

-

-

Growth at 10ºC

+

+

+

+

Growth at 6ºC

-

+

+

-

Growth in 6% NaCl

+

+

+

+

Growth in 6.5% NaCl

-

-

-

-

Citrate utilisation

+

+

+

+

 

TABLE 5. Maximum volumes 1,2 (L) of carbon dioxide available from citrate and lactose in cheese (3)

% substrate (w/w)

Volume of CO2(1)

 

Citrate(4)

Lactose(5)

0.8

NC

18.8

0.5

NC

11.8

0.2

12.6

4.7

0.1

6.3

2.4

0.02

1.3

0.48

Notes:

(1) Volumes at standard temperature and pressure (STP)
(2) No allowance made for adsorption/solution. Values are rounded
(3) Cheese mass 18 kg
(4) Assuming 3 moles of CO2 produced from 1 mole citrate
(5) Assuming 2 moles of CO2 produced from 1 mole lactose
NC. Not calculated. Citrate levels of >0.2% w/w are not normally found in Cheddar cheese.

Return to gassy cheese article.

MICROSOFT EXCEL LETHAL RATE CALCULATORS AND TEMPERATURE TIME INTEGRATORS FOR THERMAL PROCESSES

Introduction

This section provides the context to using Excel to calculate the cumulative lethal effects (at all stages during processing) of heat on microorganisms and provides an explanation of how the Excel spreadsheets and On Line calculators available for download from the Dairy Science and Food Technology (DSFT) work.

Here we provide an overview of the background, including a summary of the underlying mathematics, required to produce an Excel spreadsheet for performing basic thermal processing calculations. Note I am not providing a guide to using spreadsheets but basic information that a competent Excel user should be able to use to make their own thermal processing spreadsheet.

Download Excel Thermal Processing Spreadsheets.

Subcategories

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