This article discusses the background of the change in classification of the lactic streptococci to the genus Lactococcus.

The lactic group of the genus Streptococcus originally included the species Str. lactis and Str. cremoris and a subspecies of Str. lactis, Str. lactis subsp. diacetylactis (Deibel and Seeley, 1974). However, even in the 1970s workers were suggesting that Str. lactis strains might be variants of Str. diacetylactis that were unable to ferment citric acid, since citrate permease – negative strains of Str. diacetylactis had been described (Lawrence, Thomas and Terzaghi, 1976).

Bacteria in this group were designated as the lactic streptococci. The designation 'lactic' was used by Sherman (1937) for mainly historical reasons, including the use of the term by Lister (1878) to describe a bacterium that we now know as Lc. lactis subsp. lactis.

lee-williamsLee Williams owns and operates Valenti’s Gelato-Artisan, a Company dedicated to promoting Artisan Ice Cream and Gelato making throughout the UK. He has over 35 years’ experience in the Ice Cream Industry. Lee began his career in a family business, a second generation of Ice Cream makers in SW England. During this time he worked in various locations including Southern Africa, creating a global perspective to his service. More recently he has developed strong working partnerships with European equipment manufacturers and Italian flavour houses. Valenti’s product portfolio includes all types of Artisan Ice Cream making equipment, gelato shop with parlour design and ingredients, together with training, mix formulation and technical support, available throughout the UK and Ireland.

 Valenti’s can provide specialist training at their Academy based in Cornwall the home of Ice Cream making and also on-site training programmes at the clients own premises.

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Range of flavoured ice creams

Ice cream and gelato manufacturers produce products with a range of favours. There are often significant variations in sweetness and hardness between flavours. This article provides an explanation of sweetness, how it is measured and how it can be controlled.

Relative sweetness and the Potere Dolcificante method are discussed and calculations are used to explain the differences. The limitations and disadvantages of using numerical values of sweetness are explained. Since sweetness and hardness are closely related the reader is also referred to the article on controlling hardness or resistance to scooping.

Living microorganisms are widely used for several therapeutic purposes and their beneficial effects as biotherapeutic agents are well known. While certain strains of lactic acid bacteria and bifidobacteria are used as probiotics in pharmaceutical preparations, feed additives and so-called functional foods yeasts also possess some medicinal efficiency.

The use of high temperature short time heat treatment (HTST) of milk (72°C for 15 seconds) to destroy pathogenic bacteria, reduce the number of spoilage organisms and increase shelf life is well established (Juffs and Deeth, 2007).

The history of pasteurization (pasteurisation is also valid) is fascinating and is notable for its public health success and for the insights of many scientists and engineers. Prior to the introduction of pasteurization, consumption of raw cow milk was a major source of infection by bacteria causing tuberculosis. Pasteurization has eliminated heat-treated-milk as a source of infection. Regrettably raw milk and raw milk products remain a major source of new cases of bovine tuberculosis.

This article calculates the effect of HTST treatment on the number of log reductions of major milk pathogens and discusses the temperature milk should be pasteurized if Mycobacterium avium subsp. paratuberculosis (MAP) was designated as a human

pathogen. The log reductions refer to log10 or decimal (10 fold) reductions in the concentration of viable bacteria. The article does not discuss the effects of heat on the functional properties or the nutritive quality of milk. An updated refereed version of this paper has been published (Mullan, 2019) and is available free in a read only format at https://rdcu.be/bGnES .

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Many students have problems in understanding the mathematics describing the destruction of microorganisms by heat. Log reductions of pathogens and equivalent time-temperature treatments along with the associated lethalities account for a large part of the harder to understand topics. The quiz below is a simple test of of some of the basic concepts. Note Z value is not dealt with in this quiz. If there is sufficient interest I will provide the answers.

Heat Processing Quiz

Any agent which inhibits starter activity or kills a strain with an essential function e.g. aroma production can have serious detrimental effects on the quality of the product being produced. Infection with bacteriophage is the major single cause of fermentation failure or of problems in fermentation processes utilising lactic acid bacteria.

The major functions of starters in dairy fermentations are shown in table 1. See the section on starters also.

This article discusses the major functions of starters in dairy fermentations. Recent research on the relative importance of the antimicrobial agents produced by starters is included. The importance of undissociated lactic acid (HLac) is discussed with regard to the inhibition of the growth of Listeria monocyotgenes, Escherichia coli and Staphylococcus aureus.

The author recommends that regulators should require manufacturers of raw milk cheeses to meet a minimum value for HLac that must be achieved prior to product release for retail sale.

Characteristics - Toma del Lait brusc is a typical Piedmont cheese with a cylindrical appearance and flat surfaces. The cylindrical shape has a diameter of 25-35 cm, an edge of 12-18 cm and a weight of 4-8 kg. Ripening lasts at least 60 days but frequently is longer e.g. 180 days. The crust is wrinkled, hard, and reddish-grey with yellow and white highlights. The dough is ivory-white or dark-yellow with small holes. Typical greenish-blue veins due to mould growth may be present in ripened cheese. The texture is consistent, compact and very friable. In young cheeses, the odour is fine and delicate, becoming very strong and persistent in aged products. The taste is mainly sweet and fine but savoury, salty and intense in aged products.

Production area - The cheese is produced in the high pastures throughout Turin province.

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