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It can be difficult for entrepreneurs to obtain starter cultures for trials. This article provides contact details of some culture suppliers.
The isolation of lactic acid bacteria from raw and pasteurized milk is discussed.
George Doran graduated with a 2:1 honours degree in Food Technology from the College of Agriculture and Food Technology in Northern Ireland in 2015. Mr Doran's final year research project was entitled "An Investigation of Biofouling in Two Mozzarella Cheese Manufacturing Plants".
George completed his food technology internship at Cottage Catering, Dromore, N. Ireland and gained experience in Quality Assurance, New Product Development and Production.
George has achieved several academic distinctions and has extensive work experience gained through part-time work in the security and retail sectors.
Included amongst George's achievements are:
- Member of the winning team for the Chesapeake Product Development Challenge in December 2013
- Represented IFST Ecothrophelia in London at Food Matters Live in November 2014
Despite the global use of HACCP systems and a legal requirement for the use of HACCP in many jurisdictions' food poisoning remains an endemic problem and large numbers of people continue to be hospitalised, die and as a result companies either face substantial legal costs and / or in many cases are forced to cease trading.
While the use of HACCP systems significantly reduces the need for microbiological end point testing of foods, sampling schemes and microbial analysis have important roles in system validation and quality assurance.
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.
Refrigerated storage of raw milk is used to limit the growth of microorganisms in milk prior to processing. It has been known for some time that the quality and yield of cheese produced from bulk cooled milk may be adversely affected by this procedure (Weatherup et al., 1988; Weatherup and Mullan, 1993). The reduced yield and poor quality may be due to physico-chemical changes in the state of several milk components e.g. dissociation of micellar casein, mainly Κ-casein into a soluble phase, occurs during the first 48 h of storage at 4° and 7° C. This results in losses of fat and curd fines, weaker curd, more moist curd and a slightly lower yield. Partial reversal of dissociation occurs after further storage. The reduced yield and quality can also be due to the activity of proteases and lipases produced by psychrotrophic bacteria.
Despite the work that has been done over many years milk is still being stored for extended periods (1-3+ days on some farms) and cheesemakers are again (2019) reporting problems with the yield and quality of cheese produced using this milk.
Following several queries related to milk quality and cheese manufacture I am providing a report written by Wilf Weatherup and me some years ago that may be helpful.
A simple calculator has been provided using the total viable count of milk prior to pasteurisation and a regression equation to predict the grade value of Cheddar cheese.
These products are similar but can differ markedly from each other e.g. traditional Italian gelato is significantly different than mass produced, commercial ice cream in Ireland, GB and the US. However, high end artisan produced ice cream made using batch processes can be similar.
Traditional Italian gelato generally contains around 8% milk fat, has a low overrun usually (< 18%) and is served from a cabinet held at around -11°-12°C. The physical properties are usually different. Because of the higher temperature of storage and the concentration of sugars, gelato is served and eaten in a highly viscous, semi-frozen state. The texture is often described as being smooth and dense. Fruit-flavoured gelato is also characterised by intense natural fruit flavours and is quite sweet although natural fruit-like sour notes may be evident.
Traditional gelato is produced using batch production methods and is generally consumed within a short time from manufacture.
While there are differences between these products the scientific principles that underpin their production are similar and in the articles that follow, I will often use the terms ice cream and gelato interchangeably. Please accept that I do not equate the quality and eating experience of traditional Italian gelato with mass-produced commercial ice cream.
This article discusses the origins and role of starters in dairy fermentations, the ecology of starter bacteria, the classification of starter bacteria, the types of starter culture used and concludes with some observations on artisanal cultures. The author has provided a broader perspective on the use of starter cultures in food fermentations in the Encyclopedia of Food Microbiology. The chapter can be downloaded from Elsevier Ltd. This article should be read in conjunction with the article discussing the major functions of starters in dairy fermentations and the relative importance and effectiveness of the antimicrobial agents produced by starters.
- Written by Michael Mullan
Milk provides the newborn (neonate) with nutrients and an array of antimicrobial factors. These are believed to help protect neonates from infection until their own immune system has developed.This section of the dairy science website reviews the properties and potential nutritional and industrial significance of the major antimicrobial systems of milk, with particular reference to the lactoperoxidase system.
- Discovery of bacteriophages for lactococci
- Bacteriophages for lactic acid bacteria
- Bacteriophage lysins
- Morphology and classification of bacteriophages
- Enumeration of bacteriophages
- Isolation and purification of bacteriophages
- Preparation and storage of high titre lactococcal lysates
- Industrial significance of lactococcal bacteriophages
- Bacteriophage control in cheese manufacture
- Written by WMA Mullan
This article is based on a paper, summarising many years of research, published in the International Journal of Dairy Technology. The paper “Mullan, W.M.A. (2000). Causes and control of early gas production in Cheddar cheese. International Journal of Dairy Technology. 53, 63-68” can be downloaded from the Wiley Interscience website. Since then the author has continued to work in this area and in particular with major Cheddar cheese manufacturers in the US. This newer work is not discussed in this article.
Currently many cheesemaking plants are experiencing open texture problems including unwanted slits/cracks in cheese due to unwanted gas production. Some of these problems are caused by the growth of thermophilic / thermoduric lactic acid bacteria in biofilms in pasteurizers. Normal caustic cleaning will not eliminate these and enhanced cleaning and sanitation procedures are required. While this contribution may not specifically deal with these problems this area can be discussed further in the forums.
Characteristics - Saras del Fèn is a ripened ricotta cheese produced from a mixture of goats’, ewes’ and cows’ milk. The cheese is egg-shaped with a weight of 500-1500 g. Ripening lasts at least 20 days but can be longer than 1 year. It is wrapped during ripening, following local tradition, in hay characteristic of local alpine high pastures. There is no crust in the fresh product but ripened products have an elastic crust that is wrinkled, soft, grey with yellow and white highlights. The dough is ivory or yellowish without holes. The texture is soft, elastic and sticky. The odour is fine and delicate in fresh products but strong and persistent in aged products. The taste is mainly sweet and fine but savoury, salty and hot in aged products
- Written by Ian McCluggage
A Northern Ireland perspective
- Written by Giuseppe Zeppa
Summary in Italian
Nel Mondo vi è un elevato numero di bevande ottenute dalla fermentazione alcolica di liquidi zuccherini quali succhi vegetali, miele, latte ecc., ma le più importanti per diffusione e quantità prodotte sono senza dubbio il vino, la birra ed il sidro. Lo scopo di questo breve articolo è quello di riassumere la storia e la tecnologia produttiva di una di queste bevande, ottenuta dalla fermentazione dell'uva, il vino. Conosciuto già dagli Egizi, il vino ha accompagnato con alterne vicende l'uomo in tutta la sua storia, divenendo nella cultura cristiana simbolo, con il pane, dell'unione stessa con Dio. Prodotto in quasi tutto il modo anche in virtù dell'ampio areale di coltivazione dell'uva, il vino si presenta al consumatore in varie tipologie (rosso, bianco, rosato, dolce, secco, spumante ecc.) volte ad interpretare al meglio le caratteristiche della materia prima ed a soddisfare le esigenze del consumatore stesso. Alla base di queste diverse tipologie di prodotti vi sono altrettante tecnologie venutesi a definire nei secoli ed i cui aspetti fondamentali vengono descritti in queste pagine con la speranza di stimolare il lettore ad approfondirne lo studio sui numerosi testi specialistici attualmente disponibili.
This article explains how to convert numbers to scientific notation and back again to standard format. It also contains two calculators that will enable calculations to be checked and that provide feedback on common data entry input errors.
How do you convert numbers to scientific notation?
This section is aimed at product development technologists who need to know how to design ice cream or gelato mixes. It should also be of interest to small scale ice cream or gelato manufacturers who want to replace commercial ice cream mixes (bought in mixes) or additives by sourcing their own ingredients and additives. The article provides a basic introduction to the scientific principles involved in producing ice cream or gelato recipes using key product components e.g. fat.