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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.

Mr George DoranGeorge 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

Contact

Model probability of detecting a pathogen in food using the Poisson Distribution.

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.

Introduction

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.

Starter bacteria in yoghurt

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

This section gives an overview of developments in this area including opportunities for novel functional foods. The rare involvement of lactobacilli and starter bacteria in human infections is mentioned and a summary of traditional microbiological approaches to the enumeration of probiotic bacteria is included.

The last major update to this article was published in February 2008, since then there have been a number of significant developments. These include the failure of major European dairy companies to obtain ratification by the EFSA of health claims for probiotic products, the deaths of patients on a probiotic trial in the Netherlands, evidence that perhaps some bacteria designated as probiotics may have the potential to aggravate allergies in neonates. Additionally one major researcher has questioned where any strain of Lb. acidophilus has been shown to meet the criteria for a probiotic! However, there has been other more positive research indicating that particular strains of bacteria, in particular lactic acid bacteria, do have the potential to enhance immunity, reduce allergy, and to alleviate distant site infection. This work has very clearly shown that dairy companies and others have a responsibility to use only well characterised strains that have been shown to have probiotic effects in medical trials. Interesting Reid (2007) has stated "a potential major problem for probiotics is the misuse of the term. This can arise from products being poorly manufactured, or being referred to as probiotic without any relevant documentation. The net effect, deleterious to the overall field of probiotics, might be that such products are found to be ineffective, when in fact they were not even probiotic in the first place." Interestingly there is now a growing consensus that there is a world-wide, critical shortage of well qualified food scientists and technologists in commercial food manufacturing. These developments will be taken into consideration in the next major update to this article.

The next major update will summarise recent work on the gut flora and how this complex flora is thought to influence health. Recent research suggests that the gut flora can influence mood e.g. depression and its modification may have the potential to influence body mass and obesity. The main evidence for the latter has come from animal studies and anecdotal accounts of the consequences of faecal microbiota transplants also known as a stool transplants. This work suggests very significant potential for new generation probiotic products.

Gut problems e.g. dyspepsia (indigestion) are common and the Internet has many sites advocating probiotics for treating a range of symptoms. This article, while it may be of interest to the general public, does not promote the medical use of commercial yoghurt products, none of which currently have EFSA endorsements as probiotics in Europe, to treat gastrointestinal problems. I am aware of people experiencing dyspepsia who treated their symptoms with commercial yoghurt products and subsequently found that they had a range of physical medical conditions ranging from ulcers, hiatus hernia to more malign conditions that required surgical intervention. I am positive about the potential health benefits of probiotics but urge readers with health issues to discuss their problems with physicians, who certainly in Europe, take care not to do harm before self treating with yoghurt type products.

Growth and acid production by starter cultures may be inhibited by bacterial viruses, bacteriophages, or added substances including antibiotics, sterilant and detergent residues, or  free fatty acids produced by or as a result of the growth of microorganisms, and natural often called indigenous antimicrobial proteins.

Milk should not contain antibiotic residues.  Milk production in the UK is regulated by the Dairy Products (Hygiene) Regulations 1995.  These regulations include the standards for raw milk.  Prior to 1990 milk was deemed to be contaminated if an antibiotic concentration of > 0.01 international units (iu) /ml was present, the standard has now been increased to 0.006 iu/ml.  Manufacturers buying milk from producers impose stringent financial penalties on farmers producing contaminated milk and have procedures to exclude this from the food chain.  Despite legislation and financial penalties, there is evidence to suggest that residues occasionally still cause problems.  In a survey of the causes of slow acid production by cheese starters in the UK (Boyle and Mullan, 2000, unpublished results) found that, some 28 % of respondents attributed slow acid problems to antibiotics. 

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.

Blown cheeseThis 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

Case study

This section contains the results of an actual investigation of an apparent reduction in the yield of Cheddar cheese made in October of year X compared with the same month a year previously. 

Five  vats of cheese were manufactured in the factory and the milk and cheese were subject to chemical analysis. The samples were analysed at a reputable laboratory.

The following data (Table 1) for milk, cheese and yield (adjusted per 100 kg of milk) were obtained.

A Northern Ireland perspective

Similar to all farmers throughout Europe, Northern Ireland dairy farmers find themselves in a new era in agriculture. This has been fashioned by EU policy seeking both environmental and rural sustainability. Future farm profitability will be dictated by the market place.

Free market economics always seek to maximise returns against the most limiting resource. Therefore milk producers must make decisions on the system and scale of enterprise mix, taking into account what is limiting efficient production on their own farm.

There are two routes to remain competitive, either produce milk cheaper than others or target quality milk for high value markets. For Northern Ireland the first road is not an option due to lack of industry scale. Therefore quality milk must be delivered competitively to the processor who meets customer expectations with profits shared equitably along the supply chain.

By ensuring they are adhering to ethical production systems, farmers allow consumers to enjoy milk or dairy products and the clean and diverse countryside in which it was produced. This policy is essential and can secure an improved and sustainable return from the market place - but there must be trust and true integration within the supply chain.

Following the introduction of milk quotas in 1984 a limit was placed on potential expansion on the majority of dairy farms. However due to a combination of accessibility, profitability and farmer ability the milk quota held on Northern farms has increased by almost 40 per cent over the past 12 years. This, combined to the additional allocation of 1.5 % of milk quota to the UK as part of the Mid Term Review, has ensured a plentiful supply of quota. Current low purchase and lease prices mean that quotas are unlikely to restrict future expansion.

This section contains summary information on modified atmosphere packaging. More comprehensive treatment is available in a chapter on modified atmosphere packaging, written by the author and Derek McDowell, in the book Food Packaging Technology. Derek McDowell is Head of Supply and Packaging at Loughry Campus and is a packaging specialist.

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.

Introduction

There is a wide range of alcoholic beverages obtained by the fermentation of sweet liquids (vegetable juices, honey, milk) but the most important are wine, beer and cider. Wine is an alcoholic beverage produced by the fermentation of the juice of fruits, usually grapes, although other fruits such as plum, banana, elderberry or blackcurrant may also be fermented and used to obtain products named "wine". In this short article the word "wine" refers to the product obtained from grapes. This product is probably the most ancient fermented beverage and was mentioned in the Bible and in other documents from Asiatic peoples. Exactly where wine was first made is still unclear. It could have been anywhere in the vast region, stretching from Portugal to Central Asia, where wild grapes grow. However, the first large-scale production of Commercial grape production
wine must have been where grapes were first domesticated, Southern Caucasus and the Near East. In Egypt, wine played an important role in ancient ceremonies and winemaking scenes are represented on tomb walls. Outside Egypt much of the ancient Middle Eastern peoples preferred beer as a daily drink rather than wine. However, wine was well-know especially near the Mediterranean coast and was used in the rituals of the Jewish people. The Greeks introduced wine to Europe and spread the art of grape-growing and winemaking across the Mediterranean hence modern wine culture probably  derives from the ancient Greeks. Wine

was known to both the Minoan and Mycenaean cultures and referred to as "Juice of the Gods". Dionysus was the Greek god of wine and wine was frequently mentioned in Homer's and Aesop's operas. Many of the grapes grown in Greece are grown nowhere else and are similar or identical to varieties grown in ancient times. Greek wine was widely known and exported throughout the Mediterranean basin, and amphorae for Greek wines have been found extensively in this area.

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?

In mathematics, science and engineering students frequent have to work with very small, e.g. 0.000005, and very large, e.g. 3200000000 numbers. For example, students in microbiology are often required to write the number of colony forming units (CFU)/mL or gram in scientific notation. To avoid dealing with these large and small numbers mathematicians, scientists and engineers have developed a particular way of expressing numbers; this is called 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.

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