I have a cheddar and gouda in my cave that are bitter. In one I used MA11, and too much rennet. In the other I used MM100 and the correct amount of starter and rennet. In the interest of preventing bitterness in the first place and resolving it when it does happen, I've been nosing around for information. I came across the following which does provide some light on the situation. I think I will be adding LH to all my cheeses!
"There are several reasons why bitterness may develop in cheese. With a few exceptions bitterness is generally associated with proteolysis.
Protein breakdown is critical to texture and flavour development in many cheeses. However, the process can generate hydrophobic peptides that if present at a sufficiently high concentrations can give rise to bitterness. Because these peptides are soluble in fat bitterness tends to be more of a problem in reduced fat varieties.
There has been considerable research into the causes of bitterness in Cheddar and Gouda cheeses and there is now a good understanding of 1) the mechanisms responsible for bitterness and 2) how to prevent or control bitterness.
The following is an attempt at summarising and simplifying how bitterness is produced. The coagulant, rennet, hydrolyses casein to produce polypeptides. These are then degraded to peptides and amino acids by peptidases associated with the membrane proteins of the starter cultures, lactococci, used in the cheese making process.
Bitterness will only develop if a number of conditions are met namely, the cheese must be of relatively low salt in moisture (S/M) content, bitterness is rare in Cheddar cheese of greater than 5% S/M; there must also be a high population of starter lactococci and these lactococci must have a particular type of peptidase that produces hydrophobic peptides. Additionally the presence of certain non-starter lactic acid bacteria, NSLAB, can prevent bitterness due to their ability to degrade the hydrophobic peptides produced by lactococci. These can be naturally present in some cheese plants. When you take these factors into consideration, along with the natural variations that can occur in fat content in cheese readers will start to gain an appreciation of what is involved in the development of bitterness in cheese.
Control of bitterness starts with adjusting the cheese manufacturing conditions to ensure that salt levels are correct for the variety being manufactured, ensuring that ‘non-bitter producing starters’ are used and adjusting manufacturing to control starter populations. Many cheese makers also use starter adjuncts. The most effective for debittering contain strains of Lactobacillus helveticus that produce peptidases active against the bitter peptides. Note only some strains of Lactobacillus helveticus have a proven antibittering effect.
Some culture suppliers will have tested their starters for bitter peptide production, there are several test methods available, and may have strains of Lactobacillus helveticus that have been proven to be effective in cheese trials. Incidentally there are a number of well characterised Lactococcus lactis subsp cremoris strains that rarely produce bitter cheese; these are available commercially. Your culture supplier should therefore be part of your problem solving team!
Though not well publicised, for commercial reasons, blends of thermophilic starters along with lactococci are being increasing used in both Cheddar and Gouda manufacture. There is some anecdotal information suggesting that use of these starter blends results in less bitterness problems."
