Samples: lysate of dry yeast #1(Allinson)
Food dehydrator, 68oC, 24 hours
Observation: darken, stick to container
-->Dissolve in water and dry using freeze dryer, ~30 hours
https://www.yeastextract.info/about-yeast-extract/how-yeast-extract-is-produced/
by European Association for Specialty Yeast Products (EURaSYP)
The bitterness of yeast extract primarily arises from various compounds produced during the breakdown of yeast cells. These include:
Nucleotides and Nucleosides: When yeast cells are broken down, nucleotides such as guanosine monophosphate (GMP) and inosine monophosphate (IMP), and nucleosides like guanosine and inosine, are released. These compounds have inherent bitter tastes.
Amino Acids: Certain amino acids, particularly hydrophobic ones like leucine, isoleucine, and phenylalanine, contribute to the bitter taste in yeast extract. The concentration and presence of these amino acids can significantly influence the overall bitterness.
Peptides: During the breakdown of proteins in yeast cells, peptides are formed. Some of these peptides, especially those containing hydrophobic amino acids, have a bitter taste.
Maillard Reaction Products: The Maillard reaction, which occurs during the heating process of yeast extract production, can also produce bitter compounds. This reaction typically involves reducing sugars and amino acids that form complex molecules contributing to flavor and, sometimes, bitterness.
Other Organic Compounds: Other organic compounds produced during yeast autolysis, such as certain esters and alcohols, might also contribute to the bitterness, although their impact is usually less pronounced compared to nucleotides and amino acids.
Understanding these components helps in adjusting the production processes of yeast extract to manage and potentially reduce its bitterness, making it more palatable for various applications in food products.
User
Suggest autolysis conditions that would minimize bitterness of the yeast extract
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Minimizing the bitterness of yeast extract through optimal autolysis conditions involves careful control of several parameters during the yeast breakdown process. Here are some suggestions for adjusting autolysis conditions to reduce bitterness:
1. Temperature Control
Optimal Temperature: Conducting autolysis at a lower temperature can help minimize the activity of enzymes that produce bitter compounds. Generally, temperatures around 45-50°C are recommended. Higher temperatures can accelerate the breakdown process but may lead to increased bitterness due to enhanced enzymatic activity.
2. pH Adjustment
Optimal pH: Maintaining a slightly acidic to neutral pH during autolysis can help control the enzymatic activity that leads to bitterness. A pH range of 5.5 to 6.5 is often effective. Adjusting the pH with food-grade acids such as citric acid can help manage enzymatic reactions during autolysis.
3. Enzyme Control
Enzyme Inhibitors: Using specific enzyme inhibitors can prevent the formation of bitter peptides. For instance, protease inhibitors can be added to the autolysis mixture to reduce the breakdown of proteins into bitter peptides.
Selective Enzyme Use: Adding selected exogenous enzymes that do not result in bitter byproducts can help control the breakdown process more precisely, allowing for the selective degradation of non-bitter compounds.
4. Duration of Autolysis
Controlled Duration: Shortening the duration of the autolysis process can prevent excessive breakdown of proteins into bitter peptides. A shorter autolysis period should be balanced to ensure sufficient breakdown of yeast cells to extract useful components without generating excessive bitterness.
5. Substrate Preparation
Yeast Strain and Health: Starting with a yeast strain that is less prone to producing bitter compounds during breakdown can be beneficial. Additionally, the health and condition of yeast cells prior to autolysis (such as using freshly cultured yeast versus spent brewery yeast) can influence the flavor outcomes.
Pre-treatment: Pre-treating yeast cells with heat or chemicals to selectively inactivate certain enzymes before starting autolysis can help in reducing bitterness.
6. Post-Autolysis Treatment
Filtration and Purification: After autolysis, further refining the yeast extract through techniques like ultrafiltration can help remove smaller bitter peptides and other bitter compounds.
Adsorption Techniques: Using adsorbents such as activated charcoal during or after autolysis can help in binding and removing bitter compounds effectively.
7. Monitoring and Testing
Regular Sampling and Sensory Evaluation: Throughout the autolysis process, regularly sample the product and conduct sensory evaluations to monitor the development of bitterness. This will help in determining the optimal stopping point and adjusting conditions if necessary.
By carefully controlling these factors, the production of yeast extract with reduced bitterness is achievable, enhancing its palatability and widening its potential applications in food products.
Equipment:
References:
Primer ordered:
delta2 5'-GTGGATTTTTATTCCAACA-3'
delta12 5′-TCAACAATGGAATCCCAAC-3′
delta21 5′-CATCTTAACACCGTATATGA-3′
We should try whole genome sequencing first and if not satisfactory, we may try AP-PCR-nanopore sequencing
Phase 1--December 2023 to May 2024
1A. December 2023 to 12 January 2024
