Course:FNH200/Projects/2020/Tofu and its Varieties

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Overview

Originating in China, Tofu is made by pressing coagulating soy milk into curds, then pressing the resulting solid blocks (comparable to cheese making). There are two main categories of tofu, regular and silken, which have a variety of textures; soft, medium, firm and extra firm. In this wiki page, Tofu will be analyzed by its ingredients, processing methods, packaging, regulations, and varieties. This page focuses specifically on Sunrise extra firm tofu, although in section 6, all of the varieties are briefly summarized to add to the overall discussion of the food and its variants.[1]

Ingredients

The three main ingredients of tofu are water, soybeans, and a coagulant (or coagulants)[1]. Water makes up the majority of the content of tofu, with soybeans providing protein and coagulants are used to hold it together[2]. Calcium sulphate is the preferred coagulant as it doesn’t mask the flavour of the soybeans, allowing tofu to maintain it’s flavour. Magnesium chloride is another coagulant that is sometimes used either alone, or with calcium sulphate to give tofu its smooth texture[3].

Processing

Production of tofu requires the production of soy beans, their collection and processing into soy milk, furthermore processing the soy milk into curds (through coagulation) and finally pressing the curds into blocks which form the final consumer product.

Creation of soy milk and its preparation

Soy beans are harvested and processed in order to create soy milk. This involves grinding the soy beans before soaking them for approximately 10 hours in low temperatures (22 degrees C), then increasing the temperature (32 degrees C) for an additional 6 hours. [2] The resulting mixture is then filtered to remove the solids and produce soy milk before coagulation takes place.

Image depicting the filtration of soy milk. Courtesy of The Institute of Food Technologies, 2020.

Soy milk coagulation

Coagulation allows for the soy milk product to be further refined and solidify the oil and proteins, forming the "milk curds" resembling the cheese production process. This step of the tofu processing is the most important.[2] Three different coagulants are used in tofu processing; acid, salt and enzyme coagulants.[2] These coagulants can be used individually or in combination and depending on the coagulant results in a variety of tofu products.

Acid Coagulation

The most commonly used acid in the coagulation process for tofu is glucono delta-lactone (GDL).[2] This acid is used specifically in the production of silken tofu (or soft tofus) because it allows for the soy curds to rapidly coagulate inside a container resulting in a soft and moist texture with the absence of air bubbles.[2]

Salt Coagulation

Calcium sulfate or magnesium chloride combined with calcium chloride are the two most commonly used salt coagulants.[2] Calcium sulfate is the most commonly used salt coagulant for tofu because it does not change the taste or alter the flavour of the soy beans in the tofu. Magnesium chloride and calcium chloride salts tend to be more soluble than calcium sulfate, resulting in smoother-textured tofu like silken and soft tofu.[2]

Enzyme Coagulation

Enzymes are also used as coagulants, such as papain and proteases. This form of coagulation allows for the the amino acids in the proteins to catalyze, forming the medium to extra firm textured tofu for consumers.[2]

Pressing tofu: the curds to form tofu blocks

Image depicting tofu being pressed in cheese cloth. Courtesy of The Institute of Food Technologies. 2020.

For tofu that is medium firm to extra firm, the soy curds are taken and further pressed to reduce the water content in hydraulic presses. The soy curds are pressed in the hydraulic presses, encased in cheese cloth to expel whey permeate. The degree to which the tofu is pressed depends on which type of tofu is being processed, more firm tofu is pressed more in order to expel as much of the whey permeate as required to ensure the texture of the desired product. Tofu is often pasteurized after pressing to extend the shelf life of the product.[2]

Packaging

Tofu can also be processed using ultra high temperature (UHT) technology and aseptically packaged in order to increase storage life and improve taste and texture.[2] This process consists of the soy milk being aseptically packaged through ultra-high temperature processing [4]. The aseptic soy milk is packaged through adding a coagulant to the soy milk and incubated to form the aseptically packaged tofu [4].

Packaging of individual packs of tofu involves a pair of grasp plates, a horizontal drive device, and a driving pair of grasp plates which convey the tofu blocks above the packaging. [5]

In order for tofu to be packaged and sold in retail stores, the tofu apparatus cuts blocks of tofu into predetermined sizes.[5] Once the block of tofu is cut, the cubes are grasped with a pair of grasp plates which are then moved to be positioned above the packaging packs.[5] This process occurs at the packaging pack conveyance apparatus.[5] The block of tofu is then dropped into the packaging and held in the block state by the grasp plates.[5] The packaging process of tofu is completed through various mechanical conveyance machines.[5] Due to the texture of tofu, the processing and packaging of tofu has a specific production of a maximum capacity of 2000 to 3000 blocks of tofu per hour. [5]

Through the packaging process of tofu, tofu has the shelf life of 6 to 12 months [4]. However, the optimal shelf life for aseptically packaged tofu is between 8 and 10 months [4].

Regulations

There are a number of regulations that the manufacturer must ensure their product will pass before a product is certified for sale in Canada. All varieties of tofu must comply with both the food labelling requirements as well as processing requirements that detail sanitation.[6]

Sunrise’s tofu products, soft, firm, and extra-firm, conform to all four sections (3, 4, 5, 7) of The Food and Drugs Act. In short, section 3 regulates any claims to treat a set of (schedule A) diseases and disorders. Section 5 enforces honesty and integrity in labelling. Whereas section 4 and 7 ensures that the ingredients used in the product (s.4) and the manufacturing processes (s.7) are sanitary and safe.

Labelling

The labelling of Sunrise’s tofu products, both in-store and online, conform to the requirements outlined on Canada’s official website. Consumers may discover that the product label displayed on Sunrise’s website is not bilingual (only contains English). However, there is an option to display the entire website, and the entire label, in French. Note that the country of origin, % alcohol, and % milk are not required for labelling on tofu products in Canada. In addition, no intents of nutrient content claims, diet-related health claims or disease reduction claims are present on the packaging or label.[7]

In all types of tofu (soft, firm, extra-firm) a maximum of 0.3% of magnesium chloride is allowed as a functional food additive for purposes of coagulation (CRC, c. 870, Div.15, M.1). No information is provided on Sunrise’s website nor their packaging. However, the display of such detailed information is not mandatory under Canadian law.[6] Additionally, irradiated tofu (rare to find) is not permitted for sale in Canada.

Varieties of Tofu

There are two main categories of tofu; Silken tofu and regular tofu, which can further help describe the varieties of tofu which exist. Common varieties of regular tofu are soft, medium, firm, and extra firm. The main difference between these firmnesses is the water content, as the firmer the tofu the more water that is pressed out before packaging[8]. Therefore, softer tofu will have less protein content, while firmer tofu will have more. Soft tofu is often used in desserts or as an egg alternative in baking due to its smooth creamy texture. Medium tofu is often used in dishes like miso soup. Finally, firm and extra firm tofu is often used as a meat alternative when spices and sauces are added to it.

Silken Tofu

Silken tofu is a separate category of tofu from regular tofu due to its' high water content which creates a creamy texture often compared to a custard. Silken is often seen in baking as it acts as a replacement to other animal products such as cream, eggs or various cheeses. Silken tofu can be further categorized through it's texture (soft, medium and firm) although it is much less discernible between these variants than regular tofu.

Regular Tofu

Regular tofu is categorized by its spongey texture and has noticeably less water content than silken tofu.

Soft

Soft Tofu has high water content and therefore a more liquid-like texture. Due to this unique texture it can be used as a substitute for silken tofu and can be applied in many of the same recipes. Although both soft and silken are similar in texture, silken tofu is still smoother and creamier.

Medium

Medium tofu has been pressed more than soft tofu, therefore having less liquid. This allows it to absorb more sauces or broth creating a richer taste within the tofu. Because of its texture and absorbent properties it is often used in soups and saucy dishes.

Firm

Firm tofu has been pressed even longer to remove more of the water content from the product. This allows the tofu to hold its shape better than soft or medium tofu. Additionally, it becomes more absorbent than medium tofu so it can provide even stronger flavours. These properties are ideal as a meat substitute in dishes such as sliced chicken or beef, or can be crumbled as a substitute for scrambled eggs.

Extra Firm

Extra Firm tofu has been pressed the longest, therefore has the least amount of water content. Because of its lower water content it is a great option for pan-frying as it holds its shape well and will not leak water into the oil used to fry it.

Potential Exam Questions

  1. Are irradiated tofu products allowed for sale in Canada? True/false. (False)
  2. Which type of tofu has the highest protein content per weight? a) soft b)medium c)firm d)all have the same protein content
  3. What are the types of coagulants used in tofu production? a) salt coagulant b) enzyme coagulant c) acid coagulant d) a+b e) a+c f) a, b, c
  4. What type of processing does tofu go through for packaging? a) aseptic packaging b) flexible packaging c) carton packaging

Sources

  1. ↑ 1.0 1.1 Sunrise Soya Foods (2020). "Sunrise Extra Firm Tofu".
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 McHugh, Tara (February 1, 2016). "How is Tofu Processed?".
  3. ↑ Centoni, Danielle (January 10, 2019). "When buying tofu, be sure to read the label first".
  4. ↑ 4.0 4.1 4.2 4.3 Alan, L. J. L., Ho, L. J., & Kong, T. Y., 1999. U.S. Patent No. 5,863,590. Washington, DC: U.S Patent and Trademark Office.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 Takai (May 31, 2016). "Packaging Device for Tofu".
  6. ↑ 6.0 6.1 Government of Canada, Canadian Food Inspection Agency (2020). "Adulteration of Food".
  7. ↑ Government of Canada, Canadian Food Inspection Agency (2020). "Food Labelling for Industry".
  8. ↑ Han, Emily (March 28, 2014). "What's the Difference Between All the Types of Tofu?". Kitchn.
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