آب‌نمک

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آب‌نمک.

به محلول آب و نمک طعام که کاربردهای مختلفی دارد و ازجمله در نگهداری مواد غذایی به‌کار می‌رود آب‌نمک می‌گویند. از محلول آب نمک به عنوان تسکین‌دهنده گلودرد، میکروب‌کش و دهان‌شویه نیز استفاده می‌شود.

معمولاً زمانی که درصد نمک موجود بالاتر از ۵ درصد باشد به آن آب‌نمک می‌گویند. گاه نیز، بسته به نوع تحقیقات، اگر شوری در آب بین ۳٫۵ تا حدود ۲۶ درصد باشد به آن آب‌نمک گفته می‌شود. درصد اولی (۳٫۵ درصد) میزان نمک موجود در آب دریا است و درصد دومی درصد معمول در آب اشباع‌شده با نمک است.

کاربرد در مواد غذایی[ویرایش]

از آب‌نمک برای نگهداری سبزیجات، میوه، ماهی، و گوشت استفاده می‌شود. در علوم و فناوری غذا به آب‌نمک مورد استفاده برای عمل‌آوری مواد غذایی، مانند فراورده‌های گوشتی آب‌نمک عمل‌آوری curing brine گفته می‌شود. به گوشتی که با آب‌نمک عمل‌آوری شده باشد «گوشت آب‌نمکی» می‌گویند. آب‌نمک برای خواباندن خیارشور و غیره نیز به کار می‌رود. مادهٔ غذایی غیرگوشتی که برای حفظ یا ایجاد طعم در آب‌نمک نگهداری می‌شود به طور کل شور نامیده می‌شود.

عمل نگهداری مواد غذایی در آب‌نمک برای حفظ آنها یا ایجاد طعم شورانداختن brining و افزودن آب شیرین به مادهٔ شورانداخته برای حذف نمک‌های آن شوری‌زدایی debrining نام دارد.

برای نگهداری مواد غذایی مانند گوشت و ماهی و سبزیجات روش دیگری نیز استفاده می‌شود که در آن از نمک یا سنگ نمک استفاده می‌شود و به این روش نمک‌سود کردن dry brining می‌گویند.

اثر درمانی[ویرایش]

استفاده از آب و نمک برای تمیز کردن بینی یکی از روش‌های بسیار قدیمی است که علاوه بر تمیز کردن سوراخ‌ها از ذرات کثیف و بیماری‌زا، پوشش مخاطی بینی را هم تقویت می‌کند.[۱]

با شست‌وشوی بینی با آب‌نمک می‌توان اثربخشی بالایی به همراه درمان‌های لازم در درمان سینوزیت مزمن مشاهده کرد. محققان توصیه می‌کنند که بیماران سینوزیت مزمن از این روش برای کاهش یا از بین بردن علائم خویش استفاده کنند.[۱]

شست‌وشوی روزانه گلو با آب نمک مهمترین و کارآمدترین شیوه پیشگیری از ابتلا به بیماری‌های حلق است. ضمن اینکه شست‌وشوی روزانه بینی از بیماری‌های زیر جلوگیری می‌کند: سرماخوردگی، سرفه، التهاب چشم، بینی و گلو، التهاب سینوس‌های پیشانی، سردرد، خستگی، بیخوابی و در سرماخوردگی سر، مجاری تنفسی را باز می‌کند.[۱]

چنانچه افراد عادت به استفاده از محلول آب و نمک بعد از مسواک و نخ دندان شوند افزون بر صرفه‌جویی اقتصادی از بروز بیماری‌های دهان و دندان پیشگیری می‌کنند. استفاده از آب و نمک علاوه بر ضدعفونی محیط دهان، میزان ابتلا به پوسیدگی دندان‌ها را هم کاهش می‌دهد.[۱]

برای مؤثر بود اثر آب و نمک می‌بایست درصد نمک (نمک خوراکی و در بهترین حالت، نمک گرفته شده از آب دریا) تنظیم شده باشد. آب بدون نمک یا کم نمک موجب سوزش حفره‌های بینی می‌شود. اگر درصد نمک بیشتر از حد مشخص باشد هم تاثیر ناخوشایندی خواهد داشت. ترکیب مناسب یک قاشق چایخوری نمک در یک لیتر آب است. این ترکیب را می‌توان به صورت فردی و پس از چند بار استفاده، بهتر تنظیم کرد.[۱]

منابع[ویرایش]

  • واژه‌های مصوّب فرهنگستان تا پایان سال ۱۳۸۹ (مجموع هشت دفتر فرهنگ واژه‌های مصوّب فرهنگستان)
  • CRC Handbook of Chemistry and Physics, 63rd Edition 1982-1983.
  1. ۱٫۰ ۱٫۱ ۱٫۲ ۱٫۳ ۱٫۴ آب‌نمک؛ روشی مطمئن برای سینوزیت. در: باشگاه خبرنگاران. ۸ خرداد ۹۱.

جستارهای وابسته[ویرایش]

Brine is a high-concentration solution of salt (usually sodium chloride) in water. In different contexts, brine may refer to salt solutions ranging from about 3.5% (a typical concentration of seawater, on the lower end of solutions used for brining foods) up to about 26% (a typical saturated solution, depending on temperature). Lower levels of concentration are called by different names: fresh water, brackish water, and saline water.

Brine naturally occurs on Earth's surface (salt lakes), crust, and within brine pools on ocean bottom. High-concentration brine lakes typically emerge due to evaporation of ground saline water on high ambient temperatures. Brine is used for food processing and cooking (pickling and brining), for de-icing of roads and other structures, and in a number of technological processes. It is also a by-product of many industrial processes, such as desalination, and may pose an environmental risk due to its corrosive and toxic effects, so it requires wastewater treatment for proper disposal.

In nature

A NASA technician measures the concentration level of brine using a hydrometer at a salt evaporation pond in San Francisco.

Saline water with relatively high concentration of salt (usually sodium chloride) occurs naturally on Earth's surface (salt lakes), crust, and within brine pools on ocean bottom.

Numerous processes exist which can produce brines in nature. Modification of seawater via evaporation results in the concentration of salts in the residual fluid, a characteristic geologic deposit called an evaporite is formed as different dissolved ions reach the saturation states of minerals, typically gypsum and halite. A similar process occurs at high latitudes as seawater freezes resulting in a fluid termed a cryogenic brine. At the time of formation, these cryogenic brines are by definition cooler than the freezing temperature of seawater and can produce a feature called a brinicle where cool brines descend, freezing the surrounding seawater.

The brine cropping out at the surface as saltwater springs are known as "licks" or "salines".[1] The contents of dissolved solids in groundwater vary highly from one location to another on Earth, both in terms of specific constituents (e.g. halite, anhydrite, carbonates, gypsum, fluoride-salts, organic halides, and sulfate-salts) and regarding the concentration level. Using one of several classification of groundwater based on total dissolved solids (TDS), brine is water containing more than 100,000 mg/L TDS.[2] Brine is commonly produced during well completion operations, particularly after the hydraulic fracturing of a well.

Uses

Culinary

Brine is a common agent in food processing and cooking. Brining is used to preserve or season the food. Brining can be applied to vegetables, cheeses and fruit in a process known as pickling. Meat and fish are typically steeped in brine for shorter periods of time, as a form of marination, enhancing its tenderness and flavor, or to enhance shelf period.

Chlorine production

Elemental chlorine can be produced by electrolysis of brine (NaCl solution). This process also produces sodium hydroxide (NaOH) and Hydrogen gas (H2). The reaction equations are as follows:

  • Cathode:
  • Anode:
  • Overall process:

Refrigerating fluid

Brine is used as a secondary fluid in large refrigeration installations for the transport of thermal energy from place to place. Most commonly used brines are based on inexpensive calcium chloride and sodium chloride.[3] It is used because the addition of salt to water lowers the freezing temperature of the solution and the heat transport efficiency can be greatly enhanced for the comparatively low cost of the material. The lowest freezing point obtainable for NaCl brine is −21.1 °C (−6.0 °F) at the concentration of 23.3% NaCl by weight.[3] This is called the eutectic point.

Sodium chloride brine spray is used on some fishing vessels to freeze fish.[4] The brine temperature is generally −5 °F (−21 °C). Air blast freezing temperatures are −31 °F (−35 °C) or lower. Given the higher temperature of brine, the system efficiency over air blast freezing can be higher. High-value fish usually are frozen at much lower temperatures, below the practical temperature limit for brine.

Because of the corrosive properties of salt-based brines, glycols such as polyethylene glycol have become more common for this purpose.[5]

Water softening and purification

Brine is an auxiliary agent in water softening and water purification systems involving ion exchange technology. The most common example are household dishwashers, utilizing natrium chloride in form of dishwasher salt. Brine is not involved in the purification process itself, but used for regeneration of ion-exchange resin on cyclical basis. The water being treated flows through the resin container until the resin is considered exhausted and water is purified to a desired level. Resin is then regenerated by sequentially backwashing the resin bed to remove accumulated solids, flushing removed ions from the resin with a concentrated solution of replacement ions, and rinsing the flushing solution from the resin.[6] After treatment, ion-exchange resin beads saturated with calcium and magnesium ions from the treated water, are regenerated by soaking in brine containing 6–12% NaCl. The sodium ions from brine replace the calcium and magnesium ions on the beads.[7][8]

De-icing

In lower temperatures, a brine solution can be used to de-ice or reduce freezing temperatures on roads.[9]

Wastewater

Brine is a byproduct of many industrial processes, such as desalination for human consumption and irrigation, power plant cooling towers, produced water from oil and natural gas extraction, acid mine or acid rock drainage, reverse osmosis reject, chlor-alkali wastewater treatment, pulp and paper mill effluent, and waste streams from food and beverage processing. Along with diluted salts, it can contain residues of pretreatment and cleaning chemicals, their reaction byproducts and heavy metals due to corrosion.

Wastewater brine can pose a significant environmental hazard, both due to corrosive and sediment-forming effects of salts and toxicity of other chemicals diluted in it. It must be properly disposed, which may require permits and compliance with environmental regulations.[10]

The simplest way to dispose of unpolluted brine from desalination plants and cooling towers is to return it back to the ocean. To limit the environmental impact, it can be diluted with another stream of water, such as the outfall of a wastewater treatment or power plant. Since brine is heavier than seawater and would accumulate on the ocean bottom, it requires methods to ensure proper diffusion, such as installing underwater diffusers in the sewerage.[11] Other methods include drying in evaporation ponds, injecting to deep wells, and storing and reusing the brine for irrigation, de-icing or dust control purposes.[10]

Technologies for treatment of polluted brine include: membrane filtration processes, such as reverse osmosis; ion exchange processes such as electrodialysis or weak acid cation exchange; or evaporation processes, such as brine concentrators and crystallizers employing mechanical vapour recompression and steam.

See also

References

  1. ^ "The Scioto Saline-Ohio's Early Salt Industry" (PDF). dnr.state.oh.us. Archived from the original (PDF) on 2012-10-07.
  2. ^ "Global Overview of Saline Groundwater Occurrence and Genesis". igrac.net.
  3. ^ a b "Secondary Refrigerant Systems". Cool-Info.com. Retrieved 17 July 2017.
  4. ^ Kolbe, Edward; Kramer, Donald (2007). "Planning forSeafood Freezing" (PDF). Alaska Sea Grant College Program Oregon State University. ISBN 1566121191. Retrieved 17 July 2017.
  5. ^ "Calcium Chloride versus Glycol". accent-refrigeration.com. Retrieved 17 July 2017.
  6. ^ Kemmer, Frank N., ed. (1979). The NALCO Water Handbook. McGraw-Hill. pp. 12–7, 12–25.
  7. ^ "Hard and soft water". GCSE Bitesize. BBC.
  8. ^ Arup K. SenGupta (19 April 2016). Ion Exchange and Solvent Extraction: A Series of Advances. CRC Press. pp. 125–. ISBN 978-1-4398-5540-9.
  9. ^ "Prewetting with Salt Brine for More Effective Roadway Deicing". www.usroads.com.
  10. ^ a b "7 Ways to Dispose of Brine Waste". Desalitech. Retrieved 18 July 2017.
  11. ^ "Reverse Osmosis Desalination: Brine disposal". Lenntech. Retrieved 18 July 2017.