Dairy Science & Technology · Dairy Processing & Product Technology · also Indigenous Dairy Products, Traditional Indian Dairy Products, Ethnic Dairy Foods
Heat-desiccated, acid-coagulated and fermented traditional products of South Asia, the Middle East, Africa and Latin America, and how to scale them up.
In the exams: ICAR AICE subjects 34 Unit 6 and 37 Unit 1; ICAR AIEEA-PG group 16 (indigenous milk products); ICAR AICE subject 35a Unit 3
Traditional dairy products are the way most of the world's milk was preserved before refrigeration, and for hundreds of millions of people they remain the main way milk is eaten. India alone converts a large share of its milk into products such as ghee, khoa, chhana, paneer, dahi and the sweets made from them. Comparable traditions exist everywhere milk is produced: strained and dried yoghurts in the Middle East and Central Asia, spontaneously fermented milks in Africa, caramelised milk confections in Latin America, dried curds and milk sheets in the Himalaya and East Asia, and clotted and soured creams in Europe.
This manual covers the classification of traditional products; khoa and khoa-based sweets; chhana and its sweets; paneer; rabri, basundi and khurchan; kulfi and traditional frozen products; dulce de leche and cajeta; Middle Eastern and Central Asian products; African fermented milks; mechanisation; shelf-life extension; and standards and geographical indications. It emphasises the principles behind each product — heat desiccation, heat-acid coagulation, fermentation, drying, salting and sugar preservation — and the problems of making them safely at scale. Products with their own subjects are cross-referred rather than repeated: yoghurt, dahi, shrikhand, kefir and skyr in fermented-milks-technology; paneer and fresh cheeses in cheese-science-technology; ghee and butter in fat-rich-dairy-products; and kulfi's freezing in frozen-dairy-desserts.
ICAR AIEEA-PG Dairy Science names the physico-chemical changes during manufacture of indigenous milk products; ICAR AICE-JRF/SRF Dairy Chemistry (subject 34, Unit 6) asks for the composition and changes during manufacture of khoa, chhana and paneer, and Food Processing Technology (subject 35a, Unit 3) and Dairy Technology (subject 37, Unit 1) cover indigenous products. Compositional values, standards and regional names vary; values here are textbook examples and current regulations must always be checked.
In much of the world, most milk is still consumed not as packaged liquid milk or factory cheese but as traditional products made in homes, by small sweet-makers and by village processors. In India, a large share of milk is converted into traditional products such as ghee, khoa, chhana, paneer, dahi and the sweets made from them; similar patterns hold in Pakistan, Bangladesh and Nepal. The Middle East and Central Asia have strained and dried yoghurts and clotted creams; Africa has spontaneously fermented milks; Latin America has caramelised milk confections and fresh cheeses; East Asia and the Himalaya have dried curds and milk sheets; Europe has clotted creams, soured creams and fresh curd cheeses. These products were developed to preserve milk without refrigeration, using heat, acid, salt, sugar and drying, and they carry local flavours and textures that consumers value highly. Their technology is now being studied, standardised and mechanised so that they can be made safely and at scale.
Traditional dairy products can be grouped by the main preservation and transformation principle. Heat-desiccated products are concentrated by open-pan boiling: khoa, rabri, basundi, khurchan, dulce de leche, cajeta, kulfi mixes and the milk sheets of some East Asian traditions. Heat-acid coagulated products are made by adding acid to hot milk: paneer, chhana, ricotta-like curds and some Latin American fresh cheeses. Fermented products rely on lactic (and sometimes yeast) fermentation: dahi, mishti doi, shrikhand and lassi in South Asia; laban, labneh, kashk, qurut and jameed in the Middle East and Central Asia; amasi, nunu, suusac and ergo in Africa; kefir, kumys and skyr elsewhere. Fat-rich products include ghee, makkhan, samn, kaymak and clotted cream. Frozen products include kulfi, Iranian saffron ice cream and Turkish stretchy ice cream. Many products combine principles: a khoa-based sweet is heat-desiccated and then preserved by sugar; dried yoghurt balls are fermented, salted and dried.
This subject concentrates on the products not covered elsewhere. Fermented milks in general (yoghurt, dahi, shrikhand, kefir) are covered in fermented-milks-technology, paneer and fresh cheeses in cheese-science-technology, ghee and butter in fat-rich-dairy-products, and kulfi's freezing in frozen-dairy-desserts; this manual refers to them and adds the traditional context, regional products and scale-up.
East Asia and the Himalaya have their own dairy traditions among pastoral peoples. In Yunnan province of China, rubing is a firm, fresh acid-coagulated goat milk cheese, eaten fried or grilled, and rushan ('milk fan') is made by stretching acid-coagulated cow milk curd into thin sheets that are wrapped on poles and dried. Mongolian herders make aaruul, dried curd pieces from fermented milk, as well as clotted cream and fermented mare's milk. In the Himalaya, chhurpi is made from yak or cow milk curd: a soft form is eaten fresh, while hard chhurpi is pressed, smoked or dried until extremely hard and chewed slowly for hours. Butter tea, made by churning tea with butter and salt, is a staple in Tibet and neighbouring areas. In Europe, beyond the many cheeses, traditional products include English and Cornish clotted cream, the soured creams smetana and crème fraîche, the fresh curd cheeses tvorog and quark, and Balkan kaymak. Historic Japanese records describe concentrated milk products called so and daigo, though these did not survive as everyday foods. These examples show the same principles at work — acid or heat coagulation, stretching, smoking, drying and fermentation — adapted to local animals, climates and tastes.
Khoa (khoya, mawa) is a heat-desiccated milk product made by boiling milk in a shallow open pan (karahi) with continuous stirring and scraping until most of the water has evaporated and a semi-solid mass forms that leaves the sides of the pan. It is the base of a large family of North and West Indian sweets. Buffalo milk is preferred because its higher fat and total solids give higher yield and a softer, smoother, more granular texture suited to sweets; cow milk khoa is harder and drier and tends to be sticky when worked. Three main types are recognised by the trade. Pindi khoa is firm, with the lowest moisture, made into balls or pats and used for peda and burfi. Dhap khoa is soft and moist, used for gulab jamun and some halwas. Danedar khoa is granular, made from milk slightly acidified (traditionally with a little citric acid or sour whey) so that fine curd particles form; it is used for kalakand and some burfi. During khoa making, lactose browns slightly, whey proteins denature and casein aggregates; fat may partially separate if overheated, and scorching on the pan gives a burnt flavour. Indian food standards set minimum fat in the dry matter of khoa, and the values should be taken from the current regulation.
Yield depends on milk solids and khoa moisture: all milk solids are retained in principle, so khoa mass = milk solids ÷ (1 − khoa moisture fraction). Buffalo milk therefore gives considerably more khoa per kilogram than cow milk.
Peda is made by heating khoa with sugar (commonly in the range of a quarter to a third of the khoa weight) and flavouring such as cardamom until the mass browns lightly and becomes plastic, then shaping it into small discs; regional types include the browned, caramelised Dharwad and Mathura styles. Burfi is khoa cooked with sugar, spread in a tray, set and cut into pieces; variants add coconut, nuts, chocolate or fruit. Kalakand is made from danedar khoa, or by heat-concentrating milk with a little acid and sugar, giving a moist, granular, soft sweet. Gulab jamun is made from dhap khoa mixed with a small amount of refined wheat flour and a leavening agent, formed into balls, deep-fried in ghee or oil to a dark brown and soaked in warm sugar syrup; the khoa type and kneading control softness and whether the balls crack or harden. These sweets are preserved mainly by their low water activity (from sugar and low moisture) but are still perishable, especially in hot climates, because moulds and yeasts can grow on their surfaces and lipolysis and oxidation develop. Their quality problems include hardness, stickiness, burnt or cooked flavour, grittiness from undissolved sugar or coarse protein, and mould. Shelf-life extension is discussed in a later chapter.
During khoa making, milk loses most of its water by boiling at atmospheric pressure, so its total solids rise several-fold. Whey proteins denature early in heating and associate with casein; as concentration proceeds, casein micelles aggregate and, with the denatured whey proteins, form a continuous protein matrix that entraps fat globules and dissolved lactose. Lactose becomes supersaturated in the remaining water and may partly crystallise on cooling, contributing to the granular texture valued in some khoa; very large crystals give a sandy texture. Fat globules are damaged by stirring and heat, and some fat becomes free, which is why overcooked khoa looks oily. Maillard reactions between lactose and proteins produce the light brown colour and cooked, caramel-like notes, and form compounds with antioxidant activity; scorching on the pan bottom gives burnt flavours. Buffalo milk, with more casein, fat and calcium, gives a smooth, soft, granular khoa, while the higher proportion of whey protein relative to casein and the smaller fat globules of cow milk give a harder, sticky product. These differences underlie the choice of milk for each sweet.
Chhana is a heat-acid coagulated milk product, the base of the famous sweets of eastern India and Bangladesh. Milk is heated, commonly to boiling, then cooled slightly to a coagulation temperature of around 70–80 °C, and a dilute food-grade acid (citric or lactic acid, or sour whey from a previous batch) is added gradually with gentle stirring until the curd separates from clear, greenish whey at a pH of roughly 5.4. The curd is drained in muslin cloth but, unlike paneer, it is not pressed into a block; it remains soft, moist and smooth. Cow milk is preferred for chhana for sweets, because its curd is softer and smoother and gives spongy rasogolla; buffalo milk chhana is harder and more greasy, and is improved by mixing with cow milk or adjusting fat. The fat and moisture of chhana, the coagulation temperature, the acid strength and the rate of acid addition together control the texture. Too high a coagulation temperature or too strong acid gives a hard, coarse curd; too low gives a weak curd and losses in whey. Indian standards set maximum moisture and minimum fat in dry matter for chhana.
As with paneer, much of the whey protein is retained because the milk is heated before coagulation, so yield is higher than for rennet curd. Yields are calculated from the solids recovered (most fat, part of the solids-not-fat) and the chhana moisture.
Rasogolla (rasgulla) is made by kneading fresh chhana to a smooth dough, sometimes with a little semolina or flour as binder, forming small balls and cooking them in boiling sugar syrup, during which they swell to a spongy texture as steam forms inside; they are then held in a lighter syrup. Kneading, ball size, syrup concentration and boiling time determine sponginess, and too much fat or poor kneading causes balls to disintegrate or become hard. Regional types include the spongy Bengali rasogolla and the softer, slightly brown Odisha rasagola. Both have geographical indications in India: 'Banglar Rasogolla' for West Bengal and 'Odisha Rasagola' for Odisha. Rasogolla is often canned in syrup for long shelf life. Related sweets include rasmalai (flattened chhana balls in thickened sweetened milk), chhena poda (baked caramelised chhana from Odisha) and chhena jalebi.
Sandesh is made by cooking chhana with sugar in a pan at moderate temperature until it reaches the desired consistency: soft (naram pak) or firm (kada pak), then shaping or moulding it, often with flavourings such as date-palm jaggery (nolen gur), cardamom or saffron. Its keeping quality is limited to days unless refrigerated or treated. Mechanisation of chhana production, kneading and rasogolla forming is discussed in a later chapter.
Chhana making combines heat denaturation and acid coagulation. Heating milk close to boiling denatures most of the whey proteins, which then associate with casein micelles. When acid is added at around 70–80 °C, the pH falls towards the isoelectric region of casein and colloidal calcium phosphate dissolves; casein, now carrying denatured whey protein, aggregates rapidly in the heat and traps fat and some lactose, forming the curd. Coagulation at a pH of about 5.4 rather than at the casein isoelectric point of about 4.6 keeps more calcium in the curd and gives a softer, smoother body. Higher temperatures and lower pH give a harder, more granular curd with lower moisture; lower temperatures give a softer, moister curd that may lose fines. Cow milk chhana is preferred for rasogolla partly because its curd has a finer, more uniform structure; the greater fat and calcium of buffalo milk curd give a greasy, coarse body unless the milk is adjusted. Understanding these relationships allows a plant to adjust acid strength, temperature and milk blend for each sweet.
Paneer, the heat-acid coagulated cheese of South Asia, is covered in detail in cheese-science-technology; this chapter places it in its traditional context. Standardised milk, commonly buffalo milk or a blend with cow milk adjusted to a fixed fat-to-SNF ratio, is heated to around 90 °C, cooled to a coagulation temperature of about 70 °C and coagulated by adding a dilute (around 1–2 per cent) citric acid solution, also at about 70 °C, with gentle stirring until clear whey separates. After a short rest, the curd is transferred to hoops lined with muslin, pressed to remove whey and form a block, then cut and immersed in chilled water to firm it and cool it quickly. The heat treatment incorporates denatured whey protein, giving higher yield and a soft, spongy, cohesive body that holds its shape when fried or cooked in gravy. Cow milk paneer tends to be softer and more crumbly, and low-fat milk gives a hard, rubbery product.
Paneer's main quality attributes are a close, uniform, smooth texture, the ability to be cut cleanly, sponginess, and the absence of sourness. Defects include hardness and rubberiness from low fat or too high coagulation temperature, crumbliness from cow milk or too much acid, sour or bitter taste from old milk or poor storage, and rapid spoilage. Fresh paneer is highly perishable at room temperature and keeps only some days under refrigeration; vacuum packaging, modified atmosphere and freezing extend this. Indian food standards specify maximum moisture and minimum milk fat on a dry-matter basis, with a separate low-fat category; at present a commonly cited set is no more than 70 per cent moisture and at least 50 per cent fat in dry matter for paneer, but the current regulation must be checked. Paneer has become popular well beyond South Asia, and similar heat-acid cheeses exist elsewhere: Latin American queso blanco, some Middle Eastern fresh cheeses and Portuguese and Spanish whey-and-milk curds. Analogue products made with vegetable fat must be labelled as such, and their sale as paneer is a recurring enforcement issue.
Rabri is a sweetened, concentrated milk product of North India in which the characteristic texture comes from layers of milk skin (malai). Milk is simmered in a wide, shallow pan without boiling vigorously; as the surface dries, a skin of coagulated protein and fat forms, which is broken and pushed to the cooler sides of the pan, and fresh skins form repeatedly. When the milk has reduced to roughly a fifth to a third of its volume, sugar is added and the collected flakes are mixed back in, giving a thick, sweet mass with a flaky, layered texture. Rabri is eaten on its own or poured over sweets such as jalebi and malpua. It is very labour-intensive and time-consuming, which makes it an important target for mechanisation; continuous systems mimic skin formation using heated surfaces and scraping.
Basundi, popular in Maharashtra, Gujarat and Karnataka, is milk concentrated by boiling with sugar to a thick, creamy, uniform consistency without the distinct layers of rabri; it is less concentrated than rabri, light caramel in colour, and often flavoured with cardamom, saffron and nuts. A variant, sitaphal (custard apple) basundi, adds fruit pulp. Because it is a pourable concentrated milk, it can be made in jacketed kettles or scraped-surface concentrators and is suited to industrial production and packaging, including heat-treated cans and retort pouches.
Khurchan is a speciality of Uttar Pradesh made by heating milk in a shallow pan and repeatedly scraping (khurchna, to scrape) the thin layers of skin that form on the surface, stacking them with sprinkled sugar. It is a dense, layered, sweet product with a strongly cooked flavour, made in small quantities. All three products show the role of open-pan heating in creating Maillard flavour, partial caramelisation of added sugar, denaturation and skin formation by proteins at the air interface, and evaporation. Their composition is set by the degree of concentration and the sugar added, and simple mass balances give the yield: final mass = total solids (milk solids plus sugar) ÷ final total-solids fraction.
Kulfi, the traditional frozen dessert of the Indian subcontinent, is covered in frozen-dairy-desserts as a frozen product; here the emphasis is on its traditional preparation. Milk is concentrated by boiling (rabri-like or basundi-like), sugar and flavourings (cardamom, saffron, pistachio, almond, rose, mango) are added, and the mix is filled into conical metal moulds (or earthen pots, as matka kulfi), sealed and frozen quiescently, traditionally by immersion in a mixture of ice and salt that reaches well below 0 °C. Because it is not whipped, kulfi has almost no overrun; it is dense and chewy, with a cooked, caramelised flavour and slow melting. Malai kulfi includes cream or milk skins; some styles add khoa. Street vendors sell kulfi from earthen pots kept cold in ice and salt. Its safety depends on the hygiene of the milk concentrate, moulds and handling, since there is no further heat treatment after filling.
Other regions have their own traditional frozen dairy desserts. Iran's bastani sonnati is a saffron and rose-water ice cream with pistachios and small frozen flakes of cream. Turkey's dondurma, especially the Kahramanmaraş style, is made from goat or cow milk with salep (a flour from orchid tubers) and mastic, which give it an elastic, chewy texture that resists melting and allows vendors to stretch and twirl it. In South Asia, falooda combines kulfi with vermicelli, basil seeds and rose syrup. Italian gelato and granita and the Mexican nieve and paleta traditions show similar regional development. These products are of interest to technologists because their textures come from specific ingredients and processes — quiescent freezing, plant hydrocolloids, concentration by boiling — that differ from industrial ice cream, and reproducing them at scale requires understanding why they behave as they do.
Dulce de leche, the caramelised milk confection of Argentina, Uruguay and much of Latin America (called arequipe in Colombia and Venezuela and manjar in Chile and Peru), is made by concentrating milk with added sucrose until it becomes a thick, brown, spreadable paste. Milk is mixed with sugar (often around 20 per cent of the milk weight) and a small amount of sodium bicarbonate, which neutralises part of the natural acidity. Neutralisation prevents protein coagulation during the long boiling and raises the pH, which accelerates the Maillard reaction responsible for the characteristic brown colour and caramel flavour. The mixture is boiled in open pans or under partial vacuum in jacketed, stirred concentrators until it reaches the required total solids (commonly around 70 per cent). Glucose syrup may be added to reduce sucrose crystallisation, and starch or other thickeners are used in some industrial versions for bakery and confectionery (pastry-grade dulce de leche is thicker). Composition and naming are regulated nationally in the main producing countries.
Cajeta is the Mexican equivalent, traditionally made from goat milk (or a blend with cow milk), which gives a distinctive flavour; it may be flavoured with vanilla or cinnamon or with alcohol (cajeta envinada). The main quality defect of dulce de leche and cajeta is sandiness from lactose crystallisation: as in sweetened condensed milk, the lactose in the concentrated product is supersaturated and can form large, gritty crystals during storage. It is controlled by seeding with fine lactose crystals during cooling, partial hydrolysis of lactose with lactase before concentration (glucose and galactose are more soluble), or adding glucose syrup. Other defects are excessive darkening during storage (continuing Maillard reactions at warm temperatures), syneresis, surface moulds when water activity is too high or packaging is poor, and scorched flavour from pan deposits. The neutraliser dose is calculated from the acidity to be removed: 84 g of sodium bicarbonate neutralises 90 g of lactic acid. Yields follow from a solids balance: final mass = (milk solids + sugar) ÷ final total-solids fraction.
Alongside dulce de leche, Latin America has a strong tradition of fresh cheeses made by rennet or acid-heat coagulation, eaten within days: queso fresco and queso blanco in Mexico and Central America, quesillo and Oaxaca cheese (a stretched-curd cheese wound into balls), Colombian and Venezuelan white cheeses, and Brazilian queijo minas frescal and requeijão (a spreadable cooked cream cheese). Their technology overlaps with cheese-science-technology, but their traditional, often raw-milk, small-scale production raises the same safety concerns as other fresh, high-moisture, near-neutral cheeses, especially Listeria and Brucella. Other traditional dairy sweets of the region include natilla and arroz con leche, made by cooking milk with sugar and starch or rice.
Across the Middle East, the Caucasus and Central Asia, yoghurt (laban, mast, katyk) is turned into a range of concentrated and dried products that keep without refrigeration. Labneh is strained yoghurt, salted, eaten as a spread or rolled into balls and preserved in olive oil; its technology is shared with other concentrated fermented milks (see fermented-milks-technology). Drying goes further. Qurut (kurt, kurut), common across Central Asia and in Afghanistan, Turkey and Mongolia, is made by straining salted yoghurt, shaping the thick curd into small balls or discs, and drying them in the sun until hard; it keeps for months and is eaten as a snack or dissolved in water for cooking. Jameed, from Jordan and neighbouring countries, is salted, strained goat or sheep yoghurt formed into balls and sun-dried; it is reconstituted to make the sauce for the national dish mansaf. In Iran and neighbouring regions, kashk is a thick, fermented dairy product made from drained yoghurt or from the curd left after butter making, sold liquid or dried; in the Levant and Turkey kishk (keşkek in some areas) combines yoghurt with bulgur wheat, fermented and dried into a powder. Doogh (Iran) and ayran (Turkey) are salted yoghurt drinks, doogh sometimes carbonated.
Kaymak (qaymaq, gaymar) is a clotted cream made in Turkey, the Balkans, Iran, Iraq and Central Asia by slowly heating milk (often buffalo milk) in shallow pans and then cooling it, so that a thick layer of fat and protein forms on the surface; it is skimmed off and eaten with honey or bread. English clotted cream, especially Cornish clotted cream, which has protected designation of origin status, is made in a similar way. Samn, the clarified butter of the Arab world, is equivalent to ghee. Technologically, these products share features: concentration by straining or heating, salting, drying and the protective effect of low pH and low water activity. Their safety risks include contamination during sun-drying, mycotoxin-producing moulds, and the use of raw milk; their quality issues include excessive salt, hardness, uneven drying and rancidity. Modern production uses controlled drying (tray, tunnel or vacuum dryers), standardised cultures and pasteurised milk while trying to preserve traditional flavour.
Spontaneously fermented milks are central to diets in many African pastoral and farming communities. Amasi (maas), from South Africa and Zimbabwe, is cow milk left to ferment naturally, traditionally in calabashes (gourds), clay pots or skin bags, which carry residual microflora from earlier batches; the whey is drained off, leaving a thick, sour curd eaten with maize porridge. Commercial amasi is made from pasteurised milk with mesophilic cultures. Nunu, from Ghana, Nigeria and other West African countries, is a spontaneously fermented whole milk with a yoghurt-like consistency, often eaten with fura (millet balls) as fura da nono. Suusac, from Somalia and northern Kenya, is camel milk fermented spontaneously for one to two days in containers often smoked with burning wood chips, which gives a smoky flavour and some antimicrobial effect; camel milk does not form a firm curd, so suusac stays liquid. Ergo is the spontaneously fermented milk of Ethiopia, and ayib a fresh cottage-type cheese made from defatted soured milk; lait caillé is common in West Africa, and wagashi, a soft cheese of Benin and neighbouring countries, is coagulated with the sap of the Calotropis procera plant.
The microflora of these products is diverse and variable: lactic acid bacteria (lactococci, lactobacilli, leuconostocs, enterococci, streptococci) dominate, often with yeasts. Fermentation lowers pH, typically to around 4.5 or below, which inhibits many pathogens; however, spontaneous fermentation of raw milk in poorly cleaned containers is not reliable, and pathogens such as Escherichia coli, Staphylococcus aureus, Salmonella and Brucella, as well as mycotoxins, have been reported in traditional products. Milk-borne zoonoses are a particular concern where milk is not boiled. Improvement programmes aim to keep the traditional character while improving safety and consistency: pasteurising or boiling the milk, using cleaned containers, back-slopping from good batches in a controlled way, and developing defined starter cultures isolated from the best traditional products. Smoking of containers, as in suusac, is being studied for its antimicrobial compounds. Small-scale cooling, collection and processing centres allow women's groups and cooperatives to sell traditional fermented milks safely in towns, which is an important livelihood opportunity.
Traditional products are mostly made in small batches by hand in open pans over fires or gas burners. This is labour-intensive, consumes much fuel, gives variable quality, and makes hygiene control difficult. Mechanisation aims to make the same products in larger quantities with consistent quality, lower energy use and better hygiene, while preserving the texture and flavour that consumers expect — which is the hard part, because those attributes come from the specific heating, scraping and concentration patterns of the traditional method. Indian dairy research institutes and equipment makers have developed continuous and semi-continuous systems for several products. For khoa, these include scraped-surface heat exchangers in series, in which milk is concentrated on steam-heated surfaces with rotating scrapers, and conical process vats with scraping agitators; some systems pre-concentrate milk in a conventional evaporator before finishing in a scraped-surface unit to reduce energy use. For basundi and rabri, scraped-surface concentrators and systems that create and collect skins on heated surfaces have been developed. For chhana and paneer, continuous coagulation in tubular systems, mechanical drainage and pressing, and automatic block cutting are used.
Downstream, kneaders and dough mixers replace hand kneading of chhana and khoa; ball-forming machines make uniform rasogolla and gulab jamun balls; continuous fryers with temperature control fry gulab jamun; syrup cookers and soaking systems process rasogolla; moulding and depositing machines shape peda, burfi and sandesh; and extruders form uniform pieces. Packaging lines fill canned rasogolla, gulab jamun and basundi and seal retort pouches. Mechanisation also brings the possibility of using concentrates or milk powder as raw material, such as making khoa from evaporated milk or from reconstituted powder with added fat, which evens out seasonal milk supply but changes texture and must be labelled honestly. The economics of mechanisation depend on scale, labour costs and the premium consumers pay for handmade products; many organised dairies combine mechanised production of base products (khoa, chhana, paneer) with semi-manual finishing of sweets.
Traditional open-pan methods are inefficient in energy: heat is lost from the open surface and the burner, evaporation is slow, and scraping depends on the operator. Fuel is often wood or coal, with smoke and safety problems. Mechanised systems that pre-concentrate milk in multiple-effect evaporators before finishing in scraped-surface units use far less energy per kilogram of product. Hygiene improves with closed systems, stainless steel surfaces, cleaning-in-place and controlled cooling, which reduces the contamination that open pans and manual handling invite after the heat treatment. For small producers who cannot afford continuous plants, improved stoves, stainless steel pans, simple scraping devices and good hygiene practices give significant gains.
Many traditional dairy products have short shelf lives: fresh paneer and chhana spoil in a day or two at room temperature, khoa in a few days, sandesh and many milk sweets in days, and fermented milks in days to weeks. Spoilage comes from surface moulds and yeasts (especially on khoa-based sweets), bacteria (in high-moisture products like paneer and chhana), and chemical changes such as lipolysis, oxidation and continued Maillard browning. High ambient temperatures, unhygienic handling and lack of cold chains make the problem worse. Extending shelf life without losing traditional character is a central research and industrial goal, and a public-health one, since many reported food-safety problems involve milk sweets.
The hurdle concept combines several mild preservation factors — reduced water activity, lower pH, mild heat treatment, preservatives, packaging and refrigeration — so that none has to be severe. Specific methods include: refrigeration and freezing (frozen paneer and khoa); vacuum packaging and modified atmosphere packaging with carbon dioxide and nitrogen for paneer, khoa and sweets; hot filling and in-pack heat treatment; canning and retort-pouch processing for rasogolla, gulab jamun and basundi in syrup, which can give months of ambient shelf life; permitted preservatives such as sorbic acid or its salts in some products where national law allows; adjustment of water activity with sugar and humectants; and improved hygiene in production and packing. Irradiation has been studied for some products. Indian rules now require date marking (such as a best-before date) for sweets sold loose, which makes shelf-life studies necessary even for small sweet shops; producers determine shelf life by storage trials that follow microbial counts, acidity, free fatty acids, colour, texture and sensory quality.
Traditional products are increasingly covered by formal standards. Indian food regulations define khoa, chhana, paneer, dahi, shrikhand, ghee, kulfi and other products with compositional limits (such as maximum moisture, minimum milk fat in dry matter, and sometimes minimum protein), microbiological criteria and rules on additives; these values change over time and must be taken from the current regulation. Latin American countries regulate dulce de leche; Middle Eastern and Central Asian standards bodies define labneh, ayran and doogh; and Codex has general standards (for fermented milks, cheese, milk fat products) under which many traditional products fall. Standards protect consumers from adulteration (for example vegetable fat in khoa or paneer, starch in khoa, synthetic milk), allow trade, and give small producers a clear target. Adulteration of khoa and sweets around festival seasons is a recurring enforcement concern in South Asia, detected with tests for starch, vegetable fat (fatty acid profile, phytosterols), and foreign protein.
Geographical indications (GIs) and protected designations of origin (PDO) protect names linked to a place and a method, rewarding producers who keep traditional quality. In India, examples include Banglar Rasogolla (West Bengal) and Odisha Rasagola, and Dharwad pedha (Karnataka). In the European Union, protected designations cover many traditional dairy products, among them Cornish clotted cream and numerous cheeses such as Feta. Latin American countries and others are developing GI systems for traditional cheeses and dairy sweets. A GI or PDO specification typically sets the area, the milk (species, sometimes breed and feed), the method and the product characteristics, and is enforced by inspection. For technologists, GIs pose a particular question: how far can a process be mechanised or changed before the product no longer meets its specification or its consumers' expectations? The answer is found in the specification and in sensory testing against traditional products.
A student uses this subject to explain why buffalo milk suits khoa and cow milk suits chhana, calculate khoa, chhana and dulce de leche yields and neutraliser doses, and describe the traditional products of other regions. It feeds AIEEA-PG questions on indigenous products and practical sessions in sweet making.
A dairy technologist five years in may run a paneer, khoa or sweets line in an organised dairy: setting coagulation conditions, operating scraped-surface khoa plants, controlling yield and moisture against standards, validating shelf life for date marking, and handling festival-season demand and adulteration risks. This subject provides the principles and calculations.
A plant head or entrepreneur decides whether to mechanise traditional products, which to can or pack in retort pouches for export, whether to seek GI-linked sourcing, and how to compete with informal sweet-makers on safety and consistency. They answer to regulators for standards, labelling and date marking.
A professor or research director studies the chemistry, microbiology and engineering of traditional products, develops continuous processes and defined cultures from traditional fermentations, and advises standards bodies and GI applicants. They set AICE questions on khoa, chhana and paneer chemistry.
This manual does not yet give: current FSSAI compositional limits for each traditional product (only the commonly cited paneer limits are mentioned, with a caution); detailed engineering designs of continuous khoa and rasogolla plants; quantitative yields by milk type beyond worked calculations; detailed microbiology of each African and Asian fermented milk; the full list of GIs and their specifications; and national standards of Latin American, Middle Eastern and Central Asian countries. Temperatures, concentrations and sugar levels are representative of textbook descriptions; practice varies by region and maker.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
These notes are free to read here, with no account.
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