It goes bad. Refrigeration retards spoilage but doesn't prevent it. It has no nutritional value. The way the rotor rotates retards. If the distributor turns clockwise, then turning the distributor clockwise retards the timing. Spoilage inhibitors are chemicals added to commercially processed foods to prolong or prevent spoilage. Because they are the richest retards ever.
Six of food spoilage. It depends which side of the road the retards are on when the Chevy passes. There are several changes that occur that cause food spoilage.
A loss of ph, spoilage caused by bacteria and decomposition are contributing factors to food spoilage. One who, or that which, retards. What microorganisms is associated with spoilage in pepper.
Refrigeration does not prevent food spoilage. It slows spoilage by reducing the rate at which bacteria, yeast, and molds reproduce. No religions are not for retards. It is not if you have one anyway. Kind of it is all about believing in your god. If you don't I guess you can say that. It only delays spoilage of food. A poisonous spoilage is a poison food that cant be eaten now.
Log in. Food Spoilage. Study now. This review article presents and discusses the mechanisms, application conditions, and advantages and disadvantages of different food preservation techniques.
This article also presents different food categories and elucidates different physical, chemical, and microbial factors responsible for food spoilage. Furthermore, the market economy of preserved and processed foods has been analyzed in this article. Foods are organic substances which are consumed for nutritional purposes.
Foods are plant or animal origin and contain moisture, protein, lipid, carbohydrate, minerals, and other organic substances. Foods undergo spoilage due to microbial, chemical, or physical actions. Nutritional values, color, texture, and edibility of foods are susceptible to spoilage [ 1 ]. Therefore, foods are required to be preserved to retain their quality for longer period of time.
Food preservation is defined as the processes or techniques undertaken in order to maintain internal and external factors which may cause food spoilage. The principal objective of food preservation is to increase its shelf life retaining original nutritional values, color, texture, and flavor.
Knowing the techniques of preserving foods was the first and most important step toward establishing civilization. Different cultures at different times and locations used almost the similar basic techniques to preserve food items [ 2 ].
Conventional food preservation techniques like drying, freezing, chilling, pasteurization, and chemical preservation are being used comprehensively throughout the world. Scientific advancements and progresses are contributing to the evolution of existing technologies and innovation of the new ones, such as irradiation, high-pressure technology, and hurdle technology [ 3 , 4 , 5 ].
The processing of food preservation has become highly interdisciplinary since it includes stages related to growing, harvesting, processing, packaging, and distribution of foods. Therefore, an integrated approach would be useful to preserve food items during food production and processing stages. At present, the global market of the processed food items is about 7 trillion dollars, which is gradually growing with time [ 6 ]. Rapid globalization and industrialization are the major contributing factors for the progress of food processing industries in different countries.
This review paper presents the classification of food items and discusses different physical, chemical, and biological factors of food spoilage. The basics and advancements of different trivial and modern food preservation techniques, which are attributed to impede food spoilage and to yield longer shelf life, are discussed here along with their mechanisms, application conditions, advantages, and disadvantages. This article also reports the global market trend of preserved and processed food.
Figure 1 summarizes a flow diagram showing various categories of foods, components of food spoilage mechanisms, food preserving and processing methods, and global market analysis of preserved foods. This review offers the researchers, technologists, and industry managements a comprehensive understanding that could be highly useful to develop effective and integrated food preservative methods and to ensure food safety. Foods can be broadly classified according to the shelf life, functions and nutrient value, and processing mechanisms Fig.
Different categories of foods are summarized in Table 1 and briefly discussed in the following sections. Classification of food, recreated from references [ 9 , 10 , 11 , 12 ]. Food spoilage is a natural process; through this process, food gradually loses its color, texture, flavor, nutritional qualities, and edibility. Consumption of spoiled food can lead to illness and in the extreme situation to death [ 9 ]. Considering the self life, food items can be classified as perishable, semi-perishable, and non-perishable [ 10 ].
Perishable Foods that have shelf life ranging from several days to about three weeks are known as perishable. Milk and dairy products, meats, poultry, eggs, and seafood are the examples of perishable food items. If special preservation techniques are not apprehended, food items could be spoiled straight away [ 10 ].
Semi-perishable Different food items can be preserved for long time about six months under proper storage conditions. These foods are known as semi-perishable. Vegetables, fruits, cheeses, and potatoes are few examples of semi-perishable food items. Non-perishable Natural and processed foods that have indefinite shelf life are called non-perishable food items.
These foods can be stored for several years or longer. Dry beans, nuts, flour, sugar, canned fruits, mayonnaise, and peanut butter are few examples of non-perishable foods. According to the functions to human body, food items can be categorized as: a body building and repairing foods, b energy-giving foods, c regulatory foods, and d protective foods. Depending on the nutrition value, food items can be classified as: a carbohydrate-rich foods, b protein-rich foods, c fat-rich foods, and d vitamin- and mineral-rich foods.
Table 1 presents different food items according to their functions and nutrients. Different food processing techniques are used by the food industries to turn fresh foods into food products. Foods can be classified into three major groups based on the extent and purpose of food processing [ 14 ]: a unprocessed or minimally processed foods, b processed culinary or food industry ingredients, and c ultra-processed food products.
Classification of foods based on extent and purpose of processing is presented in Table 2. Food spoilage is the process in which food edibility reduces. Food spoilage is related to food safety [ 9 ]. The primitive stage of food spoilage can be detected by color, smell, flavor, texture, or food. Different physical, microbial, or chemical actions can cause food spoilage. These mechanisms are not necessarily mutually exclusive since spoilage caused by one mechanism can stimulate another.
Temperature, pH, air, nutrients, and presence of different chemicals are the major factors for food spoilage [ 9 ]. Different factors that affect food spoilage are presented in Fig. Key physical, microbial, and chemical factors affecting food spoilage [ 9 ]. Food spoilage due to physical changes or instability is defined as physical spoilage.
Moisture loss or gain, moisture migration between different components, and physical separation of components or ingredients are the examples of physical spoilage [ 9 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. The key factors affecting physical spoilage are moisture content, temperature, glass transient temperature, crystal growth, and crystallization. A frequent cause of degradation of food products is the change in their water content. It may occur in the form of water loss, water gain, or migration of water [ 25 ].
Moisture transfer in food is directly related to the water activity a w of food item [ 9 , 26 ]. Water activity a w is a thermodynamic property which is expressed as the ratio of the vapor pressure of water in a system to the vapor pressure of pure water at the same temperature [ 15 , 27 ]. Equilibrium relative humidity at the same temperature may also be used in lieu of pure water vapor pressure.
Water activity in food products reduces with temperature. In general, water activity of foods at normal temperature is 1. The effect of temperature is the most significant factor in the case of fruit and vegetable spoilage.
There is an optimum temperature range for slow ripening and to maximize post-harvest life. Slow ripening also requires an optimum relative humidity along with optimum air movement around fruit and vegetable. Apparently, these optimum conditions are called modified atmospheres MA. Temperature usually besets the metabolism of the commodities and contemporarily alters the rate of attaining desired MA [ 17 ].
Low temperature can also have a negative effect on foods that are susceptible to freeze damage. At a lower temperature, when food products become partially frozen, breakage in cells occurs which damages the product. Most tropical fruits and vegetables are sensitive to chilling injury. Glass transition temperature T g effects the shelf life of food products. Solids in food items may exist in a crystalline state or in an amorphous metastable state. This phenomenon depends on the composition of solids, temperature, and relative humidity [ 18 ].
The amorphous matrix may exist either as a very viscous glass or as a more liquid-like rubber [ 19 ]. At glass transition temperature, changes occur from the glassy state to rubbery state. This is a second-order phase transition process, which is temperature specific for each food.
The physical stability of foods is related to the glass transition temperature. Glass transition temperature T g depends strongly on concentration of water and other plasticizers [ 22 ]. When dry food products are kept in highly humid conditions, the state of food products changes due to glass transition phenomena [ 9 ]. Freezing can also contribute to food degradation. Foods, which undergo slow freezing or multiple freeze, suffer severely due to crystal growth. They are subject to large extracellular ice growth.
Rapid freezing forms ice within food cells, and these foods are more stable than slow freezing processed foods [ 23 ]. To minimize large ice crystal growth, emulsifiers and other water binding agents can be added during freezing cycles [ 20 ].
Foods with high sugar content can undergo sugar crystallization either by moisture accumulation or by increasing temperature. As a consequence, sugar comes to the surface from inside, and a gray or white appearance is noticed. Staling of sugar cookies, graininess in candies, and ice creams are the results of sugar crystallization [ 9 ]. Sugar crystallization can be delayed by the addition of fructose or starch. Moreover, above the respective glass transition temperature, time plays a crucial role in sugar crystallization process of food items [ 24 ].
Microbial spoilage is a common source of food spoilage, which occurs due to the action of microorganisms. It is also the most common cause of foodborne diseases.
Perishable foods are often attacked by different microorganisms. The growth of most microorganisms can be prevented or lingered by adjusting storage temperature, reducing water activity, lowering pH, using preservatives, and using proper packaging [ 28 ].
Microorganisms involved in food spoilage can be divided into three major categories, which are molds, yeasts, and bacteria. Table 3 presents the active conditions of different microorganisms that affect foods.
There are intrinsic and extrinsic factors that can affect microbial spoilage in foods [ 29 ]. The intrinsic properties of foods determine the expected shelf life or perishability of foods and also affect the type and rate of microbial spoilage.
Endogenous enzymes, substrates, sensitivity of light, and oxygen are the primary intrinsic properties associated with food spoilage [ 33 ]. To control food quality and safety, these properties can be controlled during food product formulation [ 10 ]. Intrinsic factors of food spoilage include pH, water activity, nutrient content, and oxidation—reduction potential [ 9 , 10 , 29 ].
Extrinsic factors of food spoilage include relative humidity, temperature, presence, and activities of other microbes [ 9 , 29 ].
Chemical and biochemical reactions occur naturally in foods and lead to unpleasant sensory results in food products. Chemical spoilage is interrelated with microbial actions.
However, oxidation phenomena are purely chemical in nature and also dependent on temperature variations [ 33 ]. In presence of oxygen, amino acids convert into organic acid and ammonia. This is the elementary spoilage reaction in refrigerated fresh meat and fish [ 29 ]. The consequences in food items are color alteration, off-flavor, and toxic substances formation [ 9 ]. Rancidification can be catalyzed by the presence of metal oxides and exposure to light increases the reaction rate.
After this reaction, carbonyl compounds, responsible for rancid taste of foods, are produced [ 35 ]. Figure 4 presents auto-oxidation of fatty acids RH. Auto-oxidation of fatty acids RH [ 35 ]. Proteolysis, a ubiquitous and irreversible posttranslational modification, involves limited and highly specific hydrolysis of peptide and iso-peptide bonds of a protein.
The entire phenomena require the presence of miscellaneous protease enzymes [ 36 ]. Different specialized proteases play a key role in various regulatory processes. Moreover, highly specific proteolytic events are associated with normal and pathological conditions [ 37 ].
Foods containing nitrogen compounds frequently incur this reaction. Proteins, after being incurred through proteolysis, eventually get converted into small-sized amino acids.
The following reaction presents proteolysis mechanism:. Many of these peptides have stiff taste which can be bitter or sweet [ 35 ].
Table 4 presents the taste of various amino acids [ 38 ]. Putrefaction refers to the series of anaerobic reactions through which amino acids detour to a mixture of amines, organic acids, and stiff-smelling sulfur compounds, such as mercaptans and hydrogen sulfide.
This is a biochemical phenomenon as the presence of bacteria is exigent all through the process. Along with amino acids, indole, phenols, and ammonia are also formed due to protein putrefaction [ 39 ]. Most of these chemicals have displeasing odor. This elevated temperature facilitates microbial activities [ 35 , 39 ]. Non-enzymatic browning, which is also known also as Maillard reaction, is another primary cause of food spoilage.
This reaction occurs in the amino group of proteins, or the amino acids present in foods. Color darkening, reducing proteins solubility, developing bitter flavors, and reducing nutritional availability of certain amino acids are the common outcomes of Maillard reaction. This reaction occurs during the storing of dry milk, dry whole eggs, and breakfast cereals [ 40 ].
Pectins are complex mixtures of polysaccharides that make up almost one-third of the cell wall of dicotyledonous and some monocotyledonous plants [ 41 , 42 ]. Indigenous pectinases are synthesized or activated during ripening of fruits and cause pectin hydrolysis which softens the structure of food. Damages of fruits and vegetables by mechanical means may also activate pectinases and initiate microbial attack [ 35 ]. Pectin substances may also be de-esterified by the action of pectin methyl esterase.
This esterification process is initiated in situ on damaged tissues, firm fruits, and vegetables by strengthening the cell walls and enhancing intercellular cohesion via a mechanism involving calcium. Metal ions catalyze the decomposition of heat-labile fruit pigments, which consist of pectin ingredients. This process causes the color change in fruit jams or jellies [ 42 ]. Therefore, jams and jellies are preserved in glass containers rather than metallic jars.
Hydrolytic rancidity causes lipid degradation by the action of lipolytic enzymes. In this reaction, free fatty acids are cleaved off triglyceride molecules in the presence of water. These free fatty acids have rancid flavors or odor [ 9 ]. The released volatile fatty acids have a stiff malodor and taste; therefore, hydrolytic rancidity is extremely noticeable in fats, such as butter [ 43 ].
Food preservation refers to the process or technique undertaken in order to avoid spoilage and to increase shelf life of food [ 44 , 45 ]. Different preservation and processing techniques are presented in Fig. Classification of food preservation and processing methods, recreated from references [ 46 , 47 , 48 ]. Drying or dehydration is the process of removing water from a solid or liquid food by means of evaporation. The purpose of drying is to obtain a solid product with sufficiently low water content.
It is one of the oldest methods of food preservation [ 49 ]. Water is the prerequisite for the microorganisms and enzymes to activate food spoilage mechanisms. In this method, the moisture content is lowered to the point where the activities of these microorganisms are inhibited [ 29 , 50 ]. Most microorganisms can grow at water activity above 0. Bacteria are inactive at water activity below 0. Most of the microorganisms cannot grow at water activity below 0. Drying has numerous advantages.
It reduces weight and volume of foods, facilitates foods storage, packaging, and transportation, and also provides different flavors and smells.
With all these benefits, drying is apparently the cheapest method of food preservation [ 53 ]. However, this process also has limitations. In some cases, significant loss of flavor and aroma has been observed after drying. Some functional compounds like vitamin C, thiamin, protein, and lipid are also lost because of drying [ 54 , 55 , 56 ]. Classification of drying Drying can be classified into three major groups: convective, conductive, and radiative. Depending on the mode of operation, dryers can be classified as batch or continuous.
For smaller-scale operations and short residence times, batch dryers are preferred. Continuous method of drying is preferential when long periodic operations are required and drying cost is needed to curtail [ 57 ]. Drying of different foods Food items, such as fruits, vegetables, meats, and fishes, are processed by drying. Instant coffee and tea are also produced by spray drying or freeze drying [ 58 , 59 ]. Processing temperature and drying time of different food items are presented in Table 5.
Pasteurization Pasteurization is a physical preservation technique in which food is heated up to a specific temperature to destroy spoilage-causing microorganisms and enzymes [ 64 , 65 ].
Almost all the pathogenic bacteria, yeasts, and molds are destroyed by this process. As a result, the shelf life of food increases [ 66 , 67 ]. This process was named after the French scientist Louis Pasteur — , who experimented with this process in He used this process to treat wine and beer [ 68 ].
Table 6 presents the applications of pasteurization process to preserve different food items. Pasteurization techniques The efficiency of pasteurization depends on the temperature—time combination. This combination is mostly based on the thermal death-time studies of heat-resisting microorganisms [ 55 ]. Vat pasteurizer is suitable for small plants having the capacity of — gallons [ 56 ]. Vat pasteurization requires constant supervision to prevent overheating, over holding, or burning [ 44 ].
High-temperature short-time HTST pasteurization is a continuous process pasteurizer equipped with sophisticated control system, pump, flow diversion devices or valves, and heat exchanger equipment [ 56 ]. Vat and HTST pasteurization perishes pathogenic microorganisms effectively. During heat treatment of food items, minimal physical, chemical, or biological changes take place [ 71 ]. After heating is done, the products are aseptically packaged in sterile containers [ 46 ]. UHT pasteurized products have a longer shelf life than other pasteurized products.
Table 7 presents the comparisons between the three pasteurization methods. High heat of pasteurization process may damage some vitamins, minerals, and beneficial bacteria during pasteurization. At pasteurization temperature, Vitamin C is reduced by 20 per cent, soluble calcium and phosphorus are reduced by 5 per cent, and thiamin and vitamin B12 are reduced by 10 per cent. In fruit juices, pasteurization causes reduction in vitamin C, ascorbic acid, and carotene.
However, these losses can be considered minor from nutritional point of view [ 44 , 72 ]. Thermal sterilization is a heat treatment process that completely destroys all the viable microorganisms yeasts, molds, vegetative bacteria, and spore formers resulting in a longer period of shelf life [ 44 ]. Retorting and aseptic processing are two categories of thermal sterilization [ 44 , 73 ].
Thermal sterilization is different from pasteurization. Comparison of different criteria between pasteurization and sterilization is given in Table 8. Retorting is defined as the packaging of food in a container followed by sterilization [ 73 ]. Foods with pH above 4. The attainment of such temperature can be possible in batch or continuous retorts. Batch retorts are gradually being superseded by continuous systems [ 75 ].
Hydrostatic retorts and rotary cookers are the most common continuous systems used in food industries [ 76 ]. Table 9 presents different criteria of batch and continuous retorts. Aseptic packaging involves placing commercially sterilized food in a sterilized package which is then subsequently sealed in an aseptic environment [ 79 ]. Conventional aseptic packaging utilizes paper and plastic materials.
Sterilization can be achieved either by heat treatment, by chemical treatment, or by attributing both of them [ 79 ]. Aseptic packaging is highly used to preserve juices, dairy products, tomato paste, and fruit slices [ 75 ]. It can increase the shelf life of food items to a large extent; as an example, UHT pasteurization process can extend the shelf life of liquid milk from 19 to 90 days, whereas combined UHT processing and aseptic packaging extend shelf life to six months or more.
Packages used for aseptic processing are produced from plastics having relative softening temperature. Moreover, aseptic filling can accept a wide range of packaging materials including: a metal cans sterilized by superheated steam, b paper, foil, and plastic laminates sterilized by hot hydrogen peroxide, and c a variety of plastic and metal containers sterilized by high-pressure steam [ 80 ].
Wide variation of packages thus enhances proficiency of aseptic packaging and diminishes cost. The direct approach of aseptic packaging comprises of steam injunction and steam infusion. On the other hand, indirect approach of aseptic packaging includes exchanging heat through plate heat exchanger, scrapped surface heat exchanger, and tubular heat exchanger [ 81 ].
Steam injection is one of the fastest methods of heating and often removes volatile substances from some food products. On the contrary, steam infusion offers higher control over processing conditions than steam injection and minimizes the risk of overheating products.
Steam infusion is suitable to treat viscous foods [ 81 ]. Tubular heat exchangers are adopted for operations at higher pressures and flow rates. These exchangers are not very flexible to withstand production capacity alteration, and their use is only limited to low viscous foods. Plate exchangers, on the other hand, overcome these problems. However, frequent cleaning and sterilizing requirements have made this exchanger less popular in food industries [ 81 ]. Freezing slows down the physiochemical and biochemical reactions by forming ice from water below freezing temperature and thus inhibits the growth of deteriorative and pathogenic microorganisms in foods [ 82 , 83 ].
It reduces the amount of liquid water in the food items and diminishes water activity [ 84 ]. Heat transfer during freezing of a food item involves a complex situation of simultaneous phase transition and alteration of thermal properties [ 85 ]. Nucleation and growth are two basic sequential processes of freezing. Freezing time Freezing time is defined as the time required to lower the initial temperature of a product to a given temperature at its thermal center.
In general, slow freezing of food tissues results in the formation of larger ice crystals in the extracellular spaces, while rapid freezing produces small ice crystals distributed throughout the tissue [ 85 ]. The International Institute of Refrigeration defines various factors of freezing time in relation to the food products and freezing equipment. Dimensions and shapes of the product, initial and final temperature, temperature of refrigerating medium, surface heat transfer coefficient of the product, and change in enthalpy and thermal conductivity of the product are the most important factors among them [ 16 ].
Individual quick freezing Individual quick freezing IQF generally relates to quick freezing of solid foods like green peas, cut beans, cauliflower pieces, shrimps, meat chunks, and fish.
On the other hand, freezing related to liquid, pulpy or semiliquid products, like fruit juices, mango pulps, and papaya pulps is known as quick freezing. The ice crystals formed by quick freezing are much smaller and therefore cause less damage to cell structure or texture of the food. Shorter freezing period impedes the diffusion of salts and prevents decomposition of foods during freezing. IQF also allows higher capacity for commercial freezing plants with the resultant cost reduction.
However, higher investment is required to set up a quick freezing plant [ 86 ]. Different quick freezing techniques, such as contact plate freezing, air-blast freezing, and cryogenic freezing, are used to process food items.
The comparison between different quick freezing techniques for fishery products is presented in Table Chilling process reduces the initial temperature of the products and maintains the final temperature of products for a prolonged period of time [ 88 ]. It is used to reduce the rate of biochemical and microbiological changes and also to extend shelf life of fresh and processed foods [ 89 ].
Partial freezing is applied to extend the shelf life of fresh food items in modern food industries. This process reduces ice formation in foods, known as super chilling [ 91 ].
Chilling can be done by using various equipments, such as continuous air cooler, ice bank cooler, plate heat exchanger, jacketed heat exchanger, ice implementation system, vacuum attribution system, and cryogenic chamber [ 92 ].
Chilling rate is mainly dependent on thermal conductivity, initial temperature of foods, density, moisture content, presence or absence of a lid on the food storage vessel, presence of plastic bags as food packaging equipment, and the size as well as weight of food units [ 93 ]. Table 11 describes various methods for chilling solid and liquid food items. Advantages and disadvantages of chilling Chilling storage is extensively used for its effective short-term preservation competency.
Chilling retards the growth of microorganisms and prevents post-harvest metabolic activities of intact plant tissues and post-slaughter metabolic activities of animal tissues. It also impedes deteriorative chemical reactions, which include enzyme-catalyzed oxidative browning, oxidation of lipids, and chemical changes associated with color degradation.
It also slows down autolysis of fish, causes loss of nutritive value of foods, and finally bares moisture loss [ 90 ]. Chilling is high capital intensive since this process requires specialized equipment and structural modifications. Chilling may reduce crispiness of selected food items [ 95 ]. Chilling process also dehydrates unwrapped food surfaces, which is a major limitation of chilling process [ 96 ]. Irradiation is a physical process in which substance undergoes a definite dose of ionizing radiation IR [ 97 ].
IR can be natural and artificial. Natural IR generally includes X-rays, gamma rays, and high-energy ultraviolet UV radiation; artificially generated IR is accelerated electrons and induced secondary radiation [ 98 , 99 ].
IR is used in 40 different countries on more than 60 different foods [ 97 ]. The effects of IR include: a disinfestation of grains, fruits, and vegetables, b improvement in the shelf life of fruits and vegetables by inhibiting sprouting or by altering their rate of maturation and senescence, and c improvement in shelf life of foods by the inactivation of spoilage organisms and improvement in the safety of foods by inactivating foodborne pathogens [ , ].
Different factors of food irradiation techniques are listed in Table Regulatory limits of irradiation The IR dose delivered to foods is measured in kilo grays kGy. IR regulatory limits are set by the legislative bodies. Depending on the regulatory authority, these limits may be expressed as minimum dose, maximum dose, or approved dose range [ 98 ]. Table 13 presents different regulatory limits for food irradiation applications.
Effects of Irradiation The nutritional parameters, such as lipids, carbohydrates, proteins, minerals, and most vitamins, remain unaffected by IR even at high doses [ ].
According to FDA, IR has effects on food nutritive value that is similar to those of conventional food processing techniques [ ]. High hydrostatic pressure or ultra-high pressure processing HPP technology involves pressure attribution up to MPa to kill microorganisms in foods. This process also inactivates spoilage of foods, delays the onset of chemical and enzymatic deteriorative processes, and retains the important physical and physiochemical characteristics of foods.
HHP has the potential to serve as an important preservation method without degrading vitamins, flavors, and color molecules during the process [ 58 , , ].
Freshness and improved taste with high nutritional value are the peerless characteristics of HPP technology. This process is also environmental friendly, since energy consumption is very low and minimal effluents are required to discharge [ , ].
The major drawback of this technology is the high capital cost. Their optimal dosage is 0. Because of their high degree of hydrophilicity, lactylate salts hydrate readily in water at room temperature. The sodium salts hydrate more rapidly than the calcium salts, giving SSL and CSL different functionalities in short baking processes [ 9 ]. The strengthening effect of lactylates relates to their ability to aggregate proteins, which helps in the formation of the gluten matrix.
It is believed that they interact with proteins through: i hydrophobic bonds between the non-polar regions of proteins and the stearic acid moiety of lactylates; and ii ionic interactions between the charged amino acid residues of proteins and the carboxylic portion of lactylates.
In the case of bread dough, these effects result in increased dough viscosity, better gas retention and, ultimately, greater bread volume [ 9 ]. The effects of lactylates on dough handling properties and proofed dough volume are also related to protein complexing. As proofed dough is heated in the early baking phase, the lactylates are transferred from the protein to the starch.
The coating on the starch significantly delays starch gelatinization, which keeps the viscosity low and allows additional expansion of the dough in the oven.
As the resultant dough is softer than the unemulsified dough, it allows more abusive mechanical working without causing irreversible damage to the protein structure. It also has effects on crumb softening, extending shelf-life, through binding to amylose, showing similar action to distilled monoglycerides. However, bakers tend to prefer DATEM as a dough conditioner for maximum gas retention, and add distilled monoglycerides at the desired level when extra softness is needed [ 5 ].
The need to reduce sodium in bakery products, for health reasons, has led to an increased interest in CSL as an SSL replacer [ 5 ]. Polysorbates are sorbitol derivatives and they form part of a group of emulsifiers known as sorbitan esters, which can be further modified to polysorbates [ 10 ]. The polysorbate family of products is among the most hydrophilic or water soluble emulsifiers allowed in foods, due to the long polyoxyethylene chain, so the addition of small amounts of polysorbate emulsifiers to water results initially in a dramatic decrease in interfacial tension [ 10 ].
The unique qualities of each polysorbate are attributed to the different fatty acids used in each product. The ethylene oxide chain length is controlled at an average of 20 moles and it does not change between products.
The short-chain fatty acid polysorbate 20 has the highest HLB at Sorbitan esters and polysorbates are emulsifiers regulated by governing bodies. For instance, in North America, the market where they are most popular, the specific applications for these compounds in foods are defined and the use level is controlled.
Most polysorbates are used in bakery goods. In most bakery applications, polysorbates are used below 0. Polysorbates are added as dough strengtheners to improve baking performance. They stabilize the dough during late proofing and early stages of baking, when there are great stresses on the inflating cells.
Their use results in loaves with greater volume and a fine and uniform crumb structure [ 10 ]. So, even if the potential risk of impurities in polysorbates is low, a responsible food manufacturer should be aware of these concerns. Food producers would be prudent to source their polysorbates from a reputable supplier [ 10 ]. Hydrocolloids are widely used in the food industry, because they modify the rheology and texture of aqueous systems. These additives play a very important role in foods, as they act as stabilizers, thickeners and gelling agents, affecting the stabilization of emulsions, suspensions, and foams, and modifying starch gelatinization [ 2 ].
During baking, starch gelatinization and protein coagulation take place and the aerated structure obtained during leavening is fixed, forming the bread crumb. It has been stated that granule swelling can be reduced by the presence of hydrocolloids particularly at high concentrations , which can interact with the molecules leached out from starch granules, leading to a stiffening effect.
Thus, due to these interactions, crumb structure and texture are positively influenced by the presence of gums [ 11 ]. In the baking industry, hydrocolloids are very important as breadmaking improvers, because they enhance dough-handling properties, improve the quality of fresh bread, and extend the shelf-life of stored bread. Polysaccharides such as carboxymethyl cellulose, guar gum and xanthan gum are employed as stabilizers in bakery products in particular.
Xanthan gum is an anionic polysaccharide employed to modify rheological properties of food products [ 1 ]. It is produced industrially from carbon sources through fermentation by the Gram-negative bacterium Xanthomonas campestris [ 12 ]. Structure-wise, it is a polymer with a d -glucose backbone.
Trisaccharide side-chains formed by glucuronic acid sandwiched between two mannose units are linked to every second glucose of the main polymer chain. The carboxyl groups in xanthan gum may ionize creating negative charges, increasing the viscosity of the solution in water [ 1 ]. Xanthan gum easily disperses in cold and hot water, quickly producing viscous solutions. These solutions are stable to acid, salt, and high temperature processing conditions, and show good efficiency at low concentrations, around 0.
Also, products that contain this gum have fluidity, good mouthfeel, and adhesion. These advantages make xanthan gum a suitable thickener, stabilizer, and suspending agent in many foods [ 12 ]. In bakery products, it improves wheat dough stability during proofing. Also, it has the ability to increase dough stability during freeze-thaw cycles in frozen dough [ 2 ].
Guar gum is made of the powdered endosperm of the seeds of Cyamopsis tetragonolobus , a leguminous crop. The endosperm contains a complex polysaccharide, a galactomannan, which is a polymer of d -galactose and d -mannose. This hydroxyl group-rich polymer forms hydrogen bonds with water, imparting significant viscosity and thickening to the solution. Due to its thickening, emulsifying, binding and gelling properties, quick solubility in cold water, wide pH stability, film forming ability and biodegradability, guar gum finds applications in a large number of industries, including the bakery industry.
At the level of 0. It is also used for increasing dough yield in baked goods [ 13 ]. Carboxymethylcellulose CMC is a cellulose derivative, and it is also called cellulose gum. It finds applications in the food industry as a food stabilizer and thickener. This anionic polysaccharide is often used as a food additive in its sodium salt form sodium carboxymethylcellulose. In sodium carboxymethylcellulose, some of the carboxyl groups have been replaced by sodium carboxylate groups. The degree of substitution by sodium ions, chain length of the cellulose backbone and clustering of the carboxymethyl substituents determine CMC functionality [ 1 ].
CMC has a combined effect with enzymes and emulsifiers on textural properties of both dough and fresh bread. For example, CMC contributes to yielding high volume and retarding staling. Both CMC and guar gum have proven to be beneficial in the formulation of gluten-free breads [ 2 ]. Preservatives are intended to inhibit the growth of molds and thermophilic bacteria. The preservatives permitted for use in bread are commonly limited by legislation [ 5 ].
Propionic, sorbic and benzoic acids E, E and E, respectively are among the most commonly used food preservatives. Propionic acid inhibits molds and Bacillus spores, but not yeasts to the same extent, and has, therefore, been the traditional choice for bread preservation [ 14 ].
Preservatives are often added in their salt form, which is more soluble in aqueous solutions. Their effectiveness depends on the pH of the system to which they are added, as the dissociated acid alters the antimicrobial effect.
The p K a values pH at which dissociation occurs of propionic acid and sorbic acid are 4. Maximum pH for their activity is around 6. The sodium, potassium and calcium salts of propionic acid are used as bread preservatives in many countries. Calcium propionate E is more widely used than propionic acid, because it is easier to handle the solid salt than the corrosive liquid acid [ 15 ]. Its regular dosage is around 0.
A decrease in loaf volume is caused by the combination of reduced yeast activity and altered dough rheology [ 15 ]. Regarding propionic acid, high levels of dietary intake have been associated with propionic acidemia in children. Complications of this disease can include learning disabilities, seizures, arrhythmia, gastrointestinal symptoms, recurrent infections and many others [ 16 ].
Sorbates are more effective at inhibiting mold growth than propionates by weight [ 16 ]. However, sorbic acid and its salts are of less value in bread and yeast-raised goods, because of their detrimental effects on dough and bread characteristics. They can produce sticky doughs which are difficult to handle; and the baked products may have reduced volume and an irregular cell structure. The use of encapsulated sorbic acid is an alternative to overcome these negative effects.
Also, sorbic acid or its salts may be sprayed on the surface of breads after baking [ 14 ]. In the dough, its dosage is around 0. However, at such concentrations, its effect against molds is limited. Significantly higher concentrations lead to an unacceptable odor of vinegar in the bread [ 15 ]. Among these are fermentates, which are food ingredients produced by the fermentation of a variety of raw materials by food grade microorganisms.
Such microorganisms include lactic acid bacteria or propionic acid bacteria that produce weak organic acids with a preservative effect. However, weak organic acid preservatives have actually been reported to have no effect on the shelf-life of bakery products with pH values close to 7 [ 16 ].
Preservatives inhibit microbial spoilage, but do not destroy microorganisms. Therefore, it is important to process baked goods following good manufacturing practices GMP , including the use of good quality raw-materials and appropriate hygiene systems that are correctly monitored [ 5 ].
Enzymes, also called biocatalysts, are proteins with special properties. Each kind of enzyme has its own specific substrate on which it acts, which provides excellent process control for the use in breadmaking.
The Enzyme Commission EC number for each enzyme mentioned is shown in this chapter. This is an international numerical classification for enzymes, where classifying criteria are the chemical reactions each enzyme catalyzes [ 17 ]. For a logical comprehension, we have classified food enzymes used in baking by the substrate each one acts on, as follows. The main polysaccharide present in wheat flour is starch, which is present in the form of granules composed of two fractions. Each generated dextrin has its own non-reducing end.
This fact explains why it is necessary to have damaged starch to be hydrolyzed by this enzyme: it is a more easily degradable substrate than native starch granules.
Consequently, higher gas production enhancing bread volume occurs [ 20 ]. Its activity is low in ungerminated wheat, providing high FN results. On the contrary, in germinated wheat, its activity is high, causing low FN results, and this situation can be a disaster for baking. Once it degrades damaged starch, the dough consistency decreases and machinability is enhanced [ 18 , 20 ]. Maillard reaction is responsible for the non-enzymatic browning of bread crust and generation of bread characteristics including aroma and flavor [ 18 , 20 ].
Amylases also permit oven spring to occur for a prolonged period. The bread volume is increased once they avoid quick viscosity rising during starch gelatinization [ 18 ]. This endogenous enzyme is present in mature ungerminated wheat, and hydrolyzes only damaged starch granules [ 18 ]. The generated maltoses will be substrate for yeast fermentation after maltase action, enhancing the gassing power of the dough [ 19 ].
This effect also contributes to reduce bread firmness [ 18 ]. The maltoses generated that are not consumed by the yeast contribute to crust color [ 19 ]. This effect is due to its efficiency to act on amorphous regions of starch granules, generating excessive dextrinization, with excessive decrease in dough viscosity, producing an open texture crumb [ 20 ]. Bacterial amylase provides a softer crumb, despite greater recrystallized starch content in comparison with a control. However, stickiness and gumminess were verified in crumb treated with this enzyme.
It was proven that bacterial amylase was efficient to extend bread shelf-life.
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