The Impact of Pasteurisation and Sterilisation on Bioactive Compounds of Onion By-products

Onion (Allium cepa L.) waste disposal represents a worldwide environmental problem. A solution to this issue could be the use of onion waste as food-grade ingredients, which could be added to processed foods for their enrichment in bioactive compounds. For this purpose, onion waste should be adequately processed and stabilised. Thus, the objective of this work was to study the composition of processed onion waste, assessing the effects of processing and thermal stabilisation on onion waste bioactive compounds. Onion waste was triturated (‘Paste’) and triturated?+?pressed (‘Bagasse’, solid residue and ‘Juice’, liquid fraction). All by-products were stabilised by pasteurisation and sterilisation. Results indicated that bagasse was an enriched dietary fibre product (361–453 mg/g dry weight (DW)); paste showed high alkyl or alkenyl cystein sulphoxide (ACSO) content (5.6 mg/g DW); and juice showed large fructans concentration (205–221 mg/g DW). In paste and bagasse, pasteurisation and sterilisation improved soluble/insoluble fibre ratio, with no changes in total dietary fibre concentration in pasteurised products and a slight decrease (8 % on average) in the sterilised ones. In juice, thermal treatments produced fructans losses, more pronounced after sterilisation (59 % on average) than after pasteurisation (36 % on average). However, sterilisation provided by-products with better ACSO results than pasteurisation. As a conclusion, industrial processing has an important impact on the bioactive composition, generating products with different functional applications. Moreover, pasteurisation resulted to be the most suitable treatment to obtain safe products enriched in dietary fibre and fructans, while sterilisation could be used to produce products rich in ACSOs.     

Characterisation of onion (Allium cepa L.) by-products as food ingredients with antioxidant and antibrowning properties

Processing and stabilising onion wastes (residues and surpluses of onion) could solve the environmental problem derived from a great onion wastes disposal. Moreover, obtaining stabilised onion by-products as natural antioxidant food ingredients could be advantageous to food industry, not only to improve the use of onion wastes but also to obtain new natural and functional ingredients. The aim of this study was to characterise onion by-products – juice, paste and bagasse – from two Spanish onion cultivars – ‘Figueres’ and ‘Recas’ – that have been stabilised by thermal treatments – freezing, pasteurisation and sterilisation – in order to evaluate the effect of the processing and stabilisation treatment on the bioactive composition, antioxidant activity and polyphenol oxidase (PPO) enzyme inhibition capacity. The results obtained triggered to choose one onion by-product offering better characteristics for its potential development as a food ingredient: source of antioxidant and antibrowning bioactive compounds. In this study it was shown that processing of ‘Recas’ onion wastes to obtain a paste (mixture content) and applying a mild pasteurisation were the best alternatives to obtain an interesting stabilised onion by-product with good antioxidant properties that made useful its use as functional food ingredient.     

Dietary fibre content and antioxidant activity of Manto Negro red grape (Vitis vinifera): pomace and stem

The general composition of two by-products of the vinification process of the Manto Negro red grape (Vitis vinifera) variety, namely pomace and stem, were determined. Both by-products present high contents of total dietary fibre (TDF), comprising three fourths of the total dry matter. The pomace had high protein (12.2%) and oil (13.5%) values and the stem large amounts of extractable polyphenols (11.6%). Due to the high fibre content, the soluble dietary fibre (SDF), insoluble dietary fibre (IDF), uronic acids (UA) and Klason lignin (KL) were analysed in both samples. Notable were the high percentage of soluble fibre (15%) in relation to the total dietary fibre for the pomace, as well as the high content of Klason lignin (KL) in both by-products, especially in the stem (31.6%). This fraction (KL) has important amounts of condensed tannins (CT) and resistant protein (RP).     

Antioxidant activity and dietary fibre in durum wheat bran by-products

Milling of wheat generates by-products, which can be used to improve the technological performance and/or to integrate foods with healthy compounds. The aim of this paper was to select fractions of durum wheat bran having different functional and nutritional characteristics. Wheat bran by-products were obtained by an industrial milling process. Beside the single fractions, two commercial products Bran & Brain 50 and 70, obtained by blending some of the durum wheat fractions were also studied. All samples were investigated for water holding capacity, soluble and insoluble dietary fibre content and for their antioxidant activity. The soluble fibre content of the durum wheat by-product ranged between 0.9% and 4.1%; while that of insoluble fibre between 21% and 64%. B&B 70 has a TDF content of 61%, while B&B 50 has 42%. The water holding capacity of each fraction is strictly related to the amount of insoluble fibre and to the granulometry of the by-products. Cooking-extrusion process does not affect the amount of soluble fibre; by contrast, a significant increase of the insoluble fibre was detected. The antioxidant activity is higher for the internal bran fraction and it increases in fractions having reduced granulometry. The antioxidant activity of some durum wheat by-product fractions is comparable to that of widespread fruits and fresh vegetables, likely due to the presence of fibre-bound phenol compounds. The high fibre content and antioxidant activity of durum wheat bran by-products can be of particular interest for their use in cereal-based products.     

Improve the functional properties of dietary fibre isolated from broccoli by-products by using different technologies

The aim of this study was to analyze the chemical composition of leaves, stems and inflorescences obtained from broccoli by-products in order to develop the improvement of the composition and functional properties of DF from broccoli by-products through treatment with different degradation methods, such as modifications with supercritical fluids, enzymatic, autoclave and ultrasound treatment. The results showed that the chemical composition of the different parts of the broccoli by-products, leaves, stems and inflorescences was significantly different, highlighting that the content of insoluble and soluble dietary fibre was higher in the stem. The enzymatic treatments decreased the content of neutral sugars and increased the content of uronic acids, which was related to the increase of specific functional activities. Cellulase and the multi-enzymatic visconzyme complex improved the solubility and glucose adsorption capacity, whereas supercritical fluids treatment improved the swelling, water retention and lipid absorption capacities. The value of non-extractable phenolic compounds was higher in the inflorescences and increased with enzyme and supercritical fluid treatments, as well as the antioxidant capacity. Enzyme treatment also had a greater effect on the stimulation of the growth of the lactic acid bacteria studied and, therefore, reached the highest values in the production of all short-chain fatty acids analysed. Therefore, the use of enzyme treatments of dietary fibre obtained from broccoli by-products improves the functional properties of broccoli fibre.     

Rheological properties of wheat dough supplemented with functional by-products of food processing: Brewer’s spent grain and apple pomace

The physicochemical properties of brewer’s spent grain (BSG) and apple pomace (AP), and their effect on dough rheological properties were investigated. BSG had high protein content and both by-products were found to be high in dietary fibre. The rheological and the pasting properties of dough were significantly altered by the addition of by-products, with the main effects being due to the presence of dietary fibre. The biaxial extensional viscosity was significantly higher for the supplemented doughs; the strain hardening index decreased with increasing the levels of flour substitution. The replacement of wheat flour with the by-products significantly reduced the uniaxial extensibility, while the storage modulus, G″, was found to increase, indicating changes in the structural properties of dough. These changes were reflected in the ability of dough to rise during proofing.     

Onion (<Emphasis Type="Italic">Allium cepa</Emphasis> L.) by-products as source of dietary fiber: physicochemical properties and effect on serum lipid levels in high-fat fed rats

The effect of industrial processes used to obtain onion by-products was evaluated. Fiber composition and physicochemical properties were assessed in order to choose the best process to obtain high-fiber ingredients. Moreover, the effect of the inclusion of the dietary fiber-rich onion by-products in a high-fat diet on serum lipids of rats was also evaluated. Bagasse was the best by-product since it showed the highest fiber content with a balanced soluble-to-insoluble fiber ratio and the best physicochemical properties. This fact is related to its high fiber content and also due to its composition, rich in uronic acids and polysaccharides, which explains its high cation exchange capacity, water-holding capacity and swelling capacity. In addition, the inclusion of Bagasse in a high-fat diet produced a reduction in the serum lipid and total cholesterol increases induced by high-fat diet. This effect could be related to the high cation exchange and swelling capacities that Bagasse showed, since these properties can create a concerted effect in reducing the number of intact micelles available, the transit time, and consequently the total time available for cholesterol and lipid absorption in the small intestine.     

By-products of the classification of chickpea as an alternative in the production of hummus

Chickpea (Cicer arietinum L.) is a valuable source of protein, polyunsaturated fatty acids, polyphenols, dietary fibre, vitamins and complex carbohydrates, such as oligosaccharides with prebiotic activity. This study evaluates the use of by-products derived from the classification of chickpea as functional ingredients in food production. The chemical content and thermal properties of by-products (discard and split) were determined and compared to whole grains for export. Split grains had a higher protein content, lower water hydration capacity (WHC) and lower fibre. The content of oligosaccharides was lower in discard grains. For further studies, hummus was prepared with three samples, and texture and sensory analyses were performed. The results of texture and sensory analyses show no significant differences between discard and whole grains. Chemical contents of by-products show advantages for the food industry. Discard grains can be used to prepare hummus with the same technology and sensory quality as whole grains.     

Nutrient composition of some less-familiar oil seeds

Seven less familiar oil seeds, namely gokhru, thumba, onion, tobacco, grape, niger seeds and mango seed kernels were analysed for their proximate composition, amino acid and fatty acid composition. Gokhru, niger, tobacco and onion seeds were found to be good sources of protein and fat. Crude fibre contents of thumba and grape seeds were high. The seeds of thumba, niger, onion and mango (seed kernel) contained 4 g lysine per 16 g N. The methionine content of onion-seed protein was very high. Fatty acid profiles of fat from these oil seeds revealed a high proportion of unsaturated fatty acids with the exception of gokhru.     

Effect of extraction method on chemical composition and functional characteristics of high dietary fibre powders obtained from asparagus by-products

Asparagus (Asparagus officinalis L.) by-products, which represent around 50% of the processed vegetable, are a potential source of dietary fibre. The way that these by-products are treated affects the composition and functional properties of fibre-rich powders. Factors such as treatment intensity, solvent, and drying system were studied. Only the more soluble components (soluble sugars, uronic acids and proteins) showed significant differences. All the fibre-rich powders had high concentrations of TDF (62–77%). The IF/SF proportion decreased with the severity of treatment, in this way increasing the physiological quality of the fibre. Functional properties, namely water-holding capacity (WHC), oil-holding capacity (OHC), solubility (SOL), and glucose dialysis retardation index (GDRI), varied according to the preparation procedure. WHC and GDRI were higher in intensely extracted fibres; due to the effect of thermal processing. WHC showed values (11–20 ml water/g powder) similar to those described for other agricultural by-products, but OHC and GDRI were much higher (5–8 ml oil/g powder and 25–45%, respectively). These properties make fibre-rich powders from asparagus by-products a valuable source of dietary fibre to be included in the formulation of fibre-enriched foods.     

Effects of different polarity of onion skin extracts on antioxidative properties and non-volatile profiles

Onion skins are agricultural by-products that contain high levels of antioxidants, including quercetin and protocatechuic acid. The solubility of extracts can affect their antioxidant capacity in food oil matrices. The antioxidative properties of onion skin extracts with different polarity were compared and the chemical profiles of the extracts were identified by GC-MS. Highly lipophilic, moderately hydrophilic and highly hydrophilic onion skin extracts (HLE, MHE and HHE, respectively) were prepared and their antioxidant properties were tested using in vitro assays and bulk oil or oil-in-water (O/W) emulsions. The most abundant phenolic compounds in the onion skin extracts were quercetin and protocatechuic acid. The lipophilicity levels of HLE, MHE and HHE were 0.674, 0.394 and −1.225, respectively. HLE showed higher antioxidant capacity in bulk oil and O/W emulsion matrices compared to MHE and HHE. The antioxidant capacity of HLE was higher in the O/W emulsion than in the bulk oil system. Therefore, highly lipophilic onion skin extracts can be used as effective natural antioxidants in oil matrices, especially O/W emulsions.     

Effect of tiger nut fibre on quality characteristics of pork burger

Horchata is a refreshing beverage obtained from tiger nut tubers that yields high amount of by-products. These by-products have a high content of fibre that allows its application in the development of dietary fibre rich foods. The utilization of increasing levels (0%-control, 5%, 10% and 15%) of tiger nut fibre (TNF), in the formulation of pork burgers was evaluated. This evaluation was based on: chemical composition, physicochemical, cooking characteristics and sensory properties of burgers. Pork burgers elaborated with TNF had higher nutritional value (higher fibre content) and better cooking characteristics (higher cooking yield, fat retention and moisture retention) than control burgers. Some of the negative changes in colour (a* decrease and b* increase) and texture (chewiness and springiness increase) parameters due to TNF addition observed in raw burgers were masked by the stronger modifications due to the cooking process. Burgers with TNF were perceived as less greasy, less juicy, more grainy and with less meaty flavour than controls; although this perception did not reduce the overall acceptability of burgers. Overall acceptability scores were slightly lower in burgers with 15% TNF, although no significant differences were detected with the scores of control, 5% and 10% TNF burgers. TNF addition to burgers is a promising and convenient application as dietary fibre of burgers was significantly increased without changes in sensory acceptance.     

Yogurt enrichment with functional asparagus fibre. Effect of fibre extraction method on rheological properties, colour, and sensory acceptance

In the asparagus-processing industry, the by-products constitute around 50% of the total weight. These by-products are rich in fibre and bioactive compounds which could be advantageously employed in human nutrition. In the present work, yogurts were enriched with fibre obtained from the non-edible part of asparagus shoots to assess how the method of extraction (water or ethanol) and then drying (oven or lyophilisation) affects its performance. Fibre incorporation increased the consistency of the yogurts (higher η, G′, G″), especially if the fibres had been extracted in ethanol and lyophilised. However, there were no significant changes in the viscoelastic behaviour (tan δ) for any of the fibre types. Fibres diminished the clarity and imparted a yellow-greenish colour to the yogurt, which also varied depending on the method of extraction and drying, the yogurts with water-extracted fibres being more colourful. The sample more liked according to a consumer test was the yogurt containing water-extracted and oven-dried fibre for aroma, taste, texture, and overall acceptance, and ethanol-extracted and lyophilised for colour. The consumer panel scored all the samples around to the neutral point “neither like nor dislike”, demonstrating that fibre obtained by all methods were equally compatible with yoghurt enrichment.     

A novel idea in food extraction field: Study of vacuum microwave hydrodiffusion technique for by-products extraction

Vacuum microwave hydrodiffusion and gravity (VMHG), a modified form of solvent free microwave hydrodiffusion and gravity (MHG) technique, was used for extraction of onion by-products. A detailed study concerning about optimisation of different parameters like irradiation power, degree of vacuum and extraction time was performed. Subsequently, the temperature difference in different parts of matrix and also in the reactor was evaluated both in case of MHG and VMHG. Extracts obtained by VMHG, MHG and also conventional solvent extraction method (CSE) were analyzed for quantification of flavonoids by HPLC, along with studying the distribution of flavonoids in different intervals of time at optimised conditions. Two different methods were selected for evaluating the antioxidant capacity of these extracts along with determination of their phenolic content by the Folin-Ciocalteu method: the reduction of the stable DPPH (2,2-diphenyl-1-picrylhydrazyl) radical and the inhibition of the AAPH-induced peroxidation of linoleic acid in SDS micelles. Reduction of pressure up to 0.7 bar at microwave power of 500 W helped to increase the antioxidant activity of onion extracts with 57% increase in total quercetin contents against those obtained at atmospheric pressure. VMHG proved itself an efficient and environment-friendly technique allowing the extraction of flavonols at lower reactor temperature (81 °C ± 1), with improved alterations of tissues observed by microscopic studies, from onion by-products just in 26 ± 1 min, in the absence of any solvent.     

New approaches in the preparation of high dietary fibre powders from fruit by-products

The market for dietary fibre is highly competitive and, for new products, new healthy properties are necessary in addition to those of traditional products. This article deals with the production of high dietary fibre powders from fruit by-products and the potential preparation of those fibres with associated bioactive compounds. While milling and screening have been the main steps in obtaining high dietary fibre powders from cereals; wet milling, washing, drying and dry milling are very important in producing fibres from fruits. The effects of some technological treatments on the quality of the fibres obtained from orange, mango and other materials are also illustrated.     

Non-waste technology through the enzymatic hydrolysis of agro-industrial by-products

BackgroundOne of the major challenges facing the world at present is the utilisation of by-products. European food industries generate millions of tonnes of by-products annually. Fruit and grain processing industries do not fully utilise potentially valuable raw materials (peels, husks, seeds, stones, bran) that contain a significant amount of dietary fibre and antioxidants. According to recent research, due to the complexity in structure of agro-industrial by-products, both lipophilic and hydrophilic compounds integrated into the matrix and furthermore they are linked with various macromolecules. These interactions have a great influence on bioavailability and hence antioxidant ability of biologically active compounds present in by-products. At present, one major concern is the development of efficient and green technology for the degradation of starch and non-starch polysaccharides presented in by-products, thus contributing to their reduction, as well as long-term improvements in environmental quality and enhancement of extractability of antioxidant compounds.Scope and ApproachThis review summarizes the research progress on the enzymatic hydrolysis of by-products, gives a brief insight into the current state of the amount of the by-products, and describes one possible method of waste recycling.Key findings and conclusionsProcessing of by-products, using enzymatic hydrolysis is promising technique for prebiotic substrates development. Moreover, enzymatic hydrolysis is able to increase the extractability of polyphenols including non-extractable proanthocyanidins from food matrix with no utilisation of organic solvents, nor any other toxic chemicals.     

Dietary fibre from berry-processing waste and its impact on bread structure: a review

The structure and function of by-products of berry-processing industries are reviewed, with particular attention to dietary fibre (DF) and its effects in food products. The complex chemical composition and physicochemical characteristics of DF have been investigated and strategies for extraction of specific fractions that provide tailored technological and physiological functionality have been reviewed. The aim of this review is to describe in detail the structural composition and isolation methods of dietary fibre derived from berry by-products, and to explore their potential functionality in foods. The goal is to introduce DF from berry waste streams into the food chain, for which bread is a major vehicle. However, the appeal of bread lies in its aerated structure, for which DF is generally detrimental. The technological influence of DF on the formation and stabilization of the aerated structure of bread is therefore reviewed, in order to understand how to incorporate DF into bread while maintaining palatability. The aerated structure of bread is stabilized by two mechanisms: the gluten matrix and the liquid film surrounding bubbles. Incorporating DF successfully into bread requires understanding its interactions with both of these mechanisms. DF fractions from berries offer superior nutritional value compared to cereal fibre, potentially with less damage to bread structure, due to the higher proportion of soluble fibre. By-products from berry-processing industries could be used as a source of technologically and nutritionally distinctive DF to fabricate foods with enhanced nutritional value. © 2019 Society of Chemical Industry     

High hydrostatic pressure improves the functionality of dietary fibre in okara by-product from soybean

The combined effect of high hydrostatic pressure (HHP) and controlled temperature on total (TDF), soluble dietary fibre (SDF) content, and its associated hydration properties were assayed in okara, a rich-in-insoluble dietary fibre residue from the soydrink- and tofu-making process of soybean. TDF in starting unprocessed okara was 45.7% and its SDF to TDF ratio was 4.6. When dry, hydrated and autoclaved okara samples, were subjected to HHP-treatment (200 and 400 MPa) at 30 and 60 °C, the amount of SDF went up by more than 8-fold. At 200 MPa, TDF was not significantly different from control, but at 400 MPa values varied from 38.1 to 64.8%. In vitro physicochemical properties of okara were also modified by HHP-treatment. Therefore, the effect of a combined treatment with hydration, temperature and HHP-technology on the improvement of the soluble fibre fraction (%) and functionality of certain vegetable by-products from the food industry could be very useful for the elaboration of food ingredients with potential health-promoting effects.Industrial relevanceThis article deals with the effect of HHP-treatment on dietary fibre fractions and associated physicochemical properties in okara by-product from soybean. Results suggested that the higher the hydrostatic pressure and temperature applied, the higher the ratio of soluble to total dietary fibre in okara. Likewise, the effect of combined hydration, mild temperature, and HHP-treatment could increase the soluble fraction (%) of other rich-in-insoluble dietary fibre vegetable by-products, which could potentially be used as valuable ingredients of new functional foods.     

Extrusion improved the physical and chemical properties of dietary fibre from bamboo shoot by-products

Bamboo shoot by-products are regarded as waste and environmental pollutant. This study aimed to improve the functional properties of dietary fibre from bamboo shoot by-products. After CO₂ extrusion, the particle size of CO₂-extruded bamboo fibre was 17.6% lower than that of the control, and its specific surface area was 2.85 times that of the control. The soluble dietary fibre content was significantly increased from 5.64 g/100 g to 11.05 g/100 g (P < 0.05), and the capacities for water holding, swelling and oil holding were remarkably improved. The cholesterol adsorption of CO₂-extruded bamboo fibre was increased from 96.54 μg g⁻¹ to 174.65 μg g⁻¹ (pH 7.0), and its nitrite ion adsorption capacity was increased from 503.33 μg g⁻¹ to 657.27 μg g⁻¹ (pH 2.0). In summary, the structural changes of bamboo fibre such as internal porosity, surface roughening and low crystallinity indicated that its functional properties were improved after CO₂ extrusion.     

Food uses of pineapple waste and by-products: a review

Waste from fruits and vegetable processing industry is produced in large quantities worldwide and it contains high levels of lignocellulose, fibre, sugar, bioactive and functional compounds. Their utilisation has become one of the main important and challengeable aspects due to the generation of large quantities of by-products including peels, seeds, leaves and unused flesh in different steps of processing chain. Many researches have validated the waste utilisation as novel, low-cost, economical and natural sources of dietary fibre, antioxidants, pectin, enzymes, organic acids, food additives, essential oils, etc. through different methods of extractions, purifications and fermentations. Though, obtaining these by-products from such a variable substrate requires an understanding of the composition of the polysaccharides and their associations within the overall substrate. Focus on the pineapple fruit, scientific and technological studies have already highlighted and confirmed the potential of better and more profitable markets for pineapple wastes. This review is first of all the collection of previous reports about valorisation of food processing waste, deepening the possibilities of pineapple waste utilisation and to promote the integral exploitation of the by-products rich in bioactive compounds, even as multifunctional food ingredients. More in detail, this review aims at identifying those processes that can be implemented even in disadvantaged areas by means of technologies that allow recovering waste directly on site, thus reducing pollution and providing ingredients/food products with high nutritional values that could be integrated into the diet.