Analysis of protein amino acids, non-protein amino acids and metabolites, dietary protein, glucose, fructose, sucrose, phenolic, and flavonoid content and antioxidative properties of potato tubers, peels, and cortexes (pulps)

Genetic architecture of tuber-bound free amino acids in potato and effect of growing environment on the amino acid content

Free amino acids in potato tubers contribute to their nutritional value and processing quality. Exploring the natural variation in their accumulation in tubers across diverse genetic backgrounds is critical to potato breeding programs aiming to enhance or partition their distribution effectively. This study assessed variation in the tuber-bound free amino acids in a diversity panel of tetraploid potato clones developed and maintained by the Texas A&M Potato Breeding Program to explore their genetic basis and to obtain genomic-estimated breeding values for applied breeding purposes. Free amino acids content was evaluated in tubers of 217 tetraploid potato clones collected from Dalhart, Texas in 2019 and 2020, and Springlake, Texas in 2020. Most tuber amino acids were not affected by growing location, except histidine and proline, which were significantly lower (- 59.0%) and higher (+ 129.0%), respectively, at Springlake, Texas (a location that regularly suffers from abiotic stresses, mainly high-temperature stress). Single nucleotide polymorphism markers were used for genome-wide association studies and genomic selection of clones based on amino acid content. Most amino acids showed significant variations among potato clones and moderate to high heritabilities. Principal component analysis separated fresh from processing potato market classes based on amino acids distribution patterns. Genome-wide association studies discovered 33 QTL associated with 13 free amino acids. Genomic-estimated breeding values were calculated and are recommended for practical potato breeding applications to select parents and advance clones with the desired free amino acid content.

Sustainable management of food waste; pre-treatment strategies, techno-economic assessment, bibliometric analysis, and potential utilizations: A systematic review

Food waste (FW) contains many nutritional components such as proteins, lipids, fats, polysaccharides, carbohydrates, and metal ions, which can be reused in some processes to produce value-added products. Furthermore, FW can be converted into biogas, biohydrogen, and biodiesel, and this type of green energy can be used as an alternative to nonrenewable fuel and reduce reliance on fossil fuel sources. It has been demonstrated in many reports that at the laboratory scale production of biochemicals using FW is as good as pure carbon sources. The goal of this paper is to review approaches used globally to promote turning FW into useable products and green energy. In this context, the present review article highlights deeply in a transdisciplinary manner the sources, types, impacts, characteristics, pre-treatment strategies, and potential management of FW into value-added products. We find that FW could be upcycled into different valuable products such as eco-friendly green fuels, organic acids, bioplastics, enzymes, fertilizers, char, and single-cell protein, after the suitable pre-treatment method. The results confirmed the technical feasibility of all the reviewed transformation processes of FW. Furthermore, life cycle and techno-economic assessment studies regarding the socio-economic, environmental, and engineering aspects of FW management are discussed. The reviewed articles showed that energy recovery from FW in various forms is economically feasible.

Optimization of Conventional Extraction Parameters for Recovering Phenolic Compounds from Potato (Solanum tuberosum L.) Peels and Their Application as an Antioxidant in Yogurt Formulation

The aim of this work was to optimize the conventional parameters for the extraction of phenolic compounds from potato (Solanum tuberosum L.) peels (PP). A central composite design (CCD) was used to establish the impacts of ethanol concentration (%), extraction time (min), and liquid/solid ratio (mL/g). The optimal experimental conditions that maximized extraction were ethanol at a concentration of 80% (v/v) for a time of 150 min with a ratio of 1 g/30 mL. Under optimal conditions, the total phenolic content (TPC) and the total flavonoid content (TFC) were 204.41 ± 8.64 mg GAE/100 g DW and 21.47 ± 0.76 mg QE/100 g DW, respectively. The PP extract had a potent antioxidant capacity tested by phosphomolybdate and DPPH assays with IC₅₀ of 10.65 ± 0.21 and 179.75 ± 3.18 µg/mL, respectively. Furthermore, by fortifying yogurt with PP as a natural ingredient, an improvement ofits physical, nutritional, antioxidant, and sensorial qualities was attempted in this study. The yogurts formulated with PP revealed significantly higher (p ≤ 0.05) TPC, TFC, and antioxidant capacity in comparison with the control sample. In addition, the sensory evaluation showed that the yogurts enriched with PP were preferred over the control yogurt. The results indicate that PP can be considered an interesting byproduct since it can improve the nutritional, bioactive, and sensorial profile of yogurt, highlighting that PP, due to its high phenol content, can substantially improve the antioxidant effect of the new formulated yogurt.

Characterization of Nutritional and Bioactive Compound in Three Genotypes of Mashua (Tropaeolum tuberosum Ruiz and Pavón) from Different Agroecological Areas in Puno

Bioactive compounds and nutritional characterization in three genotypes of mashua tubers (Tropaeolum tuberosum Ruiz and Pavón) from different agroecological areas of the Peruvian highlands (3747 at 3888 meters above sea level) were studied. The studied genotypes from different agroecological areas significantly differed for vitamins, amino acids, and bioactive compounds. However, the nutritional characteristics of yellow, purple, and yellow-purple mashua remained unaffected. Its tubers were shown to be important sources of protein and fiber. The nutritional analysis revealed high phosphorus and potassium values, as well as considerable amounts of vitamin C. The amounts of total free amino acids in the genotypes ranged from $2.73\pm 0.450$  mg/g dry matter (DM) to $6.825\pm 0.450$  mg/g DM. Important total anthocyanins, total flavonoids, total phenolics, tannin content, and antioxidant activity values were obtained from purple genotype. Unexploited colored mashua tubers are proposed as a valuable natural source of phenolics and anthocyanins with high antioxidant activity.

The Simultaneous Formation of Acrylamide, β-carbolines, and Advanced Glycation End Products in a Chemical Model System: Effect of Multiple Precursor Amino Acids

This study investigated the effect of multiple precursor amino acids on the simultaneous formation of acrylamide, β-carbolines (i. e., harmane and norharmane), and advanced glycation end products (AGEs) [i.e., N^ε-(carboxymethyl)lysine and N^ε-(carboxyethyl)lysine] via a chemical model system. This model system was established with single or multiple precursor amino acids, including lysine–glucose (Lys/Glu), asparagine–glucose (Asn/Glu), tryptophan–glucose (Trp/Glu), and a combination of these amino acids (Com/Glu). Kinetic parameters were calculated by multiresponse non-linear regression models. We found that the k values of the AGEs and of acrylamide decreased, while those of harmane increased in the Com/Glu model when heated to 170 and 200°C. Our results indicated that the precursor amino acid of acrylamide and AGEs compete for α-dicarbonyl compounds, leading to a decrease in the formation of AGEs and acrylamide. Moreover, compared with asparagine, the precursor amino acid of β-carbolines was more likely to react with acetaldehyde by Pictet–Spengler condensation, which increased the formation of harmane and decreased the formation of acrylamide via the acrolein pathway.

Prevention of Enzymatic Browning by Natural Extracts and Genome-Editing: A Review on Recent Progress

Fresh fruits and vegetable products are easily perishable during postharvest handling due to enzymatic browning reactions. This phenomenon has contributed to a significant loss of food quality and appearance. Thus, a safe and effective alternative method from natural sources is needed to tackle enzymatic browning prevention. The capabilities of natural anti-browning agents derived from plant- and animal-based resources in inhibiting enzymatic activity have been demonstrated in the literature. Some also possess strong antioxidants properties. This review aims to summarize a recent investigation regarding the use of natural anti-browning extracts from different sources for controlling the browning. The potential applications of genome-editing in preventing browning activity and improving postharvest quality is also discussed. Moreover, the patents on the anti-browning extract from natural sources is also presented in this review. The information reviewed here could provide new insights, contributing to the development of natural anti-browning extracts and genome-editing techniques for the prevention of food browning.

Low Acrylamide Flatbreads from Colored Corn and Other Flours

Dietary acrylamide formed during baking and frying of plant-based foods such as bread and other cereal products, coffee, fried potatoes, and olives is reported to induce genotoxic, carcinogenic, neurotoxic, and antifertility properties in vivo, suggesting the need to keep the acrylamide content low with respect to widely consumed heat-processed food including flatbreads. Due to the fact that pigmented corn flours contain biologically active and health-promoting phenolic and anthocyanin compounds, the objective of this study was to potentially define beneficial properties of flatbread by evaluating the acrylamide content determined by high-performance liquid chromatography/mass spectrometry (HPLC/MS) with a detection limit of 1.8 µg/kg and proximate composition by standard methods of six experimental flatbreads made from two white, two blue, one red, and one yellow corn flours obtained by milling commercial seeds. Acrylamide content was also determined in experimental flatbreads made from combinations in quinoa flour, wheat flour, and peanut meal with added broccoli or beet vegetables and of commercial flatbreads including tortillas and wraps. Proximate analysis of flatbreads showed significant differences in protein and fat but not in carbohydrate, mineral, and water content. The acrylamide content of 16 evaluated flatbreads ranged from 0 to 49.1 µg/kg, suggesting that these flatbreads have the potential to serve as low-acrylamide functional foods. The dietary significance of the results is discussed.

Identification and Recovery of Valuable Bioactive Compounds from Potato Peels: A Comprehensive Review

Nowadays, the potato is one of the most cultivated and consumed food crops in the world and, in recent years, its production has experienced a sharp increase. Its industrial processing generates several by-products that are wasted and cause economic and environmental problems. Among them, potato peel stands out, representing up to 10% of the total potato residues obtained in the processing. On the other hand, these wastes, in addition to presenting antioxidant compounds, are rich in interesting chemical compounds of great value in a biorefinery model. This review summarizes the main compounds present in potato skins as well as the most used and innovative extraction methods employed for their isolation, with special emphasis on the fractions with biological activities. In addition, a sustainable biorefinery proposal focused on obtaining high added-value products with potential applications in the pharmaceutical, food, nutraceutical, or cosmetic industries is included.

Impacts of different blanching pretreatments on the quality of dried potato chips and fried potato crisps undergoing heat pump drying

Hot water blanching (WB) and steam blanching (SB) have been noted to improve the quality of potato chips. In this work, the possibility of steam blanching assisted with ultrasound treatment (SUB) to enhance the quality of dried potato chips and fried potato crisps was investigated. Compared to WB and SB groups, dried potato chips of SUB groups showed lower shrinkage ratio (78.46%), higher rehydration capability (3.93:1), and lower moisture content (0.08 g/g). Meanwhile, fried potato crisps of SUB groups displayed lower hardness (1965.70 g) and oil content (12.0%). The low reducing sugar content (0.42%) and free amino acid content (6.10 mg/g) in SUB dried potato slices could explain for the higher L * value, lower a * and ΔE values of SUB fried potato crisps. Additionally, sensory evaluation results confirmed above obtained consequences. Overall, SUB could improve the quality of fried potato crisps further in comparison with WB and SB.

Phenolic composition and cell-based biological activities of ten coloured potato peels (Solanum tuberosum L.)

The present study provides an in-depth characterisation of the non-anthocyanin and anthocyanin phenolic compounds of potato peels from ten coloured potato varieties. Furthermore, the underexplored bioactive potential (antioxidant, cytotoxic and anti-inflammatory capacities) of the studied peels is comprehensively analysed. Among non-anthocyanin phenolics, caffeic and a caffeoylquinic acid were found in the highest concentrations in all samples, which also showed the presence of O-glycosylated flavonol derivatives and polyamine derivatives. Acylated anthocyanins were identified in red and purple varieties, being pelargonidin, peonidin, and malvidin the most prominent aglycones. All samples revealed antioxidant and antitumor activities, and no toxic effect. The extract of the Rosemary variety presented the best antioxidant and antitumor outcomes and was the only sample to reveal anti-inflammatory activity. These results are valuable for the food-industry by adding value to an important bio-residue, particularly concerning its potential as natural ingredients in novel food and pharmaceutical formulations.

The Free-Amino-Acid Content in Six Potatoes Cultivars through Storage

Potatoes of six cultivars (Solanum tuberosum L.) with red, purple, and yellow flesh were stored at 2 and 5 °C for 3 and 6 months, and the influence of these factors on the content of free amino acids was determined. The potato cultivar and storage time had the greatest impact on the free amino acid content. The tubers of red-fleshed (Rote Emma) and purple-fleshed (Blue Congo) potatoes contained over 28 mg/g DM of free amino acids, and the Blaue Annelise cultivar with purple flesh had over 18 mg/g DM. After 6 months, the highest increase in their content (by 36%) was recorded in tubers of the Fresco cultivar (yellow-fleshed). In the analysed potatoes, the content of alanine, proline, serine, γ-aminobutyric acid, and α-aminoadipic acid increased, while that of asparagine, aspartic acid, and glutamine decreased. Asparagine decreased to the greatest extent in “Blaue Annelise” potatoes (by 24%) and that of glutamine in tubers of Rote Emma and Vineta by 18%.

Effect of pH on volatile fatty acid production from anaerobic digestion of potato peel waste

In this study, potato peel waste was used as feedstock to produce volatile fatty acids (VFAs) by anaerobic digestion. The effects of different pH levels (pH 5.0, pH 7.0, pH 11.0, and uncontrolled pH) on VFA concentration and composition, intermediate products, and metabolic state were evaluated. The results showed that the highest total VFA production was achieved with pH 7.0 (41.9 g COD/L and 632.2 mg COD/g VS_fed), followed by that with uncontrolled pH. Butyric acid was the dominant product under acidic pH, whereas acetic acid dominated under alkaline pH. The type of acidogenic fermentation at pH 7.0 was the mixed-acid type. The change in NADH level in the mixed-acid type of fermentation consisted of small fluctuations, enhancing the stability and efficiency of fermentation. The enzymatic activities of acetate kinase and butyrate kinase were slightly inhibited at pH 5.0 and 11.0, resulting in relatively low VFAs production.

Antibrowning effect of commercial and acid-heat coagulated whey on potatoes during refrigerated storage

Potato color turns to brown after some process such as peeling, cutting, and slicing. In this research, the effect of acid-heat coagulated whey and commercial whey solutions on the color, polyphenol oxidase, phenylalanine ammonia-lyase activity, malondialdehyde, hydrogen peroxide content of potatoes were compared with pure water (control) immersion and sodium hydrogen sulfide solution. According to color results, there was no significant (P > 0.05) difference was found in the L^* and b^* values, browning index, and whitening index of the treatment groups. The polyphenol oxidase activity of the sulfide and commercial whey solution groups decreased from the initial values on day 3 then increased over that value. The use of the whey solution in preventing polyphenol oxidase activity showed a similar curve with the use of the sulfide solution. A rapid increase was observed in the malondialdehyde and hydrogen peroxide values of all treatment groups during the first 3-day storage. PRACTICAL APPLICATION: Immersion of potato cubes to whey protein solution prevents the browning and inhibits polyphenol oxidase activity. The browning index of the samples was not affected by the immersing water or whey solutions.

Exploring the relationship between potato components and Maillard reaction derivative harmful products using multivariate statistical analysis

The correlation between potato components and Maillard reaction derivative harmful products (MRDHPs) formation during heat-processing was assessed in nine commercial potato varieties in China. Principal component analysis (PCA) combined with canonical correlation analysis (CCA) approach was performed to explore their relationships. The variables contributing most to the PCA results were extracted for CCA, and the results indicated that several amino acids, including lysine, tryptophan, alanine, phenylalanine, aspartate, and glutamate, have significant impacts on acrylamide and β-carboline heterocyclic amine formation. Moreover, 5-O-caffeoylquinic acid, 3-O-caffeoylquinic acid, α-solanine, and α-chaconine were also important factors associated with acrylamide and β-carboline heterocyclic amine formation. Optimally using raw potato varieties based on the impacts of these factors can help control MRDHP formation during thermal processing. For the first time, such approach was applied, which may be a useful tool for discovering the correlation of food components and MRDHPs.

Total Polyphenol Content, Antioxidant Activity, and Individual Phenolic Composition of Different Edible Parts of 4 Sweet Potato Cultivars

The quest to determine and use polyphenolic compounds present in fruits and vegetables as natural antioxidants has recently attracted much attention due to their beneficial health effects. In this study, the total polyphenol content (TPC), total flavonoid content (TFC), total anthocyanin content (TAC), antioxidant activity (AA), and individual polyphenol components of Simon No. 1, Yuzi No. 7, Shangshu 19, and Pushu 32 sweet potato cultivars (edible parts: leaf, stalk, stem, skin, and flesh) were investigated. TPC, TFC, and TAC values ranged from 440 ± 0.17-12080 ± 0.58 CAE mg/100 g DW, 94 ± 0.08-4210 ± 0.74 QE mg/100 g DW, and 7 ± 0.01-1010 ± 0.54 CGE mg/100 g DW, respectively. Yuzi No. 7 sweet potato cultivar contained significantly higher amounts of TPC, TFC, TAC, and AA in all its edible parts, followed by Pushu 32, Simon No. 1, and Shangshu 19 in that order. Regardless of the sweet potato cultivar used, TPC, TFC, and TAC of sweet potato leaves were significantly higher than those of other edible parts. High-performance liquid chromatography revealed 19 individual phenolic compounds. In general, 3,5-di- O-caffeoylquinic acid, astragalin, and cyanidin were the predominant phenolic acid, flavonoid, and anthocyanin compounds, respectively. The correlation analysis suggested that higher AA could be attributed to higher polyphenol content. Based on our results, edible parts of Yuzi No. 7 sweet potato cultivar presented the highest amounts of polyphenol content and AA suggesting the possibility of utilizing this cultivar by farmers and the food industry as a functional food product.

The Impact of Fertilization Regime on the Crop Performance and Chemical Composition of Potato (Solanum tuberosum L.) Cultivated in Central Greece

Potato cultivation is quite demanding in inorganic nutrients and adequate fertilization is a key factor for maximizing yield and producing tubers of high quality. In the present study, a field experiment was carried out to evaluate the effect of various forms of fertilization on crop performance and the nutritional value and chemical composition of two potato varieties (cv. Spunta and cv. Kennebec). For this purpose, five different fertilizer treatments were applied namely: control (C), standard fertilizer (T1), standard fertilizer + zeolite (T2), manure (T3) and slow release nitrogen fertilizer (T4). According to the results, it was observed that slow release treatment (T4) achieved the highest yield for both varieties, while the control treatment presented significantly lower yield compared to the studied fertilization regimes. The dry matter of leaves and shoots was higher in T1 treatment for cv. Kennebec and in T2 and T4 treatments for cv. Spunta, whereas the control treatment presented the highest dry matter content in tubers for cv. Kennebec and T2 and T3 treatments for cv. Spunta. A significant effect of the fertilization regime was also observed on the nutritional value of tubers and more specifically the protein, ash and fat content was increased by treatments T1 and T4, while carbohydrate content was also increased by T3 and T4 treatments for both varieties. Similarly, the total sugars, organic acids, β-carotene and lycopene content was increased in T3 treatment for the Spunta variety, while the antioxidant capacity showed a varied response depending on the fertilizer regime and the tested variety. In conclusion, the fertilization regime has a significant effect not only on the tuber yield but also on the quality of the final product and should be considered as an effective tool to increase the added value of potato crop.

Potato Peels as a Source of Novel Green Extracts Suitable as Antioxidant Additives for Fresh-Cut Fruits

Potato is a source of different bioactive compounds, and the potato transformation industry produces conspicuous quantities of potato peels as waste. In this context, the objective of this research was twofold: (i) the evaluation of the recovery of bioactive compounds from organic potato byproducts through an innovative multistep green extraction process; (ii) to evaluate the preservation during storage of the main quality-physicochemical parameters of minimally processed apples treated with two different natural extracts obtained. The potato extracts were obtained by solid CO2 cryomaceration followed by solid/liquid extraction based on water or 10% ethanol/water solutions. The efficacy of potato extracts, with or without 1% of citric acid, was tested in comparison with traditional preserving compounds in minimally processed apple preparation. All the extracts were characterized by a high antioxidant power and were rich in phenol compounds, showing a good activity in keeping the qualitative parameters of fresh-cut apple. A significant anti-browning effect as well as a slowing down of the softening of fruits during storage were observed. The obtained results suggest the suitability of the potato extracts as antioxidant additives for fresh-cut fruits, thus avoiding the use of unsafe chemicals.

Establishment of ultrasound-assisted extraction of phenolic compounds from industrial potato by-products using response surface methodology

Potato processing generates large amounts of by-products, which include potato peels and the outer layers of flesh, which contain phenolic compounds. The purpose of this study was to establish an extraction method for phenolic compounds from industrial potato by-products by using response surface methodology (RSM). Box-Behnken design (BBD) was performed to optimize the extraction conditions of phenolic compounds considering different extraction temperature, ratios of ethanol/water, time of extraction and sample/solvent ratio. The optimum extraction conditions were obtained with ethanol/water 55/45 (v/v) by ultrasound bath during 35 min at 35 °C and 1/10 sample/solvent ratio. The best conditions were applied to determine the phenolic content in five potato by-products. The analyses by HPLC-DAD-ESI-MS showed that chlorogenic acid accounted for a 49.3-61% of the total phenolic compounds. Positive Pearson correlations between HPLC data and antioxidant activity confirmed that the phenolic compounds had significant antioxidant properties.

Dietary Supplementation of Potato Peel Powders Prepared from Conventional and Organic Russet and Non-organic Gold and Red Potatoes Reduces Weight Gain in Mice on a High-Fat Diet

The present study investigated the potential of potato peel powders, high in bioactive phenolic compounds and glycoalkaloids, to reduce weight gain in mice consuming a high-fat diet. Potato peel powders were prepared from the following fresh commercial potato varieties by hand-peeling and then freeze-drying and grinding the peels into powder: non-organic (conventionally grown) gold, red, and Russet and organically grown Russet. Mice diets (25% fat by weight) were supplemented with either 10 or 20% potato peel powders for 3 weeks. In comparison to the control diet, the isocaloric and isonitrogenous peel-containing diets induced a reduction in weight gain that ranged from 17-45% (10% peel diets) to 46-73% (20% peel diets), suggesting that differences in weight gain are associated with the potato peel source and peel concentration of the diet. Weight reductions were accompanied by reduced epididymal white adipose tissue ranging from 22 to 80% as well as changes in the microbiota analyzed using next-generation sequencing and in obesity-associated genetic biomarkers determined by the quantitative real-time polymerase chain reaction. Safety aspects and possible mechanisms of the antiobesity effects are discussed in terms of the composition of the bioactive potato peel compounds, which were determined using high-performance liquid chromatography. The results suggest that potato peels, a major peeling byproduct of potato processing used to prepare fries, chips, and potato flour, that showed exceptionally high antiobesity properties in fat mice, have the potential to serve as an antiobesity functional food.

Fruit and Vegetable Waste: Bioactive Compounds, Their Extraction, and Possible Utilization

Fruits and vegetables are the most utilized commodities among all horticultural crops. They are consumed raw, minimally processed, as well as processed, due to their nutrients and health-promoting compounds. With the growing population and changing diet habits, the production and processing of horticultural crops, especially fruits and vegetables, have increased very significantly to fulfill the increasing demands. Significant losses and waste in the fresh and processing industries are becoming a serious nutritional, economical, and environmental problem. For example, the United Nations Food and Agriculture Organization (FAO) has estimated that losses and waste in fruits and vegetables are the highest among all types of foods, and may reach up to 60%. The processing operations of fruits and vegetables produce significant wastes of by-products, which constitute about 25% to 30% of a whole commodity group. The waste is composed mainly of seed, skin, rind, and pomace, containing good sources of potentially valuable bioactive compounds, such as carotenoids, polyphenols, dietary fibers, vitamins, enzymes, and oils, among others. These phytochemicals can be utilized in different industries including the food industry, for the development of functional or enriched foods, the health industry for medicines and pharmaceuticals, and the textile industry, among others. The use of waste for the production of various crucial bioactive components is an important step toward sustainable development. This review describes the types and nature of the waste that originates from fruits and vegetables, the bioactive components in the waste, their extraction techniques, and the potential utilization of the obtained bioactive compounds.

Effects of the pH and Concentration on the Stability of Standard Solutions of Proteinogenic Amino Acid Mixtures

To prepare metrologically traceable amino acid mixed standard solutions, it is necessary to determine the stability of each amino acid present in the mixed solutions. In the present study, we prepared amino acid mixed solutions using certified reference standards of 17 proteinogenic amino acids, and examined the stability of each of these amino acids in 0.1 N HCl. We found that the concentration of glutamic acid decreased significantly during storage. LC/MS analysis indicated that the instability of glutamic acid was due to the partial degradation of glutamic acid to pyroglutamic acid in 0.1 N HCl. Using accelerated degradation tests, we investigated several solvent compositions to improve the stability of glutamic acid in amino acid mixed solution, and determined that the change of the pH by diluting the mixed solution improved the stability of glutamic acid.

Treatment of supermarket vegetable wastes to be used as alternative substrates in bioprocesses

Fruits and vegetables have the highest wastage rates at retail and consumer levels. These wastes have promising potential for being used as substrates in bioprocesses. However, an effective hydrolysis of carbohydrates that form these residues has to be developed before the biotransformation. In this work, vegetable wastes from supermarket (tomatoes, green peppers and potatoes) have been separately treated by acid, thermal and enzymatic hydrolysis processes in order to maximise the concentration of fermentable sugars in the final broth. For all substrates, thermal and enzymatic processes have shown to be the most effective. A new combined hydrolysis procedure including these both treatments was also assayed and the enzymatic step was successfully modelled. With this combined hydrolysis, the percentage of reducing sugars extracted was increased, in comparison with the amount extracted from non-hydrolysed samples, approximately by 30% in the case of tomato and green peeper wastes. For potato wastes this percentage increased from values lower than 1% to 77%. In addition, very low values of fermentation inhibitors were found in the final broth.

iTRAQ-based Protein Profiling and Fruit Quality Changes at Different Development Stages of Oriental Melon

BACKGROUND

Oriental melon is one of the most popular crops for its nutritional and flavour quality. Components that determine melon quality, such as sugar, colour, texture, flavour and aroma, among other factors, accumulate in different developmental stages. Thus, correlating the proteomic profiles with the biochemical and physiological changes occurring in the oriental melon is very important for advancing our understanding of oriental melon quality in the ripening processes.

RESULTS

iTRAQ-based protein profiling was conducted on 'YuMeiren' oriental melon fruit at different developmental stages. Physiological quality indices, including firmness, rind colour, soluble solids content (SSC), ethylene production, sugar content and volatile compounds were also characterized during four maturity periods of the melon, including 5, 15, 25 and 35 days after anthesis (DAA). A principal component analysis (PCA) revealed that the aroma volatiles at 5 DAA and 15 DAA were similar and separated from that of 35 DAA. More than 5835 proteins were identified and quantified in the two biological repeats and divided into 4 clusters by hierarchical cluster analysis. A functional analysis was performed using Blast2GO software based on the enrichment of a GO analysis for biological process, molecular function and cellular components. The main KEGG pathways, such as glycolysis, α-linolenic acid and starch and sucrose metabolism, were analyzed. The gene family members corresponding to differentially expressed proteins, including lipoxygenase (CmLOX01-18) and alcohol acetyltransferase (CmAAT1-4) involved in the α-linolenic acid metabolic pathway, were verified with real-time qPCR. The results showed that the expression patterns of 64.7% of the genes were consistent with the expression patterns of the corresponding proteins.

CONCLUSIONS

This study combined the variation of the quality index and differentially expressed proteins of oriental melon at different developmental stages that laid the foundation for the subsequent protein and gene function validation.