Characterization of lemon peel powder and its application as a source of pectin degrading enzyme in clarification of cloudy apple juice.

The presence of pectin in the apple peel creates undesirable turbidity and sediment in the final juice and hence clarification is a necessary step for producing consumer-friendly apple juice. This study aimed at evaluating the potential of lemon peel powder as a source of reusable pectinase enzyme in the clarification of apple juice. In this study, optimization of the amount of lemon peel powder addition and incubation time was carried out to produce an apple juice of acceptable clarity. Lemon peel powder as an enzyme source having an activity of 2804.4 U/g could be successfully used up to 5 cycles of pectin hydrolysis. Pectinase enzyme in the lemon peel powder had greater stability at 4 °C with an 11.11% decrease in enzyme activity on 60th day of storage. Treatment with 0.5% w/v lemon peel powder at an incubation time of 90 min was found to be optimum as it produced a clarified apple juice with good sensory acceptability. Lemon peel powder as a naturally immobilized pectinase source was found to be effective in producing clear apple juice. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05270-7.

Cloud stabilization of citrus fruit juices treated with purified pectin methylesterase inhibitor from lemon (Citrus limon L.).

BACKGROUND: Cloud destabilization is a significant quality defect of cloudy fruit juices. A proteinaceous inhibitor (PMEI) of pectin methylesterase (PME), identified in lemon, with a fold purity of 89.13, was used to stabilize the cloud of freshly prepared sweet lime, orange, and lemon juice. RESULTS: Lemon PMEI was able to inhibit the PME activity of all three fruit juices. In this study addition of calculated amounts of lemon PMEI to the three juice systems was based on the total PME units present in each juice. Relative turbidity, viscosity, pH, and ζ -potential of the PMEI-treated juices were stable, resulting in uniform distribution of cloud particles throughout the juice system. The sedimentation rate in PMEI treated juices was very low, with cloud particles having smaller particle size diameter. CONCLUSION: This work demonstrates an alternative option that might create new potential to control the quality deterioration in cloudy fruit juices. © 2022 Society of Chemical Industry.

Use of microalgal biomass as functional ingredient for preparation of cereal based extrudates: impact of processing on amino acid concentrations and colour degradation kinetics

Abstract Suitability of developing Spirulina incorporated cereal based low cost nutritious extrudates was analysed against extrusion processing parameters. Most significant extrusion processing parameters considered for present study were feed moisture (20-25%), die temperature (100-120 °C) and screw speed (50-100 rpm). Different extrusion conditions were used to obtain most acceptable rice: Spirulina blend extrudates. In present study before extrusion processing different additives (citric acid and sodium bicarbonate) were added in rice: Spirulina blend and checked its effect on colour degradation kinetics at varied packaging and storage conditions. Higher screw speed (100 rpm) indicating less residence time of feed material inside the barrel resulted in higher colour retention of rice: Spirulina (97:03) blend extrudates. Kinetics for rice: Spirulina (97:03) blend extrudates indicates faster rate of colour degradation in terms of lightness (half-life of 4 days) when packed in metalized polyethylene at 50°C with 65% relative humidity. Increased concentration of Spirulina (1-3%) in raw formulations resulted in increase in concentration of all amino acids. Impact of extrusion processing has shown non-significant (p ≤ 0.05) effect on amino acid concentrations of rice: Spirulina blend extrudates. Also, all the spirulina added samples showed good consumer acceptability with the score of 6.7

Isolation, purification, and characterization of pectin methylesterase inhibitor and polygalacturonase inhibitor protein from Indian lemon (Citrus limon L.).

Proteins acting as powerful inhibitors of plant pectin methylesterase and polygalacturonase were isolated from whole lemon fruits (Citrus limon L.). Pectin methylesterase inhibitor (PMEI) and polygalacturonase inhibitor protein (PGIP) were purified using DEAE Sepharose column, resulting in fold purity of 89.13 and 81.16 and having a molecular mass of 35 and 38 kDa, respectively as estimated using SDS-PAGE and MALDI-TOF mass spectroscopy. The optimum pH of purified PMEI and PGIP was pH 6 and pH 4.5 while the inhibitors showed good stability in the pH range of 5-8 and 3.5 to 5.5, respectively. Both the inhibitors from C. limon demonstrated an optimum temperature of 55 °C. Thermal inactivation data suggested that purified PGIP was more heat stable than PMEI. The inhibition kinetics of PMEI and PGIP towards C. limon PME and C. limon PG was of a non-competitive type. Both PMEI and PGIP obeyed first-order inactivation kinetics. The PMEI and PGIP exhibited different extent of inhibition towards PME and PG from other fruit sources analyzed in this study. As these inhibitors inhibit PME and PG from other plant sources they can be used in fruit-based products to control undesirable endogenous enzyme activities as an alternative to thermal processing.

Evaluating the effect of additives on stability of betacyanin pigments from Basella rubra in a model beverage system during storage.

The effect of selected additives (catechin, ascorbic acid, ß-cyclodextrin and EDTA) on the stability of betacyanin pigments from Basella rubra in a model beverage system was investigated and they exhibited remarkable outcomes. The major betacyanin pigment in B. rubra extract was identified to be gomphrenin-I using HPLC-ESI-MS analysis method. The degradation kinetics of betacyanin pigment in the model beverage variants was established, and temperature was found to be the most detrimental factor. If effect of additives on stability of B. rubra betacyanin pigments in model beverage stored at 4 °C in the absence of light and oxygen is considered, maximum stabilizing effect was demonstrated by catechin (t1/2 203.9 days) followed by EDTA (t1/2 187.3 days) and then ß-cyclodextrin (t1/2 144.4 days) when compared with control (t1/2 119.5 days) whereas, ascorbic acid acted as a prooxidant and reduced storage stability of the pigment (t1/2 78.8 days).

Effect of thermal processing methods on flavonoid and isoflavone content of decorticated and whole pulses.

Legumes have always been consumed as a staple source of proteins, and they are the only dietary source of isoflavones, flavonoid class of secondary plant metabolites. Isoflavones impart physiological effects via estrogenic action in humans and hence, looked upon as potential replacement of hormone estrogen in its deficiency. Legumes are an integral part of the Indian staple diet. Legumes are processed by soaking, germination, and thermal cooking. These methods have been reported to modify the nutrient composition of legumes. The sample population was surveyed to determine the most commonly used household processing methods. Soaking or germination followed by pressure cooking (with or without direct contact of water) or open pan cooking was found to be commonly followed by cooking practice in Indian households. Amongst the decorticated pulses, the highest cooking time was taken by chickpea (Cicer arietinum), and lentil (Lens culinaris) was cooked in the least amount of time. The pressure-cooked decorticated chickpea showed a 63% decrease in TFC and isoflavone content while open pan cooking lowered TFC of chickpea up to 67% and isoflavone content up to 90%. TFC of pressure-cooked and open-pan cooked decorticated lentil was only reduced by 12-17%, while isoflavone content showed 60-80% depletion. TFC of whole legumes was reduced by 30-40% on pressure cooking as well as open pan cooking; however, isoflavone content was variably affected. The black-eyed pea and desi chickpea showed 40% reduced isoflavone content while the loss of isoflavone content was 70% for kidney bean. Germination of green gram significantly increased the TFC and isoflavones, which showed a decrease of 24% and 44%, respectively, on pressure cooking.

Application of two-dimensional gel electrophoresis technique for protein profiling of Indian black gram varieties and detection of adulteration in black gram-based food products using comparative proteomics.

In the present study, protein fingerprints from six novel Indian black gram varieties were obtained using 2D-GE. The results revealed the presence of thirteen well-resolved protein spots in all six varieties. Analysis of the fingerprints using PD Quest™ revealed differential protein expression. In addition, six proteins were found to be uniquely expressed in varieties PDKV Black Gold and TAU-1. Further, analysis of 2D patterns of black gram and potential adulterants such as refined wheat flour and white pea using PD Quest™ revealed the presence of proteins with MW 15.0 kDa, pI 4.89 (refined flour) and MW 21.5 kDa, pI 5.70 (white pea), which can be considered as biomarkers for their presence in black gram food products. The method was sensitive enough to detect adulteration at 5% level and could successfully detect the potential presence of refined flour in one of the black gram papad samples analysed during the study.

Changes in ACE inhibitory and antioxidant activities in alcalase treated idli batter and idli after fermentation.

Idli is a cereal-legume fermented food consumed widely in India. Fermentation and addition of external enzymes have been suggested as methods for release of bioactive peptides from parent proteins. The present study was aimed at exploring the changes in angiotensin-I converting enzyme (ACE) inhibitory and antioxidant activity of 14 h fermented idli batter treated with alcalase in varied amounts (100-700 U/g batter) kept at 30 ± 2 °C. Various batter parameters along with sensory attributes of cooked idli were assessed. The viscosity (12170-7795 cP) and rise in volume (29-20 mL) of batter decreased with addition of alcalase in the batter when compared with control batter (14130 cP, 31 mL). The free amino nitrogen content and radical scavenging activity of alcalase treated batter exhibited an increase by 2-5 and 2-7 fold, respectively while ACE inhibitory activity showed a decrease in IC50 value (lowest being 52.53 ± 1.12 mg/mL of batter containing 600 U alcalase/g batter) when compared with the control fermented set. The hardness and bulk density values of control cooked idli was 0.59 kg and 0.53 g/cm3, respectively while alcalase treated idlis showed a range of 0.71-1.68 kg and 0.53-0.69 g/cm3. The overall acceptance of idli prepared from alcalase treated batters till 600 U/g batter was judged as 'good' by semi-trained panellists. Moreover, the ACE inhibitory and radical scavenging activity of cooked idli prepared from 600 U alcalase/g batter showed enhancement over the control idli. Thus, alcalase treated idli shows potential to be used as a functional food.

Impact of partial replacement of rice with other selected cereals on idli batter fermentation and idli characteristics.

Idli is a naturally fermented food, prepared using dehulled black gram dal and parboiled rice. In the first phase of the study, replacement of rice with some underutilized cereals like amaranth and finger millet was carried out at different proportions (25%, 50%, 75% and 100%, w/w) followed by sensory evaluation of the prepared idlis. Idlis prepared with 25% (w/w) replacement of rice with finger millet (25F) were more acceptable than idlis prepared with 25% (w/w) replacement of rice with amaranth (25A). In the second phase of the study, 50% replacement of rice was carried out with cereals in combinations (25% each, w/w) such as amaranth + finger millet (AF), amaranth + sorghum (AS), amaranth + pearl millet (AP), finger millet + sorghum (FS), finger millet + pearl millet (FP) and sorghum + pearl millet (SP), of which FS and FP batter variants were accepted by the panellists and taken ahead for further analysis. Control, 25F, FS and FP batter variants were subjected to various biochemical analysis up to 20 h of fermentation. Replacement of rice in these batter variants led to comparable changes with an increase in the levels of microbial counts, amylase, protease and phytase activities, titratable acidity, reducing sugars, soluble proteins and antioxidant activity during fermentation. A greater reduction in trypsin inhibitor activity (TIA) was also observed. Idlis prepared with replacement of rice by other cereals (25F, FS and FP) resulted in improved textural values and bulk density as compared to control idlis, though the colour was affected.

Investigation of biogenic amines content in fermented idli batter during storage.

Idli is a cereal-pulse based fermented food. This study profiles the qualitative and quantitative analysis of biogenic amines formed in the fermented idli batter prepared using varying proportions of rice to black gram dal at 1:1, 2:1, 3:1 and 4:1 (w/w) ratios and stored at 30 and 4 °C for 7 days. Histamine, tyramine, putrescine, cadaverine, spermidine, and spermine were investigated for the first time in the idli batter using HPLC technique. Putrescine and cadaverine were the predominant biogenic amines found in both prepared and market samples. Histamine and spermine were not detected in all batter samples. Increasing the proportion of rice in the idli batter resulted in the decrease in the total biogenic amines formed in the fermented batter with batter having more black gram dal (1:1) showing the maximum formation of total biogenic amines. Idli is a safe, easily digestible food to consume as the highest total biogenic amines quantified (366.87 µg/g) in 1:1 variant batter was below the harmful limit (1000 µg/g).

Effect of enzymatic hydrolysis on the functional, antioxidant, and angiotensin I-converting enzyme (ACE) inhibitory properties of whole horse gram flour.

Horse gram hydrolysate (HGH) with different degree of hydrolysis (DH) (20, 25, 35, 40, and 45%) was prepared from whole horse gram flour using alcalase. The amino acid composition of HGH showed the presence of essential amino acids. The alcalase hydrolysis (DH ≥ 20%) increased protein solubility with a notable difference in the pH range of 3-5 (p < 0.05). The emulsifying activity and stability of HGH improved with increase in pH, especially at DH ≥ 25% (p < 0.05). With increase in DH, the foaming properties reduced while the antioxidant and angiotensin I-converting enzyme inhibitory activities increased. Sensory evaluation showed no significant difference (p > 0.05) in preference between control soup and soup mixed with HGH. Thus, these results suggest the possibility of HGH to be used as an appropriate functional ingredient with different food applications including in management of oxidative stress as well as in controlling hypertension .

Consumption of Decorticated Pulses Ensures the Optimum Intake of Isoflavones by the Urban Indian Population.

Sample urban population was assessed for consumption of legumes. Genistein and daidzein content of commonly consumed legumes was evaluated to estimate the isoflavone intake through the consumption of these legumes by selected population. Total genistein content of all legumes considered for analysis was found to be in the range of 0.60 to 8.65 mg per 100 g whereas total daidzein content was found to be in the range of 1.10 to 30.37 mg per 100 g in selected legumes. Chickpea, kabuli, whole (Cicer arietinum), pigeon pea, split, decorticated (Cajanus cajan), chickpea, split, decorticated (Cicer arietinum) showed a high amount of genistein and daidzein among selected legumes. Average isoflavone consumption by selected population was found to be 18.22 mg/d through the consumption of legumes. Consumption of pigeon pea (split, decorticated) and chickpea (split, decorticated) was found to be highest at 371.6 g/month and 329.7 g/month, and hence were found to contribute 18% and 14% to total isoflavone intake, respectively. The comparatively high content of isoflavones and inclusion as a staple in the diet have resulted in making the split, decorticated pulses (chickpea, pigeon pea, lentil, green gram, black gram) a chief isoflavone source for selected population irrespective of their demographic differences.

Isolation, screening, and optimization of bacterial strains for novel transglutaminase production.

Transglutaminases are a class of transferases known to form isopeptide bond between glutamine and lysine residues in a protein molecule. Increasing demand for transglutaminase in food and other industries and its low productivity have compelled researchers to isolate and screen micro-organisms with potential to produce it. In the present investigation around 200 isolates were screened for extracellular secretion of microbial transglutaminase (MTGase). Isolate B4 showed enzyme activity of 1.71 ± 0.2 U/mL followed by isolate C2 which showed 1.61 ± 0.17 U/mL activity, comparable with the activity of industrially used microbial strains. Biochemical analysis along with 16S r-RNA sequencing revealed these isolates (B4 and C2) to be Bacillus nakamurai and a variant of Bacillus subtilis, respectively. Amongst the various production media screened, a medium containing starch and peptone was found best for MTGase production. Correlation between growth, enzyme production, and sugar utilization was also studied and maximum enzyme production was obtained after 48 to 60 hr. Highest MTGase titer (3.95 ± 0.03 U/mL for B4 and 2.65 ± 0.17 U/mL for C2) was obtained by optimization of parameters. The enzyme was characterized for temperature and pH optima, pH and thermal stability, and effect of metal ions, suggesting its potential use in future applications.

Shelf life improvement of idli batter by addition of mustard essential oil as bio-preservative.

Idli is one of the most popular naturally fermented breakfast food. In this study, essential oils have been screened for their minimal inhibitory activity against selected lactic acid bacteria (LAB) and yeast strain associated with idli batter fermentation and to identify the best potential bio preservative to preserve the idli batter. Mustard essential oil was found to be the best bio-preservative which showed a biocidal effect at 80 ppm against LAB strains and at 40 ppm against Candida versatilis. The efficacy of mustard essential oil incorporated in the idli batter at 0.1% (w/w) was evaluated by measuring the titratable acidity, pH, viscosity, batter volume, microbial count of idli batter as well as sensory parameters of idli prepared from preserved batter stored at 4 and 30 °C. Unfavorable changes in acidity, batter volume and whey separation of idli batter containing mustard oil were significantly reduced, which resulted in a reduction of sour taste and improved texture of idli. The growth of yeast and LAB was retarded evidenced by decreased microbial counts than control batter, which delayed the deterioration of the batter under both storage conditions. The addition of 0.1% mustard essential oil in the optimally fermented idli batter extended its shelf life to 5 days when stored at 30 °C and 30 days at 4 °C.

Effect of extrusion on thermal, textural and rheological properties of legume based snack.

Attempts have been made to improve dough handling properties and quality of legume based snack by incorporating extruded black gram (EBG) flour as partial substitute for raw black gram (RBG) flour. In present work overall quality improvement was achieved by analyzing (a) thermal properties of RBG and EBG flour (b) rheological properties (shear stress, shear rate, storage modulus, loss modulus, deflection angle and complex viscosity) of legume based snack dough and (c) post frying characteristics (colour and texture) of legume based snack. Three different legume based snack samples with different flour formulations (RBG flour, RBG flour incorporated with 25% EBG flour and RBG flour incorporated with 50% EBG flour) were prepared, characterized and compared with standard market sample. Dough exhibited shear thinning behaviour and G' and G″ showed rising behaviour with angular frequency whereas, complex viscosity showed decreasing behaviour. Herschel-Bulkley model was best fitted. Significant changes were observed in values of onset, peak and endset gelatinization temperatures on extraction of black gram flour which improved dough handling properties during papad processing and enhanced organoleptic profile of end product.

Partial purification and characterization of the quality deteriorating enzymes from Indian pink guava (Psidium guajava L.), var. Lalit.

Peroxidase (POD), polyphenol oxidase (PPO), ascorbate oxidase (AO) and pectin methylesterase (PME) from 'Lalit' guava variety have been purified using BioGel P-100 and UNOsphere Q resins. POD, PPO, AO, and PME were partially purified to 28, 30, 36 and 30 fold; single band on SDS-PAGE represented a molecular weight of 21, 70, 75, 50 kDa, respectively. Optimum pH for POD and AO was 6.5 whereas, PPO and PME showed optimum pH in the alkaline range of pH 8.0 and 8.5, respectively. AO showed optimum activity at 25 °C, POD and PPO showed optimum activity at 35 °C; however, PME showed maximum activity at 55 °C. AO was the most heat labile whereas, PME was the most heat stable enzyme studied and may carry an important role in the thermal processing of guava pulp as an indicator of the efficacy of treatment.

Kinetics of inactivation of quality-deteriorating enzymes and degradation of selective phytoconstituents in pink guava pulp during thermal processing.

Thermal inactivation kinetics of peroxidase (POD), polyphenol oxidase (PPO), pectin methyl esterase (PME) and ascorbate oxidase (AO) were studied over the temperature range of 45-85 °C along with the degradation kinetics of ascorbic acid (AA) and lycopene in Psidium guajava pulp. POD, PPO, PME and AO followed first-order kinetics whereas AA degradation data was explained by pseudo first-order kinetics. Lycopene degradation was suitably fitted in an exponential model, indicating continuous degradation of lycopene and higher degradation at higher temperature. Activation energy (Ea) of POD, PPO, PME, and AO was 63.79 ± 1.28, 60.36 ± 1.21, 63.22 ± 1.06 and 106.33 ± 8.51 kJ/mol, respectively. AA had Ea (95.82 ± 1.92 kJ/mol) higher than lycopene (54.92 ± 1.10 kJ/mol). PME (Z = 39.4 ± 0.1 °C) showed highest heat stability while AO (Z = 14.3 ± 1.1 °C) was least stable amongst the enzymes studied. AA (Z = 23.5 ± 0.5 °C) was weakest amongst the phytoconstituents in guava pulp and its retention was challenged during thermal processing. The thermal resistance of quality deteriorating enzyme of guava was found to be higher than that of the common spoilage organisms such as Saccharomyces cerevisiae and Lactobacillus plantarum reported for processed fruit products. Thus, this research hints towards the need for more robust thermal processing for inactivation of quality deteriorating enzymes.

Partial purification, characterisation and thermal inactivation kinetics of peroxidase and polyphenol oxidase isolated from Kalipatti sapota (Manilkara zapota).

BACKGROUND: The extraction, purification, and characterisation of peroxidase (POD) and polyphenol oxidase (PPO) were studied for Kalipatti sapota fruit. The crude enzyme extract was partially purified by ammonium sulfate precipitation followed by BioGel P100 size exclusion and Unosphere Q anion-exchange chromatography. RESULTS: Molecular weights of 20 kDa (POD) and 24 kDa (PPO) were indicated by SDS-PAGE. A single band was observed on SDS-PAGE with a fold purity of 10.38 and 7.42 for POD and PPO, respectively. Michaelis-Menten constants for POD and PPO were 22.3 and 23.0 mmol L-1 using guaiacol and catechol as substrates. Thermal inactivation kinetics was studied in the temperature range of 60-95 °C. The crude extract of POD and PPO showed D-values of 2.2-60.2 and 1.0-35.2 min; Z-values of 18.7 ± 0.4 and 16.0 ± 0.3 °C; and activation energies (Ea ) of 128.6 and 151.0 kJ mol-1 , respectively. CONCLUSION: POD and PPO showed good stability over a wide range of pH and temperature. As reflected by Z and Ea values, the fruit matrix had no significant influence towards enzyme stability. Designing of thermal process should take into consideration D- and Z-values of the enzymes along with D- and Z-values of microorganisms to obtain a product with better shelf life. © 2017 Society of Chemical Industry.

Delayed post-harvest ripening-associated changes in Manilkara zapota L. var. Kalipatti with composite edible coating.

BACKGROUND: There has been limited research on extending the shelf-life of sapota (Manilkara zapota L. var. Kalipatti) fruit. An edible coating made up of methyl cellulose (MC) and palm oil (PO) was applied to study the extension in shelf-life. Changes in physical and chemical properties of fruit were studied along with peroxidase (POD), polyphenol oxidase (PPO) and pectin methylesterase (PME) activities during post-harvest ripening of sapota. RESULTS: The fruits coated with 15 g L-1 MC and 11.25 g L-1 PO showed significant (P < 0.05) delay in physiological weight loss, decrease in fruit firmness losses as well as slower fruit darkening. The coating on the fruits resulted in better retention of ascorbic acid, delayed the loss of total phenolic content, and delayed the increase in total soluble solids and total reducing sugars as compared to control fruits. The coating either delayed or reduced the enzyme activities of POD, PPO and PME of the fruit. CONCLUSION: The results suggest that edible coating made up of MC-PO has potential to maintain the quality of sapota fruit. The edible coating extended the shelf-life of sapota fruit by 3 days preserving fruit quality up to 7 days at 24 ± 1 °C and 65 ± 5 %RH. © 2016 Society of Chemical Industry.

Use of paprika oily extract as pre-extrusion colouring of rice extrudates: impact of processing and storage on colour stability.

Suitability of paprika oily extract as a pre-extrusion colouring of rice extrudate was evaluated as a function of extrusion parameters viz. moisture content, screw speed and die temperature. Most acceptable coloured rice extrudates in terms of colour and overall acceptability was achieved with addition of 3 % paprika oily extract and which is extruded at fixed conditions of 25 % feed moisture, 120 °C barrel temperature and 100 rpm screw speed. During extrusion, retention of red colour of paprika oily extract added rice extrudates increased with an increase in feed moisture and screw speed while decreased with an increase in barrel temperature. Present study was also undertaken to check effect of addition of butylated hydroxytoluene (BHT) on colour stability of coloured rice extrudates. Coloured rice extrudates were packed in polyethylene, metallised polyethylene and vacuum packaging material and subjected to storage studies for 90 days at 25 and 50 °C with 65 % relative humidity conditions. Retention of red colour (a*) of paprika oily extract added rice extrudates follows first order kinetics, showing a faster rate of degradation with half-life of 48 days when packed in metalized polyethylene and stored at higher temperature conditions.