Characterization of peeled and unpeeled almond (Prunus amygdalus) flour after electron beam processing

Radiation Physics and Chemistry 86 (2013) 140–144

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Characterization of peeled and unpeeled almond (Prunus amygdalus) flour after electron beam processing C.M. Lanza a, A. Mazzaglia a,n, R. Paladino b, L. Auditore c,d, R.C. Barna c,d, D. Loria c,d, A. Trifiro c,d, M. Trimarchi c,d, G. Bellia e a

Universita di Catania, Dipartimento di Scienze delle Produzioni Agrarie e Alimentari (DISPA), via Santa Sofia 98, I-95123 Catania, Italy Laboratorio di analisi e ricerche V. Besana S.p.A., I-80040 San Gennaro Ves.no (NA), Italy c Universita di Messina, Dipartimento di Fisica, I-98166 Messina, Italy d INFN, Gruppo Collegato di Messina, Italy e Universita di Catania, Dipartimento di Fisica e Astronomia, I-95123 Catania, Italy b

H I G H L I G H T S c c c

Examine physical chemical and sensory changes on irradiated almond. Increase the information on irradiation treatment at low doses. Contribute to broaden the use of this technology in the food.

a r t i c l e i n f o

a b s t r a c t

Article history: Received 8 August 2012 Accepted 12 January 2013 Available online 11 February 2013

Flours of unpeeled and peeled almond seeds have been irradiated with ionising radiation at 1.5 kGy dose by means of 5 MeV energy electron beam. The effects of ionising radiation have been studied concerning microbiological parameters, such as total mesophilic counts, mould, yeast, enterobacters, coliform bacteria, as well as physicochemical parameters, free fatty acid, peroxide number, humidity, activity water, aflatoxin, pesticides, and sensory evaluation of attributes regarding only appearance, olfactory and rheological aspects in accordance with the prescription of Italian laws about the consumption of irradiated food. The results, compared with non-irradiated samples from the same supply, show a sharp decrease of pathogen loads while no significant variations of physicochemical parameters and sensory descriptors have been noticed. These results indicate that irradiation at 1.5 kGy dose, lower than values usually reported in literature, seems to be still a suitable sanitation treatment to extend the shelf-life of this kind of foodstuff while maintaining its nutritional, safe and sensory characteristics. & 2013 Elsevier Ltd. All rights reserved.

Keywords: Irradiation Electron beam Almond Sensory analysis Sanitation treatment Pathogen load

1. Introduction In the last years, many scientific evidences have shown beneficial effects of the oily dried fruit use (walnuts, hazelnuts, almonds, and pistachios) in a balanced diet thanks to the high nutritive value provided, besides of contribution of vegetal proteins, vitamin E, fibres, iron and calcium, also from contents in fat (46–76%) with a main fraction of mono- and polyunsaturated fatty acids (Ryan et al., 2006) that may induce cardio-protective effects (Kelly and Sabate, 2006). Almonds quality may be substantially reduced if the product is subjected to insect

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damage during post harvest storage on the ground or pre harvest insect attack in the field (Schatzki and Ong, 2001). Furthermore, growth of some aflatoxigenic Aspergillus species and production of aflatoxin can make almonds unsuitable for consumption. In both cases, preservation strategies are necessary to prevent mycotoxin production or insect growth. The use of ionising radiation can be an efficient strategy, alternative to chemical one, in the post harvest applications (Kabak et al., 2006) which are allowed in food products up to a maximum dose of 10 kGy by many countries in the world (Lacroix and Quattara, 2000). Navaiz et al. (1992) have noticed on almonds, irradiated at 1.0, 1.5 and 2.0 kGy doses and stored for 6 months at a temperature of 5 1C, that the initial mould and yeast load, reduced to acceptable values, was maintained throughout the storage time. Other authors (Aziz and Mousa, 2004) report on Aspergillus alutaceus

C.M. Lanza et al. / Radiation Physics and Chemistry 86 (2013) 140–144

and flavus inhibition after 5 kGy dose irradiation and aflatoxin B1 (74.3–76.7%) and ocratoxin A (51.3–96.2%) detoxification with 6 kGy dose irradiation on chick-peas and peanuts. Unsaturated fatty acid large content induces the formation of peroxides and free radicals that, by interacting with proteins and lipids, brings to oxidation products as aldehydes, esters, ketones and sulphured compounds (Sajilata and Singhal, 2006). A few works on irradiated oil of almond and shelled almonds (Sa nchezBel et al., 2008, 2005) provided encouraging results on the absence of significant changes in the composition of fatty acids, lipid oxidation or appearance of rancidity with doses up to 7 kGy. It is very important to study the effect of ionising radiations on physicochemical and sensory properties of almonds as the consumer demands, besides nutritional quality, also a complete absence of off-odour and off-flavour. The radiation effect on both peeled and unpeeled almond flour has been evaluated in order to provide data to be the spurs for the adoption of such a technology in Italy.

2. Experimental

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Table 1 Analysed microbiological and physicochemical parameters. Microbiological parameters (ufc/g)

Physicochemical parameters

Total mesophilic counts Mould/yeast Enterobacters Coliform bacteria—otal Escherichia coli ß-glucuronidase (þ) Coagulase positive staphylococci Salmonella spp Listeria monocytogenes.

Free fatty acid (% oleic acid) Rancidity (qualitative, test of Kreiss) Number of peroxide (Meq O2/kg mg) Humidity (%) Activity water Pesticides (mg/kg) Aflatoxin (B1 þ B2þG1þ G2) (mg/kg)

capsules without any compression to avoid anomalous density increases that could have conditioned the dose distribution in the irradiated samples. Forty Petri capsules were irradiated. The Petri capsule dimensions represent the best compromise between a minimum fractionation sample and the total irradiation time. Furthermore, the capsule thickness has been properly chosen as to stay in the build up region of the dose–depth curve, thus allowing to minimise the uncertainty in the dose–depth uniformity.

2.1. Samples Almonds (Prunus amygdalus) to be treated with ionising radiation have been supplied by V. Besana S.p.A. Company based in S. Gennaro Vesuviano (Na, Italy) in form of fresh ground flour from peeled and unpeeled seeds, coming from different production sites. Each kind of flour has been divided into two parts. One has been irradiated and the other one has been used as a control sample. The control sample has been subjected to the same conditions of transport, storage and analysis of the irradiated flour.

2.3. Analytical determinations Besana S.p.A. Company has determined in triple microbiological and physicochemical parameters forming its own analysis protocol, before and after ionising radiation treatment; microbiological and physicochemical parameters analysed and their relative methods are reported in the Table 1.

2.2. Ionisation radiation treatment Irradiation has been performed, at 1.5 kGy dose, by means of 5 MeV electron accelerator of the Physics Department of University of Messina (Auditore et al., 2004). This accelerator is a research tool, designed in collaboration with the ENEA Accelerators Group (Frascati, Rome); it has auto focusing accelerating structure, able to deliver an extremely collimated electron beam with 4 mm2 surface spot. An accurate measurement of the irradiation dose per unit electron current has been performed, at different distances from the electron beam exit window, by means of Gafchromic films. This allows us to measure the total dose provided to a given sample as a function of the total electron charge collected by a charge integrator, coupled with a toroidal ferrite, which continuously monitors the beam electron current stability. The uncertainty of the dose measurement is primarily affected by the beam energy stability, which is better than 2%. The dose rates for selected beam parameters were measured with alanine reference dosimeters from the accredited Risø High Dose Reference Laboratory. Doses given to samples were determined by selecting appropriate beam parameters. The treatment channel allows to put samples to be irradiated at a maximum distance of nearly 80 cm from the electron output window. The electron beam, once outside the accelerating structure, broadens in such a way to keep a uniform distribution on a circular surface with a diameter almost one tenth of the distance from the output window. This situation, on one hand avoids complicated structures to yield uniform electron distribution, on the other one limit the dimensions of the samples to irradiate. Flour samples, about 1 kg in weight for each type, have been shared in Petri capsules (6 cm diameter and 1 cm height) and individually irradiated. Flour (25 g) has been inserted in the

2.4. Sensory analysis on not irradiated samples A measurement of possible change in the sensory characters, due to the radiation effect, has been done by the sensory profile method (UNI 10957, 2003). The sensory profile was constructed by using a 12 judges trained panel (UNI EN ISO 8586, 2008), consisting of students of the DISPA.1 In a few preliminary meetings, by using commercial and Besana samples, the judges have generated a list of descriptors based on the percentage of citations referring to appearance, olfactory, gustative and mouthfeel attributes. The final set consisted of 15 descriptors for peeled samples and 20 descriptors for unpeeled samples; the descriptors for both samples are reported in Table 2. The different descriptors were quantified using a nine point intensity scale where the digit 1 indicates the descriptor absence while the digit 9 the full intensity. Evaluations have been lead in single boxes at the DISPA sensory analysis laboratory. The order of presentation was randomized between judges and sessions. Water was provided for rinsing between samples. All data were acquired by a direct computerised registration system (FIZZ Byosistemes. ver. 2.00 M, Couternon, France). The obtained profile allowed to quantify the sample characteristics separately and in perception order. The difference in number and typology of the descriptors accounts for the relevant almonds dissimilarity. The peel in the unpeeled almonds accounts for the presence, for instance, of the woody attributes which are absent on the contrary in the peeled almond. 1 The affiliation department of two of authors; it is devoted to studies on agroindustrial food production.

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(D.M. 30/08/ 1973, D.L.vo 30/01/2001, n. 94) were considered and shown in Table 3.

2.5. Sensory analysis on irradiated samples To evaluate the possible change in the profile of the two kinds of almond flour due to the irradiation treatment, only descriptors in agreement with Italian laws on irradiated food consumption

The sensory data for each attribute were submitted to one-way Analysis of the Variance (ANOVA) by software package Statgraphicss Centurion XVI (Statpoint Technologies, INC.) using samples as factors. The significance was tested by means of F-test. To differentiate the samples the mean values were submitted to the multiple comparison test using the Least Significant Difference (LSD) procedure.

Table 2 Sensory descriptors for peeled and unpeeled almonds. Peeled almond

Unpeeled almond

Colour intensity Visual moisture Grainy Tactile greasiness Almond odour Vegetal odour Off-odour Crunchiness Moisture in the mouth Sweet Bitter Astringent Almond flavour Vegetal flavour Off-flavour

Colour intensity Visual greasiness Tactile greasiness Almond oil odour Woody odour Almond odour Stale odour Off-odour Sweet Sour Bitter Astringent Chewiness Adhesiveness Almond oil flavour Woody flavour Almond flavour Stale flavour Off-flavour Ease of swallowing

3. Results Tables 4 and 5 show the microbiological and physicochemical parameters variation following the irradiation process on peeled and unpeeled almond flour. In the case of unpeeled almond flour (Table 4), mould decreases from a value of 2900 ufc/g to a value less than 400 ufc/g, enterobacteria from a value of 73 ufc/g to a value less than 40 ufc/g; a decrease in the number of peroxide and an absence of rancidity are observed. Similar results have been obtained for the peeled almond flour: TBC decreases from a value of 23,000 ufc/g to 73 ufc/g, yeasts decrease from about 400 ufc/g to o100 ufc/g, the absence of rancidity has been observed. The number of peroxides, however, is increased from a value of 0.62–0.94 Meq O2/kg mg, a value plenty inside the limits fixed by the Italian laws. Mean scores relative to each descriptor are reported in the spider plots of Figs. 1 and 2. In Table 6, the results related to irradiated and non-irradiated peeled almond flour are shown; data highlight that only one of the descriptors, the off-odour, has changed significantly at 5% confidence level. Fig. 1 reports data from Table 6 for irradiated and nonirradiated peeled almond flour. Similarly, unpeeled almond flour data do not show any significant change, at 5% confidence level, for all the descriptors. Table 7 shows averaged values for unpeeled flour. Fig. 2 reports data from Table 7. To notice that within a standard deviation, values are essentially unchanged.

Table 3 Sensory descriptors for peeled and unpeeled almonds in agreement with Italian laws on irradiated food consumption. Peeled almond

Unpeeled almond

Colour intensity Visual moisture Grainy Tactile greasiness Almond odour Vegetal odour Off-odour

Colour intensity Visual greasiness Tactile greasiness Almond oil odour Woody odour Almond odour Stale odour Off-odour

2.6. Data analysis

Table 4 Parameter value for unpeeled almond flour. Parameter

Total bacteria counts Mould Yeast Enterobacters Coliform bacteria—total E. Coli b-glucuronidase (þ ) Salmonella spp S. Aureo coagulasi (þ ) L. monocytogenes Aflatoxine B1 Aflatoxine—total Humidity Water activity Free Fatty Acid Rancidity Peroxide

Non-irradiated

Units

Irradiated

Value

Uncertainty (U)

Value

Uncertainty (U)

370 2900 o 100 73 o 10 o 10 Absent o 100 Absent o 0.5 o 0.5 3.29 0.655 0.26

260–540 1900–4500

670 o400 o100 o40 o10 o10 Absent o100 Absent

490–920 84–890

0.64

35–150

2.91 0.505 1.41 Negative 0.51

1–67

ufc/g ufc/g ufc/g ufc/g ufc/g ufc/g in 25 g ufc/g in 25 g mg/kg mg/kg % % Meq O2/kg mg

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Table 5 Parameter value for peeled almond flour. Parameter

Total bacteria counts Mould Yeast Enterobacters Coliform bacteria—total E. Coli b-glucuronidase (þ ) Salmonella spp S. Aureo coagulasi (þ ) L. monocytogenes Aflatoxine B1 Aflatoxine—total Humidity Water activity Free fatty acid Rancidity Peroxide

Non-irradiated

Irradiated

Value

Uncertainty (U)

Value

Uncertainty (U)

23,000 o100 o400 o10 o10 o10 Absent o100 Absent o0.5 o0.5 3.46 0.647 0.17

18,000–29,000

73 o 100 o 100 o 10 o 10 o 10 Absent o 100 Absent o 0.5 o 0.5 2.62 0.432 0.17 Negative 0.94

35–150

0.62

43–770

Units

Method

ufc/g ufc/g ufc/g ufc/g ufc/g ufc/g in 25 g ufc/g in 25 g mg/kg mg/kg

UNI EN ISO 4833: 2004 ISO 7954: 1987(E) ISO 7954: 1987(E) ISO 21528/2: 2004(E) ISO 4832: 2006 (E) ISO 16649-2: 2001 (E) UNI EN ISO 6579: 2008 UNI EN ISO 6888-1: 2004 UNI EN ISO 11290-1: 2005

%

MP/11 Rev. 1 2009 AOAC 978.18 AOAC 940.28 MP/03 REV. 1 2009 AOAC 965.3

% Meq O2/kg mg

Table 6 Analysis on peeled almond flour. Descriptor

F value Averaged values

Colour intensity

Fig. 1. Mean scores obtained from the judges related to peeled almond flour. Black points refer to non-irradiated flour; grey points refer to irradiated flour.

0.19 n.s. 0.18 Visual moisture n.s. 0.35 Grainy n.s. Tactile 0.46 greasiness n.s. 0.00 Almond odour n.s. 0.74 Vegetal odour n.s. Off-odour 4.85n

Nonirradiated

Irradiated

4.83

5.16

4.66

4.91

5.33

5.66

5.08

5.50

4.50

4.50

3.66

4.50

1.83

4.00

Variability (s) Nonirradiated

Irradiated

1.59

2.12

1.65

1.68

1.46

1.67

1.77

1.57

1.97

2.54

2.12

2.71

1.43

3.05

n.s.: no significant difference. n

Significant difference for pr 0.05.

Table 7 Analysis on unpeeled almond flour. Descriptor

Colour intensity Visual greasiness Tactile greasiness Almond oil odour

Fig. 2. Mean scores values obtained from the judges relative to unpeeled flour. Black points refer to non-irradiated flour; grey points refer to irradiated flour.

Wood odour

4. Discussion and conclusion

Almond odour

The results show that the effects of irradiation process have not modified the sensory characteristics of irradiated products. In the case of almond’s samples unpeeled, the differences among values are found within error value. In the case of unpeeled

Stale odour Off-odour

F value Averaged values

0.00 n.s. 0.15 n.s. 0.73 n.s. 0.01 n.s. 0.44 n.s. 0.10 n.s. 0.04 n.s. 1.51 n.s.

Variability (s)

Nonirradiated

Irradiated

Nonirradiated

Irradiated

6.50

6.50

0.97

1.09

3.69

4.00

1.54

2.30

4.83

5.33

1.43

1.44

3.83

3.91

1.12

2.11

3.11

3.50

0.71

1.36

3.38

3.25

1.16

1.68

2.22

2.33

0.90

1.78

1.33

1.75

0.51

1.06

n.s.: no significant difference.

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almond, the differences among values are found within error value. Regarding the peeled almonds only one descriptor, the offodour, is significantly different between flour samples irradiated and not irradiated. As a further comment, it is to say that the offodour descriptor is close to the detectability threshold for the non-irradiated product while the same descriptor for irradiated almond is almost at 30% of the maximum intensity level. All the results show how the irradiation process is a powerful method allowing preservation of food safety, provided that the process is performed at a dose level balancing the reduction efficiency of the pathogen loads and the maintenance of physicochemical and sensory characteristics of the goods. By means of the irradiation at 1.5 kGy dose, it is possible to achieve almost the same results of treatments made at a higher dose level as stated by other authors, indicating that further irradiations must be undertaken in order to find the minimum dose levels to obtain the same reduction on pathogenic loads; in the assumption that lower irradiation dose maintain, a fortiori, the product safeguard.

Acknowledgements This research has been granted partly by the University of Catania. The authors would thank the Besana S.p.A. Company for sample supplying and for the physicochemical and microbiological analysis before and after the irradiation process.

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